Physiological basis for controlling water consumption by two snap beans genotypes using different anti-transpirants

Abstract

Enhancing water use efficiency (WUE), while maintaining productivity, represents a challenge, particularly, in arid and semi-arid environments. The use Antitranspirants (ATs) is an effective approach to mitigate water deficit- and drought-induced yield losses, via reducing transpiration. This study aimed to determine the effects of ATs compounds on WUE and root and shoot physiological responses of two snap bean genotypes with different ozone sensitivity [tolerant (R123) and sensitive (S156)]. Under glasshouse conditions, plants were sprayed (25 days after planting) with 4% (w/v) kaolin (KPF); 0.0015% (w/v) Fulvic acid (FA); 1% (v/v) Pinolene (PIN) or water (control). Treatments were subjected to three irrigation/drying cycles, and then exposed to survivability test by ceasing irrigation. Water consumption (WC), leaf water potential (Ψw), total dry matter (TDM), dry matter accumulation rate (DMAR), leaf temperature, plant survival and root development were determined. There was a minimal genotype effect on all parameters, except TDM, DMAR, and fine-root diameter and length. KPF treatment was cooler than the control (<3.83 °C), consequently, had higher Ψw and lower WC, without affecting TDM and DMAR. Therefore, biomass-WUE (total dry matter/transpired water) of KPF treatment increased (29.4% and 13.3% for R123 and S156, respectively). Pinolene and FA treatments exerted no effects on those parameters. KPF treatment alleviated most of the physiological effects of water deficit, hence plants survived longer. KPF and FA treatments had thicker very fine (0.0726 to 0.29 mm) and fine (0.308 to 0.562 mm) roots than the control, with KPF having the strongest effect on roots development. Pinolene treatment showed no effect on the roots of R123, but conditioned significant thickening of S156 roots; a notable reversal of the observed effect of KPF and FA. In conclusion, conserved water by KPF, could reduce irrigation frequency and, later, play as a crucial water resource for plant survival. Moreover, future research with ATs must take root responses into account.