低磷和干旱胁迫对大豆植株干物质积累及磷效率的影响

土壤缺磷和季节性干旱已经成为南方酸性红壤地区大豆生产的主要限制因素之一。选取2个大豆品种巴西10号(磷高效)和本地2号(磷低效),研究其在不同磷素(0,15, 30 mg/kg P)和水分处理(分别在开花期和结荚期进行干旱胁迫)下的反应,从植株生物量、叶绿素含量、磷效率指标等方面研究不同基因型大豆对水磷耦合胁迫的适应机制。研究结果表明,随着土壤磷素水平的增加,两个品种的生物量和叶片叶绿素含量显著增加,根冠比则显著下降。在同一磷素水平处理下,干旱胁迫则导致较高的根冠比,对叶片叶绿素含量影响不大,两个品种表现一致。两个基因型大豆受到干旱胁迫后,其产量均显著低于正常水分处理。中等施磷能显著提高两个大豆品种的产量,但高磷处理对产量的增加幅度有限,甚至高磷处理还造成本地2号减产。巴西10号的产量随土壤中磷素的增加而增加,而本地2号的产量则为中磷>高磷>低磷,不管是磷处理还是水分处理,巴西10号的产量均高于本地2号。无论是花期干旱还是结荚期干旱,巴西10号和本地2号的根磷效率比、磷吸收效率及磷转移效率均随土壤磷浓度的增加而增加,磷利用效率则降低。总体上来讲,巴西10号的磷吸收效率和利用效率高于本地2号,而根磷效率比、磷转移效率则小于本地2号。

Interactive effects of low phosphorus and drought stress on dry matter accumulation and phosphorus efficiency of soybean plants

Low soil phosphorus (P) availability and seasonal drought were the main limiting factors for soybean production in acid red soils of South China. Improving and screening P-efficient genotypes of soybean germplasm which could better adapt to low P soils and drought climate was one of the efficient approaches to increasing soybean yields. Pot experiment with P-efficient (BX10) and P-inefficient (BD2) soybean genotypes was conducted to investigate the effects of P application and water deficit on dry matter accumulation and phosphorus efficiency of soybean plants. Three rates of P application were P₀: 0, P₁: 15, P₂: 30 mg/kg soil, respectively. The two soil moisture treatments were 70%-80% of field water capacity ( FWC) as control and 30%-40% of FWC as drought stress at flowering and pod-setting stages respectively.The results showed that plant biomass and leaf chlorophyll content were increased, while root/shoot ratio of the two soybean varieties were decreased when soil available P increased; Drought stress increased root/shoot ratio of BX10 and BD2 at flowing and pod-setting stages under the same P application rate, but no significant effects were found on leaf chlorophyll content. Drought stress resulted in significant decrease of yield for both two varieties. Soybean yields in low P soils are significantly affected by medium P application (P₁ treatment), but much less and even negatively by high P application (P₂ treatment). The yield of BX10 was increased when soil available P increased, but the yields for BD2 in different P application rates were in the order: P₁>P₂>P₀. BX 10 had higher yield than BD2 under all phosphorus and water treatments. Whatever drought stress in flowering or pod-setting stage, root phosphorus efficiency ratio, P uptake efficiency and P transfer efficiency of plant were increased when available soil P increased, in contrast, P utilization efficiency was decreased with the increase of P application level. In total, BX10 had higher level in P absorption efficiency and utilization efficiency, while relatively lower level in root P efficiency ratio and P transfer efficiency than BD2.