Effect of Salt Stress on Different Protochlorophyllide Forms of Wheat (Triticum aestivum)

In this investigation the effect of salt stress on the early developmental stages of dark-grown wheat seedling was studied. Grains of the salt tolerant (Seds1) and the susceptible (Giza168) cultivars of wheat were germinated and grown in darkness in nutrient solution supplied with or without 200 mM NaCl. The protochlorophyllide content was determined. The fluorescence emission intensity ratio of 655/633 nm was measured. The ratio of newly formed Chlorophyllide to non-photoactive Pchlide was measured after irradiation of leaf sections with one single flash to estimate the degree of phototransformation. The chlorophyll a content was also determined after dark-grown leaf sections were irradiated. The salt stress treatment caused a marked increase in protochlorophyllide (Pchlide) content in dark-grown material and in Chlide content after irradiation of leaf sections of both varieties. The relative ratio of phototransformable to non-phototransformable pchlide and of newly formed chlorophyllide (Chlide) was influenced by salt stresse. The results were influenced by the different growth rates found for stressed and unstressed seedlings. Leaf sections from seedlings grown under salt stress in darkness accumulates more chlorophyll a than leaf sections from unstressed seedlings when floating on nutrients or on a 200 mM NaCl solution in continuous white light. The increased accumulation of the long-wavelength form of Pchlide is suggested to be an expression for the mobilization of a part of the protective mechanisms against salt stress.