The Inflorescences of Maize

Science  16 Jul 1954:
Vol. 120, Issue 3107, pp. 77-87
DOI: 10.1126/science.120.3107.77


1) The development of the maize plant, from germination to the maturation of the seed, is divided intothe vegetative, transitional, reproductive, and seedstages. The ear and tassel differentiate and developin the reproductive stage.

2) The mature tassel is a terminal, staminate inflorescence consisting of a symmetrical, many-rowedcentral axis and asymmetrical, two-ranked lateralbranches. Paired spikelets, one terminal (pedicellate)and the other lateral (sessile), each containing twofunctional staminate flowers, are borne on the centralaxis and the lateral branches.

3) In contrast with the tassel, the ear is a pistillateinflorescence produced on a lateral branch. The earconsists of a symmetrical, many-rowed axis on whichare paired spikelets, each containing two flowers. Inthe mature ear, it is difficult to distinguish the pedicellate from the sessile spikelet. There are two pistillate flowers in each spikelet of the ear, but only theterminal flower is functional, while the lateral floweraborts.

4) The mature ear and tassel appear to be differentkinds of inflorescences, but if they are examined atthe earliest stages in their development they will befound to be basically alike. The differences in the appearance of the two inflorescences at maturity are theresult of differences in the differentiating and development of their parts.

5) Each of the morphological characteristics foundin the maize inflorescences, except one, is present inother grasses, but the collection of morphologicalcharacteristics found in the ear and tassel is unique.One morphological characteristic not found in othergrasses but found in the maize ear is the presence ofa terminal, fertile, and aborted, lateral flower in eachof the paired spikelets.

6) Axillary shoots are produced in acropetal succession in the axil of each leaf. Some of the axillaryshoots that are produced at the beginning of the development of the plant may develop as tillers (suckers).The last-produced axillary shoot (or shoots) that isfar enough advanced in its development at the initiation of the tassel develops into the ear (or ears).

7) The amount of seed produced per ear is determined by the number of rows of kernels and the number of kernels per row. The number of rows of kernelsis determined at the beginning of the initiation of theear, but the number of kernels per row may vary withthe strain and with changes in the environment. Undercomparable condition, seed produced per ear is lessin plants without tillers than in plants with tillers.The average seed yield per ear is less in multiple-eared types than single-eared types growing undersimilar conditions.

8) The three major parts of the maize kernel areendosperm, 82 percent; germ, 11 percent; pericarp,seed coats, and tip cap, 7 percent. The compositionof the maize kernel is 83 percent carbohydrate, 10to 11 precent protein, and 4.3 percent oil. Fiftygenerations of selection for high- and low-proteinstrains and high- and low-oil strains produced markedchanges in the chemical composition of the maizekernel. Beginning with 4.7 percent oil, after 50 generations of selection, the high-oil strain has 15.36 percent and the low-oil strain has 1.01 percent of oil.The protein content was 10.92 percent at the beginning of the selection and reached 19.45 percent inthe high-protein strain and 4.91 percent in the low-protein strain after 50 generations of selection. Recovered inbred lines from backcrosses to the highstrains have resulted in good-yielding hybrids thatproduce more protein or oil per acre than standardhybrids.

9) Several factors contribute to the superiority ofmaize over other cereals as a seed producer. The maizeplant is large and, concomitant with its size, it hasa large leaf surface, large stem, large root system,and an extensive vascular system. Branching is restricted to a few lateral, pistillate branches in whichvegetative development is suppressed. The lateral ear-producing branch (or branches) is so placed on theplant that there are many leaves above and below it.The ear is large in diameter and has seeds that aremany times larger than those of other cereals. All theafore-mentioned characteristics, many of which arenot present in other grasses, contribute to making themaize plant a superior seed producer.