Accumulation of Oxalate in Tissues of Sugar-beet, and the Effect of Nitrogen Supply

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Abstract
In field-grown sugar-beet concentration of insoluble oxalate was low in roots and high (about 12 per cent of ethanol insoluble material) in leaves, and for a particular leaf the concentration increased continuously during its life. Of the insoluble oxalate, 15–30 per cent was present as the magnesium salt and the remainder as the calcium salt. Oxalate contents of plants grown in culture solutions with nitrate as nitrogen source were similar to those of plants grown in soil, but when nitrogen was supplied as ammonium sulphate or ammonium nitrate both soluble and insoluble oxalate were low. Plants grown in soil with regular additions of ammonium sulphate or ammonium nitrate also had very low concentrations of soluble oxalate although insoluble oxalate was only slightly lower than with nitrate nitrogen. Disks of root or leaf tissue washed for several days in distilled water lost insoluble oxalate but when washed in tap water insoluble oxalate increased more than twofold. Addition of calcium and nitrate to the distilled water caused an increase of insoluble oxalate, while addition of potassium caused a decrease. Use of 14C labelled oxalate and washing experiments showed that oxalate can be metabolized by tissue disks and so is not necessarily a final product of metabolism. The accumulation of oxalate appears to be connected with the assimilation of nitrate and the preservation of the cation-anion balance of the plant.

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