MEMBRANE PERMEABILITY IN ROOTS OF CROTALARIA SEEDLINGS AS AFFECTED BY LOW TEMPERATURE AND LOW PHOSPHORUS STRESS

ABSTRACT

The effects of low temperature (3–4°C) and low phosphorus (P) stress on membrane permeability in the roots of crotalaria (Crotalaria lium L. Jiangxi) seedlings were investigated in hydroponic experiments. The results indicated that low temperature resulted in pronounced leakage of electrolytes, oxalic acid, and reducing sugars. Low P enhanced the exudation of oxalic acid and reducing sugars but did not induce any leakage of electrolytes. Low temperature rather than low P induced an increase in the relative proportion of phospholipid P to total P. Phospholipid P level in the plasma membrane was not related to the leakage of electrolytes, oxalic acid, and reducing sugars, indicating that the decrease in P level in the plasma membrane is not associated with an increase in membrane permeability. Anthracene-9-carboxylic acid, an anion channel blocker, inhibited low-P-induced exudation of oxalic acid and reducing sugars significantly, but did not decrease low-temperature-affected leakage of oxalic acid and reducing sugars. These findings suggest that low-P-induced exudation of oxalic acid and reducing sugars probably involves a unique activation mechanism rather than being dependent on membrane leakage. Further studies showed that lanthanum (La³⁺) and ytterbium (Yb³⁺) decreased low-temperature-induced electrolyte leakage and maintained the integrity of plasma membrane, thus enhancing resistance to low temperature stress.

ACKNOWLEDGMENTS

This research was in part supported by the National Natural Science Foundation of China (39925025/39970431), the International Foundation for Science (the No. C/3042-1), and Guangdong Natural Science Foundation (the No. 000642).