低磷胁迫对太空诱变耐低磷柱花草酸性磷酸酶活性和磷效率的影响

低磷胁迫是酸性土壤限制牧草生产的主要障碍因子之一。本课题组前期的研究中,通过太空诱变获得了一个耐低磷柱花草突变体TPRC2001-84,但其适应低磷胁迫的机制仍不清楚。以TPRC2001-84及其亲本热研2号(RY2)为试验材料,通过水培方法,比较正常供磷(+P,250 μmol·L^-1 KH₂PO₄)和低磷(-P,5 μmol·L^-1 KH₂PO₄)处理对TPRC2001-84和RY2生物量、磷吸收效率、磷利用效率、可溶性磷浓度、细胞壁磷含量和酸性磷酸酶(ACP)活性的影响。结果表明,相对于正常供磷处理,低磷处理显著降低了两份柱花草材料的植株干重和磷吸收效率(P<0.05),但显著提高了两份柱花草材料的磷利用效率(P<0.05)。并且,TPRC2001-84在低磷处理下的植株干重和磷利用效率分别是RY2的1.6和1.4倍。在低磷胁迫下,虽然TPRC2001-84叶片和根系的细胞壁磷含量只有RY2的70%左右,但是,TPRC2001-84叶片和根系的可溶性磷浓度分别比RY2高36.8%~42.6%,细胞壁ACP活性分别比RY2高46.6%~53.6%。以上结果说明,柱花草TPRC2001-84在低磷胁迫下具有较高的细胞壁ACP活性,有利于其对细胞壁中贮存磷的活化利用,从而获得较高的磷利用效率。这将为选育磷高效柱花草新品种提供理论依据和种质材料。

Effects of phosphorus deficiency on acid phosphatase activity and phosphorus efficiency in a low-phosphorus tolerant Stylosanthes mutant

Low phosphorus (P) availability is a major constraint for pasture yields in acid soils. In a previous study, a low-P tolerant stylo (Stylosanthes) mutant, TPRC2001-84, was created using space flight mutation. However, the underlying mechanisms of TPRC2001-84 tolerance of P deficiency remain largely unknown. In this study, plant biomass, P acquisition efficiency, P utilization efficiency, soluble inorganic phosphate (Pi) concentration, cell wall P content and acid phosphatase (ACP) activity were investigated in hydroponically grown TPRC2001-84 and a non-mutant control (RY2) in normal P (+P, 250 μmol·L^-1 KH₂PO₄) or low P (-P, 5 μmol·L^-1 KH₂PO₄) solutions. Plant dry weight and P acquisition efficiency were significantly decreased (P<0.05) by P deficiency, while P utilization efficiency was increased (P<0.05) by low P in both accessions, compared to the normal P treatment. Plant dry weight and P utilization efficiency of TPRC2001-84 were 1.6 and 1.4 times those of RY2 under P deficiency, respectively. Although cell wall P content in leaves and roots of TPRC2001-84 were about 70% lower than in RY2 with low P treatment, the soluble Pi concentration in leaves and roots of TPRC2001-84 were 36.8% and 42.6% higher than in RY2 under P deficiency, respectively. Similarly, cell wall ACP activity in leaves and roots of TPRC2001-84 were 46.6% and 53.6% higher than in RY2 under P deficiency, respectively. These results suggest that increased cell wall ACP activity in TPRC2001-84 may contribute to cell wall P scavenging and recycling, increasing P utilization efficiency under P deficiency. Taken together, our results provide a theoretical basis and germplasm resource for selecting and breeding stylo varieties with high P efficiency.