Phenotypic plasticity and genetic differentiation of quantitative traits in genotypes of Leymus chinensis

Aims Adaptation mechanisms of plants to environment can be classified as genetic differentiation and phenotypic plasticity (environmental modification). The strategy and mechanism of plant adaptation is a hot topic in the field of evolutionary ecology. Leymus chinensis is one of constructive species in the Nei Mongol grassland. Particularly, Leymus chinensis is a rhizomatous and clonally reproductive grass, a genotype that can play an important role in the community. In this study, we aimed to (1) investigate the phenotypic plasticity of L. chinensis under different conditions, and (2) test the genetic differentiation and reaction norms (the relationship between the environment and the phenotype of an individual or a group of individuals) under four environmental conditions among different genotypes of L. chinensis. Methods Ten genotypes of L. chinensis were randomly selected. Under the control condition, we studied the effects of genotype, defoliation, drought and their interactions on 11 quantitative traits of growth (8 traits including photochemical efficiency of photosystem II, maximum net photosynthetic rate, transpiration rate, specific leaf area, relative growth rate, the number of tillers increased, aboveground and underground biomass growth), defense (total phenol concentration of leaf) and tolerance (non-structural carbohydrate content of root, root/shoot ratio) of L. chinensis. We studied the phenotypic plasticity, genetic differentiation and reaction norms mainly through tested the effect of environment and genotype on these traits. Important findings First, all 11 traits showed obvious phenotypic plasticity (i.e., significant effect of drought, defoliation and their interactions). The expression of 10 genotypes of L. chinensis was divergent under different environmental conditions. Interactions of genotype and environment significantly affected the maximum net photosynthetic rate, transpiration rate, specific leaf area, relative growth rate, total phenolic concentration of leaf, and total non-structural carbohydrate content of root. This indicated that the phenotypic plasticity of these five traits exhibited genetic differentiation. Second, the increase of number of tillers, belowground biomass and non-structural carbohydrate content of root did not show genetic differentiation under the same condition. The other eight traits showed significantly genetic differentiation, and the heritabilities (H²) of six traits related to growth were higher than 0.5. The leaf total phenol concentration and root/shoot ratio showed genetically differentiation only under the drought and defoliation condition, with the heritabilities being 0.145 and 0.201, respectively. These results explained why L. chinensis widely distributed in the Nei Mongol grassland, and provided genetic and environmental basis for related application and species conservation in this grassland ecosystem.     

Plastic responses of stem and leaf functional traits in Leymus chinensis to long-term grazing in a meadow steppe

植物对不同功能性状进行权衡, 通过表型可塑性达到对异质生境的适应是植物的一种生态对策。羊草(Leymus chinensis)是欧亚温带草原东缘的主要优势植物, 研究其对放牧的表型反应对揭示草原生态系统的放牧响应机制具有代表意义。该文以内蒙古呼伦贝尔草甸草原为例, 通过设置不同放牧压力与围封的长期试验, 研究了羊草茎叶功能性状对放牧的可塑性响应模式。结果表明: 1)与长期围封相比, 长期放牧导致羊草茎叶性状显著小型化, 其中, 株高和个体地上生物量分别降低76.82%和89.88%, 但3年短期围封对茎性状影响不显著, 说明羊草表型矮小化现象具有一定的保守性; 2)通过排序构建羊草性状可塑性变化谱, 发现茎质量、总质量、茎高、株高、叶面积等为对放牧响应的敏感性状, 而叶片数、茎粗、叶宽等较为稳定, 为惰性性状; 3)放牧干扰下, 羊草性状可塑性程度与其变异性之间符合y = y₀ + ae^bx拟合关系, 随着植物性状的响应强度增大, 其变异性增强; 4)偏最小二乘法分析发现茎长、株高、叶面积、叶长等性状的投影重要性指标大于1, 对地上生物量变化的解释率为68.6%, 是导致长期放牧下羊草个体生物量降低的主要因子。研究认为, 矮化型变是羊草的避牧适应对策, 在亚稳态下, 通过不同性状的权衡, 充分利用环境资源完成其生活史。     

Effects of nitrogen addition on photosynthetic characteristics of Leymus chinensis in the temperate grassland of Nei Mongol,China

Aims The increased atmospheric nitrogen (N) deposition due to human activity and climate change greatly causes grassland ecosystems shifting from being naturally N-limited to N-eutrophic or N-saturated, and further affecting the growth of grass species. The aims of this study are: 1) to evaluate the effects of different N addition levels on morphology and photosynthetic characteristics of Leymus chinensis; 2) to determine the critical N level to facilitate L. chinensis growth.
Methods We conducted a different N addition levels experiment in dominant species in the temperate steppe of Nei Mongol. The aboveground biomass, morphological and leaf physiological traits, pigment contents, chlorophyll a fluorescence parameters and biochemical parameters of L. chinensis were investigated.
Important findings Our results showed that aboveground biomass first increased and then decreased with the increased N, having the highest values at the 10 g N·m^-2·a^?1 treatment, but the 25 g N·m^-2·a^?1 still significantly increased the aboveground biomass relative to 0 g N·m^-2·a^?1. Leymus chinensis accommodate low N situation through allocating less N to carboxylation system and decreasing leaf mass per area (LMA) in order to get more light energy. Moderate N addition captured more light energy through increasing total chlorophyll (Chl) contents and decreasing the ratio of Chl a/b. Moderate N addition increased LMA, carboxylation efficiency, maximum carboxylation rate (V_cmax), maximum electron transport rate (J_max) and decreased J_max/V_cmax, thus allocating more N to carboxylation system to enhance carboxylation capability. Moreover, the photochemical activity of PSII was increased through higher effective quantum yield of PSII photochemistry, electron transport rate and photochemical quenching coefficient. Excessive N addition had negative effects on physiological variables of L. chinensis due to lower carboxylation capability and photochemical activity of PSII, further leading to decreased net photosynthetic rate, whereas increased non-photochemical quenching coefficient and carotenoids played the role in the dissipation of excess excitation energy. Overall, moderate N addition facilitated the photosynthetic characteristics of dominant species, but excessive N addition inhibited photosynthetic characteristics. The most appropriate N addition for the growth of L. chinensis was 5-10 g N·m^-2·a^?1 in the temperate steppe of Nei Mongol, China.     

Response and correlation of above- and below-ground functional traits of Leymus chinensis to nitrogen and phosphorus additions

AimsLeymus chinensis is a constructive and dominant species in typical steppe of northern China. The structure and functions of L. chinensis grassland ecosystem has been degenerated seriously due to long-term overgrazing in recent decades. As an effective measure to restore the degraded grasslands, the effects of nutrient addition on plant growth and ecosystem structure and functioning have been paid more attention in manipulation experimental research. The effects of nutrient addition, especially P addition on the above- and below-ground functional traits of L. chinensis have rarely been studied; particularly the underpinning mechanisms remain unclear. Our objective is to examine the responses and adaptive mechanisms of L. chinensis to different levels of N and P additions. MethodsWe conducted a culture experiment in the greenhouse, with three levels of N (50, 100 and 250 mg N·kg^-1) and P (5, 10 and 25 mg P·kg^-1) addition treatments. The above- and below-ground biomass, leaf traits (e.g., specific leaf area, leaf N and P contents) and root traits (e.g., specific root length, root N and P contents) of L. chinensis were determined in this study.Important findings Our results showed that: 1) the aboveground biomass and total biomass of L. chinensis were mostly affected by N addition, while the belowground biomass was mainly affected by P addition. N addition greatly enhanced the aboveground biomass of L. chinensis, while P addition reduced the belowground biomass at the moderate and high N levels. The root-shoot ratio of L. chinensis was influenced by both N and P additions, and root-shoot ratio decreased with increasing N and P levels. N and P additions promoted more biomass and N and P allocations to aboveground and leaf biomass. 2) Leymus chinensis showed different responses and adaptive mechanisms to P addition at low and high N levels. At low N level, L. chinensis exhibited high photosynthetic rate and specific root length (SRL) to improve photosynthetic capacity and root N acquisition, which promoted aboveground biomass. High root P content was favorable for belowground biomass. At high N level, P addition did not significantly affect plant growth of L. chinensis, even reduced its belowground biomass. Leymus chinensis showed high specific leaf area (SLA) and SRL to improve light interception and N acquisition in order to maintain stable aboveground biomass. 3) P addition greatly impacted below-ground than above-ground functional traits. SLA exhibited a weakly positive correlation with SRL, indicating L. chinensis exhibited relatively independence of resource acquirement and utilization between leaf and root functional traits.     

Effects of drought stress on the osmotic adjustment and active oxygen metabolism of Phoebe zhennan seedlings and its alleviation by nitrogen application

以二年生桢楠(Phoebe zhennan)幼树为研究对象, 采用盆栽控水的方法, 探讨了桢楠幼树在干旱胁迫下渗透调节和活性氧代谢的变化, 以及施氮对桢楠幼树应对干旱胁迫能力的影响。试验先将土壤含水量调整到4个梯度(田间持水量的80% (80% FC)、50% FC、30% FC和15% FC), 1周后测定受胁迫植株的相关生理指标, 之后进行3个水平的施氮处理(对照N0, 中氮MN, 高氮HN, 各施氮量分4次(即干旱梯度形成后第7、14、21和28天)分别施入)。在施氮结束后30天(即开始施肥处理后51天)再次测定各项生理指标。结果表明: 1)干旱处理7天后, 桢楠叶片中游离脯氨酸(Pro)和可溶性糖(SS)含量均随胁迫强度增大而显著增加, 重度干旱(15% FC)下的Pro含量增加尤为明显, 可溶性蛋白(SP)含量则呈先增加后降低的趋势。施氮后, 各种土壤水分状态下的Pro含量进一步增加。水分充足和轻度干旱MN水平下, SS含量也增加, 而在中度和重度干旱下的SS含量显著降低, HN水平各干旱状态下SS含量变化均不显著。施氮结束后30天时, 80% FC和50% FC下的SP含量表现为施氮组低于对照组, 而30% FC和15% FC下则相反。2)施氮前随着干旱胁迫的增强, 桢楠幼树叶片中过氧化氢(H₂O₂)含量、超氧化物歧化酶(SOD)活性、过氧化氢酶(CAT)活性显著上升, 而过氧化物酶(POD)活性呈先上升后下降的趋势。施氮后, H₂O₂含量总体上表现为减少趋势, 且MN水平下降幅度最大, HN水平反而不利于降低H₂O₂的含量。3种酶活性的变化则因干旱程度和施氮水平的不同而呈现出不同的变化趋势。3)施氮前随着干旱胁迫的增强, 叶片丙二醛(MDA)含量呈显著上升趋势, 相对电导率(REC)先显著下降后显著上升; 施氮后, 除重度干旱胁迫外, 其他各干旱处理植株的MDA含量都表现为在MN水平下有所下降, 而在HN水平下有所回升, 但在重度干旱时, 无论是MN或HN处理, MDA含量均呈上升趋势, 表明在重度干旱胁迫下, 难以通过施氮的方式缓解干旱胁迫产生的伤害。4)双因素方差分析显示, 施氮与干旱胁迫间具有极显著的交互效应。以上结果表明: 施一定量的氮肥有利于缓解桢楠幼树受到的干旱胁迫, 以年施氮量计, 施中氮(N元素质量为1.35 g·株 ^-1)对除重度干旱外的干旱胁迫具有一定的缓解作用, 但施高氮(N元素质量为2.70 g·株 ^-1)时反而会对植株造成不利影响。     

黄土高原冰草叶片抗坏血酸和谷胱甘肽合成及循环代谢对干旱胁迫的生理响应

通过盆栽实验, 对干旱胁迫下黄土高原地区冰草(Agropyron cristatum)叶片的抗坏血酸和谷胱甘肽合成及循环代谢相关酶及物质含量进行了研究。结果表明: 冰草可以通过增强叶片的抗坏血酸和谷胱甘肽合成及循环代谢酶: 抗坏血酸过氧化物酶、谷胱甘肽还原酶、脱氢抗坏血酸还原酶、单脱氢抗坏血酸还原酶、L-半乳糖酸-1, 4-内酯脱氢酶和γ-谷氨酰半胱氨酸合成酶活性, 维持植物体内抗坏血酸和谷胱甘肽水平及氧化还原状态, 从而抵御干旱造成的氧化胁迫。但叶片抗坏血酸和谷胱甘肽合成及循环代谢对不同水平干旱胁迫的响应, 随胁迫时间的延长而不同。在胁迫24天以前, 严重干旱下叶片的抗坏血酸和谷胱甘肽合成及循环代谢增强较显著; 在胁迫24天后, 由于该胁迫下植物所遭受的氧化胁迫较为严重, 叶片中上述6种酶的活性均呈降低趋势。而在中度干旱下叶片抗坏血酸和谷胱甘肽合成及循环代谢相关的6种酶在整个胁迫过程中均保持较高的活性。这说明, 冰草能够长时间有效地抵御中度干旱所造成的氧化胁迫, 但只能在一定时间范围内有效地抵御严重干旱所造成的氧化胁迫, 胁迫时间延长则会降低其抵御严重干旱的能力。     

Relationships between soil nutrients and plant functional traits in different degradation stages of Leymus chinensis steppe in Nei Mongol,China

Aims Understanding ecological implications of plant functional traits is helpful in exploring community assembly under different environments of nature and human disturbances, and then to reveal the maintenance mechanism of the ecosystem services. By analyzing vegetation and soil data derived from field observations in Leymus chinensis steppe of Xilin River Basin in Nei Mongol, we aimed to explore the responses of plant functional traits to changing soil nutrients at different degradation stages. Methods We observed 69 plots for both plant community structure and soil attributes using quadrat and soil-drilling methods. Five plant functional traits, namely the specific leaf area (SLA), leaf dry matter content (LDMC), leaf carbon to nitrogen ratio (C:N), leaf lignin content (LLC), and maximum height (MH), were measured for each plot. We also tested soil attributes, such as total nitrogen (TN), total phosphorus (TP), available nitrogen (AN), available phosphorus (AP), and organic carbon (OC). The sixty-nine communities were classified into four groups (undegraded L. chinensis + forbs, slightly degraded L. chinensis + Stipa sp., moderately degraded L. chinensis + Cleistogenes squarrosa, and heavily degraded L. chinensis + Artemisia frigida) using TWINSPAN software. The relationships between plant functional traits and soil nutrient variables were analyzed for the four community groups using the Pearson’s correlation test with SPSS 21.0 software. Important findings (1) The soil nutrients decreased with the grassland degradation process and there were significant differences in TN and TP between the undegraded L. chinensis + forbs and heavily degraded L. chinensis + A. frigida communities; (2) plant functional traits also showed strong differences between the degradation stages. MH and C:N decreased with degradation. A significant difference was observed in MH between the undegraded L. chinensis + forbs and slightly degraded L. chinensis + Stipa sp. communities. The difference in C:N was also significant between the undegraded L. chinensis + forbs and heavily degraded L. chinensis + A. frigida communities; (3) the effects of soil nutrients on plant functional traits changed with grassland degradation. AN was negatively correlated with MH, LLC, and C:N in the slightly degraded L. chinensis + Stipa sp. community. In the moderately degraded L. chinensis + C. squarrosa community, those three traits mentioned above showed significantly positive correlations with TP; (4) while analyzing the degraded grassland, different relationships between plant functional traits were found. In the slightly degraded L. chinensis + Stipa sp. community, LLC was positively correlated with all other traits. Moreover, positive correlations also occurred between C:N and MH, C:N and LDMC, and C:N and LLC. In the heavily degraded L. chinensis + A. frigida community, all traits demonstrated the most significantly positive correlations.     

华北地区落叶松林的分布、群落结构和物种多样性

华北落叶松(Larix principis-rupprechtii)林、日本落叶松(L. kaempferi)林及太白红杉(L. chinensis)林是华北地区常见的3种落叶松林类型, 其中日本落叶松林为人工林, 华北落叶松林既有天然分布又有人工种植, 太白红杉林则主要是天然林。该研究基于野外调查数据, 对这3种落叶松林的分布、物种组成、群落结构、物种多样性及其与环境间的关系进行了分析。研究发现, 3种落叶松林的分布受年平均气温的影响较大, 随着年平均气温的增加, 落叶松林的天然分布减少而人工种植的分布增加。3种森林中落叶松的林分径级及树高均为右偏分布, 说明3种落叶松林均处于相对稳定的演替阶段。3种落叶松林均拥有较高的物种丰富度且差异显著, 其中太白红杉林的物种丰富度最大(39.3 ± 17.9), 而华北落叶松林的物种丰富度最小(人工林27.2 ± 17.7, 天然林27.5 ± 13.8)。除最大树高与经度的关系不显著以外, 落叶松林的最大胸径和最大树高及物种丰富度均随经纬度的增加而显著降低, 随着年降水量的增加而显著增加。此外, 年平均气温对落叶松林的总物种丰富度影响不大, 但是对其群落结构影响显著。随着年平均气温的升高, 落叶松林的最大胸径显著降低而最大树高却显著增加。落叶松天然林和落叶松人工林物种多样性的地理分布格局及与气候因子间的关系与落叶松林总体的基本一致, 但群落结构的格局不尽相同: 随着经纬度的增加, 落叶松人工林的最大树高增加而天然林的最大树高减小; 落叶松天然林的最大胸径和最大树高分别随年平均气温的升高和年降水量的增加而减小, 而落叶松人工林的最大胸径和最大树高分别随年平均气温的升高和年降水量的增加而增大。     

外源谷胱甘肽对石竹幼苗镉毒害的缓解效应

为了探讨外源谷胱甘肽(GSH)对地被植物镉(Cd)毒害的缓解效应, 采用温室盆栽土培的方法, 研究了不同浓度(0、20、40、60、80、100 mg·L ^-1)的外源GSH处理对50 mg·kg ^-1 Cd胁迫下石竹(Dianthus chinensis)幼苗生长的影响。结果发现, 50 mg·kg ^-1 Cd显著抑制了石竹幼苗的生长。喷施外源GSH后, 一定浓度范围内(≤60 mg·L ^-1)的外源GSH可显著缓解石竹幼苗的Cd胁迫, 过氧化氢酶(CAT)、过氧化物酶(POD)、抗坏血酸过氧化物酶(APX)、单脱氢抗坏血酸还原酶(MDAR)、脱氢抗坏血酸还原酶(DHAR)、谷胱甘肽还原酶(GR)的活性, 抗坏血酸(AsA)和GSH含量以及生物量、株高、分蘖数都显著高于无外源GSH处理的石竹幼苗, 而丙二醛(MDA)含量、细胞膜透性、Cd含量、O₂· ^-的产生速率以及H₂O₂的积累量则显著低于无外源GSH处理的石竹幼苗, 但随着外源GSH喷施浓度的增加, 缓解效应有下降的趋势。试验表明55-65 mg·L ^-1的外源GSH缓解效果最佳。     

Effects of precipitation intensity and temporal pattern on soil nitrogen mineralization in a typical steppe of Nei Mongol grassland

Aims Our objective is to: 1) explore the dynamics of soil nitrogen (N) mineralization in a grassland ecosystem in response to the changes in precipitation intensity and temporal distribution, and 2) identify the controlling factors.Methods The two study sites located in a typical steppe of the Nei Mongol grassland were fenced in 2013 and 1999, respectively. Our field experiment includes manipulations of three levels of precipitation intensity (increased 50%, decreased 50%, control) in three temporal patterns (increased or decreased precipitation for three years; increased or decreased precipitation for two years and no manipulation for one year; increased or decreased precipitation for one year and no manipulation for one year).Important findings 1) The soil net N mineralization and net nitrification rates decreased with changes in the temporal distributions of precipitation from one year to three years, with the maximum values of soil net N mineralization and nitrification rates observed in the treatments of increased or decreased precipitation for one year and no manipulation for one year (+PY1 or -PY1). This indicates that the high precipitation intensity and longer precipitation may have negative effects on soil net N mineralization and nitrification rates, while the moderate soilmoisture and temperature may stimulate soil mineralization. 2) The soil net N mineralization and nitrification rates, soil cumulative N mineralization, and nitrification in the fenced site in 1999 were higher than those in the site fenced in 2013, implying that a long-term enclosure may have promoted nutrient storage and soil quality restoration. 3) The long-term treatments of increased or decreased precipitation had significant effects on soil water content and temperature, whereas the short-term, discontinuous precipitation produced minor effects on soil moisture and temperature. Moreover, the controlling factors for soil N mineralization were different between the two fields. Soil moisture had a major effect on soil inorganic N content and net N mineralization rate in the site fenced in 2013, while soil temperature played a dominant role in the site fenced in 1999, with the net N mineralization rate depressed by higher soil moisture. Our findings suggest that the precipitation intensity and temporal distribution had important impacts on soil N mineralization in the Inner Mongolia grassland; these effects was site-dependent and particularly related to soil texture, community composition, and disturbance, and other factors.     

Effects of nitrogen and silicon application on leaf nitrogen content and net photosynthetic rate of Elymus nutans in alpine meadow

AimsElymus nutans is one of the dominant plant species in alpine meadow. Purpose of this research was to study the effects of nitrogen and silicon application on leaf nitrogen content and net photosynthetic rate in this species to provide scientific basis for fertilization practice in alpine meadow.MethodFour levels nitrogen combined with four levels silicon was applied to E. nutans plants in the alpine meadow. Leaf nitrogen content and net photosynthetic rate of E. nutans were measured.Important findings The results showed that there was a significant improvement in leaf nitrogen content and net photosynthetic rate of the E. nutans with nitrogen or silicon application alone; However, there was a significant interaction between nitrogen and silicon treatments on leaf nitrogen content and net photosynthetic rate; Combining with the three different levels nitrogen, low level silicon (Si₁) application did not increase leaf nitrogen content and net photosynthetic rate, but middle level silicon (Si₂) could significantly increase the leaf nitrogen content; Combining with the low (N₁) or middle (N₂) level nitrogen, middle level silicon (Si₂) application could significantly increase the net photosynthetic rate; Compared with that control without fertilization, the middle level nitrogen combined with the same level silicon treatment had the highest average of leaf nitrogen content and net photosynthetic rate, which increased by 119.99% and 85.70%, respectively. This study indicated application of nitrogen combined with silicon application enhanced leaf nitrogen content and net photosynthetic rate of E. nutans, and 8 g·m^-2silicon application had the best result among other treatments.     

睾丸酮丛毛单胞菌对羊草根际土壤PAHs降解及细菌群落结构的影响

探究睾丸酮丛毛单胞菌(Comamonas testosteroni,C.t)联合羊草修复多环芳烃(Polycyclic aromatic hydrocarbons,PAHs)污染土壤过程中,羊草根际土PAHs降解及根际微生物的变化。用气相色谱-质谱法(GC-MS)检测C.t联合羊草时根际PAHs的降解,通过高通量测序技术测定羊草根际土壤细菌群落及多样性,采用冗余分析及网络分析评价PAHs降解与细菌群落组分之间的相关性,用PICRUSt软件预测PAHs降解潜力。结果表明,C.t的接入在修复后期(60–120d)促进PAHs降解,使羊草根际细菌丰富度、多样性以及细菌与PAHs的相关性发生改变,并且提高了羊草根际PAHs的降解潜力。C.t主要通过影响变形菌门属水平中鞘氨醇单胞菌(Sphingomonas)、MND1和Nordella,放线菌门属水平上红色杆菌(Rubrobacter)和Gaiella,酸杆菌门属水平中RB41以及拟杆菌门中黄杆菌(Flavobacterium),从而加快羊草根际土中萘(Nap)、菲(Phe)、苯并芘(BaP)3种PAHs的降解。研究以期为C.t联合植物降解土壤...     

模拟喀斯特生境条件下干旱胁迫对青冈栎苗木的影响

为了研究喀斯特"双层"地质结构对植物的影响,以及在干旱环境下,喀斯特地区植物的生理变化与适应策略,建立"土壤层-岩石(石灰岩)层-岩溶水层"水分供应分层模拟柱,对‘土壤层’设置不同水分梯度,种植青冈栎(Cyclobalanopsis glauca)苗木进行干旱胁迫试验,测定青冈栎的叶面积、比叶面积、生物量、渗透调节物质含量、相对叶绿素含量。结果表明:在模拟柱‘岩溶水层’加水条件下,植物根系能下扎至‘岩溶水层’,‘土壤层’干旱胁迫对青冈栎的生理变化没有产生影响;在‘岩溶水层’无水条件下,青冈栎生理变化受‘土壤层’干旱胁迫影响显著,‘土壤层’水分含量越低,青冈栎的叶面积、生物量、叶绿素含量、叶片相对含水量越小,青冈栎干鲜比、根冠比、可溶性糖、丙二醛和脯氨酸含量越高。青冈栎幼苗利用岩溶水层水分是适应喀斯特干旱环境的重要策略。     

Effects of simulated acid rain on the activity of antioxidant enzyme and the emission of induced green leaf volatiles in Phyllostachys pubescens

为了探讨酸雨胁迫与毛竹(Phyllostachys pubescens)绿叶挥发物(green leaf volatiles, GLVs)释放规律以及抗氧化酶活性的关系, 通过盆栽试验, 采用不同pH值(5.6、4.0、2.5)的模拟酸雨对毛竹三年生实生苗进行处理, 研究酸雨对毛竹叶片可溶性蛋白质含量、丙二醛(MDA)含量和抗氧化酶活性的影响, 并采用热脱附/气相色谱/质谱联用技术对毛竹释放的GLVs成分和含量进行分析。结果表明: 酸雨胁迫下毛竹叶片MDA含量明显增加, pH 2.5模拟酸雨胁迫处理45天毛竹叶片MDA含量与对照相比增加了43.0% (p < 0.01); pH 4.0处理MDA含量增加缓慢, 处理75天时MDA含量比对照增加了0.36倍(p < 0.01)。pH 4.0和pH 2.5模拟酸雨胁迫处理45天时, 毛竹叶片可溶性蛋白质含量极显著增加, 与对照相比分别增加了32.0%和65.0% (p < 0.01)。在酸雨胁迫下, 毛竹叶片超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)的响应时间存在一定差异, 表现为互相协调, pH 2.5模拟酸雨胁迫处理SOD活性和POD活性分别在45天和60天时达到最大值, 分别为对照的1.67倍和1.31倍(p < 0.01), 随后降低。pH 4.0和pH 2.5模拟酸雨胁迫处理, 毛竹叶片GLVs含量比对照分别增加26.4%和132.9% (p < 0.01), 新增GLVs为 (E)-2-辛烯醛、2-乙基己醛、(E)-2-己烯醛和(E)-2-壬烯醛。研究表明: 酸雨胁迫条件下, 毛竹可以通过调节保护酶活性、可溶性蛋白质含量和释放GLVs来提高适应环境的能力。     

干旱胁迫对喀斯特地区野生茶树幼苗生理特性及根系生长的影响

以贵州喀斯特地区4种野生茶树(Sect Thea(L.)Dyer)无性系幼苗为材料,采用盆栽控水方法研究其对干旱胁迫的生理生长响应,初步评价其抗旱性,并采用田间模拟持续干旱试验进行验证。结果表明:(1)随着干旱胁迫程度的加强,4种野生茶树叶片的相对含水量逐渐降低;细胞质膜透性、丙二醛(MDA)含量和可溶性糖含量均呈上升趋势;游离脯氨酸含量和超氧化物歧化酶(SOD)活性先升后降;过氧化物酶(POD)活性除秃房茶随胁迫程度加强呈上升趋势外,其他种均呈先升后降趋势。(2)随着干旱胁迫程度的加强,4种茶树幼苗总生物量干重均逐渐下降,根冠比先升后降;根系总长除在秃房茶中呈先升后降趋势外,在其他3个种中均逐渐下降;根系总表面积、根系总体积在大理茶和茶中逐渐下降,而在大厂茶和秃房茶中先升后降;根系平均直径在秃房茶中逐渐降低,大厂茶中先升后降,茶中逐渐升高;根系活力在大理茶中逐渐下降,在其他3种中均先升后降;而比叶面积则在大厂茶中呈下降趋势,在其他3种中均先升后降。(3)基于生长生理指标的隶属函数抗旱性评价结果表明,MDA含量和细胞质膜透性与野生茶树抗旱性密切相关,4种野生茶树幼苗的抗旱顺序为秃房茶(Camellia gymnogyna Chang)大厂茶(Camellia tachangensis F.C.Zhang)茶(Camellia Sinensis(L.)-O.Kuntze)大理茶(Camellia taliensis(W.W.Smish)),田间持续干旱试验验证了基于隶属函数抗旱性评价方法的准确性和可靠性。     

立地条件和树龄对刺槐和小叶杨叶水力性状及抗旱性的影响

以形成黄土高原“小老树”的2种典型树种刺槐和小叶杨为对象,研究了立地条件(沟谷台地和沟间坡地)和树龄对两种树木叶水力学性质和抗旱性的影响,探讨“小老树”形成的水力生理机制.结果表明:水分较好的沟谷台地上生长的两种树木的叶最大水力导度(Kmax)明显大于水分较差的沟间坡地,叶水力脆弱性(P50)也较高;随树龄增加,两种树木的Kmax明显下降,但P50差异不大.台地上生长的两种树木的叶表皮导度和PV曲线参数(膨压损失点时的相对含水量RWCtlp、膨压损失点时的水势ψtlp饱和含水量时的渗透势ψsat)均大于 坡地;随树龄增加,两种树木的叶表皮导度显著下降,PV曲线参数出现不同程度的下降.两种树木Kmax与ψtlp呈显著正相关,P50与PV曲线参数之间存在一定的相关性,表明Kmax与抗旱性之间存在一种权衡关系,P50是反映两种树木的抗旱性特征之一.     

硅和干旱胁迫对水稻叶片光合特性和矿质养分吸收的影响

硅被认为是植物生长的有益元素,它能增强植物对非生物逆境和生物逆境胁迫的抗性。以抗旱性不同的一对水稻近等基因系w-14-和w-20为实验材料,采用盆栽实验,研究了干旱胁迫下硅处理对水稻生长性状、光合生理特性和矿质养分吸收的影响。结果表明,在正常水分条件下硅处理对水稻的生长及生理特性没有明显影响。干旱胁迫显著降低水稻植株的生长,叶绿素含量、叶绿素荧光参数Fv/Fm及Fv/F0值显著降低,光合作用受到明显抑制。加硅能提高干旱胁迫条件下水稻植株的生物量、水分利用效率、叶片叶绿素含量、净光合速率和蒸腾速率,而气孔导度和细胞间隙CO2浓度则下降。无论干旱与否,施硅后水稻的叶片硅含量均显著上升。两个水稻品系叶片的无机离子含量在干旱胁迫条件下均呈显著增加的趋势,而硅处理后材料w-14的叶片K+、Na+、Ca2+、Mg2+、Fe3+含量分别降低16.38%,24.50%,19.70%,21.52%,18.58%,w-20则分别降低11.64%,12.11%,16.06%,11.11%和19.15%,并使之回复到与对照更接近的水平。研究结果表明了硅提高水稻植株的抗旱性与光合作用的改善和矿质养分的调节有关。     

干旱胁迫下AM真菌对矿区土壤改良与玉米生长的影响

以神东矿区塌陷区退化土壤为供试基质,以玉米为宿主植物,研究在干旱胁迫下,丛枝菌根真菌(arbuscular mycorrhizalfungi)对玉米生长和养分吸收的影响,以及对矿区退化土壤的改良作用.结果表明:干旱胁迫下,接种AMF显著提高了玉米根系侵染率和生物量,玉米叶片相对含水量和叶色值明显高于对照组;接种组玉米地上部分磷、氮、钙和根系部分磷、钾、钙含量显著增加;接种AMF后,玉米根际土壤总球囊霉素和易提取球囊霉素含量分别增加了36.2％和33％,且根际土壤中有机质含量显著增加.由此可见,接种AMF促进了玉米对矿质养分的吸收,缓解了干旱造成的玉米生长的不利影响,提高了根际土壤中有机质含量,对矿区退化土壤改良有重要意义.     

干旱及复水条件下外源褪黑素对玉米叶片光合作用的影响

为探究干旱胁迫及复水后外源褪黑素对玉米叶片光合作用的影响和调控机制。以玉米陕单609盆栽苗为试验材料,叶面喷施褪黑素100 μmol/L在重度干旱和复水后分别测定了生物量、净光合速率（P_n）以及光合电子传递速率等指标。结果显示：外源褪黑激素可减轻干旱胁迫引起的生长抑制;外源褪黑激素处理的植株表现出比未处理植株更高的P_n、气孔导度（G_s）以及更低的胞间CO₂浓度（C_i）;外源褪黑素增加了干旱胁迫下OJIP曲线的荧光参数φ_P0、φ_E0、ψ₀以及光合性能指数PI_abs;外源褪黑素也提高了干旱胁迫下叶片PSⅡ和PSI有效量子产量[Y（Ⅱ）,Y（I）];也增加了干旱胁迫下叶片的PSⅡ和PSI电子传递速率（ETRⅡ,ETRI）,但降低了干旱胁迫下叶片PSI受体侧限制[Y（NA）]和供体侧限制[Y（ND）]。表明外源褪黑素对干旱胁迫下光抑制具有一定的缓解作用。复水后,干旱胁迫下褪黑素处理玉米叶片各参数都恢复到对照水平;而干旱胁迫处理玉米叶片各参数复水后不能完全恢复。可见,喷施褪黑素不仅缓解干旱胁迫对玉米PSⅡ和PSI结构和功能的损伤,而且能加速复水后光合机构功能的恢复,促进玉米植株恢复性生长。因此喷施褪黑素加强玉米叶片光合作用适应干旱环境是一种重要的调控方式。     

沼液施用对干旱胁迫下玉米幼苗生长和生理特性的影响*

为了探明干旱胁迫下沼液对玉米幼苗抗旱、光合生理、形态的缓解效应,以中度抗旱玉米杂交种‘先玉335’和较强抗旱杂交种‘中单2号’为材料,采用10%聚乙二醇-6000模拟干旱胁迫,研究50%沼液根部浇灌处理对干旱胁迫下玉米幼苗生长和生理特性的影响。结果表明,沼液根部施用可以显著提高两品种玉米的抗旱性,有效缓解干旱胁迫对玉米幼苗根系和地上部生长的抑制作用,促进两品种玉米幼苗生长和提高根系活力,降低根冠比,且‘先玉335’的变幅更大;同时显著提高两品种叶片SOD、POD和CAT活性以及可溶性糖、脯氨酸、可溶性蛋白含量(‘中单2号’的CAT除外),降低MAD含量,且对‘中单2号’的影响更显著;沼液根施还可以显著提高干旱胁迫下两品种叶片的净光合速率(Pn)、蒸腾速率(Tr),降低气孔导度(Gs)、胞间CO_(2)浓度(Ci),但‘中单2号’的Tr和Gs除外,同时使两品种叶片叶绿素含量和水分利用效率(WUE)均显著增加。可见,沼液根施处理可以有效改善干旱胁迫下玉米幼苗的光合能力,显著提高幼苗抗氧化酶活性和渗透调节物质的含量,减轻膜脂过氧化程度,有效缓解干旱胁迫对2种不同抗旱性玉米幼苗的生长抑制,从而增强玉米耐受干旱胁迫的能力,且对‘中单2号’的缓解效果更明显。