天坑森林植物叶-凋落物-土壤C、N、P生态化学计量特征

为探究广西乐业大石围天坑森林群落的C、N、P养分循环特征,比较了天坑内外森林群落的植物叶片-凋落物-土壤C、N、P含量及其化学计量比,采用相关性分析和冗余分析等统计方法研究其内在联系和相互影响。结果表明,与天坑外部森林相比,天坑内部森林植物叶片和凋落物呈现出C低N、P高,土壤为C、N低P高的格局。植物叶片C:N、C:P与凋落物C、N:P显著正相关,植物叶片C与土壤P显著负相关;天坑外部森林的植物叶片N、N:P与土壤N:P显著负相关,植物叶片C:N与土壤C、C:N显著正相关,说明天坑森林内部凋落物的C、P养分可能主要来源于植物叶片,而天坑外部森林的植物叶片C、N主要来自土壤。土壤C:N:P对植物叶、凋落物的C:N:P变化的解释率分别为90.7%和50.6%,其中土壤P对植物叶和凋落物的C:N:P计量特征变化的解释度最高,坑内生境植物对P含量变化更为敏感、坑外植物对于N含量变化更为敏感,表明天坑内部森林可能是P素受限位点、天坑外部森林是N素受限位点。喀斯特天坑内部森林和外部森林植物叶-凋落物-土壤的C:N:P的差异和联系,体现了天坑内外森林群落的养分循环特征和植物群落的适应性。

Characterization of Dye Sensitized Cells Using Natural Dye from Oil Bean Leaf (<i>Pentaclethra macrophylla</i>): The Effect of Dye pH on the Photoelectric Parameters

Fresh leaves of oil bean (P. macrophylla) were used as sensitizers for fabrication of dye sensitized solar cells (DSSCs) at four dye pH values of 2.58°C at 23.7°C, 2.62°C at 22.2°C, 2.65°C at 22.3°C and 3.61°C at 22.1 °C. The methanol extracts of P. macrophylla were extracted and used as sensitizers for the development of dye sensitized solar cells. The solar cells sensitized by P. macrophylla leaf extracts realised up to short circuit current (Jsc) 0.16 mA/cm2, open circuit voltage (Voc) 0.045 V, Pmax 0.031 mW/ cm2 and fill factor (FF) 0.50. The energy conversion efficiency (η) of the DSSCs is 0.43%. Phytochemical screening of P. macrophylla leaf extract shows the presence of flavonoids and anthraquinones. The nanostructured dye shows conversion of solar energy into electricity using low cost natural dyes as wide band-gap semiconductor sensitizers in DSSCs. This will provide economically viable substitute to silicon p-n junction photovoltaic (PV).

水曲柳叶片功能性状及C、N、P化学计量对海拔的响应

【目的】水曲柳是小陇山主要珍贵的用材树种,探讨其叶片性状对小生境变化的适应性,可为深入研究影响该树种的主要环境因子提供理论基础。【方法】以黑河保护区天然水曲柳为研究对象,分析4个海拔梯度(1268,1529,1741,1926 m)间14种叶片功能性状和叶片营养元素含量的差异显著性及其相关性。【结果】(1)随海拔升高,叶片厚度、干物质含量和叶绿素含量逐渐增大,并分别在海拔1741 m、1926 m、1741 m处达到最大,比叶面积、最大净光合速率、蒸腾速率、叶C和N含量则逐渐减少,除叶C含量外均在海拔1268 m达到最大。叶面积、气孔导度和叶C∶N随着海拔升高呈先增后降的趋势,胞间CO_(2)浓度、C∶P和N∶P呈先降后升的趋势。(2)海拔平均每上升200 m,叶片功能性状和C∶N平均增加1.13%~30.72%,比叶面积、最大净光合速率和C、N含量减小2.22%~15.75%。(3)各海拔叶N∶P为4.36~6.89,与最大净光合速率呈极显著正相关。最大净光合速率与比叶面积、C和N含量、C∶P和N∶P呈极显著正相关,与叶片厚度、干物质含量和叶绿素含量呈极显著负相关,比叶面积与干物质含量呈极显著负相关,与C和N含量和C∶P呈极显著正相关。【结论】海拔显著影响水曲柳叶片功能性状及元素含量,海拔1700 m以下有利于叶的发育和养分的积累。

Pseudocercospora leaf and fruit spot disease of citrus: Achievements and challenges in the citrus industry: A review

Citruses are the worlds’ second fruit crops by volume next to banana. It is one of the most important commodity in tropical Africa as source of foreign currency, raw material for agro-industries and source of employment. The production and productivity of citrus in tropical Africa including Ethiopia are critically threatened by a number of diseases. Among others, pseudocercospora leaf and fruit spot of citrus caused by a fungus Pseudocercospora angolensis is the most destructive disease of citrus. Literature reviews have been made by searching the available information on leaf and fruit spot of citrus. Journal articles, research papers, workshop proceedings, Thesis research, manuals, and quarantine regulations were among the information sources of the review. The disease is widespread in 22 African countries including Ethiopia with a single report around Yemen in the Arabian Peninsula. Scattered research efforts have been made by different researchers in Africa mainly dealing with its geographic distribution, biology, and management practices. Fungicides, plant extracts/essential oils, and host resistance are among the research efforts made for the control of P. angolensis. Even though the disease is not yet reported to the rest of the world, it becomes a serious concern as an important quarantine pest thereby critically affecting the world trade and germplasm exchange of the citrus industry. Therefore, the purpose of this paper is to compile the scattered information on various aspects of leaf and fruit spot of citrus mainly to avail the information for researchers, development workers and policy people. Moreover, this review will suggest future research and development direction towards better understanding and sustainable management practices of the disease.

Inheritance of the Pale—Green Leaf Marker and Sterility Trait in Photo—Thermo Sensitive Genic Male Sterile Rice

P/TGMS (photo-thermo sensitive genie male sterility) lines with pale-green leaf color have been developed in japonica rice. The marker trait is used as an assistant selection in the production of the two-lines system hybrid rice for the improvement of F, seed purity. A joint inheritance study of both leaf color and male sterility is presented for P/TGMS line with pale-green leaf color. The segregation ratios for leaf color in the F2 populations of the three crosses showed 13 : 3 and 15 : 1 at early and late sowing stages (April 26 and June 23) respectively, implying that the leaf color is controlled by two genes with fertility gene as dominant. Sterility level is higher in the early sowing stage than that in the late sowing. The inducement of male sterility is closely related to longer day-length and higher temperature at the developmental stages of young panicle. The genes to govern the leaf color and male fertility are inherited independently.

Effect of nitrogen and phosphorus addition on leaf nutrient concentrations and nutrient resorption efficiency of two dominant alpine grass species

Nitrogen(N)and phosphorus(P)are two essential nutrients that determine plant growth and many nutrient cycling processes.Increasing N and P deposition is an important driver of ecosystem changes.However,in contrast to numerous studies about the impacts of nutrient addition on forests and temperate grasslands,how plant foliar stoichiometry and nutrient resorption respond to N and P addition in alpine grasslands is poorly understood.Therefore,we conducted an N and P addition experiment(involving control,N addition,P addition,and N+P addition)in an alpine grassland on Kunlun Mountains(Xinjiang Uygur Autonomous Region,China)in 2016 and 2017 to investigate the changes in leaf nutrient concentrations(i.e.,leaf N,Leaf P,and leaf N:P ratio)and nutrient resorption efficiency of Seriphidium rhodanthum and Stipa capillata,which are dominant species in this grassland.Results showed that N addition has significant effects on soil inorganic N(NO_(3)^(-)-N and NH_(4)^(+)-N)and leaf N of both species in the study periods.Compared with green leaves,leaf nutrient concentrations and nutrient resorption efficiency in senesced leaves of S.rhodanthum was more sensitive to N addition,whereas N addition influenced leaf N and leaf N:P ratio in green and senesced leaves of S.capillata.N addition did not influence N resorption efficiency of the two species.P addition and N+P addition significantly improved leaf P and had a negative effect on P resorption efficiency of the two species in the study period.These influences on plants can be explained by increasing P availability.The present results illustrated that the two species are more sensitive to P addition than N addition,which implies that P is the major limiting factor in the studied alpine grassland ecosystem.In addition,an interactive effect of N+P addition was only discernable with respect to soil availability,but did not affect plants.Therefore,exploring how nutrient characteristics and resorption response to N and P addition in the alpine grassland is important to understand nutrient use strategy of plants in terrestrial ecosystems.

温度对大叶桃花心木(Swietenia macrophylla King)幼苗叶片的光合影响(英文)

本文研究了大叶桃花心木(Swietenia macrophylla King)一年生幼苗在经过夜温处理后的光响应曲线和在饱和光强下的CO2反应曲线。结果表明:在大气CO2浓度下,叶片的最佳光合作用温度在25-31℃之间,而在饱和CO2浓度下为31-35℃。在25℃以下光合速率开始降低,主要是由于羧化效率的降低,而当温度超过31℃时,光合速率下降,是因为羧化效率的降低和呼吸速率的增加。CO2浓度对光合的促进作用在低温下受到抑制,这意味着未来在CO2浓度增高的情况下,高浓度的CO2对热带常绿植物光合的促进在冬天低温情况下表现不十分明显。图4参23。

Spatial patterns of leaf nitrogen and phosphorus stoichiometry across southeast to central Tibet

Leaf N and P stoichiometry in terrestrial ecosystems has been widely investigated in recent years owing to the importance of these elements in improving the predicted vegetation responses to global changes.The vertical distribution of leaf N and P stoichiometry has attracted increasing attention because of the dramatic changes in environmental factors at regional scales.However,the characteristics of leaf N and P stoichiometry in the southeast Qinghai–Tibet plateau(SET)are not clear,although this area is sensitive to global change.Here,we analyzed the leaf N and P concentrations in dominant plant species on natural altitudinal gradients on the Duoxiongla(DXL),Sejila(SJL),Mila(ML),and Gangbala(GBL)mountains across the SET all the way to central Tibet.Our results showed that the leaf N concentrations were comparable among the regions,whereas the leaf P concentrations dramatically decreased from SET to central Tibet(CT).The leaf N concentrations were 23.6,21.3,20.8,and 22.4 g kg^(-1),and the leaf P concentrations were 2.40,2.49,1.94,and 1.59 g kg^(-1) on the SJL,DXL,ML and GBL mountains,respectively.The leaf N/P ratios on the DXL,SJL,ML,and GBL mountains were 8.81,10.3,11.2,and 14.2,respectively.Considering the increasing trend of the leaf N/P ratio from southeast Qinghai–Tibet plateau to central Tibet,N limitation might widely exist in well vegetated ecosystems in the Qinghai–Tibet plateau.

Modulatory Effect of Distillate of Ocimum sanctum Leaf Extract (Tulsi) on Human Lymphocytes Against Genotoxicants

Objective To study the modulatory effect of distillate of Ocimum sanctum （traditionally known as Tulsi） leaf extract （DTLE） on genotoxicants. Methods In the present investigation, we studied the antigenotoxic and anticlastogenic effect of distillate of Tulsi leaf extract on （i） human polymorphonuclear leukocytes by evaluating the DNA strand break without metabolic activation against mitomycin C （MMC） and hexavalent chromium （Cr^＋6） and （ii） human peripheral lymphocytes （in vitro） with or without metabolic activation against mitomycin C （MMC）, hexavalent chromium （Cr^＋6） and B[a]P by evaluating chromosomal aberration （CA） and micronucleus assay （MN）. Three different doses of DTLE, 50 μL/mL, 100 μL/mL, and 200 μL/mL were selected on the basis of cytotoxicity assay and used for studying DNA strand break, chromosomal aberration and micronucleus emergence. The following positive controls were used for inducing genotoxicity and clastogenicity MMC （0.29 μmol/L） for DNA strand break, chromosomal aberration and 0.51 μmol/L for micronucleus assay; Potassium dichromate （Cr^＋6） 600 μmol/L for DNA strand break and 5 μmol/L for chromosomal aberration and micronucleus assay; Benzo[a]pyrene （30 μmol/L） for chromosomal aberration and 40 μmol/L for micronucleus assay. The active ingredients present in the distillate of Tulsi leaf extract were identified by HPLC and LC-MS. Results Mitomycin C （MMC） and hexavalent chromium （Cr^＋6） induced statistically significant DNA strand break of respectively 69% and 71% （P〈0.001） as revealed by fluorometric analysis of DNA unwinding. Furthermore, the damage could be protected with DTLE （50 μL/mL, 100 μL/mL, and 200 μL/mL） on simultaneous treatment. Chromosomal aberration and micronucleus formation induced by MMC, Cr^＋6 and B[a]P were significantly protected （P〈0.001） by DTLE with and without metabolic activation. Conclusion Distillate of Tulsi leaf extract possesses antioxidants contributed mainly by eugenol, luteolin and apigenin as identified by LC-MS. These active ingredients may have the protective effect against genotoxicants.

Antimicrobial effect of <i>Anacardium occidentale</i>leaf extract against pathogens causing periodontal disease

The oral cavity is perpetually colonized by different species of microorganisms and at times it is difficult to characterize the periodontal pathogen causing breakdown of tissue and bone. But over the years, based on scientific knowledge, it has been observed that various gram negative anaerobic bacteria have been involved with the initiation of periodontal disease. Based on literature reviews, a study was undertaken to investigate the antimicrobial effect of Anacardium occidentale (cashew) leaf extract on Porphyromonas gingivalis and Prevotella intermedia. Methanol and aqueous extracts of cashew leaves were prepared. Its antimicrobial activity against P. gingivalis and P. intermedia was tested using the agar diffusion method at various dilutions of 75 μ, 50 μl, 25 μl, 10 μl and 5 μl respectively. 0.2% Clorhexidine gluconate (CHX) was used as control. Cultures of P. gingivalis and P. intermedia strains were maintained on Kanamycin blood agar. The agar plates were then incubated at 37?C for 72 hours after which the zone of inhibition was measured and the mean was recorded for each test solution. The results of this study demonstrated that, for both P. gingivalis and P. intermedia, the highest concentration (75 μl) of both the extracts showed maximum antimicrobial action. For P. ginigvalis, the aqueous extract demonstrated significant inhibitory activity compared to the methanolic extract (p = 0.005), which was comparable to that of CHX. For P. intermedia, similar results were observed with aqueous extract being more effective compared to methanolic (p = 0.007), however, CHX was most effective compared to both the extracts (p = 0.007). This study revealed that Anacardium occidentale leaf extracts have efficient antimicrobial activity against P. gingivalis & P. intermedia. Hence, this preliminary study suggests that the antimicrobial action of A. occidentale leaf could be utilized for the preparation of chemical plaque control formulations.

Patterns and driving factors of leaf C,N,and P stoichiometry in two forest types with different stand ages in a mid-subtropical zone

Background:Carbon(C),nitrogen(N),and phosphorus(P)stoichiometry is a key indicator of nutrient utilization in plants,and C/N/P ratios are related to the life histories and adaptation strategies of tree species.However,no consensus has been reached on how leaf stoichiometric characteristics are affected by forest type and stand ages.The relationships between leaf stoichiometry and geographical,meteorological,and soil factors also remain poorly understood.Methods:Leaf and soil were sampled from forest stands of different age groups(young,middle-aged,near-mature,and mature)in two forest types(Chinese fir(Cunninghamia lanceolata)forests and evergreen broadleaved forests).The relationships between leaf C,N,and P stoichiometric parameters and geographical,meteorological,and soil factors were analysed by using redundancy analysis(RDA)and stepwise linear regression analysis.Results:Leaf C concentrations peaked in the near-mature stands with increasing age irrespective of forest type.Leaf N and P concentrations fluctuated with a rising trend in Chinese fir forests,while decreased first and increased later from young to mature phases in natural evergreen broadleaved forests.Chinese fir forests were primarily limited by N and P,while natural evergreen broadleaved forests were more susceptible to P limitation.Leaf C,N,and P stoichiometric characteristics in Chinese fir forests were mainly affected by the soil total P concentration(SP),longitude(LNG),growing season precipitation(GSP)and mean temperature in July(JUT).The leaf C concentration was mainly affected by GSP and JUT;leaf N and P concentrations were both positively correlated with LNG;and leaf P was positively correlated with SP.In evergreen broadleaved forests,however,leaf stoichiometric parameters displayed significant correlations with latitude(LAT)and mean annual precipitation(MAP).Conclusions:Leaf stoichiometry differed among forest stands of different age groups and forest types.Leaf C,N,and P stoichiometry was primarily explained by the combinations of SP,LNG,GSP and JUT in Chinese fir forests.LAT and MAP were the main controlling factors affecting the variations in the leaf C,N,and P status in natural evergreen broadleaved forests,which supports the temperature-plant physiological hypothesis.These findings improve the understanding of the distribution patterns and driving mechanisms of leaf stoichiometry linked with stand age and forest type.

双叶清肺止咳糖浆止咳药效学及对大鼠感染后支气管模型BALF中P物质、CGRP、NGF的影响

目的:研究双叶清肺止咳糖浆的祛痰、抗炎作用及其作用机制。方法:通过大鼠玻璃毛细管排痰实验和小鼠气管酚红排泌实验,观察双叶清肺止咳糖浆的祛痰作用;通过小鼠耳肿胀实验观察双叶清肺止咳糖浆的抗炎作用,通过小剂量脂多糖(LPS)诱导革兰阴性菌感染,建立大鼠感染后支气管模型,用ELISA法检测空白组、双叶清肺止咳糖浆高、中、低剂量组、阳性对照组左肺BALF中P物质(SP)、降钙素基因相关肽(CGRP)、鼠神经生长因子(NGF)的含量。结果:(1)大鼠排痰实验中,双叶清肺止咳糖浆高、中剂量组、氯化铵组大鼠排痰量较空白组增加,差异显著(P<0.01);(2)小鼠气管酚红排泌实验中,双叶清肺止咳糖浆高剂量组、氯化铵组、急支糖浆组能升高排泌酚红浓度,与空白组比较,差异显著(P<0.05,P<0.01);(3)小鼠耳肿胀实验中,双叶清肺止咳糖浆高剂量组、醋酸泼尼松组、急支糖浆组耳肿胀度较空白组降低,差异显著(P<0.05,P<0.01);(4)模型实验中,与正常组比较,模型组SP、CGRP、NGF的含量明显升高,双叶清肺止咳糖浆高、中剂量组、美敏伪麻溶液组SP、CGRP、NGF的含量与模型组比较显著降低,差异具有统计学意义(P<0.05,P<0.01)。结论:双叶清肺止咳糖浆能促进排痰,减轻炎症反应,减少大鼠咳嗽次数,保护受损炎症组织,其机制可能与改善大鼠SP和CGRP、NCF表达有关。

Relationship between Leaf Micro- and Macro-Nutrients in Top Canopy Trees in a Mixed Forest in the Upper Rio Negro in the Amazon Region

The mixed forests of the upper Rio Negro at the northern of the Amazon basin grow in oxisol soils that are extremely infertile. These areas exhibit deficiencies in several macro-nutrients, and may also be characterized by the shortage or toxic excess of some micronutrients. The overall goal of this research is to collect more comprehensive information regarding the micronutrient composition of the upper Rio Negro forests as well as discern the relationship between leaf micro- and macro-nutrients that may contribute to the homeostasis and balance of the ionome. Firstly, the nutrient composition within the oxisol soil and leaf tissues of two top canopy tree species from the mixed forests was determined. We then analyzed the relationship between leaf micronutrient composition with N and P levels of the two species and that of species inhabiting the Amazon caatinga. Extractable soil Zn, B, Mn and Cu were very low in the mixed forest. In contrast, Fe and Al levels were potentially toxic. The analysis of leaf N/P ratios revealed for the first time the co-limitation of N and P in the mixed forest. This contrasts with species from the adjacent Amazon caatinga toposequence that are characterized by strong N limitation. All micronutrients within leaves of species inhabiting the mixed forest were also found to have low concentrations. Moreover, Fe and Al were detected at concentrations well below those reported for accumulator species. This suggested that leaf ion homeostasis was maintained under potentially toxic soil Fe and Al conditions. Leaf micronutrient (Fe, Zn and B) contents mirrored that of leaf N and P contents, and comparable Fe/N, Fe/P, Zn/N, Zn/P, B/N as well as B/P ratios were found across species and forest types. Therefore, forest species exhibited the capability to maintain leaf nutrient balances under soil conditions with deficient or toxic levels of micronutrients.

Genetic effects of Agropyron cristatum 2P chromosome translocation fragments in a wheat background

Agropyron cristatum(2n=4x=28,PPPP)is a wild relative of common wheat which contains a large number of desirable genes that can be exploited for wheat improvement.Wheat–A.cristatum 2P alien translocation lines exhibit many desirable traits,such as small flag leaves,a high spikelet number and density,and a compact plant type.An agronomic trait evaluation and a genetic analysis were carried out on translocation lines and backcross populations of these lines carrying different translocation fragments.The results showed that a translocation fragment from 2PT-3(2PL)reduced the length of the flag leaves,while translocation fragments from 2PT-3(2PL)and 2PT-5(2PL(0.60–1.00))reduced the width of the flag leaves.A translocation fragment from 2PT-13(2PS(0.18–0.36))increased the length and area of the flag leaves.Translocation fragments from 2PT-3(2PL)and 2PT-8(2PL(0.86–1.00))increased the density of spikelets.Translocation fragments from 2PT-7(2PL(0.00–0.09)),2PT-8(2PL(0.86–1.00)),2PT-10(2PS),and 2PT-13(2PS(0.18–0.36))reduced plant height.This study provides a scientific basis for the effective utilization of wheat–A.cristatum translocation lines.

天童常绿阔叶林不同演替阶段常见种叶片N、P化学计量学特征

对天童常绿阔叶林5个演替阶段的13个种类24个植物个体叶片的N、P化学计量学的研究表明：（1）各演替阶段植物叶片的N、P含量变异较大,N含量的值在6.49~14.69mgg^-1之间,P含量的值在0.66~1.13mgg^-1之间,叶片的N∶P值在7.45~16.38之间;总体平均值N为9.43mgg^-1,P为0.86mgg^-1,N∶P为11.17;（2）演替后期的叶片N含量和N∶P比高于演替前期,叶片N含量的变化趋势与N∶P比的变化趋势协同性较好,N∶P的变化趋势能较好地反映不同演替阶段的群落变化特征;（3）叶片N∶P可以作为植物和演替阶段的限制性营养元素的指标,不同演替阶段的群落生长基本上均是受N而不是受P的限制;演替各阶段绝大多数物种新生叶的N∶P都小于成熟的营养叶的N∶P,两者均受N元素的限制,且氮素对新叶的限制性更强,表明新叶容易缺乏氮素而发育不良。

利用花粉管通道法将叶片衰老抑制基因P_(SAG12)-IPT导入普通小麦的研究

利用花粉管通道法将叶片衰老抑制基因PSAG12 IPT导入普通小麦品种西农 1376 ,经PCR、GUS组织化学染色、点杂交和Southern杂交分析 ,证明带有特异启动子的目的基因已整合到 5个植株的基因组中 ,且在大部分转基因植株中能够稳定遗传。通过叶片细胞分裂素含量、叶绿素含量、叶片衰老进程及农艺性状分析 ,初步证明PSAG12 IPT基因在部分转基因小麦的衰老叶片中特异表达 。

紫花苜蓿生物量空间层次分布与叶片C、N、P化学计量特征对P添加的响应

以‘甘农3号’紫花苜蓿(Medicago satial L.‘Gannong No.3’)为材料,设计4个水平(0,80,120,160Kg·hm-2)的P添加田间试验,在种植第二年第一茬初花期留茬5cm刈割,刈割部分从下到上以植株枝条第3茎节及以下作为下层,第4茎节至第6茎节作为中层,以第7茎节及以上作为上层,研究不同空间草层苜蓿生物量分布与叶片C,N,P化学计量特征对P添加的响应。结果表明:随着施P量的增加,苜蓿上、中、下3层生物量显著增加,且以下层的增幅最大,尤以120kg·hm-2的P添加量最为明显;上、中、下3层叶片C、P含量与P添加量呈现正相关,施P增加了各层叶片C,N,P含量,且上、中、下3层叶片的C,N,P含量对P添加的敏感性由上到下依次递减;上、中、下3层叶片C:N,C:P和N:P均随着P添加量的增加呈现降低的趋势。与对照相比,各层叶片C:N在P添加120Kg·hm-2降幅最大,C:P和N:P在P添加160Kg·hm-2降幅最大;P添加不仅显著增加苜蓿叶片对P的吸收,而且能不同程度地促进苜蓿叶片对C和N的吸收;在120kg·hm-2的P处理下,苜蓿生物量和叶片N含量达到最大,叶片C,P含量也达到较高水平;根据N,P含量与化学计量比来判断,研究区苜蓿生长受N和P共同限制,但随着P添加量的增加,苜蓿逐渐受到N限制。

干热河谷优势灌木细根、粗根与叶片养分(C、N、P)含量及化学计量比

分析生态脆弱区植物根系与叶片的养分含量特征,可认识植物生长发育的养分限制状况以及根系与叶片间的协同作用,并确定植物在恶劣环境条件下的适应性及生存策略。本文以典型生态脆弱区——干热河谷常见灌木植物马桑、坡柳和苦刺为研究对象,对其根系和叶片养分含量、化学计量比特征以及相互之间的关系进行研究。结果表明,马桑、坡柳粗根C含量显著高于细根(P<0.05),马桑细根P含量显著高于粗根(P<0.05)。细根、粗根养分含量的不同表明细根与粗根的生理生态功能具有较大差异。马桑和坡柳粗根的C∶N、C∶P均显著高于细根(P<0.05),坡柳细根和粗根的C∶N均显著高于马桑、苦刺(P<0.05)。根据N∶P判断,马桑细根(10.61)、粗根(11.42)生长均受到N的限制;坡柳细根(7.87)、粗根(6.00)生长受N的限制更为严重;苦刺细根(18.43)、粗根(16.34)生长均受P的限制。细根、粗根养分受限一致,表明细根和粗根的养分分配具出一定的协同性。除苦刺C外,灌木C、N、P含量均表现为叶片显著高于细根、粗根(P<0.05),表明叶片具有更高的养分含量。叶片N、P含量表现为苦刺显著高于马桑、坡柳(P<0.05),说明苦刺养分吸收能力更强。三种灌木N∶P均表现为叶片>根系(P<0.05),马桑、坡柳、苦刺叶片N∶P分别为40.05、35.34、45.26,三种灌木叶片的生长均受到P的限制。细根、粗根C含量与叶片无显著相关性,说明根系与叶片的C来源不同。根系N、P含量与叶片均呈显著正相关,说明叶片N、P主要来源于根系吸收的土壤养分,叶片与细根N、P相关性更强。上述结果表明植物体在生长代谢过程中具有整体性,植物的地上与地下营养器官在养分的分配过程中具有协同作用,细根与地上部分的协同作用比粗根强。

高山草甸坡向梯度上植物群落与土壤中的N,P化学计量学特征

选择甘南亚高山草甸坡向梯度(阴坡、半阴半阳坡和阳坡)的草地为研究对象,测定植物与土壤中全N、全P等的养分,阐明在不同生境下植物与土壤的N,P化学计量特征.结果显示:1)0～20 cm土壤中ω(N)和ω(有机质)在不同坡向阴坡>阳坡>半阴半阳坡,土壤ω(P)以及土壤水分从阳坡、半阴半阳坡到阴坡逐渐递增,土壤的ω(N):ω(P)在半阴半阳坡最低为6.23;20～40 cm土壤中ω(N),ω(P),ω(有机质),土壤水分,ω(N):ω(P)及pH值在不同坡向的变化趋势与0～20 cm的相同,但ω(N),ω(P),ω(有机质)及ω(N):ω(P)均低于0～20 cm土壤的,20～40 cm土壤水分在不同坡向均高于0～20 cm土壤的,不同土层土壤的pH值变化不大.2)植物叶片ω(P)在阳坡为(0.137±0.033)%、半阴半阳坡为(0.163±0.039)%、阴坡为(0.168±0.045)%,不同坡向差异显著(P<0.05);植物叶片ω(N)在坡向上差异不显著,植物的比叶面积从阳坡到阴坡分别为121.58±35.40,143.80±43.53,153.64±41.19 cm^2/g、阴坡、半阴半阳与阳坡差异显著(P<0.05);植物叶片的ω(N):ω(P)在阳坡为17.10,半阴半阳坡为15.4,而在阴坡为13.22,阳坡明显大于阴坡.植物群落在阳坡是P限制,而在阴坡是N限制,在一定程度上体现了植物群落对不同生境的一种适应.

三峡地区香溪河流域叶片凋落物分解过程中N、P含量动态研究

在香溪河流域1160、930、658 m 3个海拔梯度,利用凋落物分解袋法,研究黄栌(Cotinus coggygriavar.pu-bescens)、五裂槭(Acer oliverianum)和扇叶槭(Acer flabellatum)3个物种叶片凋落物的分解速率和主要营养元素N、P含量动态。结果表明,凋落物分解过程中干物质流失动态符合指数衰减方程;叶片初始N含量对分解速率没有显著影响,初始P含量与分解速率呈显著负相关;N、P含量动态在不同属物种间存在显著差异;海拔梯度的差异对N、P含量变化没有显著影响;凋落物在河岸陆地分解比较稳定,分解速度慢于同海拔河流;叶片分解N含量动态在河流与陆地中没有显著差异,而P含量变化差异显著。