小盐芥营养器官的结构特点与其盐渍环境的关系研究

利用石蜡切片法研究了盐生植物小盐芥(Thellungiella halophila)营养器官的解剖结构。结果表明：小盐芥根的初生结构中表皮细胞为1层,且细胞大而高度液泡化,根毛数量较少;皮层仅由外皮层和内皮层2层细胞构成,细胞大,排列紧密;根次生维管组织发达。茎的初生结构中外剀维管束8～10束,大小不等,呈一轮排列;髓和髓射线发达;茎次生结构中维管组织也很发达。根和茎的这些结构特点提高了植物体吸收、运输水分的能力,而且根的特殊结构和输导系统将盐分限制在根内,适应于盐渍环境所造成的渗透胁迫和干旱胁迫。小盐芥叶片较小,上、下表皮细胞各1层,细胞大而高度液泡化,叶肉中栅栏组织与海绵组织分化不明显,但叶绿体体积大、数目多,细胞间隙较大,通气性能好,光合效率高。这些特点对其适应干旱盐渍环境有重要意义。小盐芥上述结构特征与典型真盐生植物、旱生植物相去其远,其营养器官内也无盐腺、囊泡等泌盐结构。由此推论,小盐芥更倾向于似盐生植物(拒盐植物)。     

盐生植物种子萌发对环境的适应对策

盐生环境是一种严峻的胁迫环境,对植物的生长、发育、繁殖等生活史的各阶段都产生着重要的影响。盐生植物是生长在盐渍土壤上的一类天然植物区系,它们在长期的进化过程中形成了一系列适应盐生生境的特殊生存策略。一般情况下,盐生植物种子对环境的适应能力,是植物对盐生环境适应性的重要体现;而植物发育早期对盐度的适应能力又是决定物种分布和群落组成的关键因素。在对国内外相关文献进行分析归纳的基础上,从盐分对种子萌发的影响机理及植物种子萌发对盐生环境的适应对策两个方面综述了植物种子休眠萌发与盐生环境的关系。     

盐生植物角果碱蓬种子二型性对环境的适应策略

角果碱蓬(Suaeda corniculata)是藜科一年生盐生植物, 在我国分布于北方盐碱滩涂和盐碱荒漠地区。角果碱蓬具有棕色和黑色两种异型体种子(简称棕色和黑色种子)。对采自内蒙古鄂托克前旗盐渍化生境的角果碱蓬二型种子的形态、休眠和萌发特性开展对比研究, 测定了二型种子休眠和萌发行为对温度、光照和盐分(NaCl)的响应, 以揭示盐生植物异型种子对温带盐漠生境的适应对策。结果表明: (1)二型性种子在大小、种皮特性和结实比例方面有显著差异。与黑色种子相比, 棕色种子个体较大, 种皮透水性强。黑色种子与棕色种子的结实比例约为5.6 : 1。(2)新成熟的棕色种子的萌发对各温度梯度和光照条件不敏感, 萌发率较高(84%-100%); 而新成熟的黑色种子萌发率较低(8%-78%), 萌发对光照敏感。(3)黑色种子具有浅度生理休眠, 种皮划破、赤霉素处理和低温层积均可有效地提高种子的萌发率。(4)二型种子萌发对土壤盐分的胁迫具有不同的响应。与黑色种子相比, 棕色种子对盐分胁迫不敏感, 在较高的盐分浓度下仍有较高的萌发率, 低温层积处理能够降低黑色种子对盐胁迫的敏感性, 有效地提高种子的初始萌发率、萌发恢复率和最终萌发率。角果碱蓬二型种子不同的形态、休眠和萌发特性, 提高了该物种在高度异质性生境中的适合度, 对种群成功地适应温带盐漠环境具有重要的意义。     

北疆荒漠几种盐生(耐盐)植物抗逆附属结构的初步研究

利用石蜡切片、扫描电镜、临时装片等方法,对北疆荒漠的3种藜科植物—灰绿藜、费尔干猪毛菜、蒙古猪毛菜和1种菊科植物—花花柴的表皮附属结构进行了显微和超微观察研究。结果表明:(1)对四种植物的解剖结构观察显示,其叶片都含有角质层;气孔器下陷;茎中含有大量的维管束;多数种的细胞中含有簇状晶体结构;(2)四种植物表皮附属结构研究表明:花花柴表皮具有多细胞组成的盐腺和表皮毛结构;灰绿藜表皮有大量囊泡结构;蒙古猪毛菜叶表皮有短硬毛和乳突状结构;费尔干猪毛菜表皮具大量表皮毛,且表皮毛有节。上述结构和特征反映出不同植物对干旱、盐碱土生境适应的多样性,也为旱生和盐生植物的生理学研究提供了新的实验依据。     

Seasonal and Spatial Variation in Nematode Communities in a Negev Desert Ecosystem

Seasonal and spatial variation in soil nematode communities was investigated in a field study conducted on a loessial plain in the northern Negev Desert, Israel. Soil samples from 0- to 50-cm depths were collected seasonally during 2001 under the canopy of Atriplex halimus and Hammada scoparia, and between shrubs (control). Total population abundance ranged from 8 to 887 individuals per 100 g soil, represented by 32 genera from 16 families. Significant temporal and vegetation effects were elucidated using most ecological indices applicable to express nematode community composition. Of those indices computed, only the Shannon index, the modified maturity index, and genus dominance distinguished differences in vertical distribution.     

The use of halophytic plants for salt phytoremediation in constructed wetlands

This research studied the use of constructed wetlands (CWs) to reduce water salinity. For this purpose, three halophytic species of the Chenopodiaceae family (Salicornia europaea, Salsola crassa, and Bienertia cycloptera) that are resistant to saline conditions were planted in the CWs, and experiments were conducted at three different salinity levels [electrical conductivity (EC)～2, 6, 10 dS/m]. EC and concentrations of calcium (Ca), magnesium (Mg), sodium (Na), and chlorine (Cl) were measured before and after phytoremediation with a retention time of 1 week. The results suggested that these plants were able to grow well and complete their life cycles at all the salinity levels within this study. Moreover, these plants reduced the measured parameters to acceptable levels. Therefore, these plants can be considered good options for salt phytoremediation.     

Epidermal bladder cells confer salinity stress tolerance in the halophyte quinoa and Atriplex species

Epidermal bladder cells (EBCs) have been postulated to assist halophytes in coping with saline environments. However, little direct supporting evidence is available. Here, Chenopodium quinoa plants were grown under saline conditions for 5 weeks. One day prior to salinity treatment, EBCs from all leaves and petioles were gently removed by using a soft cosmetic brush and physiological, ionic and metabolic changes in brushed and non‐brushed leaves were compared. Gentle removal of EBC neither initiated wound metabolism nor affected the physiology and biochemistry of control‐grown plants but did have a pronounced effect on salt‐grown plants, resulting in a salt‐sensitive phenotype. Of 91 detected metabolites, more than half were significantly affected by salinity. Removal of EBC dramatically modified these metabolic changes, with the biggest differences reported for gamma‐aminobutyric acid (GABA), proline, sucrose and inositol, affecting ion transport across cellular membranes (as shown in electrophysiological experiments). This work provides the first direct evidence for a role of EBC in salt tolerance in halophytes and attributes this to (1) a key role of EBC as a salt dump for external sequestration of sodium; (2) improved K⁺ retention in leaf mesophyll and (3) EBC as a storage space for several metabolites known to modulate plant ionic relations.     

High phenotypic plasticity of Suaeda maritima observed under hypoxic conditions in relation to its physiological basis

Background and Aims

Phenotypic plasticity, the potential of specific traits of a genotype to respond to different environmental conditions, is an important adaptive mechanism for minimizing potentially adverse effects of environmental fluctuations in space and time. Suaeda maritima shows morphologically different forms on high and low areas of the same salt marsh. Our aims were to examine whether these phenotypic differences occurred as a result of plastic responses to the environment. Soil redox state, indicative of oxygen supply, was examined as a factor causing the observed morphological and physiological differences.

Methods

Reciprocal transplantation of seedlings was carried out between high and low marsh sites on a salt marsh and in simulated tidal-flow tanks in a glasshouse. Plants from the same seed source were grown in aerated or hypoxic solution, and roots were assayed for lactate dehydrogenase (LDH) and alcohol dehydrogenase, and changes in their proteome.

Key Results

Transplanted (away) seedlings and those that remained in their home position developed the morphology characteristic of the home or away site. Shoot Na⁺, Cl⁻ and K⁺ concentrations were significantly different in plants in the high and low marsh sites, but with no significant difference between home and away plants at each site. High LDH activity in roots of plants grown in aeration and in hypoxia indicated pre-adaptation to fluctuating root aeration and could be a factor in the phenotypic plasticity and growth of S. maritima over the full tidal range of the salt marsh environment. Twenty-six proteins were upregulated under hypoxic conditions.

Conclusions

Plasticity of morphological traits for growth form at extremes of the soil oxygenation spectrum of the tidal salt marsh did not correlate with the lack of physiological plasticity in the constitutively high LDH found in the roots.     

异子蓬二型性种子的种皮结构及离子含量差异

异子蓬(Borszczowia aralocaspica)是中亚荒漠区系特有的一年生盐生植物,其种子具有二型性。通过检测异子蓬二型性种子中的生理生化物质以及观察种皮的结构,比较异子蓬二型性种子中营养物质、养分全量以及种皮结构的差异,结果表明:(1)异子蓬的棕色种子只有一层薄种皮,而黑色种子不但具有一层薄的内种皮还有一层坚硬致密的外种皮;(2)棕色种子的质量大、质量频数分布较为集中,并且吸水迅速,在吸水率较低时就能够大量萌发;(3)棕色种子的可溶性糖、可溶性蛋白质、全氮、全磷以及K+、Na+、K+/Na+和Mg2+/Na+都显著高于黑色种子。说明在繁殖子代、产生二型性种子时,异子蓬对棕色种子和黑色种子之间的繁殖投入存在着巨大的差异,这可能是导致异子蓬二型性种子产生差异性萌发机制的重要原因。     

种植碱蓬和秸秆覆盖对沿海滩涂极重度盐土盐分动态与脱盐效果的影响

为探明沿海滩涂极重度盐土盐分动态规律及其影响因子,并探讨盐生植被和秸秆覆盖下土壤的脱盐及控盐效果,2014年5月—2015年5月,在江苏沿海滩涂极重度盐土中进行田间试验,设置4种处理:对照(裸地,CK)、种植碱蓬(PS)、15 t·hm^-2秸秆覆盖(SM-A)和30t·hm^-2秸秆覆盖(SM-2A),监测气候因子和土壤盐分的动态变化.结果表明:(1)滩涂裸地表层土壤盐分具有显著的季节性变化特征,表现为在6—8月盐分降低至最低值(8.69g·kg^-1),9—12月呈现积盐作用,最大值为26.66 g·kg^-1;表层土壤盐分变化比亚表层更剧烈,而且亚表层盐分变化相对于表层具有一定的滞后性;(2)相关分析表明,滩涂裸地表层盐分变化与采样前15 d的累积降雨量及蒸降比具有显著的线性关系;多因子及互作逐步分析表明,降雨量增加可以显著促进脱盐作用,大气温度升高可加剧盐分积累,降雨量和大气温度的互作效应增加会对盐分累积产生正效应;(3)PS处理没有显著改变土壤盐分的季节性变化规律,但降低了表层土壤盐分;(4)SM-A和SM-2A条件下,土壤脱盐率与覆盖处理天数回归拟合符合Logistic曲线,且经过雨季覆盖处理90~100 d后表层土壤脱盐率均可达到95.0%以上,覆盖处理120 d后亚表层土壤脱盐率均可达到92.0%以上,之后表层和亚表层土壤盐分分别在0.60和1.00 g·kg^-1以下波动.综合考虑脱盐效果和经济投入,在梅雨季节前(4—5月)采用15 t·hm^-2秸秆覆盖,可能是未来滩涂极重度盐土进行快速脱盐和改良的重要措施.