Nitrate reduction in tendrils of semi-leafless pea

The recessive gene af produces a modification of Pisum sativum L, leaf morp hology, where leaflets are replaced by tendrils. Previous reports have sugg ested that tendrils may contribute to plant growth in a similar way to flat leaf structures, but these reports have been restricted to carbon metaboli sm. In this work, we investigate the nitrate reduction (nitrate reductase a ctivity) capacity of tendrils of a semi-leafless variety, Solara, in relati on to other leaf structures. Maximum nitrate reductase activity (EC 1.6.6.1 ), expressed on a protein basis, was significantly lower in tendrils compar ed to flat structures, However, the activation state of nitrate reductase w as significantly higher in tendrils, reaching 70%, compared to flat leaf st ructures, According to these results, tendrils contributed up to 25% of the overall plant nitrate reduction in the semi-leafless variety. This figure was even higher when nitrate reduction was calculated from in vivo measurem ents. The results are discussed in relation to nitrate, magnesium, carbohyd rates, amino acids and adenylate levels of tendrils.