MEMBRANE THERMOSTABILITY AND NITRATE REDUCTASE ACTIVITY IN RELATION TO WATER STRESS TOLERANCE OF YOUNG SUGAR‐CANE PLANTS.

Summary: An assessment of tolerance to water stress based upon measurements of cellular membrane thermostability and in vivo nitrate reductase activity (NRA) was made using young leaves of sugar‐cane (Saccharum officinarum L. commercial hybrids, Co 419, Co 740 and Co 1148) subjected to stress (51 to 61 d old) and subsequent hydration. An average reduction in leaf water potential (ΨL) from −0.97 to −1.91 MPa was associated with a decrease in NRA from 2.68 to 1.13 Ψmol g f. wt−1h−1, and an increase of the membrane injury from 30.8 to 70.9%. A highly significant positive correlation between ΨL and NRA and a negative correlation between ΨL and membrane injury were demonstrated. As ΨL declined, the concentration of malondialdehyde, a lipid peroxidation product, doubled. Following rehydration, at 63 d, increases in ΨL and NRA were higher than those of membrane thermostability and malondialdehyde concentration. [ABSTRACT FROM AUTHOR]