Interrelationships between leaf heat conductivity and tissue structures of different varieties of Populus tomentosa Carr

Plant heat conductivity largely depends on tissue structure. Different structures lead to different heat conductivity. As well, water transfer also plays a very important role in heat transfer in plants. We have studied leaf heat conductivity and tissue structure of 3- and 30-year-old Populus tomentosa Carr. trees using infrared thermal imaging, steady state heat conductivity surveys and paraffin section and investigated the relationship between leaf heat conductivity, tissue structure and water content of leaves. The results show that the temperature on leaf surfaces among the various varieties of trees was almost the same. Leaf heat conductivity, temperature and water content of leaves are positively correlated. The thicker the leaf tissue structures, the larger the heat resistance. That is, the tighter the cells and the smaller the interspaces, the smaller the heat conductivity, which is not conducive for heat transfer.

Modulation of leaf conductance by root to shoot signaling under water stress in Arabidopsis

Signal communication between root and shoot plays a crucial role in plant resistance to water stress. While many studies on root to shoot signals have been carried out in many plant species, no information is available for the model plant, Arabidopsis, whose adoption has great significance for further probing the molecular aspects of long distance stress signals. Here, we introduced the es- tablishment of techniques for investigations of root to shoot signals in Arabidopsis. Stomata! movements in relation to root signals were probed by using these techniques. The results show that Arabidopsis is a suitable plant species for partial roots drying （PRD） experiments. In the PRD system, while no significant differences were found in leaf water potential between well-watered and stressed plants, water stress led to a decrease in leaf conductance, which suggests a regulation of stomatal movements by root to shoot signals. While water stress caused a significant increase in the concentration of sap abscisic acid （ABA） of xylem, no increase in xylem sap pH was observed. Moreover, the increase in the ABA content of xylem coincided with the decrease in leaf conductance, which suggests a possible role of ABA in the regulation of stomatal movements. Infrared temperature images showed that leaf tem- peratures of PRD plant were higher compared with those of well-watered plants, which further indicates that stomatal movements can be modulated by root signals. The confirmation of root to shoot signaling in Arabidopsis has established a basis for further inves- tigation into the molecular mechanisms of the root to shoot signaling under water stress.

Physical and Thermo-Mechanical Properties of Composite Materials Based on Raw Earth and Crushed Palm Leaf Fibers (Borassus aethiopum)

The objective of this study is to seek solutions to reduce the impact of buildings on climate change and to promote the use of local bio-sourced or geo-sourced materials for sustainable construction. Different samples of raw earth from 3 sites were taken in the commune of Mlomp. Geotechnical tests showed that the raw earth samples from sites 2 and 3 have more clay fraction while site 1 contains more sand. The fact of integrating fibers from crushed palm leaves (Borassus aethiopum) (2%, 4% and 6%) into the 3 raw earth samples reduced the mechanical resistance to compression and traction of the 3 raw earths. The experimental results of thermal tests on samples of earth mixtures with crushed Palma leaf fibers show a decrease in thermal conductivity as well as thermal effusivity as the percentages increase (2%, 4% and 6%) of fibers in raw earth for the 3 sites. This shows that this renewable composite material can help improve the thermal insulation of building envelopes.

Conducting Tissue of Leaves in Nageia and Podocarpus

The conducting tissue structure of transverse and longitudinal sections was observed on leaves of Podocarpus and Nageia.Results showed:in Podocarpus leaves,there is only one midrib,the xylem tracheid of midrib vascular bundle is multi-form,transfusion tissue belongs to Cycas-type and transfusion tracheids are isodiametric,the accessory transfusion tracheids between palisade tissue and sponge tissue are developed;in Nageia leaves,there are plenty of parallel leaves,the xylem tracheids of each vein are relatively simple,transfusion tissue belongs to Taxus-type and transfusion tracheids are longer in longitudinal section than that in transverse section,the accessory transfusion tissue between palisade tissue and sponge tissue is absent.Considering other differences that in leaves of Podocarpus there are three resin ducts under vascular bundle of midrib,mesophyll cells are differentiated into palisade tissue and sponge tissue;in leaves of Nageia,there is only one resin duct under vascular bundle in each vein and no obvious differentiation in mesophyll cells,palisade tissue can be found on both sides,and sclereids can also be found in mesophyll tissue.The anatomical differences of leaf veins and mesophylls between Nageia and Podocarpus mentioned above support the viewpoint that Nageia and Podocarpus are two independent genera.

Varietal difference in the correlation between leaf nitrogen content and photosynthesis in rice(Oryza sativa L.) plants is related to specific leaf weight

Increasing leaf photosynthesis per area（A） is of great importance to achieve yield further improvement. The aim of this study was to exploit varietal difference in A and its correlation with specific leaf weight（SLW）. Twelve rice cultivars, including 6 indica and 6 japonica varieties, were pot-grown under two N treatments, low N（LN） and sufficient N（SN）. Leaf photosynthesis and related parameters were measured at tillering stage. Compared with LN treatment, A, stomatal conductance（g_s）, mesophyll conductance（g_m）, leaf N content（N_（area））, and chlorophyll content were significantly improved under SN treatment, while SLW and photosynthetic N use efficiency（PNUE） were generally decreased. Varietal difference in A was positively related to both g_s and g_m, but not related to N_（area）. This resulted in a low PNUE in high N_（area） leaves. Varietal difference in PNUE was generally negatively related to SLW. Response of PNUE to N supply varied among different rice cultivars, and interestingly, the decrease in PNUE under SN was negatively related to the decrease in SLW. With a higher N_（area）, japonica rice cultivars did not show a higher A than indica rice cultivars because of possession of high-SLW leaves. Therefore, varietal difference in A was not related to N_（area）, and SLW can substantially interfere with the correlation between A and N_（area）. These findings may provide useful information for rice breeders to maximize A and PNUE, rather than over reliance on N_（area） as an indicator of photosynthetic performance.

Leaf Photosynthesis in Response to Removing Fruit During Different Phenological Stages of Fruit Development in Peach Trees

Removing fruit (RF) and retaining fruit (CK) were carried out during different phenological stages of fruit development onone-year-old shoot of Okubo peach trees [Prunus persica (L.) Batsch.] under preventing exportation of the assimilates tothe non experimental parts of the tree by girdling one-year-old shoot and keeping the same leaves between RF and CK.The results showed that fruit removal significantly decreased net photosynthetic rate (Pn), stomatal conductance (Gs)and transpiration rate (E), but significantly increased leaf surface temperature (TLeaf ) at about midday as compared with CK.Internal CO2 concentration, soluble sugar content, reductive sugar content, starch content except that during the finalrapid fruit growth stage, ADP-glucose pyrophosphorylase and amylase activities in source leaves were not significantlyaffected by fruit removal. There was a significantly positive parabolic correlation between Pn and Gs, and a strongpositive linear correlation between Pn and E. Moreover, Pn increased with increased TLeaf if TLeaf was below 38°C, thendecreased sharply when TLeaf exceeded the above critical temperature for both RF and CK. Pn of RF was lower, however,than that of CK in the same TLeaf , especially if TLeaf exceeded 38°C. It is suggested that the decreased stomatal aperture andincreased TLeaf may be the important mechanism in regulating photosynthesis under a decreased strength of sink demandby RF in fruit trees.

How <i>Betula ermanii</i>Maintains a Positive Carbon Balance at the Individual Leaf Level at High Elevations

Generally, plant species with shorter leaf longevity maintain a positive carbon balance by decreasing leaf mass per area (LMA) and increasing photosynthesis. However, plants at high elevations need to increase LMA against environmental stresses. Therefore, plants need to increase both LMA and photosynthesis at high elevations. To examine how deciduous plants maintain a positive carbon balance at high elevations, photosynthesis and related leaf traits for deciduous broad-leaved tree Betula ermanii were measured at three elevations. LMA was greater at middle and high elevations than at low elevation. Leaf δ13C was greater at higher elevations, and positively correlated with LMA, indicating greater long-term deficiency of CO2 in leaves at higher elevations. However, the Ci/Ca ratio at photosynthetic measurement was not low at high elevations. Nitrogen content per leaf mass and stomatal conductance were greater at higher elevations. Photosynthetic rates and photosynthetic nitrogen use efficiency (PNUE) did not differ among the three elevations. Photosynthetic rate showed a strong positive correlation with stomatal conductance on a leaf area basis (R2 = 0.83, P < 0.001). Therefore, this study suggests B. ermanii compensates the deficiency of CO2 in leaves at high elevation by increasing stomatal conductance, and maintains photosynthesis and PNUE at high elevation as much as at low elevation.

Biomimic Vein-Like Transparent Conducting Electrodes with Low Sheet Resistance and Metal Consumption

In this contribution,inspired by the excellent resource management and material transport function of leaf veins,the electrical transport function of metallized leaf veins is mimicked from the material transport function of the vein networks.By electroless copper plating on real leaf vein networks with copper thickness of only several hundred nanometre up to several micrometre,certain leaf veins can be converted to transparent conductive electrodes with an ultralow sheet resistance 100 times lower than that of state-of-the-art indium tin oxide thin films,combined with a broadband optical transmission of above 80%in the UV–VIS–IR range.Additionally,the resource efficiency of the vein-like electrode is characterized by the small amount of material needed to build up the networks and the low copper consumption during metallization.In particular,the high current density transport capability of the electrode of>6000 A cm^−2 was demonstrated.These superior properties of the vein-like structures inspire the design of high-performance transparent conductive electrodes without using critical materials and may significantly reduce the Ag consumption down to<10%of the current level for mass production of solar cells and will contribute greatly to the electrode for high power density concentrator solar cells,high power density Li-ion batteries,and supercapacitors.

高接换种对核桃枝条和根系生理特征的影响

为探究高接换种对核桃枝条和根系生理特征的影响,对定植10年的实生砧+‘香玲’进行高接换种‘清香’,以短截更新为对照,成活3年后比较分析1年生枝和根系生理特征差异。结果表明:(1)高接后1年生枝导管密度为76.82 N/mm^(2),平均长度为39.85 cm,叶片N、K元素含量分别为27.20、7.17 g/kg,显著高于更新处理(P<0.05),说明高接提高了养分运输和树冠恢复效率。(2)更新处理20~40 cm土层根系导管直径为86.55μm,0~20 cm土层根系导管平均密度为149.33 N/mm^(2),显著高于高接处理(P<0.05),说明高接‘清香’一定程度上改变了根系结构。(3)高接后0~20 cm土层根系韧皮部厚度/枝条半径比例为0.39,其根系平均长度、直径、周皮厚度分别达到10.64 cm、2.36 mm和70.09μm,显著高于更新处理(P<0.05),说明高接‘清香’后,光合产物倾向于分配到0~20 cm土层根系。(4)高接‘清香’核桃后,1年生枝和20~40 cm土层根系形成层厚度分别达到36.26、76.42μm,显著高于更新处理(P<0.05),说明其具有较强的增粗生长潜力。综上,高接‘清香’核桃改变了‘香玲’核桃1年生枝和根系输导结构,提高了养分运输效率,促进了树冠和地表根系的生长。

核桃焦叶病诱导的形态响应

【目的】探明焦叶病发生进程中核桃Juglans regia的形态学变化。【方法】以新疆维吾尔自治区阿克苏地区核桃主栽品种‘温185’Juglans regia‘Wen185’1年生结果枝为研究对象,定量测量核桃焦叶病发生进程中1年生结果枝在枝条长度、基径生长速率和木质部茎比导水率;显微定性观察核桃焦叶病发生进程中叶片、叶柄及枝条的结构变化特征。【结果】焦叶病严重影响‘温185’核桃1年生结果枝的生长和结构。感病枝长度增量(健康枝条63.42 mm,感病枝条48.68 mm)、基径增量(健康枝条2.98 mm,感病枝条2.17 mm)及木质部导水率(健康枝条9.00 kg·m^(-1)·s^(-1)·MPa^(-1)、感病枝条2.55 kg·m^(-1)·s^(-1)·MPa^(-1))显著降低(P<0.05)。叶片解剖结构的多重比较结果显示,随着叶片焦叶病病级的升高,叶片、栅栏组织、海绵组织以及上表皮的厚度均呈现下降趋势。健康叶片细胞结构完好,无空洞和表皮损伤。感病叶片叶肉细胞破裂、海绵组织出现空洞、游离细胞破损。随叶片焦叶病病级的升高,叶片表皮细胞扭曲变形,严重时上表皮严重扭曲,海绵组织空洞增多,叶肉细胞破损加剧,下表皮出现断裂。同时感病叶片叶柄纹孔膜表面变得粗糙,出现白色颗粒物,并在严重情况下出现破裂。此外,感病枝条木质部螺纹导管内出现颗粒物和絮状结构,导致导管堵塞,影响水分和养分运输。【结论】核桃焦叶病发病过程中,‘温185’核桃1年生结果枝枝条生长受阻,叶片结构受损,木质部螺纹导管堵塞,导致木质部茎比导水率降低。

基于δ^(13)C估算水分利用效率的2种模型比较——以峨眉山雷洞坪植物为例

【目的】通过对基于碳稳定同位素值(δ^(13)C)估算水分利用效率(iWUE)的2种模型(是否考虑叶肉导度,gm)之间差异的研究,有助于进一步理解gm对植物iWUE的影响。【方法】选择峨眉山雷洞坪针阔混交林中不同生长型植物,采集了48个物种的117个叶片样品,通过测定其叶片δ^(13)C,对比了早期估算iWUE模型(iWUEsim模型,将gm看作无穷大)与包含gm效应的iWUE模型(iWUEmes模型)之间的iWUE差异(iWUE_(difference)),以及这种差异随植物生长型变化的趋势。【结果】结果显示,iWUEsim的平均值(42.23±1.33μmol·mol^(-1))显著高于iWUEmes的平均值(28.10±0.65μmol·mol^(-1)),高估比例为3.64%~72.11%(平均49.58%±1.30%)。不同生长型植物的iWUEsim均显著大于iWUEmes,其中草本植物高估比例3.64%~48.00%(平均29.20%±5.16%),灌木高估比例13.68%~67.73%(平均48.44%±1.83%),乔木高估比例32.04%~72.11%(平均54.08%±1.47%)。此外,叶片功能性状对iWUE_(difference)有显著影响,相比于叶片厚度、叶片干物质含量和单位质量叶片氮含量,单位面积叶片氮含量和比叶重是影响iWUE_(difference)变化的主要因素。【结论】将gm看作无穷大会造成对基于δ^(13)C估算的iWUE的高估,未来估算植物iWUE时应考虑gm的影响。

黄土高原15种木本植物叶片水力效率与水力安全的权衡关系

理清植物水力效率与水力安全之间的权衡关系有助于深入理解植物的环境适应性。目前,关于上述性状权衡关系的研究多集中于枝条,而对于较难测量的叶片,其水力效率与水力安全之间的权衡关系仍存在争议。我们选取了黄土高原15种木本植物,包括6种乔木和9种灌木,测定其叶片单位质量导水率(K_(leaf-mass))、单位面积导水率(K_(leaf-area))及导水率降低50%时叶水势(P_(50)),分析叶片中水力效率与水力安全之间的权衡关系。结果表明:3种指标在乔木与灌木之间均不存在显著差异;P_(50)与K_(leaf-mass)和K_(leaf-area)均没有显著相关性,说明黄土高原木本植物叶片水力效率与水力安全之间不存在权衡关系。这种效率与安全之间权衡关系的缺失在干旱环境中可能是有利的,允许植物同时具有较高的水力效率和水力安全性。在今后的研究中,应考虑加强干旱地区植物水力性状的研究,同时将叶片、枝条、树干及根系的水力性状相结合,从植株整体上探讨植物水力性状权衡关系及其环境适应性。

北京园林主要常绿阔叶植物抗冻性及其测定方法

采用电导法、组织变褐法、生长恢复法及TTC还原法研究了北京园林中主要常绿阔叶植物的抗冻性 .结果表明 ,随着低温胁迫的加强 ,组织的电解质渗透率、褐化指标以及生长恢复后的冻害指数都明显上升 ,TTC还原法测定的细胞活力明显下降 ,不同指标的总体趋势高度一致 ,与种类的抗冻性密切相关 .被测植物的抗冻区域如下 :八角金盘- 10℃以上 ,洋常春藤、女贞、扶芳藤 - 8～ - 12℃ ,大叶黄杨 - 10～ - 15℃ ,凤尾兰、火棘、广玉兰 - 15～ - 2 0℃ ,黄杨- 15～ - 2 5℃ .对不同方法比较后认为 ,电导法可以用于实践中快速、客观地评价和比较常绿阔叶植物抗冻性 .对抗冻性测定的注意事项进行了探讨 .

基于夏玉米叶片气孔导度提升的冠层导度估算模型

叶片气孔导度模拟及其向冠层导度的尺度提升是实现蒸散发尺度转换的基础,对农业水资源高效利用与评价意义重大。本文依据夏玉米叶片气孔导度和冠层导度实测值,在建立叶片气孔导度估算模型基础上,构建冠层导度估算模型。结果表明,夏玉米叶片气孔导度每日在10:00-14:00之间达到峰值,其日变化趋势与光合有效辐射的一致性较好,较大的饱和水汽压差对夏玉米叶片气孔导度具有一定的限制作用。根据光合有效辐射和饱和水汽压差建立的叶片气孔导度估算模型能较好反映当地夏玉米叶片气孔导度对主要环境因子的响应过程,以光合有效辐射作为尺度转换因子构建的冠层导度估算模型可较好实现从叶片气孔导度向冠层导度的尺度转换提升。

吉林省过去47年来水稻品种遗传改良过程中叶片光合指标的变化

2006-2007年对吉林省1958年至2005年间育成的25个粳稻品种产量特性及叶片光合生理指标进行了比较。结果表明,粳稻品种产量随育成年代呈线性增加。由1958年的6671.9kg/hm2增加至2005年的11853.2kg/hm2,平均每年增加110.2kg/hm2,年增幅为1.65%。收获指数、成熟期和粒叶比随育成年代推延而增加且与产量呈显著正相关。随着品种产量的增加,单叶净光合速率显著增加且与产量呈正相关,光合速率增加主要是由于品种表观叶肉导度随育成年代推延而显著增加所致。同时,胞间CO2浓度/大气CO2浓度比值呈下降趋势,说明现代品种的光合作用存在一定的气孔限制作用。现代品种叶片的蒸腾速率的增幅大于光合速率的增幅,导致水分利用效率下降。因此,在未来水稻品种选育中,筛选高光合种质资源的同时要兼顾品种的水分利用特性。

果实不同发育阶段去果对桃源叶光合作用的影响

以大久保桃为试材,在果实发育的不同阶段通过去果处理降低库力,同时设留果对照,并通过环剥和保留相同数量叶片严格控制库源关系,进行了源叶净光合速率(Pn)、碳水化合物含量及其淀粉代谢相关酶活性变化及 Pn 与气孔导度(Gs)、叶表面温度(TLeaf)等相互关系的研究。结果表明,与留果对照相比,去果处理源叶 Pn、 Gs 和蒸腾速率(E)显著降低,但在中午前后一段时间内 TLeaf显著升高;除在果实迅速生长期间的叶片中淀粉含量外,去果对源叶细胞间 CO2浓度、可溶性糖含量、还原糖含量、腺苷二磷酸葡萄糖焦磷酸化酶和淀粉酶活性无影响;源叶 Pn 与 Gs 呈极显著抛物线正相关、与 E 呈极显著直线正相关。无论是留果对照还是去果处理,源叶 Pn 在一定的温度范围内较高,当 TLeaf超过其适宜的临界温度 (38℃)后,Pn 急剧降低,且在相同 TLeaf的情况下,尤其是当 TLeaf高于 38℃时,去果处理源叶 Pn 均显著低于留果对照。因此,在果树库力降低时,气孔开张度减小、TLeaf升高,可能是其 Pn 调控的重要机制之一。

中国西北干旱区树木蒸腾对气象因子的响应

应用数值方法 ,对中国西北干旱区 5个主要树种 (樟子松、榆树、二白杨、胡杨和沙枣 )的叶面蒸腾及气孔导度对气象因子的响应进行了探讨 ,时间尺度为日。两套综合环境观测系统分别安置在黑河中游的临泽和下游的额济纳旗 ,每半小时自动记录微气象因子、土壤水分和树汁流量。应用日平均树汁流量、饱和差、总辐射、平均气温和土壤含水量拟合树木叶面蒸腾及气孔导度的经验公式。气孔导度和单个气象因子之间具有很高的相关性。应用多个气象因子所建立的经验公式能够很好的模拟气孔导度 ,模拟效果比气孔导度与单一因子的相关性高。气孔导度总体上和饱和差和气温呈指数关系 ,与总辐射的关系多种多样 ,与土壤含水量的关系较复杂。在中游地区 ,二白杨气孔导度、叶面蒸腾量和单株树木树汁流量最大。试验期间下游试验点土壤水分充足 ,耐旱树种胡杨及沙枣树汁流量较大 ,但其气孔导度及叶面蒸腾量均较小。本次研究没有发现树木叶面蒸腾量和单一环境因子之间具有明显的相关性。叶面蒸腾模拟效果没有气孔导度模拟效果好 ,原因是叶面蒸腾是气孔导度和饱和差的函数。

亚热带森林演替树种叶片气孔导度对环境水分的水力响应

利用LI-1600稳态气孔计和PMS压力室,在田间测定了群落演替早期强阳生性树种桃金娘(Rhodomyrtus tomentosa)和三叉苦(Evodia lepta)、偏中性的阳生性树种荷木(Schima superba)、群落演替后期的耐荫树种鸭脚木(Schefllera octophylla)和九节(Psychotrie rubra)的叶片气孔导度(gs)和叶片水势(ΨL),研究不同演替阶段树种的气孔导度对环境水分的响应。结果表明,早上叶片有较高的ΨL,随着时间推移ΨL逐渐降低,与此同时比叶水力导度(KL)随ΨL降低而下降,桃金娘、三叉苦、荷木、鸭脚木和九节水力导度初始最低值时的ΨL分别为-1.6、-1.42、-1.30、-0.9MPa和-1.05MPa。随着ΨL降低,田间测定的gs开始从上午的较低值上升至约中午时的最大值,随后开始降低,此时的ΨL分别为-1.58、-1.52、-1.35、-1.02MPa和-1.0MPa。不同植物种类有不同的KL初始最低值的ΨL和gs达到最大值的ΨL。但不论何种供试树种,KL最低值时的ΨL与gs开始从最大值下降时的ΨL相近;显示KL与gs在动态变化中存在协调关系。树种间的gs和KL对ΨL的不同响应显示桃金娘和三叉苦的KL最低值时和gs开始下降时的ΨL均较鸭脚木和九节对应的ΨL低(p<0.05),意味着演替早期树种能在较强水分胁迫下保持较高的气孔导度。这一水力特性保证树种在水分胁迫下维持叶片的光合速率,有利于其在群落中的生长和优势地位的维护,而演替后期树种在较高ΨL下气孔关闭,降低了光合速率。全球变暖和环境进一步干旱可能成为限制亚热带森林植物群落的正向演替进程的潜在因素之一。

高温对水稻剑叶生长和气孔导度影响

为探讨高温对剑叶生长及气孔导度的影响,采用人工气候箱模拟抽穗期高温,对不同的早稻品种采用不同温度处理。结果表明:(1)在一定温度范围内,温度越高,叶片伸长越长,胜泰1号叶片伸长量最大,籼小占叶片伸长量最小;(2)大气温度升高,叶片温度明显升高,4个品种处理间变化趋势一致,且无显著性差异,叶片温度变化与气温变化一致,叶片温度略低于气温;(3)温度升高,气孔导度明显增加,SPAD值增大,特别是气温从36℃升到38℃时,气孔导度几乎成直线增长,蒸腾作用增强;(4)4个品种中粤香占对高温敏感性较小,耐高温性较强。

NaCl胁迫对构树幼苗叶片水势、光合作用及Na^＋、K^＋吸收和分配的影响

将1年生构树幼苗置于不同NaCl浓度的土壤下,就其叶片水势、光合特性、Na+、K+在不同器官的吸收和分配对盐胁迫响应进行研究。结果显示:当土壤NaCl浓度大于3 g.kg-1,构树幼苗叶片的水势显著降低。构树幼苗净光合速率、蒸腾速率及气孔导度随土壤NaCl浓度的增加而下降,净光合速率下降的主要因素是非气孔限制。在盐胁迫下构树选择Na+而排斥K+,叶片中积累的Na+大于根系,这与多数非盐生植物所具有的排钠特性不同。盐胁迫下净光合速率与叶片水势呈显著的正相关,叶片中Na+、K+含量与叶片的水势分别成显著的负相关和正相关。