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  • Author or Editor: Frederick C. Olday x
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Abstract

‘America’ spinach (Spinacia oleracea L.) is a savoy-leafed cultivar and tends to accumulate NO 3 ¯ in its leaf blades, petioles, and roots when the level of NO3-N nutrition is relatively high. ‘Hybrid 424’ spinach is smooth-leafed, larger in size, and accumulates much less NO 3 ¯ than ‘America’ especially when NO3-N nutrition is high. A greater NO 3 ¯ reductase activity in Hybrid 424, especially in its leaf blades, may account for its lower NO 3 ¯ content compared to that of ‘America’.

Open Access

Abstract

Cucumber (Cucumis sativus L.) plants accumulate more NO 3 ¯ than pea (Pisum sativum L.) plants. The differences in accumulation appear to be due to differences in the abilities of the two species to reduce NO 3 ¯ in their roots. Only 2% of the NO 3 ¯ reductase activity of cucumber was found in its roots, whereas nearly 92% of the activity was found in the blades. In pea, NO 3 ¯ reductase activity was more evenly distributed throughout the plant;67% of the activity was in the blades, 18% in the roots, and the remainder in the stems and petioles. Nitrate-N comprised 80% of the N present in bleeding sap of roots of cucumber plants from which the shoots had been excised. In contrast, NO3-N constituted only 30% of the N in the sap from pea roots, the remaining 70% of the N consisting of amino acids and amides. Asparagine or aspartic acid was the major carrier of reduced N in pea, and glutamine was the major carrier in cucumber. The differences in N transport and assimilation appear to bear considerably on plant composition and efficiency of N usage.

Open Access