Measurement of Cell Membrane Stability Evaluated by Electrolyte Leakage as a Drought and Heat Tolerance Test in Rice (Oryza sativa L.)

Abstract

To explore possibilities of adaptation of cell membrane stability measurement as a evaluation of drought and heat t,olerance (or injury) in rice (Oi-yzfl sa/irln L.), we have measured electrolyte leakage (EL) from leaf discs exposed to desiccation and temperature stresses. In desiccation test with polyethylene glycol (PEG), EL increased from 10% to 80% with increasing from 20% to 60% of PEG concentration [PEG]. We have used 30% of [PEG] at which 25% of EL was occured. EL was increased with the time of PEG treatment; accordingly, 34 hours as a period of submerged leaf were selected. We have investigated an optimal temperature and treatment period, and around 42°C is likely to be suit,able for testing membrane thermostability. EL was increased almost linearly w&h the time of leaf tissues submerged in test temperature (42°C) solution; we selected 24 hours for t,he following experiments. EL of PEG test was greater in senescing leaf (the 4th leaf from the youngest fully expanded leaf) t,han leaf in which senescence is less advanced (the youngest, fully expanded leaf). EL of leaf tissue was also increased with water deficit, indicating physiological status of plant itself can be reflect,ed by the technique. Therefore, this t,echnique is considered to be useful to assess injury, presumably at the membrane level, resulting from an environmental stress in rice.