不同磷供应水平下小麦根系形态及根际过程的变化特征

以石麦15和衡观35两个品种小麦为试验材料,应用根袋栽培方式,研究了不同施磷量对小麦根系形态和根际特征的影响。结果表明,与施磷量P2O5 0.1 g/kg相比,高量供磷（P2O5 0.3 g/kg）条件下石麦15地上部生物量和磷累积量增加幅度大于衡观35;但不施磷处理衡观35地上部生物量降低幅度小于石麦15,磷含量和累积量高于石麦15,衡观35耐低磷能力较强。土壤供磷不足时,衡观35总根长中直径0.16 mm细根所占比例高于石麦15,根系平均直径较小;而高磷供应下,石麦15根系中直径0.16 mm细根长度较长,在总根长中所占比例较高。总根长和直径0.16 mm的细根长度与植株地上部磷累积量之间呈显著正相关关系。总根长越长尤其是细根越多,有利于促进植株对磷的吸收。与非根际土壤相比,高磷供应下根际土壤有机磷含量增加,微生物量磷含量降低;而供磷不足时根际土壤碱性磷酸酶活性较高,有机磷含量较低。与施磷量P2O5 0.1 g/kg相比,高量供磷下根际土壤pH值升高、碱性磷酸酶活性下降,不施磷处理根际土壤pH值降低。本研究表明,供磷不足时,小麦根系形态和根际过程均发生适应性变化,而高量供磷条件下,小麦植株根系形态的改变因品种而异。

Changes of root morphology and rhizosphere processes of wheat under different phosphate supply

A rhizobox experiment was carried out to study effects of various concentrations of phosphate(Pi) supply on root morphology,rhizosphere processes,and plant P uptake of two wheat genotypes(Shimai 15 and Hengguan 35).The results showed that Shimai 15 had more increases of shoot biomass and phosphorus(P) content with high Pi application compare with Hengguan 35.While the decreases of shoot biomass and P accumulation of Hengguan 35 under limited Pi supply were much lower than those of Shimai 15,indicating Hengguan 35 might have higher tolerance to low Pi stress than Simai 15.Under the high Pi supply,the fine root length within ≤0.16 mm diameter and its percentage in total root length of Shimai 15 were greater than those of Hengguan 35.Contrarily,without Pi fertilization,the total root length and the proportion of fine roots with diameter ≤ 0.16 mm in total roots of were larger in Hengguan 35 than Shimai 15.Under the high Pi supply,the higher soil organic P content and the lower soil microbial biomass P were in rhizosphere,while without Pi supply,the activity of soil alkaline phosphatase was higher and soil organic P content and soil pH were lower in rhizosphere.Compared with the optimum Pi supply,the high Pi supply increased soil pH and decreased the activity of alkaline phosphatase in rhizosphere.However,low Pi supply decreased soil pH in rhizosphere.It is suggested that the adaptations of plants on two fronts would occur when subjected to the low Pi stress.One is better root characteristics,such as longer roots,especially with more fine roots,which are important for plant to efficiently utilize soil Pi,and the other is the rhizosphere processes,such as soil acidification and the transformation of soil organic P to Pi,which help plant to acquire more Pi from rhizosphere soils and benefit plant’s tolerance to the low Pi stress.However,the changes of root morphology under high Pi supply may be associated with the wheat cultivars with different capacity of P uptake and P accumulation.