Effect of water stress on oxalic acid concentrations in spinach leaves

摘要

Spinach cv. Okame plants were grown in solution culture in standard nutrient solutions or in solutions containing polyethylene glycol (PEG) 6000. The changes in oxalic acid concentration in response to water stress were monitored to evaluate the contribution of oxalic acid to osmotic adjustment; potassium and oxalic acid are the predominant solutes in spinach leaves. The addition of PEG 6000 to the nutrient solution significantly decreased osmotic potential at full turgor (pi100) in rapidly growingleaves. The decrease in pi100 in response to PEG treatment could be accounted for by the accumulation of potassium, phosphate, nitrate, sugars, and amino acids, but not of oxalic acid. These results indicate that oxalic acid plays a minor role in osmotic adjustment, although potassium oxalate is a major osmoticum in spinach leaves.