Characterising response of root and shoot traits in cowpea (Vigna unguiculata L.) under water stress in laboratory and greenhouse

The present study was based on the hypothesis that natural variation in cowpea landraces for response to polyethylene glycol (PEG), root architecture, biomass partitioning parameters can be harnessed effectively to improve water stress resilience. There was a reduction of 38.09% and 69.57% in radicle length and 37.50%, and 95.39% in root biomass at 10 and 20% PEG, respectively with progressive decline in both parameters across all genotypes with increase in PEG from 0–20% and both the parameters had the highest value under control. Significant variability (p≤0.001) was observed for root traits, root biomass partitioning and shoot traits among cowpea genotypes. Water stress caused largest decrease in rooting depth followed by root biomass at top and root diameter, whereas there was an increase in mean value of root biomass at bottom and root shoot ratio. Among shoot traits, water stress caused largest decrease in plant height followed by shoot biomass, leaf area and number of leaves. Under water stress, leaf area was found to be positively correlated with rooting depth and root volume but negatively correlated with tissue biomass density. Number of leaves was positively correlated with rooting depth, root volume, shoot biomass but negatively correlated with tissue biomass density.