盐胁迫对玉蕊幼苗生长及矿质元素吸收和转运的影响

【目的】探明盐胁迫对玉蕊幼苗生长和矿质元素吸收及转运的影响，从离子转运机制角度解析玉蕊的盐胁迫耐受性，为玉蕊的野生种群保护、迁地保育、推广利用及造林的立地选择提供科学参考。【方法】以二年生玉蕊实生苗为试验材料，采用自动潮汐模拟全日潮装置，对玉蕊幼苗设0（CK）、15‰、20‰、25‰、30‰、35‰和40‰共7种盐度胁迫处理，对比分析玉蕊在盐胁迫下根、茎、叶对钙（Ca）、镁（Mg）、铁（Fe）、氯（Cl）、钠（Na）5种矿质元素的吸收量、转运系数及生长指标与矿质元素吸收的相关性。【结果】低盐度（0~15‰）胁迫下，玉蕊植株生长良好，高盐度（30‰~40‰）胁迫导致玉蕊叶片急剧脱落，生物量下降，严重抑制玉蕊植株的生长发育。盐胁迫使玉蕊体内Na和Cl元素的积累量升高，玉蕊幼苗根部对Ca和Mg元素的吸收量下降，而叶片部位对Ca、Mg和Fe元素的吸收量升高，茎段部位对Ca、Mg和Fe元素的吸收量无明显差异。盐胁迫下玉蕊幼苗对Ca、Mg和Cl元素的转运系数均大于1.0，对Fe元素的转运系数小于1.0，对Na元素的转运系数在盐度为35‰~40‰时大于1.0。相关分析结果表明，玉蕊生物量与地上部分各元素间均呈负相关，叶片脱落率、根冠比与地上部分各元素间均呈正相关。【结论】全日潮淹浸6 h/d的环境下，玉蕊幼苗在水体盐度为0~15‰范围内生长良好，在20‰~25‰盐度范围内有一定的耐受能力，而当水体盐度≥30‰时，玉蕊幼苗无法正常生长。其耐盐性主要是通过根系对Na元素的聚积，限制Na元素向茎叶运输，同时增强Ca、Mg、Fe和Cl元素向茎叶的转运来实现。在玉蕊迁地保育过程中，可将盐度作为立地选择的一个重要因素，同时在热带亚热带地区进行半红树林人工造林时应选择高潮位、中低盐度区域种植玉蕊。

Effects of salt stress on growth of Barringtonia racemosa and absorption and translocation of mineral elements in it

【Objective】 In order to explore the effects of salt stress on the growth of Barringtonia racemosa seedlings and the absorption and translocation of mineral elements, study salt stress tolerance of B. racemosa from the perspective of ion transport mechanism, and to provide protection, ex situ conservation, promotion and utilization of B. racemosa wild populations, and site selection during afforestation scientific basis.【Method】 This study used two-year-old B. racemosa seedlings as the test material, and adopted an automatic tide simulation all-diurnal tide device. This study set up 7 salt stress treatment groups, namely 0(CK), 15‰, 20‰, 25‰, 30 ‰, 35‰, 40‰, and comprehensively analyzed absorption, translocation coefficients and correlation of mineral elements calcium(Ca), magnesium(Mg), iron(Fe), chlorin(Cl) and sodium(Na) in B. racemosa roots, stems and leaves under salt stress.【Result】 B. racemosa plants grew well under low salinity(0-15‰) stress conditions, and high salinity(30‰-40‰) salt stress conditions caused rapid leaf shedding and reduces in biomass, which severely inhibited the growth and development of B. racemosa plants. Salt stress increased the accumulation of Na and Cl in B. racemosa plants, absorption of Ca and Mg in the roots of B. racemosa seedlings decreased, while the leaf parts increased the absorption of Ca, Mg, and Fe. There is no significant change in the absorption of Ca, Mg and Fe in stem parts. Under salt stress, the translocation coefficient of B. racemosa seedlings for Ca, Mg, and Cl were all greater than 1.0, the translocation coefficient for Fe was less than 1.0, and the translocation coefficient for Na was greater than 1.0 when the salinity was 35‰-40‰. There was a negative correlation between the biomass and the above-ground elements, and the leaf abscission rate, root-shoot ratio and the above-ground elements were all positively correlated.【Conclusion】 The seedlings of B. racemosa grow well in the water salinity range of 0-15‰ under the environment of full-day tide flooding for 6 h/d, and have certain tolerance in the range of 20‰-25‰ salinity. When the water salinity is ≥30‰, B. racemosa seedlings cannot grow normally. The salt tolerance is mainly achieved by the accumulation of Na in the root system, restricting the transportation of Na to the stems and leaves, and enhancing the transport of Ca, Mg, Fe, and Cl to the stems and leaves. In the process of ex situ conservation of B. racemosa, the salinity level can be used as an important factor in site selection. At the same time, when semi-mangrove plantation in tropical and subtropical areas is carried out, B. racemosa should be planted in areas with high tide and medium and low salinity.