Maize is a tall, determinate annual C4 plant varying in height from <1 to >4 metres producing large, narrow, opposing leaves, borne alternately along the length of a solid stem. The botanical features of various plant parts are as follows:
Root: Normally maize plants have three types of roots, i) seminal roots -which develop from radical and persist for long period, ii) adventitious roots, fibrous roots developing from the lower nodes of stem below ground level which are the effective and active roots of plant and iii) brace or prop roots, produced by lower two nodes. The roots grow very rapidly and almost equally outwards and downwards. Suitable soils may allow corn root growth up to 60 cm laterally and in depth.
Stem: The stem generally attains a thickness of three to four centimeters. The internodes are short and fairly thick at the base of the plant; become longer and thicker higher up the stem, and then taper again. The ear bearing internode is longitudinally grooved, to allow proper positioning of the ear head (cob). The upper leaves in corn are more responsible for light interception and are major contributors of photosynthate to grain.
Flower: The apex of the stem ends in the tassel, an inflorescence of male flowers and the female inflorescences (cobs or ears) are borne at the apex of condensed, lateral branches known as shanks protruding from leaf axils. The male (staminate) inflorescence, a loose panicle, produces pairs of free spikelets each enclosed by a fertile and a sterile floret. The female (pistillate) inflorescence, a spike, produces pairs of spikelets on the surface of a highly condensed rachis (central axis, or “cob”). The female flower is tightly covered over by several layers of leaves, and so closed in by them to the stem that they don’t show themselves easily until emergence of the pale yellow silks from the leaf whorl at the end of the ear. The silks are the elongated stigmas that look like tufts of hair initially and later turn green or purple in color. Each of the female spikelets encloses two fertile florets, one of whose ovaries will mature into a maize kernel once sexually fertilized by wind-blown pollen.
As the internodes of the shanks are condensed, the ear remains permanently enclosed in a mantle of many husk leaves. Thus the plant is unable to disperse its seeds in the manner of a wild plant and instead it depends upon human intervention for seed shelling and propagation.
The explanation for each maize male and female floral organ has been given below:
Tassel: inflorescence of male flowers; the tassel consists of several long, in determinate branches bearing short determinate branches (spikelet pairs) that bear two spikelets (compact auxiliary branches of grass inflorescence, that in maize consists of two bracts subtending one reduced male flower).
Stamen: pollen-producing reproductive organs which are collectively referred as androecium.
Stalk: also filament; the part of the stamen on which anther develops.
Anther: the terminal part of a stamen in which the pollen grains are produced.
Microspore: smaller of the two types of spore produced in heterosporous plants; develops in the pollen sac into a male gametophyte.
Male gametophyte: microspores divide twice to produce 3 celled pollen grain/tube (a male gametophyte); two of the cells are sperm; other is called vegetative cell, or tube cell.
Sperm cell: two sperm cells are produced; one sperm cell fuses with the egg resulting in zygote; other sperm cells fuses with central cell giving start to development of triploid tissue called endosperm which surrounds the embryo and serves an absorbtive/nutritive function in seed.
