Zea shoot development in response to red light interruption of the dark-growth period. I. Inhibition of first internode elongation.

Brief, low energy (approximately 400 Kerg cm(-2)) red light interruption of the early dark-growth period of Zea mays L. cv F-M Cross induced inhibition of first internode elongation which was maximal whenever light interruption occurred from 2.5 to 4 days of seedling age. Two-thirds of the maximal inhibition occurred in the tissues constituting the region 0 to 2 mm below the coleoptilar node at time of light treatment. The coleoptile tip showed the greatest sensitivity for red light reception in the internode response. Far-red light exposures following red light treatments reversed the red light effect. However, far-red light alone inhibited first internode elongation as effectively as red light of similar dosage.