Morphology – (Morphe = form + logos = study). It deals with the study of forms and features of different plant organs like roots, stems, leaves, flowers, seeds, fruits etc.
2. CLASSIFICATION OF PLANTS
• Depending upon their life span, plants are classified as –
• Annuals – Complete their life cycle in one year or single growing season or few weeks to a few months. They pass the unfavourable period in the form of seeds, eg., Mustard, Pea.
• Biennials – Complete their life cycle in two years-growing, vegetative and storing food in the first year; flowering and fruiting in the second year. They die off after producing flowers and fruits, e.g., Radish, turnip, carrot are biennial in colder areas. They become annual in warmer places.
• Perennials – Survives for several years. These plants usually bear flowers and fruits every year and do not die after producing flowers. E.g., Mango, Banana, Guava
• Smallest angiosperm: Wolffia (0.1mm diameter). Aquatic Lemna has a diameter of 0.1cm. Arceuthobium is another small angiosperm plant which is parasitic over Pinus and other trees.
• Tallest plant (angiosperm): Eucalyptus regnans (114 metres or 375 feet height). Tree having largest crown: Banyan tree (Ficus benghalensis).
• Majority of angiospermic plants are autotrophs. There are, however, many plants, which draw their organic food from different sources and are called heterotrophic plants. They are of three types:
• Saprophytes: They obtain their nourishment from dead organic matters. Angiospermic saprophytes are also called humus plants, e.g., Indian pipe (Monotropa), bird’s nest orchid (Neottia), chain orchid (Pholidota), coral root (Corallorhiza), etc.
• Parasites: These are the plants, which obtain their nourishment partially or wholly from other living organisms called hosts by their sucking roots. Common examples of different types of phanerogamic parasites are as follows:
♦ Total stem parasites, e.g., dodder (Cuscuta reflexa), Arceuthobium, etc.
♦ Partial stem parasites, e.g., Viscum, Loranthus, etc.
♦ Total root parasites, e.g., broomrape (Orobanche indica), Aeginetia indica, etc.
♦ Partial root parasites e.g., sandalwood tree (Santalum album), Striga lutea.
• Carnivorous plants: These are predator plants, which capture insects. They often grow in nitrogen deficient soils. They are green in colour and prepare their own carbonaceous food, while they partially depend on insects and other animals for nitrogenous food. Some examples are sundew (Drosera), venus fly-trap (Dionea), bladderwort (Utricularia), butterwort (Pinguicula), Aldrovanda, Nepenthes (The Asiatic pitcher plant) Sarracenia (The north-American pitcher plant).
It is direct elongation of the radicle, it develops and forms primary root. It bears lateral roots of several orders that are refered to as secondary and tertiary roots.
Characteristics of Root
• Roots are positively geotropic, positively hydrotropic and negatively phototropic.
• Root is protected at its tip by a protective structure called root cap. But in aquatic plants, there are root pockets for balancing. In screwpine (Pandanus racemosus), there is multiple root caps. An injured root pocket is not replaced.
• Root is not differentiated into nodes and internodes.
• Root does not bear buds, leaves, flower, fruits, etc. However, radical bud for vegetative reproduction is found in sweet potato (Ipomoea batatas), wood apple (Aegle marmelos), pointed gourd (Trichosanthes dioica), Indian redwood tree (Dalbergia sissoo), etc.
• Root bears unicellular root hair occurring in cluster for the absorption of water and minerals.
• Lateral roots are endogenous in origin.
Types of Roots
Roots are of two types :
✧ Tap root ✧ Adventitious root
Tap root: It develops from radicle and made up of one main branch and other sub branches. The primary root and its branches constitute tap root system. E.g., Dicot roots.
Adventitious roots : In monocots some and other plants, after sometime of the growth of tap root which arises from radicle, stops and then roots, develop from other part of plant, which are branched or unbranched, fibrous or storage, are known as adventitious roots and constitute fibrous root system. e.g. Monocot roots.
Regions of Roots
Morphologically four distinct regions are present in roots.
The regions of the root-tip
• Root cap : It is terminal structure. It protects tender apex of root and it is a thimble like structure.
• Meristematic zone : Present few millimeter above the root cap. Cells of this region are very small and thin walled with dense cytoplasm. They divide repeatedly and increase cell number.
• Elongation region: The cells proximal to meristematic zone undergo rapid elongation and enlargement and are responsible for rapid growth of roots.
• Maturation region : Cells proximal to region of elongation gradually differentiate and mature. Root hair are present in maturation zone, these root hair absorbs water and mineral from the soil.
Modification of Roots
1. Modified tap root for storage :
Modification of root for : storage
• Fusiform roots : These roots are thicker in the middle and tapered at both ends. In this type of roots both hypocotyl and root help in the storage of food. E.g., Radish.
• Conical roots : These roots are thicker at their upper side and tapering at basal end. E.g., Carrot.
• Napiform : These roots become swollen and spherical at upper end and tapered like a thread at their lower end. E.g., Turnip (Brassica rapa), Sugarbeet.
2. Nodulated root : Nodules are formed on branches of roots by nitrogen fixing bacteria, (Rhizobium). E.g., Plants of leguminosae family (Papilionatae) – Pea.
3. Respiratory roots: Halophyte or mangrove grow in oxygen deficient marshy area. Some branches of tap root in these plant grow vertically & comes out from the soil. These roots are called pneumatophores through which air enters inside the plant. E.g., Rhizophora, Sonaratia and other mangrove plant.
Respiration: pneumatophore in Rhizophora
Modification of adventitious roots
1. Storage adventitious roots
- Tuberous root : When food is stored in these roots, they become swollen and form a bunch. E.g., Sweet potato (Ipomea batata).
- Fasciculated – Roots arise in bunch (cluster) from lower node of the stem and become fleshy, e.g., Dahlia, Asparagus.
2. Stilt roots or brace roots :
When root arises from lower nodes and enter in soil obliquely, known as stilt roots, e.g., Maize, Sugarcane, Pandanus (screwpine).
3. Prop root or pillar roots : When roots arise from branches of plant and grow downwards towards soil. It functions as supporting stem for the plant. E.g., Banyan.
4. Foliar roots or Epiphyllous roots: When roots arise from leaf they are called as foliar roots. E.g., Bryophyllum, Bignonia.
5. Sucking or haustorial roots or Parasitic roots : In parasitic plant, roots enter in the stem of host plant to absorb nutrition from host. E.g., Cuscuta, Viscum.
6. Assimilatory roots : The aerial roots of Tinospora and submerged roots of Trapa (Water chestnut) become green and synthesize food. Podostemon also has green assimilatory roots.
7. Hygroscopic roots : These are found in epiphytes, specially in orchids and help in absorption of moisture from the atmosphere using special tissue called velamen. E.g., Orchids, Vanda.
Functions of Root
• Fixation (Primary function)
• Absorption of water and minerals
• Storage of food
• Synthesis of plant growth regulators
• Stem is ascending part of plant, i.e., it shows negatively geotropic growth. It has nodes and internodes. Stem arises from plumule.
• The region of stem which bears leaf is referred as nodes and the portion between two nodes is referred as internodes.
• The stem bears buds, which may be terminal or axillary.
• It is generally green when young and later becomes woody and dark brown.
Modifications of Stems
Change in form to perform functions other than normal is called modification. On the basis of habitat, modified stems can be classified into three categories: Underground modifications, Sub-aerial modifications and Aerial modifications.
Underground Modifications Of Stem
- After modification such stems become subterranean and are meant for storage of food, perennation and vegetative reproduction. Underground modifications of stem are of following types:
- Rhizome: It is a modified main stem, which grows horizontally under the surface of the earth exhibiting diageotropic mode of growth. It is thick, prostrate, dorsiventral and branched and has distinct nodes and internodes. The nodes bear small scaly leaves in the axils of which, there are axillary buds. Adventitious roots develop on the lower surface of the nodes. Food materials are stored in both nodes and internodes, e.g., banana (Musa sapientum), mankand (Alocasia indica), Dryopteris (a fern), ginger (Zingiber (officinale), Canna, lotus (Nelumbium spaciosum), etc.
- Tuber: It is the swollen end of a special underground branch. It is round or oval or cylindrical shape growing horizontally under the ground. The stem tuber is covered by a corky skin. Each tuber possesses a number of spirally arranged depressions called eyes, each representing a node. At each node there is a scaly leaf in the axil of which, a bud is present and adventitious roots are absent. There is a heavy deposit of food material, e.g., potato (Solanum tuberosum), Jerusalem artichoke (Helianthus tuberosus).
Bulb: It is highly reduced underground-modified main stem. It assumes a disc or convex-lens or cone-shape. Nodes are very closely situated so internodes are very small. From upper surface of nodes scaly leaves are borne and from their lower surface numerous adventitious roots arise. Scaly leaves are of two types: outer dry, brown and inner fleshy, white or red scaly leaves. Fleshy scaly leaves store food at their base in the form of carbohydrates. At the apex of bulb there is an apical bud which gives rise to an aerial shoot, known as scape. In the axils of fleshy scaly leaves, axillary buds develop, e.g., onion (Allium cepa), tulip (Tulipa), tuberose (Polyanthes), lily (Lilium sp.) garlic (Allium sativum) etc.
- Corm: It is the underground modification of the basal part of main stem. It is a short, thick, swollen, unbranched, solid and fleshy stem growing vertically in the soil. It bears a number of circular nodes, which are situated very closely so that internodes are very small. There is a heavy deposit of food materials in both nodes and internodes. From the base of nodes many contractile adventitious roots arise. Scale leaves bear axillary buds, which give rise to daughter corms. A terminal bud is always present in a corm which gives rise to aerial branch under favourable conditions, e.g., elephant-foot, ver. zamikand (Amorphophallus campanulatus), Colocasia, Gladiolus, Freesia, etc.
Sub-Aerial Modifications Of Stem
- These are modified branches, which either grow along the surface of the soil or may be partially underground. These are mainly meant for vegetative reproduction and perennation. These are o£ following four types:
- Runner: It is a slender, prostrate branch creeping on the ground. It arises from axillary bud present at the lower node of main stem. It has long internodes. The nodes bear scale leaves and axillary buds. Axillary buds can form new aerial shoots or crowns. Many such runners are produced by the mother plant and they spread out on the ground an all sides. They may break off from the mother plant and grow as independent daughter plants, e.g., wood sorrel (Oxalis corniculata), doob grass (Cynodon dactylon), Indian pennywort ver. brahmi booti (Centella asiatica = Hydrocotyl asiatica), strawberry (Fragaria sp.), etc.
- A special type of underground runner with three internodes is called as sobole. It is sometimes included into rhizomes but it is thin and does not store food, e.g., couch grass (Agropyron), kans (Saccharum spontaneum), ulu (Imperata arundinacea), etc.
- Stolon: It is a slender lateral and sub-aerial branch arising from the base of the main stem. Initially it grows obliquely upwards to some extent and then bends to the ground, striking roots at the tip and producing a bud. The bud soon grows into a daughter plant. Many such stolons, each provided with long or short internodes, may grow out of the mother plant and spread out in different directions, e.g., wild strawberry (Fragaria indica), jasmine (Jasminium), passion flower (Passiflora suberosa), etc
- Sucker: Like the stolon, it is also a lateral branch developing from the underground part of the stem at its lower node. It grows obliquely upwards and directly gives rise to a leafy shoot or new plant. It is shorter and stouter than runner, e.g., guldaudi (Chrysanthemum), raspberry (Rubus idaeus), etc.
- Offset: It is similar to runner but has shorter and thicker internodes. It originates in the axil of a leaf. It produces at the apex, a tuft of leaves above and a cluster of small roots below. It breaks away from the parent plant and grows into an independent plant, e.g., water hyacinth (Eichhornia crassipes), water lettuce (Pistia stratiotes).
Aerial Modifications Of Stem
- To perform some special functions like climbing, protection, food manufacture, vegetative reproduction, etc., vegetative and floral buds often undergo modification in certain plants. The various aerial modifications of stem are as follows:
- Phylloclade or cladophyll: It is a green, flattened or cylindrical, thick, succulent modified main stem. It has several distinct nodes (areoles, the raised areas) and internodes. Leaves get modified into scales or spines. It is an adaptation of plants of xerophytic conditions. It serves as photosynthetic and storage organ e.g., prickly pear (Opuntia tuna), cocoloba (Muchlenbeckia platyclados), several species of Euphorbia, Prunus, etc.
- Cladode: It is similar to phylloc1ade with the difference that it may be made up of only one internode, e.g., satavar (Asparagus racemosus) or two internodes e.g., butcher’s broom (Ruscus aculeatus). It is a modified branch arising from axillary bud. Leaves are reduced to scales or spines. It performs the function of foliage leaves.
Thorns: It is a hard, straight and pointed structure meant for protection. It may arise fron axillary bud, e.g., garden hedge plant (Duranta), lemon (Citrus), pomegranate (Punica)., etc. or from apical bud, e.g., karonda (Carissa). It may bear leaves, flowers and fruits, e.g., Duranta, Prunus, etc.
- Stem tendril: It is a thin, wiry, leafless, spirally coiled and sensitive structure meant for climbing. It may be branched or unbranched. Branched stem tendrils may bear scale leaves in the region of forking. It may arise from axillary bud, e.g., passion flower (Passiflora suberosa) or from apical bud, e.g., Vitis, or from extra-axillary buds, e.g., Cucurbits, or from floral bud, e.g, sandwitch island climber (Antigonon) and balloon vine (Cardiospermum).
Bulbil: It is a special multicellular body meant for vegetative reproduction. It may be the modification of a vegetative or floral bud. It gets swollen because of accumulation of food. It gets detached from the mother plant and grows into a new independent plant e.g., Dioscorea, Oxalis, Globba, Agave, Allium, Lilium, etc.
Functions of Stem
(a) Bearing (b) Mechanical support
(c) Conduction (d) Transportation
(a) Storage of food (b) Water storage (c) Perennation (d) Vegetative
(e) Photosynthesis (f) Protection against browsing
5. LEAF (PHYLLOPODIUM)
- The leaf is a lateral, generally flattened structure borne on the stem.
- The leaves develop from the nodes.
- Their main function is photosynthesis.
- Axillary buds are found in its axil, which later develops into a branch.
- Leaves originate from shoot apical meristem and are arranged in acropetal order.
Leaf is divided into 3 main parts
Leaf base (Hypopodium) –
- Leaves are attached to stem by leaf base.
- In some plants, leaf base becomes swollen and is called pulvinus which is responsible for sleep movement, e.g., Cassia, Mimosa, Bean.
- In monocot plants, leaf base expands into sheath covering the stem partially or wholly (Sheathing leaf base), e.g., grasses and banana (monocots).
- The part of leaf connecting the lamina with the branch of stem. Petiole helps to hold the blade towards light. In Eichhornia petiole swells up and in citrus it is winged.
- Petiole is modified into tendrils in Nepenthes.
- In Australian Acacia petiole is modified in phyllode.
- Long, thin and flexible petiole allows leaf blade to flutter in air, thereby, cooling the leaf and bringing fresh air to leaf surface.
- Lamina (Epipodium) – It is a broad and flattened green part of the leaf. Its main functions are photosynthesis and transpiration.
- Lamina contains vein and veinlets.
- Middle prominent vein is known as the mid-rid.
- Vein provides rigidity to the leaf, and acts as channel of transport for water, mineral and food.
- The shape, margin, apex, surface and extent of incision of lamina varies in different leaves.
- Leaves of some plants have lateral appendages on either side of the leaf base, known as stipules. If stipules are present in leaf it is called stipulated leaf, if it is absent then leaf is called exstipulated.
- Foliaceous – These type of stipules form a leaf like structure. E.g., Pea.
- Tendrillar – Stipules are modified into tendril like structure. E.g., Smilax.
Venation of Lamina
- The arrangement of veins and veinlets in leaves (Lamina) is known as venation. It is of 2 types:
- Reticulate : It is found in dicots. Exception – Calophyllum, Eryngium have parallel venation.
- Parallel : It is found in monocots. Exception – Smilax, Dioscorea, Alocasia, Colocasia have reticulate venation.
- Main vein divides into various branches (veinlets) and form a network structure. Reticulate venation is of 2-types.
- In this type of venation, all veins run parallel to each other and they do not from network. They are of 2 types.
Types of Leaf
On the basis of incision of lamina, leaves are grouped into two categories, simple and compound.
- Simple leaf: A leaf is said to be simple when it has a single lamina which is either entire or incised, but the incisions do not reach up to the mid rib or petiole, e.g., mango, guava, banyan, papaya, etc. On the basis of the direction of incision, the simple leaf with incised leaf margins may be of two types:
- Pinnate simple leaf: Incisions point towards the different points of mid rib, e.g., radish.
- Palmate simple leaf: Incisions point towards the base of mid rib, e.g., castor.
Compound leaf: If incisions in the margins of lamina reach up to the mid rib, it gets segmented into small pieces, each piece being called a leaflet or pinna and the entire leaf is called a compound leaf The mid rib of a simple leaf becomes an axis bearing leaflets, called rachis in a compound leaf.
Types of Compound Leaf
- On the basis of mode of lamina incisions reaching upto mid rib or petiole, compound leaves are of two types, pinnate and palmate.
- Pinnate compound Leaf: In this type, incisions reach up to different points of the mib-rib. It may be of following types:
- Unipinnate: Leaflets are borne directly on rachis. It is of two types:
- Paripinnate: Leaflets are borne in pairs i.e., even number of leaflets, e.g., tamarind (Tamarindus indicus), amaltas (Cassia fistula), etc.
- Imparipinnate: The rachis is terminated by an unpaired odd leaflet, e.g., rose (Rosa indica), neem (Azadirachta indica), etc.
- Bipinnate: The pinnae are dissected again into pinnules so that they are borne on secondary axes known as rachillae or rachules, e.g.. Acacia, Mimosa, Caesalpinia, etc.
- Tripinnate: Here pinnules are borne on tertiary axes, e.g., drumstick (Moringa pterigosperma), etc.
- Decompound: Here division of rachis occurs more than three times. The rachis and its branches become flattened while the pinnules are largely suppressed, e.g., coriander, carrot, fennel, etc.
- Palmate compound leaf: In this type, incisions of lamina reach upto the base of mid rib. The rachis does not develop at all. The petiole bears leaflets in this type. Depending upon the number of the leaflets present, a palmate compound leaf may be:
- Unifoliate: Only a single leaflet is articulated to the top of the winged petiole. The articulation shows that the leaf is not a simple one but compound, e.g., Citrus sp.
- Bifoliate: The petiole bears two leaflets, e.g., Balanites, Hardwickia, etc.
- Trifoliate: The petiole bears three leaflets, e.g., Aegle, Hydrocotyl, Desmodium, etc.
- Quadrifoliate: Four leaflets are present at the apex of petiole, e.g., Paris quadrifolia.
- Pentafoliate: Five leaflets are present at the apex of petiole, e.g., hurhur (Gynandropsis pentaphylla).
- Multifoliate: More than five leaflets are present at the apex of petiole, e.g., Bombax malabarica, Cleome viscosa, etc.
- Pattern of arrangement of leaves on the stem.
- It is of following types:
- Alternate or spiral – Single leaf arising at each node in an alternate manner. E.g., Chinarose, Mustard & Sunflower.
- Opposite – Leaves occuring in pairs at the node opposite to each other, they may be:-
- Decussate : Leaves that stands at right angle to next upper or lower pair, e.g., Calotropis, Mussaenda.
- Superposed : Successive pairs of leaves stand directly over a pair in the same plane, e.g., Psidium (guava), Ixora.
Whorled – More than two leaves at each node, e.g., Nerium, Alstonia.
Modification of Leaves
- Leaflet tendril – When leaflet is modified into tendril like structure than it is called leaflet tendril. E.g., Pisum sativum (Garden pea), Lathyrus odoratus (sweet pea).
- Leaf spine – Leaves or any part of leaflet are modified into pointed spine. E.g., Asparagus, Opuntia, Aloe, Argemone.
- Leaf pitcher – Leaves of some plants are modified into pitcher shape. E.g., Nepenthes, Dischidia.
- Leaf bladder – In some plants, leaves are modified into bladder like structure. E.g., Utricularia.
- Leaf Hooks – In some plants terminal leaflets are modified into curved hooks for helping the plant in climbing. E.g., Cat’s nail (Bignonia unguis – cati)
- Phyllode – Petiole becomes flat and functions as normal leaf. E.g., Australian acacia.
- Fleshy leaves – In onion and garlic food storing fleshy leaves are present
Functions of Leaves
- Normal functions
- Manufacture of food, so it is called as the kitchen of the plant.
- Interchange of gases.
- Subsidiary functions
- Storage of water and food, e.g., Aloe, Portulaca, onion, lilies, etc.
- Vegetative propagation, e.g., Bryophyllum, Begnonia, Kalanchoe, Adiantum (walking fern), etc
- Protection by modifying themselves into different forms like spines, scaly leaves, etc.
- Climbing by modifying themselves into various forms, i.e, hooks, tendrils, etc
Arrangement of flower on floral axis is called inflorescence.
Racemose – The main axis continues to grow and does not terminate into a flower but flowers are formed laterally in an acropetal manner, where old flowers are arranged toward base and young flowers are at tip.
This is of following different types :
- Raceme – When peduncle (main axis) is elongated and flowers are pedicellate. E.g., Radish, characteristic feature of Cruciferae family
- Compound Raceme –When peduncle is branched and each branch bear pedicellated flowers like racemose and are arranged in acropetal manner or panicle. E.g., Gulmohar, Neem.
- Spike – Peduncle is elongated but flowers are bisexual and sessile. E.g., Achyranthes
When peduncle is branched and each branch bear spike, like inflorescence then the small branch having flower is called spikelet and this arrangement is called as spike of spikelet. Characteristic inflorescence of family Gramineae.
- Catkin – Peduncle is thin, long and weak; flowers are sessile and unisexual. Peduncle is pendulus. E.g., mulberry, betula, oak.
- Spadix – Peduncle is thick, long, fleshy and have small sessile and unisexual male and female flowers, covered with one or more green or colourfull bracts known as spathe. E.g., Colocasia, Maize, Palms.
- Corymb – Peduncle is short and all flowers are present at the same level because the lower flower has much long pedicel than the upper one, e.g., Candytuft (Iberis amara).
- Compound Corymb – Peduncle is branched and each branch has flower cluster. E.g., Cauliflower.
- Umbel – Flower stalks of different flowers are of more or less equal length, arise from the same point. At the base of flowers stalks, there is whorl of bracts forming the involucre. eg. Centella.
- Compound Umbel – In umbel inflorescence peduncle is branched and each branch has flower cluster. E.g., Coriander, Foeniculum, Cuminum.
Characteristic feature of family umbeliferae.
- Scapigerous umbel is found in onion.
- Capitulum / Racemose head – Growth of the peduncle is retarded and it becomes broad, flattened, concave or convex. Small flowers are present on it and these flowers are called floret. If all the flowers of capitulum are same , then it is called homogamous. If two different types of floret; ray floret and disc floret are present on the same inflorescence than it is known as heterogamous. In this type of inflorescence florets may be unisexual, bisexual or sterile. This inflorescence is surrounded by one or more involucre. It is most advanced type of inflorescence. E.g., Sunflower, Zinnia, Marigold, Cosmos.
It is Characteristic feature of Asteraceae family.
- In this type of inflorescence, the peduncle terminates in a flower. The older flowers are present at tip and young buds are arranged towards the base. This arrangement is called basipetal succession. It is of following types.
- Uniparous cyme / Monochasial cyme – The peduncle end in a flower producing lateral branch at the time of ending in flower. It is of two types –
♦ Helicoid cyme – When all lateral branches develop on the same side on peduncle then it is called helicoid cyme. E.g., Heliotropium, Saraca, Atropa, Datura.
♦ Scorpioid cyme – When the lateral branch develops alternately on left and right side. E.g., Bignonia,
- Dichasial or biparous cyme – Peduncle ends in a flower, from the basal part of peduncle two lateral branches arise which also end in a flower. This same arrangement occurs on these lateral branches. E.g., Bougainvillea, Jasmine, Teak, Mirabilis, Dianthus, Nyctanthes.
- Multiparous cyme / polychasial – Peduncle ends in a flower and from the base of it many lateral branches arise which also terminates into flower. This arrangement also occur on the lateral branches. E.g., Calotropis (Madar), Nerium, Asclepias, Hamelia.
Special Type of Inflorescence
- Cyathium – The bracts or the involucre become fused to form a cup shaped structure on the margin. In the central part of the cup shaped structure a single female flower is found, which matures earlier. Due to the growth of pedicel female flower come out from the cup shaped structure. Female flower is surrounded by large no. of small male flowers. The male flower, which lies toward the centre matures earlier than the flower which are towards the periphery. This inflorescence is found in Euphorbiaceae family like Euphorbia, Poinsettia, Pedilanthus.
- Verticillaster – A cluster of subsessile or sessile, 3-9 flowers are borne on a dichasial cyme ending in monochasial cyme (scorpioid), in the form of condensed whorl on either side of the node. The opposite clusters give the appearance of whorl or verticel due to over crowding. The verticels are further arranged in a racemose manner e.g., Ocimum (Tulsi), Salvia. Characteristic inflorescence of labiateae family.
- Hypanthodium – Peduncle is modified in a narrow cup like structure. At the base of cup female flowers develop, while towards mouth male flowers develop. E.g., Banyan, Peepal, Ficus.
- Coenanthium : In Dorsitenia, the receptacle becomes saucer shaped and its margins are slightly curved. Arrangement of florets are similar to hypanthodium.
- Flower is defined as highly condensed and modified reproductive shoot. The part from where flower arise is called bract. Flower has short or long flower stalk which is called pedicel. The upper part of pedicel is swollen, spherical shaped or conical which is called thalamus / receptacle.
- Floral leaves are present on it.
- In a flower there are 4 parts.
✧ Sepal ✧ Petal
✧ Stamen ✧ Carpel
Some Words Related To Flower
- Complete Flower – When calyx, corolla, androecium and gynoecium are present.
- Incomplete Flower – Flower with one of the four whorls missing.
- Bisexual Flower – Both gynoecium and androecium present in the same flower.
- Unisexual Flower – Androecium (staminate flower) or gynoecium (Pistillate flower), any one of them are present in the flower.
- Monoecious Plant – When both male and female flowers are present on the same plant. E.g., Cocos, Ricinus, Colocasia, Zea, Acalypha.
- Dioecious Plant – When male and female flowers are present on separate plant, e.g., Mulberry, Papaya.
- Polygamous Plant – When unisexual (male or female), bisexual and neuter flowers are present on the same plant, e.g., Mango, Polygonum.
Symmetry of flower: If the floral plants are cyclic arranged in a flower, then it is called cyclic flower. If floral leaves are spirally arranged then it is called spiral flower. Floral symmetry is of three types:
♦ Actinomorphic / Radial / Regular – When flower is divided by any vertical plane into two equal halves, then it is called actinomorphic flower. E.g., Mustard, China rose, Datura, Chilli.
♦ Zygomorphic / Bilateral – When the flower is divided into two equal halves only by one vertical plane, then it is called zygomorphic flower. E.g., Pea, Bean, Gulmohur, Cassia.
♦ Asymmetrical / Irregular – When the flower cannot be divided into two equal halves from any plane, then it is called asymmetrical flower. E.g., Canna,Opuntia.
Insertion of Floral Parts
- Hypogynous condition : When petals, sepals and stamens are situated below the ovary, the flower is called hypogynous and in this condition ovary is considered superior. E.g., Mustard, Chinarose, Brinjal.
- Perigynous condition: When thalamus grow upwardly and form a cup shaped structure. Gynoecium is situated in the centre and other parts of flower are located on the rim of the thalamus almost at the same level. The ovary is said to be half inferior. E.g., plum, peach, rose.
- Epigynous condition: The margin of thalamus grows upward enclosing the ovary completely and getting fused with it, the other parts of flower arises above the ovary. The ovary is said to be inferior and this condition is known as epigynous. E.g., Guava, Cucumber and ray florets of sun flower.
- The outermost whorl of flower is called calyx. Each member of this whorl is called sepal. When all the sepals are free from each other, then it is called polysepalous condition, e.g., Mustard, Radish. When sepals are fused each other, then it is called gamosepalous condition, e.g., Cotton, Datura, Brinjal.
- In Trapa, calyx is modified into spines and helps in protection of fruit.
- In Asteraceae family, sepals are modified into hairy structure. It is called pappus. The pappus is a modified calyx and helps in dispersal of fruit.
- Sometimes below calyx, a whorl similar to sepals is found which is called epicalyx. E.g., Malvaceae family.
- The second whorl of flower is called corolla and each member of it is called Petal. When all the petals are free, then it is called polypetalous while when petals are fused, then it is called gamopetalous.
- Corolla may be tubular, bell-shaped, funnel shaped or wheel shaped.
- The mode of arrangement of sepals or petals in floral bud with respect to the other members of the same whorl is known as aestivation. It is of following types –
- Valvate – When the petals of a whorl lie adjacent to each other and just touches it. E.g., Calotropis, Custard-apple, Mustard.
- Twisted – When one part of a petal covers adjacent petals and the other part is covered by posterior petal. One margin of the petal overlaps that of the next one, and the other margin is overlapped by the third one. E.g., Cotton, Ladyfinger, Chinarose
- Imbricate – When both margins of the one petal are covered by the other two petals and both margins of another one covers other, rest are arranged in twisted manner.
- It is of two types –
- Ascending imbricate – The posterior petal is innermost i.e., its both margins are overlapped. E.g., Cassia, Bauhinia, Gulmohur etc.
- Vexillary or Descending imbricate – The anterior petal is innermost and posterior petal is outermost and largest. E.g., Pea, Bean.
Quincuncial – It is a modification of imbricate type. Out of the five petals, two are completely internal, two completely external and in the remaining petal, one margin is internal and the other margin is external. E.g., Murraya, Ranunculus.
- When there is no distinction between calyx and corolla the whorl is described as perianth.
- Individual perianth segments are called Tepals. Green tepals are called sepaloid and coloured tepals are called petaloid. Tepals are free (polytepalous) or fused (gamotepalous). eg. Liliaceae and Graminae family.
- It constitutes the third whorl of the flower and is made up of one or more stamens. Each stamen consists of filament, anther and connective. Each anther is usually bilobed and each lobe has two chambers, the pollensac. The pollen grains are produced in pollen sac.
Cohesion of stamens
- When the floral parts of similar whorl are fused, then it is called cohesion. When the stamens of an androecium are free from one another, it is called polyandrous condition.
Adelphous : when stamens are united by their filament only, it is called adelphous. It is of following
- Monoadelphous – When all the filaments are united into a single bundle but anthers are free from each other. In this type of cohesion a tube is formed around the gynoecium which is called staminal tube, e.g., Cotton, Ladyfinger, Chinarose.
- Diadelphous – When the filaments are united in two bundles but the anther remains free, e.g., Gram, Pea, Bean.
In these plants out of 10 stamens, 9 stamens are arranged in bundle while 1 remains free.
- Polyadelphous – When filaments are united into more then two bundles, E.g., Citrus, Castor.
Synandrous – When anthers as well as filaments of stamens are united through out their entire length. E.g., Colocasia, Alocasia, Cucurbitaceae family.
Syngenesious – Only anthers are united in bundle but filaments remain free. E.g., Compositae family.
Adhesion of stamens
When the stamens are attached to other parts of flower, then it is called adhesion of stamens.
- Epipetalous – When stamens are attached to petals. E.g., Brinjal, Datura, Tobacco, Sunflower, Potato.
- Epiphyllous – When stamens are attached to tepals. E.g., Onion, Lily.
- Gynandrous – When stamens are attached to gynoecium either throughout their entire length or by their anther. E.g., Calotropis
Length of stamens
- Didynamous – When four stamens are present, out of them two are long and two are short, then it is called didynamous. E.g., Labiatae family.
- Tetradynamous – When there are six stamens and they are arranged in two whorls. In the outer whorl, there are two short stamens while in inner whorl, there are four long stamens, this condition is called tetradynamous. E.g., Cruciferae family.
- Staminodes – When stamens are without pollen grains and remain sterile through out life are called staminodes. E.g., Salvia verbascum.
- It is the fourth whorl of the flower. It is female part of the flower comprising of the inner whorl of megasporophylls in the form of carpels bearing ovules. It consists of ovary, style and stigma. Ovary is the enlarged basal part, on which lies the elongated tube the style, which connects the ovary to the stigma. The stigma is usually at the tip of the style and is receptive surface for pollen grains. The gynoecium may be monocarpellary or multicarpellary.
- If only one carpel is present in gynoecium this condition is called monocarpellary.
- If more than one carpel is present in gynoecium this condition is called polycarpellary.
- If all the carpels in polycarpellary / multicarpellary condition are free, then condition is called apocarpous. E.g., Lotus, Rose.
- If all the carpels are fused together, then condition is called syncarpous. E.g., Mustard and tomato.
The ovules are attached on ovary walls on one or more cushion called placenta. The arrangement of ovule within ovary wall is known as placentation. It is of following types –
- Marginal: Marginal placentation is found in unilocular ovary. The placenta forms a ridge along the ventral suture of the ovary and the ovules are borne on this ridge forming two rows. E.g., Leguminosae.
- Parietal: This type of placentation is found in unilocular syncarpus ovary. In it the ovule develops on the innerwall of the ovary or on peripheral part. Ovary becomes bi or multilocular due to the formation a false septum. E.g., Cucurbita, Argemone, and Cruciferae family (Mustard).
- Axile: It is found in multicarpellary syncarpous gynoecium. The fusion margin of the carpels grows inward and meet in the centre of the ovary. Thus an axis forms in the centre of the ovary and ovary becomes multi chambered. The ovules are borne at the central axis. Number of these chambers are equal to the number of carpels. E.g., Potato, China rose, Onion, Lemon, Orange, Tomato.
- Free central: This type of placentation is found in syncarpous gynoecium. In it, the ovary is unilocular and the ovules are borne on the axis in the centre of the ovary. Septum are absent in ovary and placentation is axile in beginning. After sometime walls of chamber destroy and only ovulated central axis is left. E.g., Primrose, Dianthus (Caryophyllaceae)
- Superficial – This type of placentation is found in multicarpellary syncarpous gynoecium. The ovules are attached on the walls of locule. E.g., Nymphea (Water lily)
- Basal: The ovary is unilocular and a single ovule is borne at the base of ovary. E.g., Marigold, Sunflower (Asteraceae family), wheat.
- Fruit may be defined as a mature and ripened ovary. Fruit formed without fertilization is called parthenocarpic or aspermic fruit and this phenomenon is called parthenocarpy or aspermy (F. Nou), e.g., banana, grapes, pineapple, etc. Such fruits do not have seeds.
True and False Fruits
- In most of the fruits only the ovary takes part in the formation of fruit; such fruits are known as true fruits or eucarp. Sometimes other floral parts such as thalamus (as in apple, pear, fig), calyx (as in. pineapple), etc., form a major part of the fruit; such fruits are described as false fruits, accessory fruits or spurious fruits or pseudocarp.
Parts of Fruits
- A fruit has two main parts, seeds and pericarp (fruit wall). Seeds are fertilized and ripened ovules. The structure of pericarp varies greatly in different kinds of fruits. Pericarp develops from the wall of the ovary. Depending upon its nature, the fruit is dry or succulent (fleshy pericarp). In fleshy fruits (e.g., peaches, plums, cherries, etc.) it is clearly differentiated into three layers- the outer epicarp, the middle mesocarp and the inner endocarp.
Types of Fruits
- On the basis of the number of ovaries involved, fruits are of following three types: simple fruits, aggregate fruits and composite or multiple fruits.
- A fruit that develops from a single ovary (either monocarpellary or polycarpellary and syncarpous) of a flower is called simple fruit. Simple fruits are of two types, dry and fleshy.
Types of Simple Fruits
♦ The pericarp becomes more or less dry when ripe. The dry fruits are of three types: Capsular fruits (Dehiscent fruits), Achenial fruit and Schizocarpic fruits.
- Capsular fruits: Dehiscent fruits burst automatically on ripening, liberating seeds.
- Indehiscent fruits or achenial fruit: Indehiscent fruits do not burst automatically on ripening. Their seeds are discharged after the decay of pericarp.
- Schizocarpic fruits: Schizocarpic fruits split into a number of indehiscent units called mericarps. But when the broken piece gets dehisced, it is called coccus. Each mericarp contains one seed. However, the pericarp does not burst and seed is liberated only after the decomposition of pericarp. Thus these are intermediate between dehiscent and indehiscent types.
Types of dehiscent or capsular fruits
- They are simple dry many seeded dehiscent fruits. Depending upon the mode of dehiscence these are of five types: Pod, Follicle, Siliqua, Silicula and Capsule.
- Legume or pod: It develops from a monocarpellary, unilocular and superior ovary with marginal placentation. At maturity the fruit dehisces along both the sutures from apex to the base e.g., Pisum (pea), Cicer (gram), etc.
- Follicle: The follicle resembles legumes in that it develops from a monocarpellary, unilocular, superior ovary but differs from the legumes in that it splits open at maturity along one suture, i.e., ventral suture, e.g., Larkspur, Calotropis (madar), Catharanthus (periwinkle), etc.
- Siliqua: It is a long, narrow fruit developing from bicarpellary, syncarpous ovary with parietal placentation. The ovary is one chambered in the beginning but later on becomes two chambered due to the formation of a false partition wall called replum. The seeds are attached on both sides of replum. At maturity the fruit dehisces along both the sutures from base upward e.g., Brassica, (mustard), etc.
- Silicula: A short and broad siliqua with relatively few seeds is known as silicula, e.g., Capsella bursa-pastoris (shepherd’s purse). Iberis amara (candytuft), etc.
- Capsule: It is one or more chambered fruit developing from a polycarpellary syncarpous, multilocular and superior ovary. Depending upon the mode of dehiscence, it is of several kinds:
♦ Porocidal capsule: It dehisces by means of pores, e.g., Papaver, Luffa, etc.
♦ Pyxidium or Pyxis: It dehisces transversely removing the lid and exposing the box of seeds e.g., Portulaca, etc.
♦ Valvular capsule: It dehisces by longitudinal slits. Depending upon the manner of dehiscence, it is subdivided into three categories:
♦ Locudicidal capsule: Here the slits appear in the locule along the dorsal suture and the seeds remain attached to the septae, e.g., Malvaceae, Acanthaceae, etc.
♦ Septicidal capsule: In this type the slits appear in the region of septae where the seeds are also attached, e.g., Linum
♦ Septifragal capsule: In this type the slits in the fruit may appear either in the region of locule or in septae but the seeds are attached to the central column, e.g., Datura.
Types of indehiscent or achenial fruits
- Caryopsis: It is a small one seeded fruit developing from a monocarpellary, unilocular and superiar ovary. In caryopsis the seed coat is fused with the pericarp to form husk. It is the characteristic of Poaceae (Gramineae); e.g., Triticum aestivum, (wheat) Oryza sativa (rice), Zea mays (maize), etc. Such fruits are called grains.
- Achene: It is similar to caryopsis but seed coat is not fused with pericarp, e.g., Ranunculus, Mirabilis (4’O clock plant), etc.
- Cypsela: It is one seeded fruit developing from a bicarpellary, syncarpous, unilocular and inferior ovary. Here the pericarp and the seed coat are separate. Cypsela is a characteristic fruit of the family Asteraceae (Compositae), e.g., Helianthus annuus (sunflower), Tagetes (mariglod), Dahlia, etc.
- Nut: It is a one seeded fruit developing from a bicarpellary, syncarpous, unilocular and superior ovary. Nut is characterised by a very tough and stony pericarp; e.g., Anacardium occidentale (cashewnut), Litchi sinensis (litchi), etc. The edible part is fleshy aril whereas in other nuts it is seed.
Types of schizocarpic or splitting fruits
- Lomentum: It is modified legume in which pericarp gets constricted in between seeds. On ripening it gets broken into as many mericarps as there are seeds, e.g., Arachis hypogaea (ground nut), Tamarindus (tamarind), Mimosa pudica (sensitive plant), etc.
- Cremocarp: It is a dry schizocarpic two seeded fruit developing from a bicarpellary, inferior ovary. At maturity it splits into two one-seeded mericarps. Each mericarp is borne on an elongated axis called carpophore, e.g., Coriandrum (coriander), Foenicum vulgare, (fennel, saunf), etc.
- Regma: It is a dry schizocarpic fruit developing from a tricarpellary, syncarpous, trilocular and superior ovary. At maturity the regma splits into three one seeded cocci e.g., Ricinus communis (castor), Jatropha, etc.
- Carcerulus: It is a dry fruit, which develops from a bi-or multicarpellary, syncarpous, superior ovary. At maturity it splits into four mericarps, e.g., Ocimum, Salvia, etc.
- Samara: It is one or two seeded winged fruit developing from a bicarpellary superior ovary. The wings are the outgrowths of the pericarp, e.g., Holoptelea. In sal (Shorea robusta) fruit is one seeded and winged like samara but the wings are formed by the persistent calyx. Such fruits which are not the samara but look like it are called samaroid. Hopea, Dipterocarpous, etc. are some other common examples of samaroid fruits.
- Fruits in which the entire pericarp or a part of it and/or accessory structures associated with it become fleshy and juicy at maturity.
Types of fleshy fruits
- Drupe (stone fruits): It is one or more seeded fleshy fruit developing from a mono or polycarpellary, syncarpous and superior ovary. The pericarp of drupe consists of a thin epicarp (forms the skin), a fleshy mesocarp (forms the edible part) and hard and stony endocarp. The name stone fruit is given to them due to stony endocarp. Prunus amygdalis (almond), Cocos nucifera (coconut), Prunus persica (peach), Mangifera indica (mango), Trapa bispinosa (water chestnut), etc.
In coconut, the mesocarp is fibrous (not fleshy as in other drupes) and the edible part is the endosperm of seed.
- Berry: It is one or many seeded fleshy fruit developing usually from a bicarpellary or polycarpellary, syncarpous and superior or inferior ovary. In berries the seeds are attached to the placenta in the beginning but at maturity they are found loose in the pulp.
The pericarp of berries is differentiated into epicarp, mesocarp and endocarp (like drupes) but here the endocarp is not stony as in drupes. The endocarp becomes thin, mucilaginous and gets broken into pieces, each piece surrounding a seed, e.g.. Lycopersicum esculentum (tomato) Vitis vinifera (grapes), Musa paradisica (banana), Carica papaya (papaya), Phoenix dactylifera (date plant), Capsicum annum (chilli), Areca catechu (betel or arecanut), Psidium guayava, etc.
- Pome: It is a fleshy fruit surrounded by the thalamus. It develops from bicarpellary, syncarpous, inferior ovary. In pome the edible part is thalamus whereas the true fruit remains embedded, e.g., Pyrus malus (apple), Malus pumila (pear), etc.
- Pepo: Like berry, pepo is also a many seeded fleshy fruit but it develops from a tricarpellary, syncarpous, unilocular, inferior ovary with parietal placentation. Although the seeds in pepo are embedded in the pulp but unlike berry they remain attached to the placenta. It is a characteristic fruit of the family Cucurbitaceae, e.g., Lagenaria siceraria (bottle gourd), Citrullus lanatus (water melon), Cucumis sativus (cucumber), etc.
- Hesperidium: It is many chambered fleshy fruit developing from a polycarpellary, syncarpous, multilocular, superior ovary bearing seeds on axile placentation. The leathery epicarp of hesperidium has many glands of aromatic oil. The mesocarp, represented by white fibres is fused to the epicarp. The epicarp and mesocarp together form the rind. The endocarp is thin and papery. It projects inwards and forms many compartments. The inner wall of endocarp gives out many juicy succulent hairs, which form the edible part of the fruit. Hesperidum is a characteristic fruit of the family Rutaceae, e.g., Citrus aurantifolia (lemon), Citrus reticulata (oranges), etc.
- Balausta: This is many chambered, many seeded fruit developing from a polycarpellary, syncarpous but inferior ovary. The pericarp of balausta is leathery or tough. The carpels are arranged in two rows. Calyx is persistent. The seeds have succulent seed coat (testa), which forms the edible part, e.g., Punica granatum (Pomegranate).
- Amphisarca: It is many seeded fleshy fruit with a stony pericarp. It develops from a polycarpellary, syncarpous, superior ovary. The edible part of the fruit is the inner fleshy layer of pericarp and the placentae e.g., Aegle marmelos, (wood apple), Feronia limonia, etc.
- Fruits developed from a flower having a number of free (apocarpous) carpels, all of which ripe together and are aggregated as a unit on a common receptacle are known as aggregate fruits. Thus, each fruitlet of an aggregate fruit represents a single ovary of an apocarpous pistil.
- The fruitlets of a group are collectively termed as etaerio. In an etaerio, fruitlets may be follicles, achenes, drupe or berries.
- Etaerio of follicles: It consists of number of follicles clustered together on a pedicle. It is found in Calotropis, Catheranthus roseus and Aconitum
- Etaerio of achenes: It is an aggregate of achenes clustered together on a common thalamus e.g., rose, strawberry, Clematis and lotus.
- Etaerio of drupes: In this type of fruit, many small drupes, developed from different carpels are arranged collectively on the fleshy thalamus, e.g., Raspberry (Rubes idaeus).
- Etaerio of berries: It is an aggregate fruit of small berries. Apical part of berries fuses with each other and makes a common rind, e.g., Polyalthea, Anona squamosa (custard apple).
Multiple or Composite Fruits
- These fruits being complex fruits develop from the whole inflorescence. Such fruits are of two types:
- Sorosis: It develops from spike or spadix inflorescence. Here the flowers fuse by their succulent petals and axis bearing the flowers becomes fleshy or woody, thus forming a compact mass e.g., Ananas sativus (pineapple), Artocarpous
Syconus: It develops from hypanthodium inflorescence. A characteristic feature of syconus is a hollow or pear shaped fleshy receptacle which forms the edible part of the fruit, e.g., Ficus carica (fig), Ficus benghalensis (banyan), Ficus religiosa (peepal), etc.
Edible Parts of Some Common Fruits and Their Types
|Common Name||Botanical name||Type of fruit||Morphology of edible part|
|Lady finger||Abelmoschus esculentus||Capsule||Entire fruit (Pericarp and seeds)|
|Wheat||Triticum aestivum||Caryopsis||Endosperm and embryo|
|Rice||Oryza sativa||Caryopsis||Endosperm and embryo|
|Maize||Zea mays||Caryopsis||Endosperm and embryo|
|Barley||Hordeum vulgare||Caryopsis||Endosperm and embryo|
|Litchi||Litchi sinensis||Nut||Fleshy aril|
|Walnut||Juglans regia||Nut (formerly drupe)||Lobed cotyledons|
|Ground nut||Arachis hypogea||Lomentum||Embryo|
|Dhania||Coriandrum sativum||Cremocarp||Entire fruit|
|Zeera||Cuminum cyminum||Cremocarp||Entire fruit|
|Sauf||Foeniculum vulgare||Cremocarp||Entire fruit|
|Ajwain||Trachyspermum ammi||Cremocarp||Entire fruit|
|Khumani||P. armeniaca||Drupe||Epicarp and mesocarp|
|Cherry||P. avium||Drupe||Epicarp and mesocarp|
|Plum (alucha)||P. domestica||Drupe||Epicarp and mesocarp|
|Peach (aru)||P. persica||Drupe||Epicarp and mesocarp|
|Indian plum||Zizyphus jujuba||Drupe||Epicarp and mesocarp|
|Coconut||Cocos nucifera||Drupe||Seed – endosperm|
|Singhara (water chest nut)||Trapa bispinosa||Drupe||Seed-endosperm|
|Jamun||Eugenia jambolana||Berry||Epicarp and mesocarp|
|Common Name||Botanical name||Type of fruit||Morphology of edible part|
|Cheeku||Achras sapota||Berry||Mesocarp and endocarp|
|Areca nut (supari)||Areca catechu||Berry||Endosperm|
|Bnnjal||Solanum melongena||Berry||Pericarp, placenta and seeds|
|Tomato||Lycopersicon esculentum||Berry||Pericarp, placenta and seeds|
|Red pepper||Capsicum annum||Berry||Pericarp, placenta and seeds|
|Grape||Vitis vinifera||Berry||Pericarp and placenta|
|Date||Phoenix dactylifera||Berry||Eipcarp and Mesocarp|
|Banana||Musa sapientum||Berry||Mesocarp and endocarp|
|Guava||Psidium guavava||Berry||Pericarp and placenta|
|Kakari||Cucumis melo var. utillisima||Pepo||Entire fruit (Peri carp, placenta and seed)|
|Phoot||C. melo var. momordica||Pepo||Mesocarp and endocarp|
|Pumpkin||Cucurbita pepo||Pepo||Pericarp and cotyledons|
|Watermelon||Citrullus lanatus||Pepo||Mesocarp, endocarp and cotyledons|
|Bottle gourd||Lagenaria vulgaris||Pepo||Mesocarp, endocarp and cotyledons|
|Bitter gourd||Momordica charantia||Pepo||Peri carp and placenta|
|Pointed gourd||Trichosanthes dioica||Pepo||Mesocarp, endocarp and placenta|
|Lemon||Citrus Union||Hesperidium||Endocarpic, juicy hair|
|Apple||Malus pumila,(Pyrus malus)||Pome||Fleshy thalamus|
|Pear||P. communis||Pome||Fleshy thalamus|
|Anar||Punica granatum||Balausta||Testa – Seed|
|Bel||Aegle marmelos||Amphisarca||Inner pericarp and placenta|
|Custard apple||Anona squamosa||Etaerio of berries||Mesocarp of individual fruit let|
|Strawberry||Frageria vesica||Etaerio of berries||Fleshy thalamus|
|Lotus||Nelumbo nucifera||Etaerio of achenes||Thalamus and seeds|
|Raspberry||Rubus idaeus||Etaerio of drups||Thalamus|
|Pineapple||Ananas sativus||Sorosis||Bract, perianth and pericarp|
|Jack fruit||Artocarpus integrifolia||Sorosis||Bract, perianth and pericarp|
|Fig||Ficus carica||Sorosis||Peduncle and seeds|
- Seed, is defined as the ripened and fertilized ovule, which contains an active embryo, reserve food protective covering. The angiospemic seed may have either one (monocotyledons) or two (dicotyle ledons.
- The seed may also be defined as the integumented megasporangium containing a single megaspore, which after germination and fertilization gives rise to embryo while in situ.
Parts of Seeds
- It is the outer covering of the seed. It develops from integuments of the ovule. In most of the seed, the seed coat is made of two layers. The outer layer is called testa and the inner layer is tegmen. Seeds developing from the unitegmic ovules (i.e., ovules with one integument only) have single layered seed coat. The function of seed coat is to protect the delicate embryo within.
- The seed remains attached to the pericarp (fruit wall) by a short stalk called seed stalk or funicle. In a mature seed the position of seed stalk is represented by a small oval depression called hillum.
- The young or miniature plant, enclosed within the seed coat is called as embryo. It develops from the fertilized egg. Embryo has two parts, cotyledon and embryonal axis (tigellum).
- The point on tigellum where cotyledons get attached is called as cotyledonary node. The part of tigellum lying immediately above the cotyledonary node is known as epicotyl and at the tip of epicotyl lies the plumule. It gives feathery appearance due to presence of one or more leaf primordia i.e., young leaves at its apex.
- The part of the tigellum below the cotyledonary node is known as hypocotyl. It represents the root stem transition region i.e., the part where stem changes into root. The radicle is the basal part of hypocotyl. Externally the radicle may or may not be differentiated from the hypocotyl but these two parts are quite different.
- In seeds, food is stored either in the cotyledons or in a special food storage tissue (endosperm). In legumes, for example, the food is stored chiefly in the cotyledons and there is no endosperm. Absence of endosperm in seeds indicates that it (the endosperm) has been completely utilized by the developing embryo. Such seeds are known as non-endospermic or exalbuminous. In some dicotyledons, e.g., castor, and in monocotyledons e.g., cereals and grasses, food is stored mainly in the endosperm and such seeds are known as endospermic or albuminous.
Germination of Seeds
- The process by which the dormant embryo of the seed resumes active growth and forms a seedling is known as germination.
Conditions Necessary For Germination
- Water: In dormant seeds food material is stored in concentrated form and, therefore, have low physiological activity. Water is essential for germination so that the concentrated food is converted in the form that may be utilized by the seedling. Water also serves as a medium where enzymatic reactions occur. Besides the seed coat becomes soft after absorbing water and allows the expanding embryo to come out of it. Usually moisture present in the soil is sufficient for germination, but some seeds, particularly those with hard seed coat or growth inhibitors, require more water. Seeds do not germinate if they are completely immersed in water because they do not get enough oxygen due to its poor solubility in water.
- Oxygen: During germination embryo resumes growth and for this energy is required. This energy comes from the oxidation of food material stored in the cotyledons or the endosperm, which requires oxygen.
- Suitable temperature: A number of physiological processes occur within the seed during germination. Therefore, a suitable temperature is always essential for germination. The range of optimum temperature varies greatly in different types of seeds. Most of the seeds fail to germinate below 0°C and above 48°C. The optimum temperature usually lies between 25°C to 30°C.
- Food and growth regulators: Food is essential for growing embryo. Some growth regulators are required for growth during germination.
- Completion of rest period: Seeds must complete a period of rest before germination.
- Viability: The germinating capacity of seeds is called viability. The embryo must be intact. The dormancy of the seed must be broken. The period for which seeds retain their viability varies greatly. Nelumbo nucifera (lotus) is reported to have exhibited longest period of viability.
Types of seed germination (on the behaviour of cotyledons)
- Epigeal germination: The cotyledons are brought above the ground due to the elongation of hypocotyl. In cotton, papaya, onion and castor, flat green leaf like cotyledons can be seen in the young seedlings. Here the cotyledons, besides food storage, also perform photosynthesis, till seedling becomes independent. In some other plants like tamarind and bean, the cotyledons being thick, do not become leaf like; they get shrivelled and fall off.
- Hypogeal germination: The cotyledons do not come out of the soil surface. In such seeds the epicotyl elongates pushing the plumule out of the soil. All monocotyledons show this germination. Among dicotyledons gram, pea, groundnut, mango, etc. are common example of hypogeal germination. In monocotyledons (e.g., maize, wheat) radicle and plumule come out by piercing the coleorrhiza and coleoptile, respectively. The plumule grows upward and the first leaf comes out of the coleoptile. The radicle forms the primary root, which is soon replaced by many roots
- Vivipary or Viviparous germination: It is a special type of germination found in mangrove plants (Rhizophora. Heritiera. Ceriops, Aviceniaex). In this process the embryo does not undergo any period of rest and the seed germinates inside the fruit while it (fruit) is still attached to the plant. The radicle elongates considerably and projects out of the fruit.
- The lower part of the radicle becomes thick and swollen. Finally, the seedling breaks off the parent plant due to its increasing weight and gets embedded in the muddy soil below. Soon lateral roots develop at the basal end of the radicle.
Semi-Technical Description of a Typical Flowering Plant
- Various morphological features are used.
- Scientific language is used and presented in sequence.
- Begins with vegetative character, than floral characters.
- A floral diagram and floral formula are presented.
- Fusion is indicated by enclosing the figure within bracket.
- Adhesion by a line drawn above the symbols of the floral parts.
- The position of mother axis with respect to flower is represented by a dot on the top of the floral diagram.
Floral diagram with floral formula
♦ The floral characters and their symbols, by which they are represented, are as follows:
- Bracteate flower…………………….. Br
- Ebracteate flower……………………. Ebr
- Bracteolate flower…………………… Brl
- Ebracteolate flower…………………. Ebrl
- Actinomorphic flower……………….
- Zygomorphic flower………………… % or
- Male(staminate)flower……………… ♂
- Female (pistillate) flower…………… ♀
- Perfect or bisexual flower……………
- Neuter flower……………………….. N
- Calyx ……………………………… K
- Corolla……………………………… C
- Perianth …………………………….. P
- Androecium ………………………… A
- Staminodes …………………………. Std.
- Gynoecium …………………………. G
♦ The number of floral parts are written at the right foot of the symbol. If the number is up to five or so, actual number of parts is written. If the number is much more, the sign of infinity ‘ ∞ ‘ is used. More than one whorl or group of a type of floral organ is represented by using sign ‘+’ and writing the actual number of parts in each group or whorl, e.g.,
- 5 sepals……………………………………………..
- 4 sepals in 2 groups or sub whorls of 2 each………… K2+2
- Indefinite stamens…………………………………
If the floral parts of a series are united in one or more groups, the number of parts is written within brackets, e.g.,
- Calyx – sepals – 5, gamosepalous……………………. K(5)
- Corolla – petals – 5, gamopetalous…………………… C(5)
- Androecium – stamens – 10, diadelphous (one group contains 9 united stamens, the other group having single free stamen) …………………….. A(9)+1
- Gynoecium – bicarpellary, syncarpous………………. G(2)
- The epipetalous or epiphyllous condition of androecium is represented by an arc ‘ ’which joins androecium with the corolla or perianth as the case may be, e.g., or .
♦ Superior ovary is indicated by a bar below the number of carpels while the inferior ovary is represented by a bar or horizontal line above the number of carpel. Perigynous condition (semi superior ovary) is shown by a bar just in front of the number of carpels, e.g.,
- Gynoecium bicarpellary, syncarpous, superior …………………….. G(2)
- Gynoecium bicarpellary, syncarpous, inferior …………………….
- Gynoecium bicarpellary, syncarpous, semi-superior ………………… G(2)–
♦ The floral formula of mustard plant is
10. DESCRIPTION OF SOME IMPORTANT FAMILIES
|Vegetative characters||FABACEAE (Papilionoideae)||SOLANACEAE (Potato family)||LILIACEAE (Lily family|
|Tree, shrubs, herbs, root nodule present erect or climber, alternate leaf with leaf base, pulvinus, reticulate venation||Herbs, shrubs rarely small, herbaceous, rarely woody, underground stem in potato||Monocotylednous, perennial herb with under ground bulbs/corms / rhizome, leaf with parallel / venation|
|Inflorescence||Racemose||Solitiary, axillary or cymose||Solitary / cymose; often umbellate clusters|
|Flower||Bisexual, Zygomorphic||Bisexual, actinomorphic||bisexual; actinomorphic|
|Calyx||Pentamerous, Gamosepalous, imbricate||Pentamerous, gamosepalous persistant, valvate.||Perianth – Calyx and corolla fused tepal six (3+3), often united into tube; valvate aestivation|
|Corolla||Pentamerous, Polypetalous, Papilionaceous, vexillary||Pentamerous, gamopetalous valvate|
|Androecium||Ten, Diadelphous, anther dithecous||Five, epipetalous||Stamen six, (3+3)|
|Gynoecium||Hypogynous, monocarpellary, unilocular with many ovules||Bicarpellary, Syncumpous, hypogynous, bilocular, swollen placenta, with many ovule||Tricarpellary, syncarpous, ovary superior, trilocular with many ovules; axile placentation|
|Fruit||Legume||Berry or capsule||Capsule, rarely berry|
|Seed||one or many, non-endospermic||Many, endospermic||Endospermous|
plant : (a) Flowering twig