Impact of drought stress and stress modifiers on water use efficiency, membrane lipidation indices, and water relationship indices of pot marigold (Calendula officinalis L.)

Abstract

This study was conducted as a factorial layout based on completely randomized design in three replications in the 2018. The experimental factors included irrigation intervals with 4 levels (3, 6, 9, and 12 days) and drought stress modifiers at four levels (control (non-spraying), spraying with salicylic acid (2 mM), Glycine betaine (5 mM), and zinc sulfate (5 g L−1). The results indicated that the effect of different levels of drought stress and stress modifiers on yield, water use efficiency, membrane lipidation indices, and water relationship indices were significant. The highest water use efficiency based on dry yield (WUEDY) (2.33 kg m−3) and water use efficiency based on essential oil yield (WUEEOY) (0.22 kg m−3) were obtained from irrigation intervals of three days. With increasing irrigation interval from three days to 12 days, dry yield, leaf water content, WUEEOY, cellular membrane stability (CMS), membrane stability index (MSI), total chlorophyll, chlorophyll index, canopy temperature depression (CTD), and relative water content decreased. However, injury index (I), water saturation deficit (WSD), osmotic potential (OP), electrolyte leakage (EL), essential oil percentage, and leaf temperature increased significantly. It seems that at all levels of irrigation, spraying with glycine betaine compared to other modifiers was more effective in increasing WUEDY, WUEEOY, CMS, MSI, total chlorophyll and relative water content, and decrease in I and WSD and EL. Based on the findings, it can be stated that with increasing the irrigation intervals, quantitative and qualitative yields of the pot marigold plant are reduced. The application of drought stress modifiers can reduce the effects of drought stress on this plant, thereby raising WUEDY and WUEEOY.