Stomatal and physiological response of contrasting Z. mauritiana (Lamk.) clones to water stress.

Water stress is one of the major limitations to fruit production worldwide. Identifying suitable indicators, screening techniques, and quantifiable traits would facilitate the genetic improvement process for water stress tolerance. In the present study, we evaluated the ability of physiological parameters (Transpiration, E; Fv/Fm; Leaf Water Potential, LWP; leaf temperature, LT; and, leaf relative water content, RWC) to distinguish between contrasting Z. mauritiana clones subjected to a 30-d drought cycle. Four field-grown clones Seb and Gola (tetraploid) and Q 29 and B 5/4 (diploid) were studied. By 30 d after the onset of water stress treatment, the E, Fv/Fm, LWP and RWC of drought-stressed plants had declined significantly in all genotypes compared to values of well-watered treatments. However, the reductions were more severe in leaves of diploid clones. Under drought stress, the Seb and Gola, maintained higher E (31.5%), Fv/Fm (6.28%), LWP (11.2%), and RWC (9.3 %) than Q 29 and B 5/4 clones. In general, LT of drought-stressed plants was higher (around 4 degree Celsius) than that of well-watered plants but the relative increase was greater among later than former ones. Under maximum drought stress, LT of Seb and Gola clones was on average 3.0 degree Celsius lower than that of Q 29 and B 5/4. Former clones yielded 20% more than later ones, mainly reason being (14.8%) less fruit drop as an effect of water stress. The results indicate that presented parameters can be reliable in screening for water stress tolerance ability, with Fv/Fm, LWP, RWC and LT having the added advantage of being easily and quickly assessed.