Recovery of maize seedling growth, development and photosynthetic efficiency after initial growth at low temperature

In general, the recovery of photosynthetic efficiency followed the development of leaves. It was delayed in the CM 109 more than in the KW 1074 inbred line relative to control plants grown continuously at the optimal temperature. The growth difference of 2-3 days between the two lines persisted even after the growth temperature was elevated. This suggested that the primary factor responsible for the different chilling-sensitivities of the two model lines was leaf development and the differences in development of the photosynthetic apparatus had only a secondary role. The delay in leaf development appeared as early as the stage of the 1st leaf. The same delay was observed when only the shoot apex was cooled. The importance for further recovery of the early stages of morphogenesis was confirmed by a correlation of laboratory and field data that were obtained using a set of 12 inbred lines. Our results suggest that early stages of shoot morphogenesis determine the duration of the vegetative phase in cool regions, since the delay in growth at a low temperature cannot be compensated for during later growth at a higher temperature.