Features of gas exchange and use of reserve substances in pumpkin seedlings in conditions of skoto- and photomorphogenesis under the influence of gibberellin and chlormequat-chloride

We investigated the effect of gibberellin and the antigibberellic agent chlormequat-chloride on gas exchange and use of reserve substances in pumpkin seedlings during germination in the light and in the dark. We established that an artificial strengthening or growth inhibition of pumpkin seedlings in conditions of skotomorphogenesis caused an increase in of respiration intensity. Gibberellin treatment increased the proportion of assimilation processes in carbon dioxide gas exchange of seedlings, and growth inhibition by retardant caused an increase in respiratory costs when the nutrition type switches in the light from heterotrophic to autotrophic. The formation by seedlings of the demand for reserve assimilates from cotyledons was largely determined by change of activity of subapical meristems, which is manifested in the acceleration of seed germination, enhancing of histogenesis for the actions of gibberellin and in the weakening of these processes under the influence of retardants. Reserve substances used both oil and nitrogen-containing compounds. The content of protein nitrogen in pumpkin cotyledons decreased more in the light than in the dark, moreover growth inhibition by the retardant slowed down and growth increase by gibberellin accelerated this process both in conditions of photomorphogenesis and skotomorphogenesis.