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1.
MethodsCO2 efflux measurements were conducted during freezing experiments for saplings of three Scots pine (Pinus sylvestris) and three Norway spruce (Picea abies) trees under laboratory conditions, and the magnitudes of the freezing-related bursts of CO2 released from the stems were analysed using a previously published mechanistic model of CO2 production, storage, diffusion and efflux from a tree stem. The freezing-related bursts of CO2 released from a mature Scots pine tree growing in field conditions were also measured and analysed.ConclusionsAll gases dissolved in the xylem sap are not trapped within the ice in the stem during freezing, as has previously been assumed, thus adding a new dimension to the understanding of winter embolism formation. The conduit water volume not only determines the volume of bubbles formed during freezing, but also the efficiency of gas efflux out of the conduit during the freezing process.  相似文献   
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渍水对冬小麦生长的危害及其生理效应   总被引:7,自引:0,他引:7  
小麦受渍后叶片的光合和蒸腾速率迅速下降,而后则显微弱的回升趋势。渍害不仅削弱小麦光合产物的积累,并且改变光合产物在地上部分和根系中的分配比例;植株根/冠比下降,而黄叶的发展与根/冠比的变化呈显著负相关;渍害改变小麦的发育进程,尤其是后期渍害明显促使小麦早衰。认为清水使叶片光合速率降低、光合有效面积损失和衰老加速,从而危害小麦的生长。  相似文献   
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A role for nitrogen reserves in forage regrowth and stress tolerance   总被引:20,自引:0,他引:20  
Carbohydrate accumulation and utilization during shoot regrowth after defoliation and winter has been studied extensively in most species used as forage. However, recent work suggests that N reserves found in vegetative tissues also are important for defoliation tolerance and winter hardiness. Results suggest that these N reserves constitute an alternative N source used when N2 fixation and/or mineral N uptake are reduced. 15N labelling experiments indicate that a large proportion of herbage N is derived from N reserves mobilized from stem bases or roots to developing leaves and shoots. Amino acids and specific proteins (i.e. vegetative storage proteins, VSPs) are deposited in roots and stem bases and, in the case of VSPs, are degraded rapidly after defoliation. Identification and characterization of VSPs will increase our understanding of the role N reserves play in stress tolerance and may lead to innovative approaches for improving forage persistence and productivity.  相似文献   
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莼菜为世界著名珍稀水生蔬菜,具有很高的食用和药用价值。已有研究显示,可通过冬芽实现莼菜复壮,找出休眠解除的最佳方法是复壮的基本前提。本实验以莼菜冬季型休眠芽(冬芽)为实验材料,通过光照、温度等处理探求莼菜冬芽的休眠解除方法。莼菜冬芽生根率随着光照强度的增加,其生根率由全黑暗0%显著增长至(16.0±1.3)%;温度和处理时间对莼菜冬芽生根率、根长、生根根数和含水量有显著性影响。其中,35 °C水浴处理6 h后各项指标均到达较大值,上述指标分别为(96.1±2.8)%、(7.2±0.2) cm、74.5±6.0和(83.6±0.3)%;40 °C(6 h)、45 °C(1、3和6 h)和50 °C(10、20和30 min)水浴处理后莼菜冬芽绝大部分失绿变黄;随着培养时间的延长,其冬芽全部腐烂。光照能够促进莼菜冬芽生根;土培生根效果较为显著;适度水浴加热处理能有效解除莼菜冬芽的休眠,35 °C水浴处理6 h为最佳处理方案。  相似文献   
7.
Phenotypic plasticity is important for species responses to global change and species coexistence. Phenotypic plasticity differs among species and traits and changes across environments. Here, we investigated phenotypic plasticity of the widespread grass Arrhenatherum elatius in response to winter warming and frost stress by comparing phenotypic plasticity of 11 geographically and environmentally distinct populations of this species to phenotypic plasticity of populations of different species originating from a single environment. The variation in phenotypic plasticity was similar for populations of a single species from different locations compared to populations of functionally and taxonomically diverse species from one environment for the studied traits (leaf biomass production and root integrity after frost) across three indices of phenotypic plasticity (RDPI, PIN, slope of reaction norm). Phenotypic plasticity was not associated with neutral genetic diversity but closely linked to the climate of the populations’ origin. Populations originating from warmer and more variable climates showed higher phenotypic plasticity. This indicates that phenotypic plasticity can itself be considered as a trait subject to local adaptation to climate. Finally, our data emphasize that high phenotypic plasticity is not per se positive for adaptation to climate change, as differences in stress responses are resulting in high phenotypic plasticity as expressed by common plasticity indices, which is likely to be related to increased mortality under stress in more plastic populations.  相似文献   
8.
高温胁迫对华北地区冬小麦灌浆及产量的影响   总被引:2,自引:0,他引:2  
谭凯炎  杨晓光  任三学  房世波 《生态学报》2015,35(19):6355-6361
冬小麦灌浆期高温是制约我国北方冬小麦产量的一个重要气候因素,随着全球气候变暖,日趋频繁的极端温度事件可能引起该地区冬小麦产量的大幅波动。为了明确冬小麦灌浆期异常高温对冬小麦产量的影响程度,在河北固城生态与农业气象试验站自然大田条件下,采用自由空气红外辐射增温技术,开展了冬小麦灌浆中后期短期高温处理模拟试验。结果表明,灌浆中后期短期高温胁迫致使冬小麦灌浆速率下降及灌浆持续时间缩短从而使粒重降低,在消除了影响粒重的其它因素的作用后,短期高温处理期间的午间平均冠层气温与粒重之间存在显著的负线性相关关系。高温对冬小麦产量的威胁程度由高温强度及其持续时间两个因素决定。结合了高温强度及其持续时间综合作用的高温有效度时被证明是一个能全面反映灌浆中后期高温胁迫影响的特征量。  相似文献   
9.
未来气候变化对河南省冬小麦需水量和缺水量的影响预估   总被引:1,自引:1,他引:0  
姬兴杰  成林  方文松   《生态学杂志》2015,26(9):2689-2699
采用美国农业部土壤保持局推荐的方法计算有效降水量,应用Penman-Monteith模型和作物系数法计算需水量,在对河南省1981—2010年冬小麦生育期内有效降水量、需水量和缺水量分析的基础上,结合《排放情景特别报告》的两种排放情景A2(强调经济发展)和B2(强调可持续发展)预估的未来气候情景,探讨了未来气候情景下河南省冬小麦的有效降水量、需水量和缺水量的时空演变规律及其主要气候影响因素.结果表明: 从整体上看,相对于基准时段(1981—2010年),A2和B2情景下,不同时段冬小麦全生育期的有效降水量、需水量和缺水量均表现出增加趋势,有效降水量均以2030s时段增加最多,分别增加33.5%和39.2%;需水量均以2010s时段增加最多,分别增加22.5%和17.5%,年代间呈现明显递减趋势;缺水量在A2情景下以2010s时段增加(23.6%)最多,B2情景下以2020s时段增加(13.0%)最多.偏相关分析表明,A2和B2情景下,太阳总辐射是影响河南省冬小麦需水量和缺水量变化的主要气候因素.由于地理环境和气候条件的差异,不同时段河南省冬小麦全生育期有效降水量、需水量和缺水量的距平百分率在空间分布上具有差异.未来河南省水资源可能更趋于短缺.  相似文献   
10.
Much of the recent changes in North American climate have occurred during the winter months, and as result, overwintering birds represent important sentinels of anthropogenic climate change. While there is mounting evidence that bird populations are responding to a warming climate (e.g., poleward shifts) questions remain as to whether these species‐specific responses are resulting in community‐wide changes. Here, we test the hypothesis that a changing winter climate should favor the formation of winter bird communities dominated by warm‐adapted species. To do this, we quantified changes in community composition using a functional index – the Community Temperature Index (CTI) – which measures the balance between low‐ and high‐temperature dwelling species in a community. Using data from Project FeederWatch, an international citizen science program, we quantified spatiotemporal changes in winter bird communities (= 38 bird species) across eastern North America and tested the influence of changes in winter minimum temperature over a 22‐year period. We implemented a jackknife analysis to identify those species most influential in driving changes at the community level and the population dynamics (e.g., extinction or colonization) responsible for these community changes. Since 1990, we found that the winter bird community structure has changed with communities increasingly composed of warm‐adapted species. This reshuffling of winter bird communities was strongest in southerly latitudes and driven primarily by local increases in abundance and regional patterns of colonization by southerly birds. CTI tracked patterns of changing winter temperature at different temporal scales ranging from 1 to 35 years. We conclude that a shifting winter climate has provided an opportunity for smaller, southerly distributed species to colonize new regions and promote the formation of unique winter bird assemblages throughout eastern North America.  相似文献   
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