ABSTRACT
Physiological and biochemical changes in response to deficit irrigation (drought stress) were studied at three moisture regimes based on available soil moisture (ASM) and four commercial sugarcane varieties differing in their maturity i.e. CoS 767 (Mid late), CoH128 (Mid late), CoJ 64 (Early) and Co 0238 (Early) Plant water status was affected significantly with duration and severity of stress with maximum reduction at 30% ASM level at 90 DAP. The water potential (from -0.62 to -1.16 MPa), osmotic potential (from -0.88 to -1.77 MPa) and relative water content (from 87.59 to 65.51%) decreased significantly at 30% ASM level than at 50% ASM in all the varieties. After stress revival, a remarkable recovery was recorded in all the varieties at all the ASM levels with maximum recovery in varieties Co 0238 and CoS 767. Higher membrane injury was recorded in CoJ 64 followed by CoH 128, Co 0238 and CoS 767at 30% ASM at 60 and 90 DAP. Remarkable decrease were observed in gaseous exchange parameters in leaves viz. photosynthetic rate, transpiration rate and stomatal conductance at 30 and 40% ASM levels in all the varieties. Significant reduction was also recorded in chlorophyll fluorescence (Fv/Fm). Severe stress conditions of 30% ASM led to approx. two fold increase in total soluble carbohydrates, four folds in proline and two fold increase in lipid peroxidation. ASM levels of 40% and 30% also significantly reduced total chlorophyll content. From the results, it can be concluded that varieties Co 0238 and CoS 767 are relatively more tolerant at moderate stress to severe stress than CoH 128 and CoJ 64.