Red-light-induced changes in the distribution of growth inhibitors A-2 alpha and A-2 beta in dwarf pea seedlings

The distribution of the endogenous growth inhibitors, A-2 alpha and A-2 beta, was determined in light-grown dwarf pea seedlings (Pisum sativum L. cv. Progress No. 9). Red-light-induced changes in this distribution in dark-grown pea seedlings was monitored. The concentration of both inhibitors in light-grown pea seedlings was maximal in the terminal bud and decreased to the lower parts of the seedlings; their concentration in internodes was 7-10 times that in leaves of the same nodes. After the onset of continuous red-light-irradiation, the concentration of the inhibitors in dark-grown pea seedlings increased rapidly in the terminal bud, epicotyl hook and third intermode, and the longitudinal gradients of the inhibitors showed a close correlation with the red-light-induced growth inhibition of the stem. The present results suggest that the endogenous growth inhibitors, A-2 alpha and A-2 beta may be responsible for the red-light-induced growth inhibition of the dwarf pea seedlings.