Physiological and morphological responses of corn genotypes to planting date and plant population

Use of male-sterility for increasing the population tolerance of corn (Zea mays L)

“…Grain yield per unit of leaf surface was found to be slightly more efficient for earlier dates of planting (Pendleton and Egli, 1969) with the adverse effects of high plant population accentuated with latter dates of planting. Cardwell (1967) found population intolerant genotypes reacted as population tolerant geno types and produced higher yields than population tolerant genotypes at the earliest planting date (April 15) but had the lowest yield with latter plantings. High population tolerant hybrids were less affected by planting date.…”

“…Knipmeyer et al (1962) agreed that carbohydrate metabolism was not the limiting factor. Cardwell (1967), however, found that as the date of planting was delayed, barrenness increased with an associated decrease in the stalk sugar level; therefore, he concluded that the level of stalk sugar prior to pollination could explain the barrenness observed due to planting date. Williams et al (1968) suggested that stalk sugar concen tration just prior to pollination may even have predictive value relative to fruit set.…”

“…Increasing plant ;:.opulation is known to elicit diverse responses by a corn community. Examination of yield components, ears per plant or per 100 plants, weight per ear, and weight per kernel, revealed that ears per 100 plants is the major factor and ear weight a lesser factor contributing to reduced yields at high plant densities (Lang et al, 1956;Dungan et al, 1958;Zuber ot al., 1960;Hinkle and Garrett, 1961;Colville, 1962;Woolley et al, 1962;Stinson and Moss, 1960;Schwanke, 1965;Cardwell, 1967).…”

“…Planting date has an interesting effect on plant barrenness. Late April to early May plantings in the cornbelt have been shown to exhibit yields superior to later plantings (Boone et al, 1966;Hatfield et al, 1965;Pendleton and Egli, 1969;Cardwell, 1967). Grain yield per unit of leaf surface was found to be slightly more efficient for earlier dates of planting (Pendleton and Egli, 1969) with the adverse effects of high plant population accentuated with latter dates of planting.…”

“…Schwanke (1965), examining 26 genotypes, observed a greater total dry weight for intolerant hybrids as compared to tolerant hybrids at tasseling; however, he was unable to sub stantiate Sowell's et al (1961) results. Cardwell (1967) found detasseling or male-sterility to delay or reduce the dry matter percentage for two geno types , Hageman and Flesher (1960), Hageman et al (1961), Knipmeyer et al (1962), Zieaerl et al (1963) have impli cated the level of the enzyme, nitrate reductase, in the differential responses of genotypes to plant populations. The nitrate reductase enzyme is a substrate inducible enzyme which is light dependent (Hageman and Flesher, 1960).…”