Phenotipic plasticity of root system and shoots of Sorghum bicolor under different soil water levels during pre-floowering stage

Abstract

In order to understand possible relationships among the features of plant organs located above and below soil, their correlation and how it might affect strategies for drought adaptation, two sorghum lines contrasting in drought tolerance (BR007-sensitive and 99100-tolerant) were cultivated under different soil water levels during pre-flowering stage. Half of the plants of each genotype remained under daily irrigation to maintain the soil moisture close to FC, and the other half was subjected to WD. After 10 days in these conditions, physiological and anatomical characteristics of the lines were evaluated and then water supply was restored and maintained at optimum levels by the end of the cycle. At physiological maturity, the root morphology and agronomic parameters associated to productivity were analyzed. Regardless the variation in the soil moisture, plants of the line 99100 presented values significantly superior for HI, RDB and LA compared to plants of the BR007 line, whereas the A values were lower. Only line 99100 plants increased VFRL compared to its counterparts under FC. The lack of change in root morphology in line BR007 plants was accompanied by increase in CAT activity and lower DBV in leaves. The increase in CAT activity was not sufficient to reduce the pool of H2O2 in leave cells of BR007 under WD, leading to a decrease in FvFm. Thus, the H2O2 accumulated in the leaf was deviated to the lignin biosynthesis, corroborating the lower DVB in leaves of BR007 line under WD, compared to line 99100 under WD. In addition, BR007 plants showed smaller DBC under WD, which simultaneously led to an increase in NBC. Such structural and functional adjustment at the leaf level would compensate the absence of changes in the root architecture in response to the stress generated by the WD. Phenotypic plasticity of root system and shoots of 'Sorghum bicolor' under different soil water levels during pre-flowering stage.