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1.
利用光学显微镜和扫描电镜对中国西南地区独活属16种1变种植物(分隶于中国独活属的全部4个组)的叶表皮微形态进行了观察,测量并统计气孔器大小、密度和气孔指数,并用统计学方法对远轴面气孔器长轴进行显著差异性分析.结果显示:无规则型气孔器普遍存在于所有研究类群的叶远轴面及个别类群叶近轴面,气孔器的分布和密度具有种间特异性.表皮毛普遍存在于远轴面及大部分类群近轴面,长短和覆盖密度因种而异.近轴面表皮细胞为多边形或者不规则形,垂周壁平直、浅波状或波状;远轴面表皮细胞形态多不规则形,表皮细胞垂周壁浅波状或波状.在扫描电镜下,叶表皮气孔器外拱盖内缘为近平滑、浅波状或波状;角质膜条纹状,有的附有颗粒状、鳞片状蜡质等结构.气孔器外拱盖形态以及蜡质类型是稳定的鉴别特征.研究表明独活属植物叶表皮特征存在较大的种间差异,对独活属的系统分类及进化研究具有重要意义,文中对叶表皮特征在独活属植物分类处理中的应用及系统进化问题等进行了讨论,并建立了以叶表皮微形态特征为依据的分类检索表.  相似文献   
2.

Background and Aims

Experimental evidence challenges the approximation, central in crop models, that developmental events follow a fixed thermal time schedule, and indicates that leaf emergence events play a role in the timing of development. The objective of this study was to build a structural development model of maize (Zea mays) based on a set of coordination rules at organ level that regulate duration of elongation, and to show how the distribution of leaf sizes emerges from this.

Methods

A model of maize development was constructed based on three coordination rules between leaf emergence events and the dynamics of organ extension. The model was parameterized with data from maize grown at a low plant population density and tested using data from maize grown at high population density.

Key Results

The model gave a good account of the timing and duration of organ extension. By using initial conditions associated with high population density, the model reproduced well the increase in blade elongation duration and the delay in sheath extension in high-density populations compared with low-density populations. Predictions of the sizes of sheaths at high density were accurate, whereas predictions of the dynamics of blade length were accurate up to rank 9; moderate overestimation of blade length occurred at higher ranks.

Conclusions

A set of simple rules for coordinated growth of organs is sufficient to simulate the development of maize plant structure without taking into account any regulation by assimilates. In this model, whole-plant architecture is shaped through initial conditions that feed a cascade of coordination events.  相似文献   
3.
茶园冬季乔木落叶的分解和矿质元素释放   总被引:1,自引:0,他引:1  
在我国南方存在着一种传统植茶方式——茶林复合生态系统,近年来人们已逐步认识到它在维持土壤肥力,抗御自然灾害和保证茶叶内质特性等方面的作用,然而对冬季乔木落叶分解和矿质元素释放的作用尚无报道。本文是对安徽省黄山市休宁县茶树-乌桕复合园和茶树-板栗复合园的冬季乔木落叶分解的研究,为全面认识茶林复合生态系统的性质提供依据。  相似文献   
4.
5.
Communities change with time. Studying long-term change in community structure permits deeper understanding of community dynamics, and allows us to forecast community responses to perturbations at local (e.g. fire, secondary succession) and global (e.g. desertification, global warming) spatial scales. Monitoring efforts exploring the temporal dynamics of indicator taxa are therefore a critical part of conservation agendas. Here, the temporal dynamics of the Otongachi leaf litter ant community, occurring in a cloud forest in coastal Ecuador, were explored. By sampling this community six times over eleven years, I assessed how the ant fauna caught by Winkler traps (more diverse and cryptic fauna) and caught by pitfall traps (larger, more mobile fauna) changed over time. The Otongachi leaf litter ant community was dynamic. Although species richness in the community remained constant, temporal turnover of species was high: on average, 51% of the ant species in Winkler traps, and 56% of those in pitfall traps, were replaced with other ant species from one year to the other. Shifts in the rank abundance of species in the community were also large across the eleven years and, on average, shifts in the rank abundance of species collected by Winkler traps doubled those occurring in pitfall traps from one census to the other. In spite of these trends, the Otongachi ant fauna showed no (Winkler) or weak (pitfall) evidence of directional change (towards a new community). Thus, this tropical ant community can be divided in two community compartments. The Winkler compartment composed by a more diverse and cryptic ant fauna appears to be resilient and stable in time. The pitfall compartment composed by larger and more mobile ants may be prone to respond to disturbance. This study suggests that 1) species appearing/disappearing from a site may be rather the rule, difficult to separate from responses to ecological stress. 2) Conclusions made in short-term studies, or studies comparing two (e.g. before and after) snapshots of a community, should thus be revisited. Finally, 3) the ant fauna caught by pitfall traps (a rather simple and cheap survey method) is the most likely community compartment to indicate ecological perturbation. This study adds to the growing evidence that using ants as ecological indicators should incorporate long-term temporal dynamics.  相似文献   
6.
The COP9 (constitutive photomorphogenesis 9) signalosome (CSN) is a protein complex involved in the ubiquitin proteasome system and a common host target of diverse pathogens in Arabidopsis. The known derubylation function of the COP9 complex is carried out by subunit 5 encoded by AtCSN5A or AtCSN5B in Arabidopsis. A single CSN5‐like gene (designated as TaCSN5) with three homeologues was identified on the long arms of wheat (Triticum aestivum L.) group 2 chromosomes. In this study, we identified and characterized the function of TaCSN5 in response to infection by the leaf rust pathogen. Down‐regulation of all three TaCSN5 homeologues or mutations in the homeologues on chromosomes 2A or 2D resulted in significantly enhanced resistance to leaf rust. Enhanced leaf rust resistance corresponded to a seven‐fold increase in PR1 (pathogenesis‐related gene 1) expression. Collectively, the data indicate that the wheat COP9 subunit 5‐like gene acts as a negative regulator of wheat leaf rust resistance.  相似文献   
7.
季节性冻融期间亚高山森林凋落物的质量损失及元素释放   总被引:4,自引:1,他引:3  
季节性冻融期间的凋落物分解对季节性冻土区的森林生态系统过程可能具有重要的影响,但已有的研究报道很少.因此,采用凋落物分解袋法研究了岷江冷杉 (Abies faxoniana Rehder & E. H. Wilson)林和白桦(Betula platyphylla Sukaczev)林凋落叶的分解.一个季节性冻融期间,冷杉林和白桦林凋落物的质量损失率分别为(19.4 ±2.0)%和(21.5±3.5)%,约为1a中凋落物分解的64.5%和65.6%,表明季节性冻融对亚高山森林凋落物分解影响显著.冷杉凋落物中C、N、P、K、Ca和Mg的释放率为(15.0±1.0)%、(34.1±3.6)%、(17.0±0.9)%、(22.8±5.9)%、(20.1±0.1)%和(36.3±2.1)%,白桦凋落物中C、N、P、K、Ca和Mg的释放率为(20.7±0.1)%、(29.4±3.4) %、(15.7±1.3)%、(16.8±5.1)%、(21.3±1.8)%和(20.5±2 8)%.结合叶凋落物产量可以推断,冷杉林凋落物在一个季节性冻融期间释放到土壤的N、P、K、Ca、Mg为(10.17±1.14) kg · hm-2、(0.68±0.08) kg · hm-2、(4.08±0.46) kg · hm-2、(0.46±0.05) kg · hm-2、(0.09±0.01) kg · hm-2,白桦林为(5.61±1 12) kg · hm-2、(0.34±0.07) kg · hm-2、(1.21±0.24) kg · hm-2、(0.300±0.059) kg · hm-2、(0.051±0.010) kg · hm-2,这对于春季亚高山森林植物生长具有重要的生态学意义.  相似文献   
8.
水稻上部叶片叶绿素含量的高光谱估算模型   总被引:10,自引:1,他引:9  
杨杰  田永超  姚霞  曹卫星  张玉森  朱艳 《生态学报》2009,29(12):6561-6571
叶片叶绿素 (Chl) 状况是评价植株光合效率和营养胁迫的重要指标,实时无损监测Chl状况对作物生长诊断及氮素管理具有重要意义.以不同生态点、不同年份、不同施氮水平、不同类型水稻品种的4个田间试验为基础,于主要生育期同步测定了水稻主茎顶部4张叶片的高光谱反射率及Chl含量,并计算了350~2500 nm范围内任意两波段组合而成的比值(SR[λ1,λ2])和归一化(ND[λ1,λ2])光谱指数以及已报道的对Chl敏感的光谱指数,进一步系统分析了叶片Chl含量与上述光谱指数之间的定量关系.结果表明,红边波段的比值和归一化光谱指数可以较好地预测水稻上部4叶的Chl含量(R~2>0.9),但对于不同Chl指标其最佳组合波段有所差异.估算叶绿素a (Chla)、叶绿素总量(Chla+b)和叶绿素b (Chlb)的最佳比值光谱指数分别为SR(724,709)、SR(728,709)和SR(749,745),方程拟合决定系数R~2分别是0.947、0.946、0.905;最佳归一化光谱指数分别为ND(780,709)、ND(780,712)和ND(749,745),R~2分别是0.944、0.943、0.905.引入445 nm波段反射率对上述光谱指数进行修正,可以降低叶片表面反射差异的影响,提高模型的应用范围.利用不同年份独立的试验资料对所建模型进行了检验,结果表明,修正型比值光谱指数 mSR(724,709)、mSR(728,709) 和 mSR(749,745),以及修正型归一化光谱指数mND(780,709)、mND(780,712) 和 mND(749,745) 预测 Chla、Chla+b 和 Chlb 的效果更好,其测试的RMSE分别为 0.169、0.192、0.052、0.159、0.176、0.052,RE分别为8.18%、7.74%、13.01%、8.26%、7.59%、12.96%,均较修正前降低,说明修正后的光谱指数普适性更好.  相似文献   
9.
Leaf venation is diverse across plant species and has practical applications from paleobotany to modern agriculture. However, the impact of vein traits on plant performance has not yet been tested in a model system such as Arabidopsis thaliana. Previous studies analysed cotyledons of A. thaliana vein mutants and identified visible differences in their vein systems from the wild type (WT). We measured leaf hydraulic conductance (Kleaf), vein traits, and xylem and mesophyll anatomy for A. thaliana WT (Col‐0) and four vein mutants (dot3‐111 and dot3‐134, and cvp1‐3 and cvp2‐1). Mutant true leaves did not possess the qualitative venation anomalies previously shown in the cotyledons, but varied quantitatively in vein traits and leaf anatomy across genotypes. The WT had significantly higher mean Kleaf. Across all genotypes, there was a strong correlation of Kleaf with traits related to hydraulic conductance across the bundle sheath, as influenced by the number and radial diameter of bundle sheath cells and vein length per area. These findings support the hypothesis that vein traits influence Kleaf, indicating the usefulness of this mutant system for testing theory that was primarily established comparatively across species, and supports a strong role for the bundle sheath in influencing Kleaf.  相似文献   
10.
采用盆栽实验,通过向土壤(每盆8kg)中添加0g·pot-1(CK)、20g·pot-1(L)、40g·pot-1(M)和80g·pot-1(H)天竺桂(Cinnamomum japonicum)凋落叶,模拟其自然分解对凤仙花(Impatiens balsamina)生长和光合特性的影响。结果显示:(1)添加天竺桂凋落叶M和H处理下,凤仙花生物量和地径均显著降低,而株高无明显变化;其叶绿素含量受到显著抑制,净光合速率(Pn)和水分利用效率(WUE)显著低于CK,而气孔导度(Gs)、胞间二氧化碳浓度(Ci)和蒸腾速率(Tr)3个气体交换参数显著高于CK。(2)Pn-PAR曲线和Pn-Ci曲线拟合表明,凤仙花在光饱和以及CO2饱和状态下的最大净光合速率(Pn max)、表观量子效率(AQY)、暗呼吸速率(Rd)、RuBP羧化效率(CE)和光呼吸速率(Rp)均随添加天竺桂凋落叶处理量的增加而呈下降趋势。(3)添加天竺桂凋落叶36d和67d时对凤仙花生长影响不明显,而处理58d时有明显抑制作用。研究表明,在模拟天竺桂凋落叶自然分解的土壤环境中,凤仙花的光合色素含量降低,抑制了其光合能力,对环境适应能力降低,导致凤仙花的生长受到抑制。  相似文献   
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