ISHS Acta Horticulturae 275: International Symposium on the Culture of Subtropical and Tropical Fruits and Crops
COMPARISON OF SOME ASPECTS OF NITROGEN METABOLISM OF AVOCADO WITH CITRUS |
| Authors: | Carol J. Lovatt, Anne H. Cheng |
| Abstract:
Comparison of NH3-NH4+ metabolism during low temperature stress-promoted flowering in the Hass avocado and Citrus species identified differences in nitrogen metabolism between avocado and Citrus: (1) the basal level of NH3-NH4+ was 10-fold lower in Hass avocado leaves than in leaves of the Washington navel orange; (2) concomitantly, the basal activity of the pathway for the de novo biosynthesis of arginine was 10-fold lower in avocado leaves; (3) avocado leaves developed symptoms of ammonia toxicity at lower NH3-NH4+ concentrations than the Washington navel orange; and (4) there was virtually no urea uptake by Hass avocado leaves in response to a foliar application of urea that significantly raised the leaf NH3-NH4+ content of the Washington navel orange. The results suggested that leaves of avocado scions may have a limited role in nitrate reduction and ammonia assimilation compared to the roots of avocado rootstocks. This interpretation is supported by the preliminary results presented here demonstrating that the activities of nitrate reductase and glutamine synthetase are frequently greater in roots of avocado rootstock varieties than in the leaves of avocado scion varieties. | |
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