低磷条件下硅对番茄幼苗生长及生理特性的影响

Effects of silicon on the growth and physiological properties of tomato seedlings under low phosphorus condition

为探究低磷条件下硅对番茄幼苗的生理调节作用,以‘中杂9号’番茄为试验材料,采用水培法,设置对照(0.66 mmol/L NaH2PO4)、轻度低磷(0.44 mmol/L NaH2PO4)、重度低磷(0.22 mmol/L NaH2PO4)、缺磷(0 mmol/L NaH2PO4)4个磷浓度水平,研究外源硅(1.5 mmol/L K2SiO3·nH2O)对不同供磷水平下番茄干质量、叶片相对含水量、根系形态指标、叶绿素含量、膜脂过氧化程度、质膜完整性、活性氧水平、抗氧化酶活性和硅、磷含量的影响。结果表明:与正常的磷供应水平(对照)相比,低磷胁迫显著降低番茄叶片叶绿素含量和总根长,膜脂伤害程度增加,植株体内磷含量下降,从而影响番茄生长。外源硅明显缓解了低磷胁迫对番茄生长的抑制效应,使番茄幼苗在低磷条件下仍保持较高的叶片相对含水量、叶绿素含量和良好的根系长势,降低了叶片和根系中丙二醛含量、O2·-含量和H2O2水平,增强了超氧化物歧化酶、过氧化物酶和过氧化氢酶活性,促进了植株对磷的吸收,其中,在轻度低磷胁迫下硅对番茄幼苗生长的改善效应最显著。可见,外源硅处理能够基于改善根系生长和叶片水分状态、诱导增强植株的抗氧化防御能力来提高番茄幼苗的磷缺乏耐受性,且对轻度低磷胁迫的调控效应更明显。本研究结果可为探讨硅、磷这2种营养元素的协同作用,以及硅缓解番茄幼苗低磷胁迫的生理机制提供理论依据。

To explore the physiological effects of silicon on tomato seedlings under different low phosphorus conditions,we performed this study using ’Zhongza 9’ tomato cultivar as the experimental material,with seven combination treatments of two silicon levels(0 and 1.5 mmol/L K,SiO3·nH2O) and four phosphorus levels(0.66,0.44,0.22 and 0 mmol/L NaH2PO4) under hydroponic cultivation,and investigated the effects of silicon on the plant dry mass,leaf relative water content,root morphological parameters,chlorophyll contents,membrane lipid peroxidation,plasma membrane integrity,reactive oxygen species levels,antioxidant enzyme activities,silicon and phosphorus contents of tomato seedlings exposed to different phosphorus supply levels.The results showed that,compared with the control treatment(0.66 mmol/L NaH2PO4),the leaf chlorophyll content and total root length were significantly reduced under the low phosphorus condition,while the membrane lipid damage was intensified and the phosphorus content in plant was declined,which led to the growth inhibition of tomato seedlings.Addition of exogenous silicon significantly alleviated the inhibitory effects of low phosphorus stress on the seedling growth,and the stressed-plants were maintained with higher leaf relative water contents,chlorophyll contents and better root growth.Besides,the corresponding malondialdehyde(MDA) content,O2·- content and H2O2 level in leaves and roots were decreased due to the enhancement of superoxide dismutase(SOD),peroxidase(POD) and catalase(CAT) activities,and the assimilation of phosphorus in plants was promoted.Interestingly,there was the most significant facilitation of silicon on the growth of tomato seedlings when subjected to mildly low Phosphorus stress.In general,exogenous silicon could promote the tolerance of tomato seedlings to phosphorus-deficiency,through improving the root growth and leaf water status,as well as inducing the enhancement of plant antioxidation capacity,and the silicon-mediated regulatory effect was more pronounced for mildly low phosPhorus stress.These results are helpful for further understanding the synergistic effects of silicon and phosphorus elements,and will provide a theory basis for illuminating the physiological mechanism of silicon-mediated alleviation of tomato seedlings under the low phosphorus stress.