Kang Jianjun, Zhao Wenzhi, Zhu Xi
Linze Inland River Basin Research Station, Key Laboratory of Inland River Basin Ecohydrology, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Science, Lanzhou 730000, Gansu, China.
Linze Inland River Basin Research Station, Key Laboratory of Inland River Basin Ecohydrology, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Science, Lanzhou 730000, Gansu, China.
J Plant Physiol. 2016 Jul 20;199:76-86. doi: 10.1016/j.jplph.2016.05.009. Epub 2016 May 24.
One main strategic adaptive mechanism adopted by succulent xerophyte species, resistance to drought stress is absorbing and accumulating large amounts of sodium (Na) from poor and dry soil which was stored in photosynthesizing branches as well as leaves as major osmoregulators, while still accumulating and storing a great deal of silicon (Si) in roots to resist to arid environments. To understand the possible adaptive strategies underlying how Si accumulation stimulates growth and ameliorates the adverse environmental impacts of drought stress on the C succulent xerophyte Zygophyllum xanthoxylum, plants grown for 3 weeks were suffered different KSiO concentrations (1.5-7.5mM) (3-15mM KCl as control) treatments in sand culture experiments. Plants were also treated with different osmotic stresses caused by polyethylene glycol (PEG 6000) and drought stress (maintain water content about 30% of field water capacity) (30% of FWC) with or without additional 2.5mMKSiO (5mMKCl as control) treatment in sand culture and pot experiments, respectively. We found that 2.5mMKSiO (5mMKCl as control) resulted in optimal plant growth and alleviated adverse influences of drought stress on Z. xanthoxylum, by strengthening the activities of superoxide dismutase, peroxidase and catalase, reducing membrane lipid peroxidation and decreasing soluble sugar and free proline concentrations, concomitantly, increasing tissue water content, leaf area and chlorophyll a concentration. The result of ion analysis indicated that the Si absorption of Z. xanthoxylum was markedly induced by drought stress and that the 2.5mMKSiO (5mMKCl as control) treatment significantly increased the aboveground and root Si concentration under different osmotic stresses and 30% of field water capacity compared with the drought and drought with 5mMKCl treatments. Although the K concentration in root in the drought with 2.5mMKSiO treatment was no significant changes compared with the drought treatment, K concentration in aboveground and root in drought with 2.5mMKSiO treatment were significantly decreased by 42% and 65.2% compared with drought with 5mMKCl treatment under 30% of FWC, indicating that Si replaced the function of K, thus stimulating the growth and mitigating adverse effects of Z. xanthoxylum under water deficit. These findings showed that the positive roles of Si in the drought tolerance of Z. xanthoxylum might be due to the ability of plant to accumulate a great quantity of Si and utilize it as an osmoregulator to copy with water deficit, which was coupled with an obvious improvement in photosynthetic activity and anti-oxidative enzyme activities.
肉质旱生植物物种采用的一种主要战略适应机制是抗旱胁迫，即从贫瘠干旱的土壤中吸收并积累大量的钠（Na），这些钠作为主要的渗透调节剂储存在光合枝和叶片中，同时仍在根部积累和储存大量的硅（Si）以抵御干旱环境。为了了解硅积累如何刺激生长并减轻干旱胁迫对肉质旱生植物霸王的不利环境影响的潜在适应策略，在砂培实验中，对生长3周的植株进行了不同KSiO浓度（1.5 - 7.5mM）（以3 - 15mM KCl作为对照）的处理。在砂培和盆栽实验中，还分别用聚乙二醇（PEG 6000）引起的不同渗透胁迫和干旱胁迫（保持含水量约为田间持水量的30%）（FWC的30%）对植株进行处理，处理时添加或不添加2.5mMKSiO（以5mMKCl作为对照）。我们发现，2.5mMKSiO（以5mMKCl作为对照）通过增强超氧化物歧化酶、过氧化物酶和过氧化氢酶的活性，减少膜脂过氧化，降低可溶性糖和游离脯氨酸浓度，同时增加组织含水量、叶面积和叶绿素a浓度，从而使植株生长达到最佳状态，并减轻干旱胁迫对霸王的不利影响。离子分析结果表明，干旱胁迫显著诱导了霸王对硅的吸收，与干旱处理和5mMKCl干旱处理相比，2.5mMKSiO（以5mMKCl作为对照）处理在不同渗透胁迫和田间持水量30%的条件下显著提高了地上部和根部的硅浓度。虽然2.5mMKSiO干旱处理根部的钾浓度与干旱处理相比没有显著变化，但在田间持水量30%的条件下，2.5mMKSiO干旱处理地上部和根部的钾浓度与5mMKCl干旱处理相比分别显著降低了42%和65.2%，这表明硅取代了钾的功能，从而在水分亏缺条件下刺激了霸王的生长并减轻了其不利影响。这些发现表明，硅在霸王耐旱性中的积极作用可能归因于植物积累大量硅并将其用作渗透调节剂以应对水分亏缺的能力，同时光合活性和抗氧化酶活性也有明显提高。
