Sweetcorn Maize
Zea mays var. saccharata. Less sugar (sucrose) is converted into starch than in other
maize types, so the grain is sweeter. Not only that, it makes the best and the
strongest beer. It is mainly grown in North America.
Popcorn Maize
Zea mays var. everata. There are two types, both mainly grown and eaten in North
America; one, the rice popcorn, has pointed grains, while the pearl popcorn has very
compact, rounded grains.
Podcorn Maize
Zea mays var. tunicata. This is the most primitive form of maize and is not grown
commercially other than as an ornamental. It was this form of maize pollen found in
Mexico that is at least 80,000 years old. Wild maize and also the earliest cultivated
maize were podcorn types. The grain is enclosed in glumes, like other cereals.
Some South American Indians believe that podcorn maize has magical
properties—as a result of a genetic throwback, plants of this type occasionally
appear in a field of regular maize.
Waxy Maize
Zea mays var. ceritina. The starch of the grain is 100% amylopectin, while the other
non-waxy types have a mixture of amylose and amylopectin. It is grown mainly in
East Asia, and in some other areas for use as a substitute for starch.
POLLINATION OF MAIZE
The maize plant is one of the few in the plant kingdom in which the male and the
female are situated on different parts of the plant. The male tassel appears on top of
the plant, and produces an astonishing 2–5 million pollen grains—up to 20 million
on a big tassel. These pollen grains drift off into the air until they make contact with
a style, or silk from the female part of another maize plant. On the same plant, a few
days later, the female inflorescence appears, somewhere in the middle of the stem.
This female part consists of up to 1000 ovules, which can be fertilised by the pollen
when it comes in contact with the silk. Normally only one or two cobs develop per
plant, though some very prolific varieties, normally hybrids, can produce several cobs.
Maize is thus mainly cross-pollinated, as explained above, though because the
plant is still producing some pollen when the styles appear some self-pollination
does inevitably occur, but normally in no more than about 5% of cases.
Cross-pollination can occur between plants that are very widely separated, as the
wind can carry pollen for great distances. Because of this habit it is difficult to
maintain for any number of seasons a variety of maize which is genetically uniform.
So farmers who “grow on” their own supply of seed every year have large and
diverse collections of germplasm and plant types, known as composite varieties
(1Fd). These farmers can be quite confident that these plants, or most of them, will
succeed next year because during previous years they have selected seed from the
best, most highly adapted, plants.
In this way man has selected for thousands of years maize (and other crops),
which are best suited to grow in the particular area where they were farming.