Blackwell Publishing Journal Backfiles 1879-2005
Abscisic acid inhibited the rate of 14CO2 fixation in leaves of Pennisetum typhoides (Burm. f.) Stapf & Hubbard seedlings, but increased the activities of phosphoenol-pyruvate-carboxylase and malic enzyme. The leaves of the seedlings grown in the presence of abscisic acid incorporated, in comparison to the control, more radioactivity in the fraction of organic acids, but less radioactivity was recorded in the amino acid fraction. On the other hand, gibberellic acid which also inhibits photosynthetic 14CO2 assimilation and decreases the activities of photosynthetic enzymes, favours greater incorporation in alanine, and reduces that in malate. It is deduced that bio-regulants can greatly influence the flow of 14C into individual photosynthetic products. As in growth, abscisic and gibberellic acids in combination tended to antagonize each other in their effects on enzyme activity as well as in incorporation of 14CO2 into photosynthetic products.
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