Integrated Drought-Response Profiles Reveal Genotypic Variation Among Commercial Oil Palm (Elaeis guineensis Jacq.) Genotypes

Drought stress significantly limits oil palm productivity, highlighting the need to characterize integrated responses to water deficit. This study evaluated morphological, stomatal, anatomical, and biochemical responses of ten commercial oil palm genotypes under well-watered and water-withholding conditions for 45 days. Quantitative analyses focused on 0–30 days after treatment (DAT), while 45 DAT represented a qualitative endpoint of severe injury. Water withholding restricted vegetative growth and altered stomatal characteristics, chlorophyll, soluble sugar, and starch contents, with responses varying among genotypes. Qualitative observations also revealed changes in bulliform cell morphology. Correlation analysis based on Δ30–0 values showed contrasting trait associations between water regimes. Principal component analysis of genotype-level relative responses at 30 DAT, based on five traits with complete data (CW, FN, TC, SC, and ST), showed that PC1 and PC2 explained 52.10% and 35.11% of the total variation, respectively, accounting for 87.21% cumulatively. Hierarchical cluster analysis of the same standardized relative-response dataset separated the ten genotypes into three groups with contrasting multivariate response profiles. These findings demonstrate substantial genotype-dependent variation in integrated responses to water withholding and indicate that combining multiple complementary traits can distinguish contrasting response profiles among young oil palm genotypes. This multi-trait approach may provide a useful basis for subsequent drought evaluation and breeding, although further validation using direct measurements of soil and plant water status, recovery responses, and field-based drought conditions is required.