Roles of Some Plant Growth Regulators on Natural and Dark-Induced Senescence in Wheat Leaf Segments

Abstract

Senescence is an important developmental process in the life span of a plant. It is affected by several endogenous and exogenous factors such as hormones, darkness, and drought. Hormones are major endogenous factors that affect senescence intensively. In this study, our aim was to investigate the effects of different plant growth regulators; benzyl adenin (BA), spermine (Spm) and spermidine (Spd) on both natural and dark-induced senescence and on gamma-aminobutyric acid (GABA) content in wheat leaf segments. Following the incubation, fresh and dry weight, chlorophyll and carotenoid contents; peroxidase activity, soluble protein, GABA and malondialdehyde (MDA) contents and cell death amount were determined. Our results demonstrate that Spm and Spd accelerated senescence under light and delayed it under dark conditions. BA has delayed leaf senescence under both conditions. Cell death and MDA content showed a correlation with the senescence process. GABA content was enhanced considerably by BA, Spm and Spd applications under light conditions. According to our results we can conclude that Spm and Spd could promote senescence on wheat segments under light conditions, whereas inhibit senescence under dark conditions. In addition, BA could retard the deleterious effects on senescence under both light and dark conditions.