Effect of Different Killing Techniques on Early Labeled Photosynthetic Products in C4 Plants

The choice of leaf-killing technique was found to affect significantly the distribution of label among early labeled photosynthetic products in two C(4) plants, Portulaca oleracea and Zea mays. The major effect of these procedures was on the amount of amino acids present, particularly alanine, and the ratio of malate to aspartate. Killing Portulaca leaves in alcohol generally results in more alanine and the predominance of malate over aspartate. When the leaves are killed by immediate freezing, however, aspartate contained more radioactivity than malate, and alanine was present in much reduced amounts. The various methods also differ in the relative amounts of C(3) cycle compounds and other, secondary intermediates which were obtained.