Promotive Effects of the Peptidyl Plant Growth Factor, Phytosulfokine-α, on the Growth and Chlorophyll Content ofArabidopsisSeedlings under High Night-time Temperature Conditions

In order to investigate the function of the peptidyl plant growth factor, phytosulfokine-α (PSK-α), in plants, we examined the effect of PSK-α on the growth and chlorophyll content of Arabidopsis seedlings under high night-time temperature conditions. Although exposure to high night-time temperatures markedly reduced the fresh weight and chlorophyll content of the seedlings, these parameters in the plants supplied with PSK-α remained at the same levels as those of non-treated controls. These effects were not apparent when [2-5]PSK, Tyr-SO3H and kinetin were similarly supplied. The results suggest that PSK-α not only promotes cell proliferation, but may aid plants in their tolerance of heat stress.