ABSTRACT

The root phosphorus (P) uptake efficiency (RE), defined as plant P uptake per unit root mass or root area, may contribute to the P efficiency of upland rice grown in acid, P-deficient soils. The identification of root traits conferring RE of rice has been compromised by the lack of attention given to P speciation when evaluating P-mining mechanisms. Here we disentangled the effect of soluble organic P (P_O) from that of total soluble P (P_T) on the RE in rice seedlings in acid soil. Six rice genotypes were grown for 21 days in P-deficient substrates, i.e. a sample of an acid mineral soil, an acid peat and a mixture thereof. Each of the three substrates were amended with different P doses, partially limed and incubated, yielding substrates with significant differences in total soluble P (0.005–0.41 mg P/L) and in the percentage of organic P in that pool (P_O/P_T, 0–55%). Plants showed a large growth response to the P addition. There was a significant genotypic variation in P uptake (0.9–1.5mg P/plant) and RE (4.4–8.3 mg P/g root mass) under moderate P deficiency but these traits were unaffected by the P_O/P_T in the soluble fraction of the substrates. Along the same lines, phosphatase activity in the rhizosphere soil was unaffected by genotypes and did not explain the RE among all data (R² = 0.17, ns). A multiple regression model showed that the RE of rice seedlings was mainly affected by the inherent genotypic effects, the P_O/P_T and the total soluble P concentration in soil (R² = 0.73), while the genotype-P_O/P_T interaction only marginally improved the RE model (R² = 0.78). This suggests limited genotypic effects due to the better use of organic P. A root elongation test in the acid mineral soil that was either or not limed suggests that the differences in acid soil tolerance may play a larger role in the genotypic performance of RE than organic P utilization potential.

摘要

根磷（P）吸收效率（RE）定义为每单位根质量或根系面积的植物P吸收量，可能有助于在酸性，缺磷的土壤中生长的旱稻的P效率。由于在评估P采矿机制时缺乏对P物种形成的关注，因此难以确定赋予水稻RE的根系特征。在这里，我们将可溶性有机磷（P _O）的影响与总可溶性磷（P _T）在酸性土壤中的水稻幼苗中的可再生能源。六种水稻基因型在缺磷的基质（即酸性矿物土壤，酸性泥炭及其混合物的样品）中生长21天。三种底物中的每一种都用不同的P剂量修正，部分撒石灰并孵育，产生的底物在总可溶性P（0.005-0.41 mg P / L）和该池中有机P的百分比（P _O / P _T，0-55％）。植物对磷的添加表现出较大的生长响应。中度磷缺乏时，磷的吸收（0.9-1.5mg P /株）和稀土（4.4-8.3 mg P / g根质量）存在显着的基因型差异，但这些特性不受P _O / P _T的影响在底物的可溶部分中。同样，根际土壤中的磷酸酶活性不受基因型的影响，在所有数据中均不能解释RE（R ²  = 0.17，ns）。多元回归模型表明，水稻幼苗的稀土元素主要受内在基因型效应，P _O / P _T和土壤中总可溶性磷浓度（R ²  = 0.73）的影响，而基因型-P _O / P _T互动仅略微改善了RE模型（R ² = 0.78）。这表明由于更好地利用有机磷而造成的基因型效应有限。在石灰性土壤中进行过或未石灰化的根系伸长试验表明，耐酸性土壤的差异可能比有机质在RE的基因型性能中发挥更大的作用。磷利用潜力。