In MGCNL 56 we reported data for five sweet corn lines. The present report concerns six field corn lines and two hybrids. Methods of seed germination and light treatments were detailed in the previous report.
As reported for the sweet corn lines, temperature sensitivity is best observed for seedlings germinated in the dark. Filtered and unfiltered light conditions tend to reduce performance differences at the two temperatures, 21 and 27 C. It is interesting to note for epicotyls and coleoptiles that less growth takes place in continuous white light, but under all light filters tested, coleoptiles, especially, grow longer when the light is continuous throughout the seven-day period. The longest coleoptiles are found under far-red light, even longer than those following continuous darkness. Though epicotyl growth is longest under dark conditions, a considerable range of variation is found among the six lines tested. Far-red light produces epicotyls which stand out as longer than those produced under blue, green, yellow and red. The two hybrids of Table 1 show epicotyls longer than those of the Mo17 parent under the conditions of darkness and far-red light. Though in the same direction as the epicotyls, less difference is noted for hybrid coleoptiles when compared back to the Mo17 parent coleoptiles.
An interesting observation from a comparison of sweet corns and field corns under the germination conditions above is that a sweet corn such as Sprite 142, with one fifth of the seed weight of certain hybrids, can produce similar volumes of germinating tissues with far less endosperm reserves. Where the number of seedlings produced per weight of dry seed is an economic consideration, sweet corns could deliver five times as many seedlings without serious sacrifice of tissue volume following seed germination (the help of Ohio Foundation Seed Inc. and Pioneer Hi-bred International in supplying seed is gratefully acknowledged).
Bernard C. Mikula and Amy Smith
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