硅在多浆旱生植物适应干旱环境中的作用机制研究

The groundwater level has been very deep (mostly below 15m) in northwest desert regions, the growth of desert plants are very difficult to rely on groundwater, how they adapt to arid environment? The project applicant and wang suo min (supervisor of applicant) found that the desert succulent xerophytes can not only absorb and accumulate a great quantity of Na+ than K+ by roots from low-salinity soil that was stored in the vacuole and use it as an important physiological osmoregulatory substance to osmotic adjustment, but also can absorb and accumulate a great quantity of silicon (SiO2) to adapt to arid environment. This study based on Si may enhance the drought resistance of arid desert plants; we used the xerophyte specie Haloxylon ammodendron as the representative specie, to explore the physiological mechanism of Silicon (Si) on the succulent xerophytes Haloxylon ammodendron to adapt to arid environment through the indoor sand culture and pot soil methods. Firstly, the different concentrations of Si ( K2SiO3) on the growth of Haloxylon ammodendron were analyzed to search the suitable concentrations of Si and provide evidence on the physiological mechanism of Haloxylon ammodendron; secondy, the different concentrations of silicon ( K2SiO3) on the growth of Haloxylon ammodendron to adapt to arid environment under different osmotic stress were analyzed to discuss the drought resistant relationship between silicon and Haloxylon ammodendron, and reveal the mechanism of silicon in enhancing the drought resistance of Haloxylon ammodendron; finally, the positive effect of silicon on the growth of Haloxylon ammodendron to adapt to the arid environment under drought stress were further discussed and analyzed to verify the mechanism of silicon in enhancing the drought resistance of Haloxylon ammodendron. The project will lay the foundation for the plant drought resistance theory of arid enhancement, and provide a theoretical basis for the ecological environment construction of desert regions.

对地下水位很深（多已在15m以下）的西北荒漠区，荒漠植物已很难依赖于地下水生长，它们是怎样适应干旱环境的呢？项目申请人及导师王锁民发现荒漠区多浆旱生植物能从含盐量很低的干旱土壤中吸收并积累钠（Na+）而不是K+，并将其储存于液泡中作为有益的渗透调节剂外，还能吸收并积累硅（SiO2）来适应干旱环境。本项目基于硅可能对干旱区荒漠植物增强抗旱性的认识，试图以梭梭为材料，通过室内沙培和盆栽土培分析法，首先分析不同浓度的硅（K2SiO3）对梭梭生长的影响，寻找适宜其生长的最适硅浓度，为揭示硅在梭梭生理过程中的作用机制提供证据；其次，不同渗透胁迫下分析硅在梭梭适应干旱环境中的作用，探讨硅与梭梭抗旱的作用关系，揭示硅增强梭梭抗旱的作用机制；最后，自然干旱胁迫下进一步探讨硅在梭梭适应干旱环境中的作用以及对其抗旱性的影响，验证硅增强梭梭抗旱性的作用机制。项目的开展将为干旱区增强植物抗旱性理论奠定基础，为荒漠区生态环境建设提供理论依据。

荒漠植物是我国西北干旱区的重要植物资源，揭示其抗旱机理，对荒漠区生态环境重建和保护具有重要意义。多浆旱生植物梭梭、霸王和白刺等适应干旱环境的有效策略是能够吸收并积累大量（Na+），而不是 K+ 作为重要的渗透调节剂外，还能吸收积累有益元素硅（SiO2）来适应干旱环境，并且发现钙（Ca）为多浆（Na+ 后）和少浆（K+ 后）植物抗旱的第二大渗透调节剂。目前关于硅、钠硅互作及钙促进荒漠植物生长及提高其抗旱性的系统研究较少，特别是硅和钙在旱生植物适应干旱环境的作用机制还未见报道。本研究以梭梭、霸王和白刺为研究对象，通过室内沙培和盆栽土培分析法，围绕以下科学问题开展研究：① 硅在霸王抗旱性中的最适施肥范围、发挥方式以及生理机制；② 钙在梭梭抗旱性中的最适施肥范围、渗透调节方式以及调控机制；③ 钠硅互作对白刺抗旱性的影响及最适施肥量的确定。主要结论如下：⑴ 15 mmol.L-1 K2SiO3（15 mmol.L-1 KCl 对照）对梭梭生长的促进作用最佳。15 mmol.L-1 K2SiO3降低梭梭体内丙二醛含量和相对电导率，减轻了渗透胁迫对梭梭生长造成的伤害，增强了梭梭的抗旱性；2.5mmol﹒L-1 K2SiO3（5mmol﹒L-1 KCl对照）对霸王生长的促进作用最佳。在不同（-0.5MPa，-1.0MPa 和-1.5MPa）、相同（-1.0MPa）渗透胁迫和缓慢干旱胁迫（30%的田间持水量）下，2.5mmol﹒L-1 K2SiO3均显著促进了霸王生长并增强了其抗旱能力。Si增强霸王抗旱性的生理作用机制在于Si显著改善干旱胁迫下霸王的光合活性和水分特征，增强了叶片保护酶活性以降低膜脂过氧化作用。⑵ 0.4g CaCl2﹒kg-1 干土对梭梭生长的促进作用最佳。干旱胁迫下，0.4g CaCl2﹒kg-1 干土显著降低了梭梭光合同化枝的水势，增加了光合同化枝膨压和叶绿素含量，梭梭光合同化枝的光合活性和水分利用效率显著提高。Ca增强梭梭抗旱性的生理机制在于梭梭能够吸收并积累大量的Ca2+ 作为重要的渗透调节剂并直接参与渗透调节作用来改善梭梭光合同化枝的光合作用和水分特征，从而增强了其抗旱能力。⑶ 1.2 g.kg-1 NaCl或0.3 g.kg-1 NaCl+0.72 g.kg-1 Na2SiO3的互作最适施用量均能显著促进白刺的生长并提高其抗旱性，且0.3 g.kg-1N