Peculiarities of mesostructure and pigment complex formation in leaves of scoto- and photomorphic seedlings of horse beans under the gibberellin and tebuconazole impact

Abstract

Peculiarities of leaf mesostructure formation, synthesis of photosynthetic pigments under the impact of gibberellic acid and its antagonist tebuconazole in scoto- and photomorphic seedlings of horse beans were analyzed. It was established that gibberellins take an active part in the regulation of scoto- and photomorphogenesis. Gibberellic acid and tebuconazole (retardant) significantly affected the histogenesis in leaves of scoto- and photomorphic seedlings. Under the conditions of photomorphogenesis, leaves were formed thicker in comparison to seedlings that developed in the dark. At the same time, under the influence of tebuconazole the highest thickening of leaves was noted both in the dark and light. There was a decrease in leaf thickness in scotomorphic seedlings under gibberellin action. In the dark, the gibberellin effect caused the formation of thinner tissues complexes — chlorenchyma, abaxial and adaxial epidermis. The ratio between chlorophyll a and b in the control was 4.3, under the impact of tebuconazole— 4.5, and gibberellin — 3.7. Insofar as the content and ratio of chlorophylls a and b decreased under the action of gibberellin, and increased under the action of antigibberellic drug tebuconazole, this indicates the gibberellin influence on the formation of photosynthetic apparatus light-harvesting complexes. In scotomorphic seedlings, the process of conversion of unsaturated to saturated fatty acids (FA) was most inhibited by tebuconazole, and under the action of gibberellin the ratio was less. In photomorphic seedlings, this process was not inhibited either by exogenous gibberellin or by retardant, compared to control. Thus, light affects the processes of FA metabolism during the heterotrophic phase of development. Blocking the native gibberellin synthesis by tebuconazole in seedlings leads to a decrease in linolenic acid outflow from the cotyledons due to growth retardation and, consequently, the use of this fatty acid in chloroplastogenesis.