Parts of a flower :
Calyx :
- It is the outermost whorl
- Each member called sepals.
- Sepals are green leaf like protect the flower in the bud stage.
- Gamosepalous: sepals are united.
- Polysepalous: sepals are free.
Corolla :
- It is the second whorl of a flower.
- Each member called petal.
- Usually brightly colored to attract insect for pollination.
- Polypetalous: petals are free.
- Gamopetalous: petals are united or fused.
Aestivation : the mode of arrangement of sepals or petals in the floral bud with respect to the other members of the same whorl is known as aestivation.
- Valvate : sepals or petals in a whorl just touch one another at the margin, without overlapping. E.g. Calotropis.
- Twisted : one margin of the appendage overlaps that of the next one and so on. E.g. china rose.
- Imbricate : the margin of sepals or petals overlap one another but not in any particular direction as in Cassia and gulmohur.
- Vexillary : The large petal (standard) overlaps the two lateral petals (wings) which in turn overlap the two smallest anterior petals (keel).
Androecium :
- It is the male sex organ of the flower.
- Composed of stamens.
- Each stamen consists of a stalk or filament and an anther.
- Each anther is usually bilobed and each lobe has two chambers, pollen sac.
- Pollen grains are produced inside the pollen sacs.
- A sterile stamen is called staminode.
- Epipetalous: stamens attached to the petals. E.g. brinjal.
- Epiphyllous: stamens attached to the perianth. E.g. lily.
- Polyandrous: stamens are free.
- Monoadelphous: stamens united into one bunch or one bundle e.g. China rose.
- Diadelphous: stamens fused to form two bundles as in pea.
- Polyadelphous: stamens fused to form more than two bundles as in citrus.
Gynoecium :
- It is the female reproductive part of the flower.
- Members are called carpel.
- Each carpel has three parts namely stigma, style and ovary.
- Ovary is the enlarged basal part on which lies the elongated tube, the style.
- The stigma usually at the tip of the style.
- Stigma is the receptive surface for pollen grain.
- Each ovary bears one or more ovules.
- Ovule attached to a flattened cushion-like placenta in the ovary.
- When more than one carpel is present they may be:-
- Apocarpous: all carpels are free. E.g. rose, lotus
- Syncarpous: carpels fused. E.g. Tomato mustard.
- After fertilization:-
- Ovules develop into seed.
- Ovary developed into fruit.
Placentation : arrangement of ovules within the ovary is known as Placentation.
- Marginal: Placenta forms a ridge along the ventral suture of ovary.
- Axile: Margins of carpels fuse to form central axis.
- Parietal: Ovules develop on inner wall of ovary.
- Free central: Ovules borne on central axis, lacking septa.
- Basal: Placenta develops at the base of ovary.
THE FRUIT :
- It is the ripened or matured ovary after fertilization.
- Parthenocarpic fruits developed from the ovary without fertilization.
- Generally fruits consist of a wall or pericarp and seeds.
- Pericarp may be dry or fleshy.
- Pericarp differentiated into –
- Outer epicarp.
- Middle mesocarp.
- Inner endocarp.
- Fruit developed from monocarpellary superior ovary and are one seeded. Such fruit is said to be drupe as in mango and coconut.
- Edible part of the mango is mesocarp.
- Mesocarp of coconut is fibrous.
THE SEED :
- After fertilization ovules developed into seed.
- A seed is made of seed coat and embryo.
- The embryo is made up of
- A radicle
- An embryonal axis
- One or two cotyledons.
Structure of dicotyledonous seed :
- Outer most covering of seed is seed coat.
- Seed coat has –
- Outer testa
- Inner tegmen.
- The hilum is a scar on the seed coat, the point of attachment of developing seed with the fruit.
- Above the hilum is a small pore called the micropyle.
- Embryo present inside the seed coat, consists of -
- An embryonal axis.
- Two cotyledons
- Cotyledons are fleshy and store reserve food.
- At the two end of embryonal axis are present the radicle and the plumule.
- In some seed endosperm store the reserve food as in castor.
- Mature seed without endosperm called non-albuminous seed or non-endospermous as in bean, gram and pea.
Structure of monocotyledonous Seed :
- Generally monocotyledonous seeds are endospermic, orchids are non-endospermic.
- In seeds of cereals such as maize, the seed coat is fused with the fruit wall.
- The outer covering of separates the embryo by a proteinous layer called aleurone layer.
- Embryo is small and located one side of the endosperm and consists of
- One large shield shaped cotyledon known as scutellum.
- A short axis with radicle and plumule.
- Plumule covered by a sheath called coleoptile.
- Radicle covered by a sheath called coleorhiza.
