Transpiration rate is the key trait for selecting species for better water use efficiency: A case study on four agroforestry tree species

Abstract

Water stress has been the prime concern for plant survival and productivity. In this context a physiological trait, water use efficiency has been the center of focus over the past decade. Selecting species for better water use efficiency without compromising on productivity have been shown to ne effective in coping with water stress without losing productivity. Therefore, a pot experiment was conducted on four agroforestry tree species (Ziziphus mauritiana, Bombax ceiba, Moringa oleifera and Morus alba) where growth, biomass production and water use efficiency was measured under controlled and water stress. The results showed that growth traits like plant height, stem diameter, biomass production, leaves, stem and roots decreased in all the species under water stress. however, the highest decreased was evidenced in the species showing high growth rate (Morus alba and Moringa oleifera), and lowest was recorded in slow growing species (Ziziphus mauritiana and Bombax ceiba). Water use efficiency was found the highest in show growing species as compared to fast growing species. A large decrease in transpiration rate and stomatal conductance was evidenced in fast growing tree species (Morus alba and Moringa oleifera) as compared to slow growing species (Ziziphus mauritiana and Bombax ceiba). However, CO₂ assimilation rate although varied across the species but remained insignificant across the control and water stress treatment. Therefore, it can be concluded that Ziziphus mauritiana is better adapted to water stress and this adaptivity is controlled by transpiration rate rather CO₂ assimilation rate.