Responses of apical ion fluxes to NaCl stress in Elaeagnus angustifolia seedlings

Aims Elaeagnus angustifolia is one of the most salt-tolerant species. The objective of this study was to understand the mechanisms of ion transporation in E. angustifolia exposed to different salt concentrations through manipulations of K⁺/Na⁺ homeostasis.
Methods Seedlings of two variants of the species, Yinchuan provenance (YC, salt-sensitive type) and the Alaer provenance (ALE, salt-tolerant type), were treated with three different NaCl application modes, and the ion fluxes in the apical regions were measured using non-invasive micro-test technology (NMT). In mode 1, Na⁺ and K⁺ fluxes were measured after 150 mmol·L^-1 NaCl stress lasted for 24 h. In mode 2, K⁺ and H⁺ fluxes were quantified with a transient stimulation of NaCl solution. In mode 3, Amiloride (Na⁺/H⁺ antiporters inhibitor) and tetraethylammonium (TEA, K⁺ channel inhibitor) was used to treat apical regions of E. angustifolia seedlings after NaCl stress for 24 h, respectively.
Important findings Under NaCl stress for 24 h, net effluxes of Na⁺ and K⁺ were increased significantly. The net Na⁺ effluxes of YC provenance seedlings (720 pmol·cm^-2•s^-1) were lower than that of ALE provenance (912 pmol·cm^-2·s^-1), but the net K⁺ efflux was higher in YC provenance. Under the instantaneous NaCl stimulation, net K⁺ efflux was remarkably increased, with the net K⁺ efflux of YC provenance always higher than that of ALE provenance. Interestingly, H⁺ at the apical regions was found from influx to efflux, with the net H⁺ efflux of ALE provenance greater than that of the YC provenance. Under the NaCl and NaCl + Amiloride treatment, the net Na⁺ efflux of ALE provenance seedlings was higher than that of YC provenance, while the net K⁺ efflux was less in ALE provenance seedlings. On the other hand, the differences in net Na⁺ and K⁺ effluxes were insignificant between the two provenances under the control group and NaCl + TEA treatment. In conclusion, NaCl stress caused Na⁺ accumulation and K⁺ outflows of E. angustifolia seedlings; The E. angustifolia seedlings utilize Na⁺/H⁺ antiporters to reduce Na⁺ accumulation by excretion; and the maintenance of K⁺/Na⁺ homeostasis in salt-tolerant E. angustifolia provenance seedlings roots accounted for a greater Na⁺ extrusion and a lower K⁺ efflux under NaCl stress. Results from this study provide a theoretical basis for further exploring salt-tolerant E. angustifolia germplasm resource.     

Molecular Cytogenetic Characterization of a Wheat - Leymus mollis 3D（3Ns） Substitution Line with Resistance to Leaf Rust

Leymus mollis （Trin.） Pilger （NsNsXmXm, 2n = 28）, a wild relative of common wheat, possesses many potentially valuable traits that could be transferred to common wheat during breeding programs. In this study, the karyotypic constitution of a wheat - L. mollis 3D（3Ns#1） disomic substitution line isolated from the F5 progeny of octoploid Tritileymus M842-16 x Triticum durum cv. D4286, which was designated as 10DM57, was determined using genomic in situ hybridization （GISH）, fluorescent in situ hybridization （FISH）, SSR markers, and EST- STS markers. Screening of mitosis and meiosis showed that 10DM57 had a chromosome karyotype of 2n = 42 =21Ⅱ. GISH indicated that 10DM57 was a line with 40 chromosomes from wheat and two of the Ns chromosomes from L. mollis, which formed a ring bivalent in pollen mother cells at metaphase I. FISH analysis showed that the chromosome 3D may be replaced by 3Ns#1 in 10DM57. DNA markers, including SSR and EST-STS primers, showed that the pair of wheat chromosome 3D in 10DM57 was substituted by the pair of chromosome 3Ns#t from L. mollis. Evaluation of the agronomic traits showed that, compared with its common wheat relative 7182, 10DM57 was resistant to leaf rust while the spike length and number of spikes per plant were improved significantly, which correlated with a higher wheat yield. The new germplasm, 10DM57, could be exploited as an intermediate material in wheat genetic and breeding programs.     

山西牛奶子群落优势种种间关联性研究

基于2×2联列表,应用方差比率法、χ2检验、Pearson相关系数及Spearman秩相关系数检验等数量分析方法对山西牛奶子群落的25个优势种,共300个种对间的关联性进行分析研究。结果表明,25个优势种群的总体种间关联性呈不显著关联,种的分布相对独立。χ2检验结果有121个种对呈正相关,155个种对呈负相关,正负关联比为0.78;Pearson相关系数检验有111个种对呈正相关,189个种对呈负相关,正负关联比为0.59;Spearman秩相关系数检验有128个种对呈正相关,172个种对呈负相关,正负关联比为0.74;Spearman秩相关系数比Pearson相关系数的检验方法灵敏度更高。山西牛奶子群落总体上呈不显著负关联,表明其处于演替过程的初期。     

土壤水分对翅果油树幼苗生理生化特性的影响

通过盆栽试验,研究了土壤水分含量对翅果油树幼苗地上部分和根系生物量和含水量,以及叶片保水力、相对电导率和保护酶活性的影响.结果表明:与对照(处理前)相比,各土壤水分条件下翅果油树幼苗叶片保水力均降低,而叶片相对电导率(REC)、超氧化物歧化酶(SOD)和过氧化物酶(POD)活性均升高.随着土壤含水量的降低,幼苗地上部分和根系的生物量、含水量及叶片保水力均呈先升高后降低的趋势,而叶片REC、SOD和POD活性均呈先降低后升高趋势,并均以轻度干旱胁迫处理(田间持水量的55%~60%)的REC、SOD和POD活性最低,而叶片保水力最高.在相同土壤水分条件下,随着处理时间的延长,叶片REC逐渐升高,而叶片保水力降低,SOD和POD活性先升后降并以处理10d时活性最高.研究发现,在轻度干旱胁迫下,翅果油树幼苗能协调其保护酶系统降低干旱伤害,维持正常生长,表现出一定的抗旱能力.     

翅果油树群落优势种群生态位分析

应用Shannon-Weaver指数和Petraitis的方法,研究了山西翅果油树群落21个优势种群的生态位宽度和生态位普遍重叠和特定重叠,结果表明：翅果油树和黄刺玫的生态位宽度最大,这主要是由于它们具有广泛的适应性。翅果油树在其它种群上的特定重叠远远小于其余20种植物在翅果油树群种上的特定重叠值。21个优势种群之间并不存在完全的普遍重叠。主要与它们对水分和光照不同的适应性有关。草本植物之间的特定重叠大于灌木。21种植物仅有4个种对(本氏针茅和野古草、野古草与本氏针茅、本氏针茅与多花枸子木和金花忍冬与白刺花)之间存在完全的特定重叠。     

山西南部翅果油树种群动态与谱分析

从种群生态方面,探讨山西南部濒危树种——翅果油树（Elaeagnus mollis Diels）的濒危机制,具有重要的科学价值。本文利用生存分析理论研究了翅果油树种群径级结构,编制了特定时间生命表,并绘制存活曲线、死亡曲线等曲线,同时又分析了生存率、积累死亡率和死亡密度等生存函数;而且应用谱分析理论分析了翅果油树种群的周期性。结果表明：（1）径级结构分析说明翅果油树种群属于增长型。（2）生命表分析表明,翅果油树种群损失度动态趋势和死亡率变化基本相似,呈现波动变化。存活曲线经统计检验更趋于DeeveyⅡ型。生命期望在17～21 cm径级出现高峰,说明此径级阶段翅果油树的生存质量相对较高。（3）生存函数分析表明,积累死亡率单调增加,生存率单调下降,其增加或下降幅度是前期高于后期。死亡密度函数曲线和死亡曲线变化趋势基本一致,危险率函数曲线也和死亡率变化趋势一致。（4）谱分析表明在自然更新过程中翅果油树种群动态表现出大周期内的小周期迭加现象,并且受基波的影响较大。     

Nodulation and nitrogenase activity in nitrogen-fixing woody plants stimulated by CO2 enrichment of the atmosphere

The responses of three species of nitrogen-fixing trees to CO₂ enrichment of the atmosphere were investigated under nutrient-poor conditions. Seedlings of the legume, Robinia pseudoacacia L. and the actinorhizal species, Alnus glutinosa (L.) Gaertn. and Elaeagnus angustifolia L. were grown in an infertile forest soil in controlled-environment chambers with atmospheric CO₂ concentrations of 350 μl ⁻¹ (ambient) or 700 μl ⁻¹. In R. pseudoacacia and A. glutinosa , total nitrogenase (N₂ reduction) activity per plant, assayed by the acetylene reduction method, was significantly higher in elevated CO₂, because the plants were larger and had more nodule mass than did plants in ambient CO₂. The specific nitrogenase activity of the nodules, however, was not consistently or significantly affected by CO₂ enrichment. Substantial increases in plant growth occurred with CO₂ enrichment despite probable nitrogen and phosphorus deficiencies. These results support the premises that nutrient limitations will not preclude growth responses of woody plants to elevated CO₂ and that stimulation of symbiotic activity by CO₂ enrichment of the atmosphere could increase nutrient availability in infertile habitats.     

Biomass partitioning and water content relationships at the branch and whole-plant levels and as a function of plant size in Elaeagnus mollis populations in Shanxi, North China

Understanding of the biomass (dry weight) allocation and water relations in populations will provide useful information on the growth patterns and resource-allocation dynamics. By destructive sampling, foliage, branch and root biomass were measured in the endangered shrub Elaeagnus mollis populations growing in Shanxi province, North China. Biomass partitioning and water content relationships were compared at the branch and whole-plant levels, and as a function of basal diameter (plant size). The biomass was mainly distributed in the bigger branches at the branch level, and in the branch wood at the whole-plant level, and branch biomass (but not foliage or root biomass) increases significantly with increasing basal diameter. As a result, branch wood became the major biomass pool, even though considerable biomass was also allocated to the roots. However, the relative water content decreased from the periphery of the crown to the interior of the shrub at the branch level, and from the aboveground to the belowground at the whole-plant level though no significant variation among foliage, branches, and roots. Yet it increased significantly for the whole-plant with increasing basal diameter. The ratio of belowground to aboveground biomass was smaller than 1.0, even as a function of basal diameter. These growth responses indicated a strong adaptation to the shrub’s growing conditions. Biomass was primarily allocated above the ground and the aboveground components grew faster than the belowground one.     

干旱胁迫对沙枣和孩儿拳头的生理特性的影响

以沙枣和孩儿拳头2年生盆栽苗为材料,采用称重控水的方法对4个梯度土壤干旱胁迫条件对沙枣和孩儿拳头生理特性的影响进行了研究.结果显示:(I)干旱胁迫造成了两物种体内水分的严重亏缺,重度胁迫(6.4%～8.0%)下,两物种自然饱和亏为对照的3～4倍;同一干旱胁迫梯度下沙枣自然饱和亏总高于孩儿拳头,但水分临界饱和亏和需水程度低于孩儿拳头;沙枣自由水含量随干旱胁迫加剧下降幅度较大,自由水向束缚水转化率较高;沙枣最高水势的下降幅度低于孩儿拳头,最低水势的下降幅度高于孩儿拳头,且沙枣的绝对水势比孩儿拳头低.(2)随着干旱胁迫程度的加剧,两物种叶片中的脯氨酸含量、可溶性总糖含量均有不同程度的增加,特别是在重度干旱胁迫下,脯氨酸含量高出对照4倍多,且孩儿拳头脯氨酸含量明显高于沙枣,但可溶性总糖含量低于沙枣;沙枣本身的可溶性蛋白含量较孩儿拳头高,随干旱胁迫的加重沙枣的可溶性蛋白含量先增加后下降,而孩儿拳头逐渐下降.结果表明,沙枣和孩儿拳头对干旱胁迫均具有积极的水分生理响应方式,推测两种植物的水分耐受极限为6.4%～8.0%,但物种间生理响应方式存在差异,沙枣较孩儿拳头具有更强的防御干旱的生理机制.     

沙枣组织脱分化培养与快繁体系建立的研究

研究了以沙枣的种子为外植体诱导形成愈伤组织以及植株再生的过程,对培养中出现的愈伤组织和不定芽的类型进行了探讨。通过正交试验及单因素试验方法,确定了沙枣快繁体系的最适培养方案：①诱导材料：苗期为10 d的沙枣无菌苗子叶;②有效愈伤组织诱导培养基：MS+NAA 0.5 mg·L^-1+BA 2.0 mg·L^-1+3%蔗糖;③有效芽的分化培养基：MS+NAA 0.1 mg·L^-1+BA1.0 mg·L^-1+3% 蔗糖;④壮苗培养基：MS+NAA 0.1mg·L^-1+BA 1.0 mg·L^-1+GA 30.2 mg·L^-1+3%蔗糖;⑤生根培养基：1/2MS+ABT生根粉（1号）1.0 mg·L^-1+1.5%蔗糖。