春季辽宁西北部主要绿化树种根叶抗旱生理性状评价

对辽宁西北部主要绿化树种杨树、榆树、丁香和山杏的抗旱生理性状进行研究,分析春季干旱胁迫下4个树种叶片与根系生理性状间的关系,采用隶属函数法和灰色关联度法对其抗旱性进行评价.结果表明: 渗透调节物质可溶性糖、可溶性蛋白和脯氨酸含量、抗氧化酶——超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性,以及丙二醛含量在4个树种及不同器官(叶片与根系)中均存在显著差异.4个树种平均隶属函数值在叶片中的顺序为榆树(0.673)>丁香(0.412)>杨树(0.346)>山杏(0.245),在根系中的顺序为杨树(0.558)>丁香(0.552)>山杏(0.383)>榆树(0.315);杨树、丁香和山杏叶片平均隶属函数值小于根系,而在榆树叶片中大于根系.各项生理指标与抗旱性的关联顺序在叶片中表现为丙二醛>SOD>CAT>可溶性蛋白>脯氨酸>可溶性糖>POD,在根系中为丙二醛>可溶性蛋白>可溶性糖>CAT>POD>脯氨酸>SOD.4个树种的叶片和根系中抗旱能力不同,各抗旱指标在叶片与根系中的作用不同,对不同树种的不同器官应该采取不同的管护措施.     

红花尔基樟子松优良抗旱菌树组合的筛选

为筛选红花尔基樟子松（Pinus sylvestris var.mongolica）优良抗旱菌树组合,采用樟子松林下5个优势外生菌根真菌菌株为接种体,分别对5个月龄樟子松实生苗进行人工接种,接种8个月后观察菌根侵染情况及菌根形态,并在非干旱胁迫和干旱胁迫条件下测定不同菌树组合的生长和生理生化指标。结果表明：5个乡土菌种均能成功侵染樟子松并形成典型的外生菌根;干旱胁迫下,菌根化樟子松的各项生长指标均显著高于对照（P<0.05）,且接种粘盖牛肝菌（Suillus bovinus）具有最高的菌根侵染率、苗高、地上及地下生物量和根茎比;外生菌根共生体可通过提高植物SOD活性与POD活性,同时降低MDA含量来提高樟子松对干旱的耐受力;干旱胁迫下,所有接种处理苗木的萎蔫时间较对照处理均推迟,推迟时间最长的是粘盖牛肝菌接种处理,较对照推迟96.3 h;另外,接种处理均能显著延长宿主临界致死时间,尤其是接种粘盖牛肝菌可延长113.8 h。因此,可以认为粘盖牛肝菌与樟子松是一个较为理想的抗旱菌树组合。     

Betaine aldehyde dehydrogenase in sorghum.

The ability to synthesize and accumulate glycine betaine is wide-spread among angiosperms and is thought to contribute to salt and drought tolerance. In plants glycine betaine is synthesized by the two-step oxidation of choline via the intermediate betaine aldehyde, catalyzed by choline monooxygenase and betaine aldehyde dehydrogenase (BADH). Two sorghum (Sorghum bicolor) cDNA clones, BADH1 and BADH15, putatively encoding betaine aldehyde dehydrogenase were isolated and characterized. BADH1 is a truncated cDNA of 1391 bp. BADH15 is a full-length cDNA clone, 1812 bp in length, predicted to encode a protein of 53.6 kD. The predicted amino acid sequences of BADH1 and BADH15 share significant homology with other plant BADHs. The effects of water deficit on BADH mRNA expression, leaf water relations, and glycine betaine accumulation were investigated in leaves of preflowering sorghum plants. BADH1 and BADH15 mRNA were both induced by water deficit and their expression coincided with the observed glycine betaine accumulation. During the course of 17 d, the leaf water potential in stressed sorghum plants reached -2.3 MPa. In response to water deficit, glycine betaine levels increased 26-fold and proline levels increased 108-fold. In severely stressed plants, proline accounted for > 60% of the total free amino acid pool. Accumulation of these compatible solutes significantly contributed to osmotic potential and allowed a maximal osmotic adjustment of 0.405 MPa.     

乡土风箱果和紫叶风箱果叶片光合特性对土壤干旱的响应

研究叶片光合气体交换参数和叶绿素荧光参数对土壤干旱的响应,分析濒危的乡土风箱果和引种紫叶风箱果的抗旱能力及其差异.结果表明: 土壤干旱第7天时,紫叶风箱果叶片明显失水萎蔫,而乡土风箱果却有较高的叶片含水率和水分利用效率.土壤干旱降低了2种风箱果叶片的净光合速率、气孔导度和蒸腾速率,紫叶风箱果降低幅度明显大于乡土风箱果.土壤干旱7 d时,紫叶风箱果叶片的胞间CO₂浓度(C_i)高于未干旱处理,而乡土风箱果C_i低于未干旱处理.乡土风箱果叶片的电子传递速率(ETR)和光化学淬灭系数(q_P)明显降低,而PSⅡ反应中心光能捕获效率(F_v′/F_m′)没有发生明显变化;但是紫叶风箱果叶片的F_v′/F_m′、ETR和q_P均明显降低,并且其降低幅度大于乡土风箱果.土壤干旱7 d时,乡土风箱果叶片OJIP曲线上J点的相对可变荧光(V_J)没有发生明显变化,而紫叶风箱果叶片V_J明显增加.紫叶风箱果的叶片碳同化能力和PSⅡ功能对土壤干旱的敏感性明显大于乡土风箱果,土壤干旱降低乡土风箱果光合能力的原因以气孔因素限制为主,而紫叶风箱果以非气孔因素限制为主.     

Comparison of the physiological responses of Phaseolus vulgaris and Vigna unguiculata cultivars when submitted to drought conditions

Three cultivars differing in their susceptibility to water stress were compared—Phaseolus vulgaris cv. Carioca (susceptible), Vigna unguiculata cv. IT83D (intermediately tolerant) and V. unguiculata cv. EPACE-1 (tolerant)—during an imposed water stress treatment. Variation in leaf gas exchange (i.e. assimilation and stomatal conductance) and leaf relative water content in response to progressive substrate water depletion were investigated. To verify the extent of the injury caused by the drought treatment, leaf gas exchange was measured after rehydration. In the three cultivars, stomatal conductance declined before leaf relative water content was affected. P. vulgaris showed the largest decrease in the rate of stomatal conductance with decreasing substrate water content compared to both V. unguiculata cultivars. Photosynthetic assimilation rates were largely dependent on stomatal aperture, but there was evidence of the participation of non-stomatal factors in the reduction of CO₂ fixation. The response of leaf gas exchange parameters to severe water stress conditions differed significantly between P. vulgaris and V. unguiculata cultivars. After rehydration, cultivars can be characterised according to the degree of injury induced by the drought treatment: V. unguiculata cv. EPACE-1 as the least affected, V. unguiculata cv. IT83D slightly affected and P. vulgaris cv. Carioca strongly affected. Similar ranking was obtained with experiments previously performed at a cellular and subcellular level. Our results confirm the utility of physiological parameters as early screening tools for drought resistance in bean cultivars.     

Effects of water condition on photochemical efficiency and physiological characteristics in artificially cultivated moss Syntrichia caninervis

Aims The desert moss Syntrichia caninervis is a dominant species in the moss biocrust of the Gurbantünggüt Desert. It plays an important role in soil stability and artificial biocrust reconstruction in desert ecosystems. Previous studies have demonstrated that although artificial cultivation techniques can promote the micropropagation of S. caninervis, the resulting moss performs poorly in maintenance ability. Water availability has been considered as a critical factor to stimulate the physiological activities in moss species. Our objective in this study was to determine the optimum water condition for growth of sand-cultivated shoots of S. caninervis in the process of transplanting cultured materials from laboratory to the field. Methods We used sand-cultivated S. caninervis grown from fragmented gametophyte leaves and stems above ground. The experiment was run for 30 days under conditions of three water treatments, including intermittent water supply (watering every three days), fully watered (watering every day), and drought (watering every six days) . Fluorescence and physiological indices of shoots, such as photochemical efficiency, pigment content, soluble sugar, free proline, soluble protein, catalase, peroxidase, superoxide dismutase activities and malondialdehyde were measured. Important findings The content of total chlorophyll, chlorophyll a and b in drought and fully watered treatments were significantly lower than in intermittent water supply treatment. Drought reduced the chlorophyll a/b ratio, and fully watered treatment deceased carotenoid content. Drought and fully watered treatments significantly reduced the maximal and actual photochemical efficiency and the soluble protein content, while increased most indices in osmotic adjustment substances and antioxidative enzyme activities, such as soluble sugar content, free proline content, catalase, peroxidase, superoxide dismutase and malonaldehyde content. Our results showed that the sand-cultivated S. caninervis accumulated osmotic adjustment substances and strengthened the antioxidative enzyme activities to survive under different water conditions, such as in the fully watered treatment. Compared with the intermittent water supply treatment, drought may lead to more damages in sand-cultivated shoots of S. caninervis, with the membrane lipid peroxidation being aggravated. Thus, intermittent water supply results in better development of artificial-cultivated S. caninervis than drought and fully watered treatments. This conclusion could provide theoretical basis for water saving management of artificially cultivated bryophyte in wild engraftment.     

Biophysical and morphological leaf adaptations to drought and salinity in salt marsh grasses

Leaf energy budgets were constructed for 13 species of estuarine C₄ grasses (Poaceae) to elucidate the biophysical effects of drought and salinity on the interception and dissipation of solar energy. Spartina alterniflora, S. anglica, S. argentinensis, S. bakeri, S. cynosuroides, S. densiflora, S. foliosa, S. foliosa × S. alterniflora hybrids, S. gracilis, S. patens, S. pectinata, S. spartinae, and Distichlis spicata plants were grown under controlled soil water potential gradients in a greenhouse. Species were grouped into four major ecological functional types, based on elevational zonation ranges: low marsh species, middle marsh species, high marsh species, and freshwater species. Different functional types are adapted to different environmental conditions, and responded differently to reduced water potentials. Latent heat flux decreased similarly across species in response to decreasing water potential. Latent heat loss was found to decrease by as much as 65% under decreasing water potential, leading to an increase in leaf temperature of up to 4 °C. Consequently, radiative and sensible heat losses increased under decreasing water potential. Sensible heat flux increased as much as 336% under decreasing water potential. Latent heat loss appeared to be an important mode of temperature regulation in all species, and sensible heat loss appeared to be more important in high marsh species compared to low marsh species. High marsh species are characterized by narrower leaves than middle and low marsh species, leading to a smaller boundary layer, and providing higher conductance to sensible heat loss. This may be an adaptation for high marsh species to regulate leaf temperature without access to large amounts of water for transpirational cooling. Stomatal conductance decreased with decreasing water potential across species: leaf conductances to water vapor and CO₂ decreased as much as 69% under decreasing water potential. Additionally, oxidative stress appeared to increase in these plants during times of drought or salinity stress. Ascorbate peroxidase activities increased with decreasing soil water potential, indicating increased cellular reactive oxygen species. High marsh species had higher ascorbate peroxidase activities compared to low marsh species, indicating higher tolerance to drought- or salinity-induced stresses. It was concluded that different species of marsh grasses are adapted for growth in different zones of salt marshes. Adaptations include biophysical, biochemical, and morphological traits that optimize heat exchange with the environment.     

Strongylus asini (Nematoda, Strongyloidea): Genetic relationships with other strongylus species determined by ribosomal DNA

Genomic DNA was isolated from adult Strongylus asini collected from zebra. The second ribosomal transcribed spacer (ITS-2) was amplified and sequenced using polymerase chain reaction (PCR) based techniques. The DNA sequence was compared with previously published data for 3 related Strongylus species. A PCR-linked restriction fragment length polymorphism method allowed the 4 species to be differentiated unequivocally. The ITS-2 sequence of S. asini was found to be more similar to those of S. edentatus (87.1%) and S. equinus (95.3%) than to that of S. vulgaris (73.9%). This result confirms that S. asini and S. vulgaris represent separate species and supports the retention of the 4 species within 1 genus.     

五种西北旱区植物对干旱胁迫的生理响应

以黑果枸杞、金露梅、蒙古莸、柠条和花棒5种西北旱区植物为材料,采用盆栽试验研究了干旱胁迫对植物叶片光合、水分和生理生化的影响.结果表明: 随干旱胁迫时间的延长,5种植物叶片的保水力均升高,叶片相对含水量先升后降,叶绿素含量和叶绿素荧光参数均不同程度地降低,花棒和黑果枸杞的光合系统受到的影响最小,金露梅的光合系统受损最严重.干旱胁迫后金露梅叶片的电导率和丙二醛含量先降低后急剧上升,超氧化物歧化酶(SOD)和过氧化物酶(POD)活性先升高后急剧降低.其余4种植物随土壤含水量的降低电导率先升后降,丙二醛含量先升后降或先降后升,SOD和POD活性总体呈上升趋势,其中蒙古莸SOD活性和花棒POD活性在所有植物中升幅最大,干旱28 d后分别升至为胁迫前的2.1、14.1倍.随胁迫时间的延长,5种植物各有机溶质的积累量存在较大差异,金露梅积累最多的可溶性糖和游离脯氨酸,28 d后分别增至为原来的2.1、23.4倍,花棒积累最多的可溶性蛋白,28 d后增至为原来的2.0倍.隶属函数法表明,植物耐旱能力为花棒>黑果枸杞>柠条>蒙古莸>金露梅.5种旱区植物可通过提高抗氧化酶活性和积累有机溶质对干旱胁迫进行积极的反馈,以减轻细胞受到的伤害.金露梅对水分亏缺的敏感性最高,试验期间其干旱程度已经超出了自身调节能力的阈值.     

水位提升和泥炭藓繁殖体移植对泥炭地植被恢复的影响

泥炭藓繁殖体移植是影响泥炭地植被恢复的重要因素之一,不同移植方式的效果往往缺乏比较研究。选取长白山区白江河退化泥炭地为研究地,以自然生境的丘间种喙叶泥炭藓(Sphagnum flexuosum)和藓丘种中位泥炭藓(S.magellanicum)(后者耐旱能力较强)为实验材料,通过野外移植实验,研究水位提升与不同泥炭藓繁殖体移植方式对退化泥炭地植被恢复的影响。数据分析显示:水位条件显著影响了喙叶泥炭藓和中位泥炭藓的建植,随着水位上升,地表湿度增加,两种泥炭藓的盖度均呈明显的上升趋势;移植方式的变化短期内对泥炭藓的建植作用并不明显,但在移植2个月后,移植方式对喙叶泥炭藓表现出显著影响,即耐旱能力较强的中位泥炭藓置于上层时,喙叶泥炭藓盖度最高;水位和移植方式不存在交互作用,即在低水位条件下,中位泥炭藓置于上层的移植方式也未能提升泥炭藓的建植盖度。研究表明,水位提升是泥炭地植被恢复的十分有效的手段,因物种间存在对水分保持的差异,采用合理植物繁殖体移植方式,将会明显提升植被恢复的成效。     

Exogenous proline and glycinebetaine increase NaCl-induced ascorbate-glutathione cycle enzyme activities, and proline improves salt tolerance more than glycinebetaine in tobacco Bright Yellow-2 suspension-cultured cells

Up-regulation of the antioxidant system provides protection against NaCl-induced oxidative damage in plants. Antioxidants and activity of enzymes involved in the ascorbate-glutathione (ASC-GSH) cycle in tobacco Bright Yellow-2 (BY-2) were investigated to assess the antioxidant protection offered by exogenous proline and glycinebetaine (betaine from now on) against salt stress using cells grown in suspension culture. Reduced ascorbate (ASC) was detected in BY-2 cells but dehydroascorbate (DHA) was not. Large quantities of a reduced form of glutathione (GSH) and smaller quantities of an oxidized form of glutathione (GSSG) were detected in BY-2 cells. Salt stress significantly reduced the contents of ASC and GSH as well as activities of ASC-GSH cycle enzymes such as ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR). Exogenous proline or betaine increased the activities of all enzymes except MDHAR involved in NaCl-induced ASC-GSH cycle. Levels of ASC and GSH in BY-2 cells under salt stress were lower in the presence of proline or betaine than in the absence of proline or betaine whereas there was no difference in redox status. Proline proved more effective than betaine in maintaining the activity of enzymes involved in NaCl-induced ASC-GSH cycle. Neither proline nor betaine had any direct protective effect on NaCl-induced enzyme activity involved in the antioxidant system; however, both improved salt tolerance by increasing enzyme activity. The present study, together with our earlier findings [Hoque MA, Okuma E, Banu MNA, Nakamura Y, Shimoishi Y, Murata Y. Exogenous proline mitigates the detrimental effects of salt stress more than exogenous betaine by increasing antioxidant enzyme activities. J Plant Physiol 2006;164:553-61.], suggests that proline offered greater protection against salt stress than betaine did because proline was more effective in increasing the activity of enzymes involved in the antioxidant system.     

N-Deacetylation and depolymerization reactions of chitin/chitosan: Influence of the source of chitin

The deacetylation and depolymerization reactions of chitin/chitosan from three crustacean species (Paralomis granulosa, Lithodes antarcticus and Palinurus vulgaris) were evaluated under the same conditions. The average molecular weight and the mole fraction of N-acetylated units were the parameters studied in the resulting chitosans. During the N-deacetylation process P. granulosa, L. antarcticus and P. vulgaris follow a pseudo-first order kinetics and their apparent rate constants are very similar. However, the degradation rate of chitosan in the first 45 min of this process is higher for P. vulgaris. The depolymerization process follows a pseudo-first order kinetics for the three species, but in the first 9 min P. vulgaris shows a slightly lower depolymerization rate. Hence, depending on the ash contents, crystallinity and the physicochemical characteristics of chitin from these sources, the obtained chitosans show different qualities.     

Water availability – a physiological constraint on nitrate utilization in plants of Australian semi-arid muiga woodlands

Nitrate was found to be the predominant form of available nitrogen in mulga soils. Nitrate reductase activities on a fresh mass basis of a range of plants from eastern (Queensland) mulga ecosystems 2 weeks after partial relief from drought were uniformly low for both herbaceous species (165 ± 25 pkat g^?1) and woody perennials (77 ± 14 pkat g^?1). Supply of nitrate for 24 h to cut transpiring shoots of woody species or application of nitrate solution to the rooting zone of herbaceous species promoted little further increase in mean shoot nitrate reductase activities. Most species exhibited high tissue nitrate concentrations during water stress and soluble organic N profiles were in many cases dominated by the osmoprotective compounds, proline or glycine betaine. Species with low levels of proline or glycine betaine showed high foliar concentrations of other compatible osmotica such as polyols or sugars. Effects of relieving water stress on nitrate reductase activity, proline, glycine betaine and nitrate levels were followed over, 3d of irrigation. Available soil nitrate rose 10-fold immediately and, following rapid restoration of leaf water status of the eight study species, a 4-fold increase occurred in mean nitrate reductase activity together with progressive decreases in mean tissue concentrations of nitrate, proline and glycine betaine over the 3 d period. Similar changes in soil nitrate, nitrate reductase activity, proline and tissue nitrate were observed in the same ecosystem following a natural rainfall event and in western (S.W. Australia) mulga following irrigation. It is concluded that, although nitrate nitrogen is present at high concentrations and is the predominant inorganic nitrogen source in soils of the mulga biogeographic region, its assimilation by perennial and ephemeral vegetation is limited primarily by water availability. A scheme is presented depicting interrelated physiological and biochemical events in typical mulga species following a rain event and subsequent drying out of the habitat.     

Antioxidative defense and proline/phytochelatin accumulation in a newly discovered Cd-hyperaccumulator, Solanum nigrum L.

Changes in the activity of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and the contents of malondialdehyde (MDA), chlorophyll, free proline and phytochelatins (PCs) in Solanum nigrum, the newly discovered Cd-hyperaccumulator were examined and compared with a non-hyperaccumulator Solanum melongena. It was indicated that leaf SOD and POD activity of S. nigrum was significantly higher than that of S. melongena. The Cd treatments significantly increased root SOD activity, leaf POD activity, and CAT activity and free proline content in the leaves and roots of S. nigrum. On the contrary, the Cd treatments decreased SOD activity, and did not change CAT activity in the leaves and roots of S. melongena. Moreover, there were no significant differences in free proline levels in the roots of S. melongena. These results validated that S. nigrum had a greater capacity than S. melongena to adapt to oxidative stress caused by Cd and free proline accumulation might be responsible for the tolerance of S. nigrum to Cd. Treated with 10 μg Cd g⁻¹, growth of S. nigrum and its contents of chlorophyll and MDA were basically unaffected. In contrast, there were a decrease in the growth and chlorophyll content, and an increase in MDA in the roots of S. melongena. Although lipid peroxidation was promoted in both the hyperaccumulator and non-hyperaccumulator by high Cd stress, the greater increase took place in the tissues of S. melongena. The PCs level in roots of S. nigrum was significantly lower than that of S. melongena. On the contrary, the content of leaf PCs was much higher in S. nigrum than that in S. melongena. These results further suggested that antioxidative defense in the Cd-hyperaccumulator might play an important role in Cd tolerance, and PCs synthesis is not the primary reason for Cd tolerance although PCs in S. nigrum increased significantly by Cd.     

光和水分胁迫对臭柏实生幼苗光化学效率及色素组成的影响

为探明毛乌素沙地3年生臭柏(Sabina vulgaris)实生苗在不同光照和水分条件下的光抑制响应机制,研究了各处理臭柏实生苗的最大光化学效率(F_v/F_m)及叶绿素(Chla+Chlb)和叶黄素(A+V+Z)含量,分析了其叶绿素循环和叶黄素循环的变化规律。结果表明,77%透光区通过减少Chlb含量,升高Chla/Chlb,避免光能过剩;同时,增加A+V+Z及热散逸色素(A+Z)含量、提高(A+V+Z)/(Chla+Chlb)和(A+V)/(A+V+Z)值,耗散过剩光能,避免光破坏。25%透光区的叶绿素和叶黄素循环机制随着水分条件的变化迅速发生改变。10%透光区通过增加Chlb含量,降低Chla/Chlb,捕捉更多的光能,几乎不存在光抑制。毛乌素臭柏实生幼苗能够适应不同的光照和水分条件,在恶劣的沙漠中完成天然更新,形成独特的群落景观,与叶绿素循环和叶黄素循环有着密切的关系。     

阿魏酸对凤丹干旱胁迫的缓解效应

以凤丹为材料,研究阿魏酸(FA)对植株自然干旱胁迫的缓解效应。结果表明:与对照相比,FA处理可显著提高叶片含水量、抗氧化酶活性,降低活性氧积累、脯氨酸含量和相对电导率,从而减少干旱胁迫对植株的伤害。此外,干旱胁迫同样引起了光合特性与叶绿素荧光参数发生变化,而FA处理不仅提高了植株的光能利用效率,而且增强了叶片的热耗散,进而维持了光合机构的完整性。本研究明确了FA对凤丹干旱胁迫具有一定的缓解效应,这可为凤丹在干旱地区的栽培奠定基础。     

四种抗旱植物在不同区域的生长稳定性

我国抗干旱林木种质资源十分丰富,评价和筛选适合多样化干旱逆境的优良种质,是造林工作者亟待解决的难题。本研究以不同种源的山桃、山杏、黄柳、蒙古莸4个林木树种为试材,选择内蒙古自治区中东部的达拉特旗、四子王旗、库伦旗扣河子镇和库伦旗六家子镇4个不同土壤类型进行区域化多点试验,分析不同物种、不同种源树种的生长生理状况,并采用AMMI模型评价种质的区域适应性和稳定性。结果表明: 山桃、山杏、黄柳、蒙古莸的生长和生理指标在种源间和地点之间表现出一定的差异;不同地点的土壤条件(K、N含量、pH值)和气候条件(年均温、年降水量、潜在蒸散量)均对不同种源树种的生长产生一定的影响。从物种层面来讲,黄柳和蒙古莸更适应达拉特旗和四子王旗的沙壤土和栗钙土环境;山桃和山杏更适应库伦旗扣河子镇和六家子镇的黄土和风沙土环境。从种源层面来讲,土左旗种源的山桃,宁城、原州种源的山杏,蓝旗种源的黄柳和靖边种源的蒙古莸为区域稳定性较高且生长适应性较好的种源树种,适宜在相似区域推广造林。     

大青杨对不同干旱胁迫强度的形态和生理响应

为了研究大青杨对干旱环境的耐受性,通过聚乙二醇(PEG-6000)模拟干旱胁迫,对不同胁迫强度下大青杨的生长状态、生物量分配、生理生化应答特征进行测定分析。结果显示,随着干旱胁迫时间的延长和强度的增加,大青杨幼苗的苗高、地径生长量和生物量积累明显减少,轻度、中度、重度胁迫下苗高生长量分别下降了17.71%、20.29%、45.96%,地径生长量下降了4.78%、13.62%、17.29%,根冠比上升了11.93%、32.61%、64.10%。叶片相对含水量呈下降趋势,相对电导率呈上升趋势,轻度、中度、重度胁迫下相对含水量分别比对照低23.60%、38.56%和66.78%,相对电导率比对照高106.97%、161.84%、241.75%,说明干旱胁迫对叶片造成了明显的损伤。脯氨酸、可溶性蛋白、可溶性糖含量均呈现先上升再下降的趋势,且轻度胁迫比中度、重度胁迫变化幅度小。在胁迫前期和中期均高于对照,说明大青杨幼苗有一定的抗旱能力。在胁迫末期有低于对照的趋势,此时幼苗细胞、组织受到了不可逆转的伤害。大青杨叶片的净光合速率明显呈现双峰模式,受胁迫幼苗显著低于对照且到达峰值的时间不同。胁迫后幼苗的第一个峰值出现的时间比对照提前2h。大青杨能够忍耐短时轻度的干旱胁迫环境,中度和重度干旱胁迫对大青杨幼苗期的生长和生理过程有显著影响。     

基于MaxEnt模型的黄河三角洲滨海湿地优势植物群落潜在分布模拟

采用千米网格的方法,对黄河三角洲滨海湿地进行土壤采样和植被群落调查,利用MaxEnt模型和GIS空间分析技术,模拟该地区优势物种的潜在分布,定量分析优势物种的主导环境影响因子及其生态位参数.结果表明: 黄河三角洲滨海湿地的优势物种为柽柳、芦苇和盐地碱蓬.影响柽柳、芦苇和盐地碱蓬潜在分布的主导环境因子分别为硝态氮、盐分、坡度、镁、海拔和铵态氮,硝态氮、盐分、全磷、pH、海拔和铵态氮,硝态氮、盐分和铵态氮.黄河三角洲滨海湿地优势物种的存在概率与盐分呈正相关,与其他主导环境影响因子呈负相关.黄河三角洲滨海湿地优势物种的潜在核心适生区主要分布在滨海地区,芦苇的分布范围较柽柳和盐地碱蓬更广泛.     

枸杞岛海藻场6种大型海藻光合荧光特性比较

海藻光合荧光特性研究对分析藻类光合作用和固碳能力具有重要的作用.利用水下调制荧光仪(DIVING-PAM)测定了枸杞岛后头湾夏季常见6种大型海藻孔石莼、斯氏刚毛藻、舌状蜈蚣藻、鼠尾藻、多管藻和羊栖菜的量子产量、快速光曲线(RLC)相关参数.结果显示: 6种常见海藻孔石莼、斯氏刚毛藻、舌状蜈蚣藻、鼠尾藻、多管藻和羊栖菜最大量子产量(F_v/F_m)分别为0.702、0.704、0.457、0.618、0.421、0.567,各物种的开放PSⅡ反应中心原初光能捕获效率(F_v′/F_m′)的大小依次是斯氏刚毛藻>孔石莼>鼠尾藻>羊栖菜>舌状蜈蚣藻>多管藻,且孔石莼、斯氏刚毛藻、羊栖菜的F_v′/F_m′与其他5种大型海藻的差异均达到显著水平;在快速光响应曲线中,羊栖菜、鼠尾藻和孔石莼的最大相对电子传递速率与初始斜率α较高,证明其具有较强的光合能力和捕光能力;舌状蜈蚣藻较高的RLC初始斜率α和较低的I_k表明其有较强的耐弱光能力.3种门类大型海藻之间光合特性有较为显著的差异,其中褐藻门的羊栖菜、鼠尾藻与绿藻门的孔石莼拥有极高的光合活性和抗强光能力,研究结果可为藻场保护工作和大型海藻固碳能力评估提供理论依据.