Classification
- Kingdom – Plantae
- Division – Angiospermae
- Class – Monocotyledonae
- Order – Poales
- Family – Poaceae
- Genus – Zea
- Species – Zea mays
Important points
- Scientific name – Zea mays
- Belongs to the Poaceae family of monocots.
- Produces unisexual flowers borne on the same plant, i.e. a monoecious plant with unisexual flowers.
- Cannot perform autogamy (pollination within the same flower) due to the absence of bisexual flowers. However, geitonogamy (pollination between flowers of the same plant) can occur.
- Each maize grain represents a special type of fruit in which the fruit wall (pericarp) is fused with the seed coat. This type of fruit is called a caryopsis.
- Chromosome number – 2n = 20.
Morphology of the maize plant
- Root – fibrous root system. Supporting roots called stilt roots grow from the lower nodes of the stem and help to hold the tall plant upright.
- Stem – erect, cylindrical and clearly divided into nodes and internodes.
- Leaves – long and narrow, with a sheathing leaf base that wraps around the stem, and parallel venation.
- Male flowers – grouped at the top of the plant in a branched inflorescence called the tassel, which produces large amounts of light pollen.
- Female flowers – grouped on a thick axis in the leaf axils, forming the cob (ear). Their long styles and stigmas hang out of the cob as the silk.
- Pollination – by wind (anemophily).
NCERT’s example of wind pollination: in the corn cob, the “tassels” you see hanging out of the cob are the stigma and style, which wave in the wind to trap pollen grains. Note that NCERT calls these the tassels, while botanists use “tassel” for the male inflorescence at the top and “silk” for the styles. Wind-pollinated flowers like these have a single ovule in each ovary.
Structure of the maize grain
The maize grain is NCERT’s example of a monocotyledonous seed. Its main parts are:
- Seed coat – membranous and fused with the fruit wall (caryopsis).
- Endosperm – bulky and stores food. It makes up most of the grain.
- Aleurone layer – the outer, proteinous layer of the endosperm, which separates it from the embryo.
- Embryo – small, situated in a groove at one end of the endosperm.
- Scutellum – the single, large, shield-shaped cotyledon.
- Embryonal axis – a short axis with a plumule and a radicle.
- Coleoptile – the sheath enclosing the plumule.
- Coleorhiza – the sheath enclosing the radicle.
Maize is an endospermic (albuminous) seed, as the endosperm persists in the mature grain. Remember the pairs: coleoptile – plumule and coleorhiza – radicle.
Maize in other NEET topics
- Photosynthesis – maize is a C4 plant. Its leaves show Kranz anatomy, with large bundle sheath cells around the vascular bundles.
- Biotechnology – the Bt toxin gene cryIAb is used to protect plants from the corn borer.