The influence of low temperature on seedling development in two inbred lines of corn

This paper deals with a study of the comparative ability of seedlings of two inbred lines of corn to grow at low temperatures and maintain a well-balanced type of metabolism during the early stages of seedling development. The studies were limited to two contrasting inbreds known as RYD4 and GG26 and subsequent progenies produced from crosses between these two inbreds. When grown in the greenhouse during the winter at a temperature range of 16 degrees to 19 degrees C, the seedlings of RYD4 were a normal green color, whereas the seedlings of GG26 were typically virescent, being almost devoid of chlorophyll. Both inbreds were green when grown at a temperature of 24 degrees C. This virescent character is probably inherited as a simple recessive to normal green. Extraction of the chlorophyll and carotinoid pigments showed that in the seedlings of GG26 carotin was formed only when chlorophyll formation occurred. Xanthophyll, however, was formed in the absence of the chlorophyll pigments. Endosperm utilization was more rapid in seedlings of GG26 than in seedlings of RYD4 when grown at a temperature of 17 degrees or 24 degrees C. The endosperm reserves of GG26 were practically exhausted when the seedlings had developed to the third leaf stage, whereas seedlings of RYD4 had considerable reserve materials left at this stage of development. The amount of top growth produced by the seedlings of these two inbreds was essentially the same when grown at 17 degrees and 24 degrees C. There was a greater amount of top growth produced by inbred RYD4, however, when the plants were grown to the third leaf stage at a temperature of 24 degrees C then shifted to a temperature of 17 degrees C for a period of 4 and 8 days. At a soil temperature of 16 degrees C the seedlings of RYD4 were highly resistant to Gibberella seedling blight, whereas seedlings of GG26 were very susceptible. The F1 progenies showed about the same degree of resistance as the resistant parent. Seedlings of the cross RYD4 X GG26 were more resistant than the F1 progenies of the reciprocal cross.