Flowers
The flowers are the reproductive part of the plant. The arrangement of flowers on
the floral axis is called inflorescence, which has two major parts called racemose
which let the main axis continue to grow and cymose which terminates the main
axis in a flow.
The flower consists of four different whorls:
Calyx, the outermost.
Corolla, composed of petals.
Androecium, composed of stamens.
Gynoecium, composed of one or more carpels.
The reproduction in plants occurs by the process of pollination. It is the process of
transfer of pollen from the anther to the stigma of the same or different plants.
Functions of Flowers
The flower performs the following important functions:
1. They help in the process of reproduction.
2. They produce diaspores without fertilization.
3. The gametophytes develop inside the flower.
4. The flowers attract insects and birds which then act as a medium to transfer
the pollen from the anther of one flower to the stigma of some other
flower.
5. The ovary of the flower develops into a fruit that contains seed.
Fruits
The fruit is the characteristic feature of flowering plants, which is a
ripened or mature ovary and the seed is what the ovules develop into
after fertilization. The fruit that develops without fertilization is known as
parthenocarpy.
Types of Fruits
There are three different types of fruits and are classified mainly based on
their mode of development.
1. Simple— Developed from the monocarpellary ovary or multicarpellary
syncarpous ovary. Examples of simple fruits.
2. Aggregate–Developed from the multicarpellary apocarpous ovary.
Examples of aggregate fruits.
3. Composite–These are false fruits, developed from the entire
inflorescence rather than from single flower. Examples of composite
fruits include blackberries, Raspberries strawberries, etc.
The Seed
A seed is a basic part of a plant, which is found enclosed within the fruit. It
is made up of a seed coat and an embryo. During the development of the
fruit, the wall of the ovary becomes the pericarp. In some plants, the
ovary wall dries out completely, while in some it remains fleshy.
Types of Seeds
Based on the number of cotyledons, seeds are further classified into two
types- dicotyledonous and monocotyledonous seeds.
1. Monocotyledonous— The embryo consists of an embryo axis and has
only one cotyledon. The monocotyledonous is also known as monocot
seeds. Grains including rice, millet, wheat and other plants like onions,
corn, ginger banana, palm tree, are examples of monocot seeds.
2. Dicotyledonous— The embryo consists of an embryo axis and has
two cotyledons. The dicotyledons are also known as dicots or dicot
seeds. Legumes including beans, lentils, pea, peanuts, and tomato are
examples of dicot seeds.
STRUCTURE OF SEED Dicotyledonous seed (non-endospermic seed)
GRAM SEED Parts of gram seed
Seed Coat
Cotyledons
Embryonic axis Seed Coat: The gram seed coat has two integuments
surrounding the ovule. Seed coat is protective in nature.
Testa: It is the outer seed coat and is leathery, thick and brown in
colour. Tegmen: It is the inner coat that is thin, white, and often
inseparable from the testa
Hilum: It is a scar on the seed coat through which the developing
seeds are attached to the fruit.
Micropyle: It is the opening in the integuments and is visible in gram
seed. Water is absorbed through the micropyle during the germination
of seed.
Cotyledons When the seed coats are removed, the large embryo
becomes visible. The bulk of it consists of a pair of fl eshy structures
called cotyledons in dicot seeds.
In gram seed, the cotyledons store food (carbohydrates and
proteins) and provide nourishment to the developing embryonal axis.
They lack endosperm.
Such seeds are also found in many other plants such as groundnut,
pea, mustard etc
The internal structure of the grain in longitudinal
section shows the following parts:
Pericarp: On the outer side, a single covering called pericarp and testa are
found. Inner to pericarp, the grain is divided into two unequal portions:
Endosperm and Embryo.
Endosperm: The upper half of the grain is made up of massive endosperm.
The bulk of endosperm is laden with starch, but its outer layer next to the grain
coat contains abundant protein. It is called aleurone layer. Proteins present in
this layer help in the synthesis of some enzymes, needed for germination of
the grain.
Embryo: The lower half of the grain is occupied by the embryo. Maize
embryo has a single cotyledon attached laterally to the embryonal axis. This
cotyledon is called scutellum. The scutellum has a secretory epidermis, found
in close contact with the endosperm. The epithelium helps the scutellum in
absorbing the food material stored in the endosperm.
The upper end of the embryonal axis is the plumule surrounded by a protective
sheath called plumule sheath or coleoptile.
Brief description
Root: Tap root, often have nitrogen-fixing bacteria forming roots nodules.
Stem: Herbaceous or woody, usually erect, sometimes climbing e.g.,
Leaf: Alternate, often stipulate, stipules may become leafy pulvinate leaf base,
pinnately compound or simple by suppression of leaflets.
Inflorescence: Variable, simple raceme, axillary cyme or solitary.
Flower: The flower may be sessile or pedicellate, bracteate or ebracteate
complete or incomplete, unisexual or hermaphrodite, if unisexual, staminate or
pistillate, zygomorphic or actinomorphic, hypogynous, perigynous or
epigynous, isomers or heteroamorous, if isomers, tri-, tetra- or pentamerous.
Calyx: Sepals 5, gamosepalous, odd sepal anterior, often persistent.
Corolla: Petals 5, polypetalous, or gamopetalous, aestivation descending or
vexillary, imbricate, papilionaceous (butterfly -shaped) with five unequal petals
– posterior largest petal called standard or vexillum, which overlaps two
smaller lateral petals called wings or alae. The latter overlap a boat-shaped
structure called keel or carina, which is formed by two anterior petals fused
slightly on the anterior side.
androecium: Stamens 10, amadelphous 1 + (9) sometimes free, polyandrous,
anther bithecous, basifixed.
Gynoecium: Monocarpellary, ovary superior, unilocular with marginal
placentation, style bent, stigma simple and hairy.
Fruit: Legume (Pod).
Seed: Non-endospermic
SOLANACEAE (potato family)
Brief description Root: Taproot, often having N 2-fixing bacteria forming
roots nodules.
Stem: Herbaceous or woody, often with bicollateral vascular bundles, hair
or prickles often present, sometimes as underground tubers (e.g.,).
Leaf: Alternate or opposite, exstipulate, simple, rarely compound (e.g.,).
Inflorescence: Solitary or extra-axillary, Scorpii cyme.
Flower: Bracteate or ebracteate, pedicellate, complete, bisexual, regular,
actinomorphic, hypogynous, pentamerous.
Calyx: Sepals 5, gamosepalous, campanulate, valvate or imbricate, often
persistent, green, inferior.
Androecium: Stamens 5, polyandrous, epipetalous, anther bithecous,
basifixed dehiscence longitudinal.
