The effects of temperature on vegetative and early reproductive growth of a cold-tolerant and a cold-sensitive line of Phaseolus vulgaris L. 2. Nodular uricase, allantoinase, xylem transport of N and assimilation in shoot tissues

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

Annals of Botany 53(4): 589-597


ISSN/ISBN: 0305-7364
Accession: 001485177

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Activities of uricase and allantoinase in nodules, the composition of the N fraction of bleeding sap, estimated rates of N translocation in xylem and the assimilation of ureides in shoot tissues were investigated in nodulated plants of P. vulgaris cv. Seafarer and the cold-tolerant line 194 grown at 15/10, 20/15 and 25/15 degrees C day/night temp. Uricase activity increased with increasing growth temp. and was generally greater in line 194, while allantoinase activity was highest at the lowest temp. and did not differ between lines. Ureides contributed 80-91% of total sap N in both lines at the 2 higher temp. and 65-84% at the lowest temp. Estimated N translocation was greater in line 194 at the lowest temp. Increases in rates of N translocation with delay in sampling were often correlated with increases in total N accumulation and also with accumulation of ureides in stems plus petioles but not in leaves. In general the leaves assimilated all the ureides into other compounds at all temp. Nodules and shoots did not accumulate ureides at the lowest temp. At higher temp. line 194 accumulated greater amounts of ureides in stems and petioles than did Seafarer. Nodulated plants of cold-sensitive Seafarer (SF) and cold-tolerant 194 grown in controlled environment chambers at 15/10, 20/15 and 25/15 degrees C (day/night) were evaluated at three growth stages. Uricase activity increased with increasing temperature and was generally greatest in nodules of 194; the reverse trend applied for allantoinase activity, which was similar in both lines. Neither line accumulated ureides at 15/10 degrees C, but at the higher temperatures 194 accumulated more of these in stems and petioles than did SF. Large increases in N translocation rate between successive harvests were usually accompanied by increases in the percentage of transported ureides stored in stems and petioles and increases in total N accumulation.