Synergistic effect of phytohormones on pigment and fine structure of chloroplasts in flag leaf of wheat plants irrigated by seawater

Abstract

Plant hormones play vital roles in the ability of plants to acclimatize to varying environments by mediating growth, development and nutrient allocation. The present investigation was undertaken to have some information about interactive effects of seawater salinity and some plant growth regulators (gibberellic acid, indole acetic acid or abscisic acid) on leaf area, pigment and chloroplast ultrastructure as well as saccharides and protein content of wheat flag leaf. In the majority of cases, seawater at 10 or 25% increased pigment content, particularly carotenoids. On the other hand seawater reduced leaf lamina area, Hill activity and sucrose as well as polysaccharides and protein. The interactive effect of seawater and growth regulators accelerated the production of Chl a, Chl b and carotenoids by increasing the values of these pigment. Furthermore, grain pretreatment with gibberellic acid, indole acetic acid or abscisic acid induced marked increase in leaf lamina area, Hill activity and sucrose as well as polysaccharides and protein. Irrigation of wheat plants by seawater at 10 or 25% caused dramatic changes in chloroplast ultrastructure of flag leaf. These changes include disorganized membrane system, disruption of bounding membrane, reduction in the size and number of starch grains and an increase in plastoglobuli. The presoaking of wheat grains in GA3, IAA or ABA resulted in an increase of plant tolerance against the adverse effect of seawater particularly at 10%. This resistance was estimated by the presence of normal chloroplast.