科研之友
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摘要
Background and aims Phosphorus (P) is a commonly limiting nutrient for plant growth in natural environments. Many legumes capable of N-2-fixation require more P than non-legumes do. Some legume crops can use sparingly soluble forms of P such as iron phosphate much better than other species, but reports on the ability of woody legumes to access iron phosphate are rare. %26lt;br%26gt;Methods Plants of four Acacia species (Acacia stipuligera F. Muell., A. ancistrocarpa Maiden %26 Blakely, A. stellaticeps Kodela, Tindale %26 D. Keith and A. robeorum Maslin), native to the Great Sandy Desert in north-western Australia, were grown in a glasshouse in river sand with different levels of iron phosphate, between 0 and 16 mu g P g(-1) sand. Plant growth, tissue P concentrations, and pH and carboxylates in the rhizosphere were measured. %26lt;br%26gt;Results Growth of A. stipuligera and A. ancistrocarpa was not responsive to increased P supply; in contrast, A. stellaticeps and A. robeorum produced significantly more root and shoot dry mass at 8 and 16 mu g P g(-1) sand than at 0 mu g P g(-1) sand; differences in root mass ratio were significant between species but not between P treatments. A. robeorum was the only species colonised by mycorrhizal fungi, and the colonisation percentage decreased with increasing P supply. In all species, P-uptake rates and tissue P concentrations were significantly higher at greater P supply. Rhizosphere pH and the amount of carboxylates in the rhizosphere decreased with increasing P supply. %26lt;br%26gt;Conclusions Net P uptake increased with increasing P supply, showing that the present Acacia species can access P from iron phosphate. However, due to their inherently slow growth rate, enhanced P supply did not increase growth of two of the four studied species. The ability of the Acacia species to access P from iron phosphate is presumably related with carboxylate exudation and rhizosphere acidification.
- 出版日期2012-9
