Fig. 2

Heatmap and hierarchical clustering for morphological and physiological parameters under well-watered and drought stress conditions in 49 switchgrass genotypes after 30 days of treatment. Clustering analysis of switchgrass genotypes (left) showed two main groups where the group a represents 49 genotypes under the well-watered condition; while group b represents those genotypes under the drought treatment. The clustering analysis of different parameters (top) showed three major groups: group I includes all morphological parameters, group II include the other five physiological parameters, while group III include two key physiological parameters associate with drought tolerance. RWC relative water content, EL electrolyte leakage, Pn photosynthetic rate, g _s stomatal conductance, Tr transpiration rate, Ci intercellular CO₂ concentration, WUE water use efficiency, LL leaf length, LW leaf width, SL leaf sheath length