Total Oxalate Contents Research Articles

Oxalate and Nitrate Contents of Four Tropical Leafy Vegetables Grown at Two Soil Fertility Levels1

AbstractTotal oxalate, soluble oxalate, and nitrate (NO3) were determined for leaves of Amaranthus cruentus L., Basella alba L., Brassica oleracea var. acephala D.C., and Ipomoea aquatica Forsk. grown on soils of medium and high fertility.Differences among species were much greater than differences due to fertility. Average total oxalate contents on a dry weight basis were: Basella, 10.62%; Amaranthus, 8.86%; Ipomoea, 2.81%; and Brassica, <1.50%. Higher soil fertility resulted in increased total oxalate of about 25% in Amaranthus and Basella but no increase in Brassica and Ipomoea. Soluble oxalate ranged from 4.14% for Basella to 0.20% for Brassica.Average nitrate contents were: Brassica, 2.80%; Amaranthus, 0.67%; Basella, 0.61%; and Ipomoea, 0.39%. Leaves grown on high‐fertility soil had an average of 125% more nitrate than those from medium fertility.Implications of the results are discussed.

The Effect of Maturity on the Oxalate Content of Spinach (Spinacia oleraceae L.)

SUMMARYDark Green Bloomsdale spinach was grown in the fall and in the spring to study the effect of stage of development upon the distribution of total and soluble oxalates in the plant. The total oxalate content of fall‐grown spinach was highest 32 days after planting, with the amount decreasing as the plant developed vegetatively. Spring‐grown spinach was highest in total and soluble oxalates 32 days after planting, with the amounts decreasing as the plants developed vegetatively. Leaves harvested earlier in growth were higher in total oxalates than leaves harvested when older. The concentration of total and soluble oxalates was highest in the leaves, petioles, and roots, in that order. The total oxalates were closely correlated between the leaves, petioles, and roots. Soluble oxalates were closely correlated between leaves and petioles, but not in the roots. The oxalates in all plant parts were predominantly in the soluble form. Analysis of leaf tissues for total oxalates could indicate the level to be expected in the petioles and roots. The level of soluble oxalates in the leaves and petioles could also be predicted.