Intra-specific variation in growth and P accumulation of Leucaena leucocephala and Gliricidia sepium as influenced by soil phosphate status |
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Authors: | N. Sanginga G. D. Bowen S. K. A. Danso |
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Affiliation: | (1) Soil Science Unit, International Atomic Energy Agency, P.O. Box 100, A-1400 Vienna, Austria;(2) Soil Fertility, Irrigation and Crop Production Section, International Atomic Energy Agency, P.O. Box 100, A-1400 Vienna, Austria;(3) Present address: International Institute of Tropical Agriculture (IITA), PMB 5320, Oyo Road, Ibadam, Nigeria |
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Abstract: | Twenty-three provenances of Gliricidia sepium and eleven isolines of Leucaena leucocephala were examined at a low and at high phosphate levels (20 and 80 mg P kg-1 soil) for growth, phosphate (P) uptake and use efficiency. Large differences in growth at the low P level, and in growth response to the higher P rate occurred among L. leucocephala isolines and G. sepium provenances. Shoot dry weight at low P varied from 1.30 to 3.01 g plant-1 for L. leucocephala and from 1.44 to 3.07 g plant-1 for G. sepium.Leucaena isolines had only half the root weight of G. sepium provenances yet produced approximately 90% of the shoot weight of the corresponding G. sepium treatments, i.e. more than a 2-fold difference in root/shoot ratios. Total P in shoots of G. sepium was some 85% greater than of the respective L. leucocephala isolines in corresponding treatments. Physiological phosphate use efficiency (g shoot/mg P in shoots) (PPUE) was not a simple reciprocal relation, being markedly lower at higher shoot % P and content. However, for the same shoot P both species produced the same shoot weight. Nevertheless, there were apparent genotypic differences within species in the root development, shoot P and PPUE.In another study, the numbers of rhizobia in the rhizosphere of L. leucocephala, nodulation, N2 fixation at five different levels of P were determined. The numbers of rhizobia in the rhizosphere of inoculated L. leucocephala during the first two weeks were lower when P was added but later became similar to those without added P. Nodules formed earlier than inoculated plants fertilized with P and in greater numbers (4- to 5-fold) and dry weights than in those without P. However, the percentage of N2 derived from fixation did not change with increasing levels of P application. These results suggest that the observed P effect did not operate via stimulated growth of rhizobia in the rhizosphere, nor through increased N2 fixation rate. The major effect appeared to be due to effects via plant growth. |
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Keywords: | isolines nodulation N2 fixation P uptake P use efficiency provenances Rhizobium rhizosphere |
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