Correlative associations of photosynthetic and rooting attributes of sesame: Drought-induced reversed associations are corrected upon salicylic acid exposure

Abstract

Concomitant rooting and photosynthetic responses of crop plants to water availability and plant growth regulators lack clarity. Three pot-grown sesame genotypes were subjected to three irrigation regimes, ranging from control to severe moisture stress, and two levels of salicylic acid (SA) (0 and 0.6 mM) to address this lacuna of data. Drought led to decreases in gas exchange, water relation, and rooting attributes, and shoot dry mass of the three genotypes in different extents, but it resulted in increases in substomatal CO2 concentration, proline concentration, and root/shoot dry mass. Cumulative root length, root length density, specific root length, and root surface tended to increase in genotype Yekta upon experiencing stress, in contrast to more or less decreasing tendencies in rooting characters of genotypes Shiraz and Naz-Takshakhe. Such genotype-specificity led to the reversal of correlations between gas exchange attributes and rooting characteristics under drought conditions. External SA led to enhancements in gas exchange, water relation, and rooting attributes, and dry mass; the degree of the enhancements tended to be greater in the stress-stricken plants. These findings indicate that genotype Yekta benefits from rooting characteristics with drought tolerance significance and SA is effective in enhancing photosynthetic, physiological and rooting attributes, drought tolerance, and growth of sesame under drought circumstances.