GROWTH, ORGANIC NITROGEN FRACTIONS, AND BUFFER CAPACITY IN RELATION TO HARDINESS OF PLANTS

Abstract

Winter wheat, cabbage and other plants were grown in the greenhouse in sand culture under various conditions of mineral nutrition. When transferred to a room at 2[degree]C, with constant light, winter wheat plants increased greatly in dry wt., sugar, and N. Plants free from mineral N hardened at 2[degree]C. Plants low in carbohydrates did not harden at 2[degree]C in the dark. Whether hardening occurred or not, and regardless of the presence or absence of mineral N, all plants increased in soluble organic N when placed at 2[degree]C for a few days. There was no relationship between increase in soluble organic N and the hardening reaction. Plants high in carbohydrates were acid and poorer buffers than plants of the same age but low in carbohydrates. Those high in carbohydrates hardened at 2[degree]C; the others did not. There was no evident change in buffer capacity on exposure to low temps.; the acidity became slightly less whether hardening occurred or not. Continuous low temps. (2[degree]C) were more effective than alternating temps. (20[degree]-2[degree]C) in producing hardening in high carbohydrate plants stored in complete darkness.