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1.
To address how the ratios of nitrogen and phosphorus (N:P ratios) in soil affect plant growth, we performed a two-factor (soil available N:P ratios and plant density) randomized block pot experiment to examine the relationships between soil N:P ratios, and the N:P ratios and growth rate of Artemisia ordosica seedlings. Under moderate water stress and adequate nutrient status, both soil N:P and plant density influenced the N:P ratios and growth rates of A. ordosica. With the increase of soil N:P ratios, the growth rates of A. ordosica seedlings decreased significantly. With the increase of soil N:P ratios, N:P ratios in A. ordosica seedlings increased significantly. While the nitrogen concentrations in the plant increased slightly, the phosphorus concentrations significantly decreased. With the increase of plant density, the shoot N:P ratios and growth rates significantly decreased, which resulted from soil N:P ratios. Thus, soil N:P ratios influenced the N:P ratios in A. ordosica seedlings, and hence, influenced its growth. Our results suggest that, under adequate nutrient environment, soil N:P ratios can be a limiting factor for plant growth.  相似文献   

2.
A greenhouse experiment was conducted to explore whether additional nitrogen (N) supply could enhance carbon (C) accumulation, and phosphorus (P) use efficiency (NUEP) of Sophora davidii seedlings under dry conditions. Two-month-old seedlings were subjected to a completely randomized design with three water (80, 40 and 20% water field capacity (FC)) and three N supply (N0: 0, Nl: 92 and Nh: 184 mg N kg−1 soil) regimes. Water stress decreased C, N and P accumulation, NUEP, N and P uptake efficiency (NUtEN and NUtEP) regardless of N supply. The S. davidii seedlings exhibited strong responses to N supply, but the responses were not consistent with the various N supply levels. Nl increased C, N and P accumulation, and improved NUEP, NUtEN and NUtEP in the same water treatment. In contrast, Nh did few or even depress effects on C, N and P accumulation, and NUEP, although NUtEN and NUtEP increased with Nh in the same water treatment. Even so, NUEN decreased with increase of N supply in the same water treatment. The results suggested that appropriate or low N supply should be recommended for S. davidii seedling establishment in dry environment by improving C accumulation and NUEP.  相似文献   

3.
应用PCR-DGGE技术研究了连续2年氮素、水分添加处理对贝加尔针茅草原土壤氨氧化细菌(AOB)16S r RNA基因和古菌(AOA)amo A基因遗传多样性的影响。结果表明,土壤硝化势在水分添加低氮(N30)和非水分添加高氮(N300)处理下较对照显著升高(P0.05),在水分添加高氮(N200、N300)处理下较对照急剧下降(P0.05)。不同处理下氨氧化细菌的群落结构变化较氨氧化古菌敏感,氮素添加显著改变了氨氧化微生物的群落结构,在高氮素处理下,氨氧化细菌的多样性指数有下降的趋势,而古菌的多样性则有升高的趋势,表明氨氧化古菌在高氮素下生长比较活跃。发育树分析的结果表明,非水分添加处理下,氨氧化细菌的群落由亚硝化螺菌属的Cluster 1、Cluster 3和Cluster 4组成,水分添加处理下由亚硝化螺菌属Cluster 3、Cluster 4和亚硝化单胞菌属的Cluster 6组成,而氨氧化古菌群落在水分添加处理下主要由泉古菌门的Cluster 1、Cluster 2和water lineage组成,在非水分添加处理下主要由泉古菌门的Cluster 1、Cluster 2和Cluster 5组成,两种水分输入机制下,氨氧化微生物群落的不同组成说明,水分在调节氨氧化微生物群落结构方面有重要作用。此外,氨氧化细菌群落多样性与全氮,NH4+和NO3-的含量呈显著负相关,而古菌群落与其呈显著正相关,说明氨氧化细菌与古菌对氮素和水分添加有不同的且互补的反应机制。  相似文献   

4.
We examined and compared the contents of organic chemical components (lignin-like compounds, total carbohydrates and extractives), carbon and nutrients (nitrogen, phosphorus, potassium, calcium, magnesium) among the mosses Calliergon giganteum, Hylocomium splendens, Racomitrium lanuginosum, and among three populations of H. splendens collected from habitats in contrasting water regimes in the Canadian high-arctic tundra. C:N:P ratios were analyzed among and within moss species. Mosses from hydric habitats had lower total carbohydrate and higher nutrients contents than did mosses from drier habitats; however, we found no intraspecific variations in nitrogen and calcium contents in the different populations of H. splendens along water-regime gradients. The contents in lignin-like compounds, extractives and carbon showed no clear trends along water-regime gradients. Mosses from hydric habitats had lower C:N, C:P and N:P ratios than mosses from drier habitats, although we found no intraspecific variations in C:N ratios in H. splendens along water-regime gradients. These results suggest that chemical properties of mosses, especially nutrient contents, are strongly correlated with water availability in high-Arctic tundra.  相似文献   

5.
Three-week old soybean (Glycine max) plants were subjected to a factorial combination of four regimes of soil matric water potential (ψm=−0·03, −0·5, −1·0 and −1·5 MPa), two levels of supplementary Zn (O and 20 mgl−1) and two levels of foliar IAA application (O and 10 mgl−1). Under control conditions (no Zn, no IAA), increasing soil drying progressively retarded shoot and root growth (length and dry mass production), reduced leaf relative water content (RWC) and decreased the contents of chlorophyll (Chl) and shoot soluble sugars (SS), but increased soluble sugar content of roots and lowered osmotic water potential of shoots and roots (osmotic adjustment). Total free amino acid (TAA) content increased in shoots but decreased in roots whereas contents of soluble proteins (SP) decreased in shoots and roots. The effect of water stress was statistically significant (p<0·05) and had a major effect (as indicated by η2values) on leaf RWC, shoot and root dry masses and osmotic potential. Supplementary Zn improved root growth at all levels of stress and shoot growth under severe stress. Improvement of growth was positively correlated with the internal tissue Zn concentrations (r=0·91 and 0·86 for shoot and 0·94 and 0·82 for root length and dry mass respectively). Exogenous IAA raised (p<0·05) RWC, Chl, DM (slightly), root SS, and SP, whereas shoot TAA was lowered. Effects on root TAA and shoot SS were more complex: they were lowered at zero stress and raised under severe stress. IAA and Zn in combination had additive effects on Chl, growth and osmotic potential, but their combined effects on SP and TAA were more complex. It is concluded that the treatment of soybean plants grown under conditions of low soil water potentials and Zn deficiency with Zn and IAA solutions counteracted the deleterious effects of stress, especially at high stress levels, and helped stressed plants to grow successfully under these adverse unfavourable conditions.  相似文献   

6.
种培芳  李毅  苏世平 《中国沙漠》2014,34(5):1301-1306
以3个地理种源(武威、张掖、酒泉)蒙古沙拐枣(Calligomum mongolicum)两年生苗木为试材,研究干旱胁迫对其光合及荧光参数的影响,并采用投影寻踪法对其进行了抗旱性评价。结果表明:干旱胁迫导致3个地理种源蒙古沙拐枣光合作用均有所下降,但下降幅度不同,尤其在张掖和酒泉种源间差异显著(p0.05)。在重度干旱时,3个种源的光合速率(Pn)酒泉武威张掖,蒸腾速率(Tr)张掖武威酒泉,气孔导度(Gs)酒泉武威张掖。干旱胁迫下,3个地理种源蒙古沙拐枣的荧光特性表现为初始荧光(Fo)和非光化学淬灭系数(qN)升高,最大光学效率(Fv/Fm)、实际光能转化效率(ФPSⅡ)和光化学淬灭系数(qP)降低。在重度胁迫下,3个种源的Fo和qP大小排序分别为张掖武威酒泉,Fv/Fm、ФPSⅡ和qN为酒泉武威张掖。以投影寻踪法对3个地理种源蒙古沙拐枣的抗旱性排序结果为酒泉武威张掖。  相似文献   

7.
大叶黄杨对土壤水分梯度胁迫的生长与生理响应   总被引：1，自引：1，他引：0  
包玉  王志泰 《干旱区地理》2011,34(2):208-214
以盆栽大叶黄杨为试材,研究了大叶黄杨生长与生理指标对不同程度土壤水分胁迫的响应.结果表明:土壤水分胁迫对生长指标(苗重、苗高和地径)有明显的影响,变化表现出一致的规律性,即随胁迫程度加剧均呈现出下降趋势.干旱胁迫下生理指标的变化表现出差异性:束缚水/自由水的比值随胁迫程度加强而增大;水分饱和亏缺变化和丙二醛活性在轻、中...  相似文献   

8.
This investigation was carried out to better understand the effects of nitrogen stress on the growth and yield of tomato(Solanum lycopersicon L.). Seeds of S. lycopersicon(Ife No. 1 variety) were collected from the Osun–State Ministry of Agriculture, Oshogbo, Nigeria and planted in analyzed top soil. The plants were grown for a period of five weeks within which they were supplied with water and kept under optimum environmental conditions that enhanced normal growth. After this period, the plants were subjected to different levels of nitrogen stress which include: plants supplied with distilled water only(n), plants supplied with complete nutrient solution(N), plants supplied with nutrient solution in which nitrogen concentration sources was increased by a factor of 5(N5), and plants supplied with nutrient solution in which nitrogen concentration sources was increased by a factor of 10(N10). Analysis of Variance(ANOVA) results shows that there is no significant effect of stress on the growth and morphological parameters of tomato plants. However, there was a significant effect of nitrogen stress on the yield parameters. Nitrogen stress also caused an increase in the number and size of fruits produced in plants subjected with high nitrogen concentration.  相似文献   

9.
Over the course of a day, aridland plants experience a range of incident photosynthetic photon flux (PPF) spanning three orders of magnitude. Rapid photosynthetic responses to changes in PPF have large effects on individual plant carbon gain and water use patterns, hence are important to plant distribution and success. We investigated the response over time of photosynthesis (A), stomatal conductance (g), and inter-cellular CO2 concentration (Ci) to step changes in PPF in a long-lived aridland perennial that typically occurs in two contrasting microhabitats, shade under shrubs of other species and unshaded inter-shrub spaces. An initial rapid response in A and Ci for plants in both microhabitats occurred after abrupt changes in PPF. This was followed by slower changes in these parameters during the rest of the light or dark period. Stomatal conductance responded more gradually to step changes in PPF. The initial increase in A after a dark cycle was significantly greater for plants under shrubs than for plants in inter-shrub spaces, but other changes in A, g and Ci did not differ. We attribute the similar responses in plants from different microhabitats to natural variations in solar radiation and limited selection for differentiation due to population gene pools dominated by plants in the open. Our results support the hypothesis that variable light regimes select for photosynthetic gas exchange processes that closely track changes in incident PPF. Our data also support the hypothesis that gas exchange responses to variable light regimes in aridland plants minimize trade-offs between carbon gain and water loss.  相似文献   

10.
Nonstructural carbohydrates(NSC) and nitrogen metabolism strongly influence growth and development in plants. The biosynthesis of cellulose and lignin(structural carbohydrates, SC) depends largely on the supply of NSC. We desire to examine which hypothesis, carbon limitation or growth limitation, best fits the alpine plant response between NSC, SC, carbon(C), nitrogen(N) and altitude. We compared the foliar concentrations of carbohydrates, C and N between the leaves of Picea crassifolia(lower-elevation tree-line species) and Sabina przewalskii(high-elevation tree-line species) in their response to changing elevation. Our site was located in the mid-northern area of Qilian Mountains, China. We found that foliar soluble sugar(SG) concentrations were significantly higher in P. crassifolia than in S. przewalskii at the 2,700–3,400 m level. Foliar NSC levels in P. crassifolia increased at the 2,700–3,100 m level, indicating that growth was limited gradually resulting in a surplus of NSC(to conform to GLH), subsequently decreasing at the 3,100–3,400 m level, the assimilation declined leading to C deficit(to conform to CLH). SC(SC metabolism disorders at 3,100–3,400 m), C, N and starch were significantly lower in P. crassifolia than in S. przewalskii. Conversely, foliar SG concentration shows a fall-rise trend with increasing elevation for S. przewalskii. SC concentration in S. przewalskii leaves decreased with an increase of elevation and has a significantly positive correlation to N concentration marking the assimilation of plants. Therefore, the high-elevation tree-line species(S. przewalskii) utilize or store more foliar SG leading to a decrease of SG concentration for survival and growth/regrowth in an adverse environment, higher total C, N, SC, starch contents and lower NSC level. Also, their change trends along the elevational gradient in leaves of S. przewalskii indicate better assimilation strategies for SG use under environmental stress compared to P. crassifolia. This indicates that foliar C metabolism along the elevation follows the principle of the growth-limitation hypothesis(GLH) or carbon limitation hypothesis(CLH), which depends on the acclimation of different alpine life-forms to the environment.  相似文献   

11.
Nitraria sphaerocarpa Maxim., a typical desert plant which often appears in nebkha form, is widely distributed along the periphery of oasis in arid regions of Northwest China, and plays an important role in desertification control around oases. In this paper, the characteristics and distribution patterns of N. sphaerocarpa nebkhas were investigated in a Gobi environment outside an oasis. Results shows that about 200 N. sphaerocarpa nebkhas per hectare was recorded and total sand sediments was 25 m3/ha. Nebkhas vary in size, and the mean height (H) and horizontal composition (L) were 15 cm and 80 cm, respectively. There exists a significant linear relationship between H and L, suggesting that the investigated nebkhas are mostly in the growth stage. The numbers, height and sand deposit of nebkhas decreased with increasing distance away from the oasis. Grain-size analysis indicates that the mean grain size of sediments at the crests of nebkhas increased with increasing nebkha height. Organic C and total N concentrations were related to the mean grain size. It was concluded that N. sphaerocarpa shrubs are efficient horizontal sand traps for wind-driven sediments. A better understanding of the development of nebkha can provide information for the design of biological sand control measures around oases in arid regions.  相似文献   

12.
Antioxidant enzyme activity, photosynthetic pigment content, and free malondialdehyde (MDA), as well as flavonoid content and the key enzyme activity in the flavonoid pathway were determined in two desert shrubs, Caryopteris mongolica Bunge and Reaumuria soongorica (Pall.) Maxim. under drought stress. The free MDA content was enhanced during the experimental period, which may be an indicator of oxidative stress. Superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX) activities in C. mongholica showed a significant increase during the experiment, but catalase (CAT) activity was slightly decreased. On the other hand, POD and APX activities showed a significant increase and SOD and CAT activity data had no significant changes in R. soongorica. APX, SOD, and CAT activities were higher in R. soongorica than in C. mongholica, but MDA content was lower, indicating that the lower values of MDA were attributed to higher activities of antioxidant enzyme in R. soongorica. Chlorophyll content decreased significantly in the two shrubs during the experiment, which indicated that there was a photoprotection mechanism through reducing light absorbance by decreasing pigments content. Caretonoids content increased in C. mongholica and decreased in R. soongorica. The ratio of Chla/Chlb decreased significantly but caretonoids/Chl revealed a significant increase in the two shrubs, which could be explained as no decrease of peripheral light-harvesting complexes and a higher tolerance to drought. Total flavonoid content and the activities of phenylalanine ammonialyase (PAL) and chalcone isomerase (CHI) showed different changes between C. mongholica and R. soongorica after treatment. These values decreased in R. soongorica and increased in C. mongholica except for PAL activity. However, anthocyanin content increased in the two shrubs, indicating that there was a different regulation response in the flavonoid pathway in the two shrubs under drought stress, and anthocyanin should be an important antioxidant both in the shrubs. Our results demonstrated the different responses of antioxidant defense and drought tolerance ability between the two shrubs.  相似文献   

13.
The effects of temperature, water stress, hydration–dehydration cycles and seed priming on the germination of Callitris verrucosa and Callitris preissii, two Australian semi-arid coniferous tree species, were investigated. Optimum germination occurred at 18°C, with a minimum germination time of 8–9 days for both species. At this temperature, germination was inhibited at osmotic potentials lower than −1·0 MPa, but the capacity to germinate at low osmotic stress increased as the temperature decreased. Seed priming and hydration–dehydration cycles did not reduce seed viability, and Callitris seeds appear to retain the physiological changes induced by short-term hydration, as the time to the onset of germination was decreased to about 3 days. The capacity of Callitris seeds for incremental germination is likely to increase overall germination success in a low rainfall environment.  相似文献   

14.
水分胁迫条件下棉花生理变化及其高光谱响应分析   总被引：19，自引：4，他引：15  
利用ASD地物光谱仪,测定水分胁迫条件下棉花不同生育时期内叶片的光谱反射率,应用微分技术处理棉花的反射光谱,并结合棉花叶面积指数(LAI)、叶绿素(a b)含量(Chlt)、叶片全氮(TN)含量等生物参数进行分析,研究棉花水分胁迫情况下的高光谱特征,结果表明,一阶微分光谱720nm波段的数值与LAI的正相关(R=0．7656);750nm处一阶微分值与叶绿素含量呈显著正相关关系(R=0．7774);微分光谱690nm～740nm数值积分面积与TN含量呈正相关(R=0．7669),采用比值反射率对反射光谱1300nm～1500nm波段范围内最小值与棉花叶片的含水量作相关分析,达到极显著水平(R^2=0．8298),验证了一阶微分光谱数据与棉花的生理参数有很好的相关性,可见光和近红外波段光谱反射率能够反映出棉花生长发育的动态特征;证明了棉花的花铃期是高光谱遥感对棉花长势和生理参数定量诊断的最佳时期。本研究通过建立一系列线性光谱模型对棉花生理参数进行估测,为基于高光谱数据的棉花生长模型和棉花长势的遥感监测提供了理论依据。  相似文献   

15.
4树种主要生理指标对模拟水分胁迫的响应   总被引：7，自引：4，他引：3  
比较了白毛锦鸡儿、荒漠锦鸡儿、驼绒藜和霸王的主要生理指标叶片含水量、自然饱和亏、超氧化物歧化酶（SOD）活性、可溶性糖和丙二醛（MDA）含量,在不同生长期（夏季和秋季）对不同浓度聚乙二醇（PEG=10%、20%、30%）及不同胁迫时间（0 h、12 h、24 h）模拟水分胁迫的响应差异。结果表明：①霸王、驼绒藜抗干旱损伤的能力总体比两种锦鸡儿强;②同样处理水平下,种间SOD活性差异不显著,各指标夏秋响应差异显著,秋季较夏季敏感,树种抗旱能力与生长期及生理状态有密切的关系;③相关性分析表明,水分胁迫后水分亏缺大的树种,质膜受伤重,SOD保护酶与可溶性糖对树种抵抗水分胁迫起到一定的保护作用,调节协同机制及响应时间存在差异。  相似文献   

16.
张静  张元明 《中国沙漠》2014,34(2):433-440
新疆古尔班通古特沙漠地表具有发育完好的生物土壤结皮,本文以参与组成生物土壤结皮的优势藓类———齿肋赤藓(Syntrichia caninervis)为研究对象,在实验室内对其进行模拟降雨处理,降雨量分别为0mm(对照)、2mm、6mm、10mm和15mm,研究模拟降雨影响下齿肋赤藓植株含水量、光合色素含量及可溶性糖、游离脯氨酸、可溶性蛋白、抗氧化酶(SOD、CAT和POD)、丙二醛含量的变化,以探讨其对降雨的生理生化响应。结果表明:随降雨量的增加,齿肋赤藓植株含水量显著增加;随齿肋赤藓植株含水量的增加,其光合色素含量和可溶性蛋白含量显著增加;随降雨量增加,抗氧化酶(SOD、CAT和POD)活性和可溶性糖含量呈大致递减的趋势,游离脯氨酸和丙二醛含量呈先下降后上升的变化趋势。在干燥状态下齿肋赤藓通过提高体内保护酶(SOD、CAT和POD)活性,增加可溶性糖和游离脯氨酸含量来抵御外界干旱胁迫的环境;而降雨能够增加齿肋赤藓植株含水量,激活其光合生理活性,显著提高光合色素含量,但是降雨量过大又将加剧齿肋赤藓膜脂过氧化的程度。  相似文献   

17.
Shoots ofTamarix niloticaandT. aphyllawere collected from north Sinai, the Nile Delta and North Western Desert of Egypt and analysed forin vitrototal digestible nutrients, nutritive value, gross energy and element contents. Pronounced differences were recorded between the two species for all the estimated variables. Variation in gross energy in the tissues of both species in relation to different locations was insignificant. The two evaluated species have relatively low contents of N, K, Ca and crude protein and high contents of P, Mg and Na. There was a moderate positive correlation between the N–NDF, K–CF and EE–NDF ofTamarix aphylla. The present study evaluated the nutrient status of both species as poor forage.  相似文献   

18.
Testate amoebae are now commonly used in paleoenvironmental studies but little is known of their taphonomy. There is some experimental evidence for differential preservation of some testate amoeba shell types over others, but it is unclear what, if any impact this has on palaeoenvironmental reconstruction. To investigate this issue we looked at palaeoecological evidence for the preservation of different shell types. We then investigated the possible impact of selective preservation on quantitative palaeoenvironmental inference. We first used existing palaeoecological data sets to assess the vertical patterns of relative abundance in four testate amoeba shell types: (1) shells made of secreted biosilica plates (idiosomes, e.g. Euglypha), (2) idiosomes with thick organic coating (Assulina), (3) proteinaceous shells (e.g. Hyalosphenia), (4) shells built from recycled organic or mineral particles (xenosomes) (e.g. Difflugia, Centropyxis). In three diagrams a clear pattern of decay was only observed for the idiosome type. In order to assess the implications of differential preservation of testate amoeba taxa for paleoenvironmental reconstruction we then carried out simulations using three existing transfer functions and a wide range of scenarios, downweighting different test categories to represent the impact of selective test decomposition. Simulation results showed that downweighting generally reduced overall model performance. However downweighting a shell type only produced a consistent directional bias in inferred water table depth where that shell type is both dominant and shows a clear preference along the ecological gradient. Applying a scenario derived from previous experimental work did not lead to significant difference in inferred water table. Our results show that differential shell preservation has little impact on paleohydrological reconstruction from Sphagnum-dominated peatlands. By contrast, for the minerotrophic peatlands data-set loss of idiosome tests leads to consistent underestimation of water table depth. However there are few studies from fens and it is possible that idiosome tests are not always dominant, and/or that differential decomposition is less marked than in Sphagnum peatlands. Further work is clearly needed to assess the potential of testate amoebae for paleoecological studies of minerotrophic peatlands.  相似文献   

19.
测定了荒漠地区超旱生小灌木红砂在3种生境(山前荒漠、山前戈壁和中游戈壁)下的叶片水分状态、抗氧化酶活性及渗透调节物质含量,以探讨荒漠植物在不同生境下的生理生化特征及对荒漠极端环境的适应机制。结果表明:在3种生境下,红砂叶片相对含水量和叶片水势随着土壤含水量的下降而下降,叶绿素含量随着土壤含水量的下降而升高。随着生境土壤干旱的加剧,超氧化物歧化酶(SOD)及过氧化物酶(POD)活性逐渐升高,而过氧化氢酶活性下降。在土壤含水量较少的戈壁生境,渗透调节物质含量上升。SOD和POD活性的升高是红砂抵御干旱环境的主要抗氧化保护机制;渗透调节在红砂叶片适应干旱胁迫的过程中发挥着重要作用,高的渗透调节能力使红砂在水分不足的条件下维持较低的渗透势,有利于植物吸水,从而增强其耐旱性。  相似文献   

20.
Light may be an important limiting resource that influences community structure of chenopod shrublands. As part of a larger study that aimed to determine the factors that influence chenopod community structure, the focus of this study was the influence of plant canopy on the growth and establishment of smaller plants. We therefore measured the height and cover of three chenopods (Enchylaena tomentosa, Maireana brevifolia and Maireana georgei) when growing within and outside of the canopy of Atriplex bunburyana under field conditions. All three chenopods had lower cover and E. tomentosa was taller when growing within the canopy of A. bunburyana in comparison to those growing outside of the canopy. The chenopods were then grown under three artificial shade regimes. Plant height, cover, biomass, relative leaf area and photosynthetic surface area measurements showed that each species responded differently to shade. E. tomentosa biomass was facilitated by shade. This was inferred by an increase in total plant biomass. M. brevifolia, in contrast, tolerated shade by increasing above-ground biomass allocation. M. georgei was adversely affected by the shade regimes: root biomass decreased in response to shade. Competition for light is, therefore, likely to influence chenopod community structure of semi-arid and arid environments.  相似文献   

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