The effects of temperature on vegetative and early reproductive growth of a cold tolerant and a cold sensitive line of phaseolus vulgaris 2. nodular uricase allantoinase xylem transport of nitrogen and assimilation in shoot tissues

Thomas, R.J.; Sprent, J.I.

Annals of Botany 53(4): 589-598


ISSN/ISBN: 0305-7364
Accession: 006668354

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The activities of nodular uricase and allantoinase, the composition of bleeding sap N, estimated rates of xylary N translocation and ureide assimilation in shoot tissues were compared in a cold-tolerant (Accession No. 194, Ac 194) and sensitive ('Seafarer', SF) line of nodulated P. vulgaris grown under 3 different temperature regimes. Uricase activity increased with increasing growth temperature and was generally greater in nodules of Ac 194 than in SF at any particularly temperature. Extractable allantoinase activity, on the other hand, was highest in nodules from plants grown at the coolest temperature ( C day/night) and there was little or no difference in activity between the lines. There was little difference in sap composition between lines or among temperture treatments. Ureides contributed 80-91% of the total sap N in both lines grown at or C with a slightly lower percent (65-84) when grown at C. Estimated rates of N translocation were higher in Ac194 than SF at the coolest growth temperature. Increases in rates of N translocation between successive harvests of either line were often correlated with increases in total N accumulation and also an accumulation of ureides in stems plus petioles but not leaves. Generally, leaves assimilated all of the ureides into other compounds at all growth temperatures. Nodules and shoots of either line did not accumulate ureides at C, Ac194 accumulated greater amounts of ureides in stems and petioles than SF when grown at the 2 warmer temperatures. The results are discussed in relation to the ability of Ac194 to fix greater amounts of N than SF at suboptimal growth temperatures.