墨兰幼叶和成熟叶不同部位叶绿体超微结构和光合作用

墨兰试管苗植株成熟叶片叶绿体基粒较发达,类囊本膜垛叠较紧密。幼叶叶绿体中少有亲锇颗粒,成熟叶的叶绿体中往往既有亲锇颗粒又有淀粉粒。幼叶中基粒数目比成熟叶的少,叶绿体也比成熟叶的小。幼叶的光合放氧速率比成熟叶的低。幼叶中叶尖部叶绿体最大而叶基部最小,但叶尖部的光合放氧速率比叶基部小。成熟叶中叶绿体大小及光合放氧速率区别不明显。通过对各部位叶绿素含量的测定发现,叶绿素含量与光合放氧速率之间没有正相关性     

低浓度硫酸甲酯吩嗪（PMS）对叶片光合放氧的促进作用

外加低浓度循环光合磷酸化电子递体硫酸甲酯吩嗪(PMS)对菠菜、大豆、水稻和小麦叶片光合放氧有促进作用,与此同时叶片ATP含量也得到增加。PMS对经8 mmol L~(-1)NH_4Cl处理过的菠菜叶片的光合放氧也有促进,最适促进浓度比未经NH_4Gl处理的叶片高,促进的幅度也大。幼龄叶与成长叶相比,幼龄叶的光合磷酸化活性和P/O比值低于成长叶片,其光合放氧速率受PMS促进的幅度大于成长叶片。因此光合磷酸化也可以成为光合作用的一个重要限制因素。     

水稻叶切片在光合反应液中气孔状态的扫描电镜观察

用溶氧电极测定水稻叶片光合放氧速率,其叶切片浸沉在光合反应液中,切面能与溶液进行气体交换。由于水稻叶切片用的是2.5mm~2,背腹两面气孔数总共有1400—1900多个,因此通过气孔进行气体交换,应该也是一个重要的途径。这方面未见     

光合作用中水氧化放O_2的预备反应的探讨

许多学者利用强而短的闪光来研究绿色植物放O_2动力学过程以来,发现放O_2既需要光又需要暗的预备反应,即从H_2O到放O_2之间存在着放氧前体,并且认为放O_2的预备反应为PSⅡ所敏化。Joliot等(1969)与Kok等(1970)在继续研究放O_2动力学过程中分别观察到,开始两个闪光(第一、二闪光)的放O_2量几乎等于零,第三闪光产量最大,     

榕-蜂互惠关系中榕树对未传粉榕小蜂的惩罚效应

为验证榕树与其传粉榕小蜂这一严格的、一对一的互利共生系统中是否存在寄主惩罚效应,作者于2007年在云南省西双版纳热带植物园中对雌雄同株的垂叶榕（Ficus benjamina）进行了单果放蜂实验。将为垂叶榕传粉的榕小蜂（Eupristina koningsbergeri）处理成带粉和不带粉的两组,每组又分一只和两只两个水平,分别放进单个隐头花序果中。结果发现：没有传粉榕小蜂进入的隐头花序果会很快终止发育并脱落;而在放了传粉榕小蜂的隐头花序果里,除少数几个放一只不带粉的外,隐头花序果基本都能完成其生活史。但是,带粉雌蜂繁殖的后代小蜂数量显著高于没有带粉的雌蜂,特别是在放两只蜂的处理中。研究结果说明传粉榕小蜂的主动传粉对其繁殖不是必需的,但是主动传粉能增加其繁殖成功的几率。这些结果预示着寄主惩罚效应在榕-蜂互惠系统中发挥着作用。     

间歇性溪流米槠凋落叶分解过程胞外酶活性动态

以米槠(Castanopsis carlesii)凋落叶为研究对象,于2021年4—7月,对照森林地表和持续流水的溪流,研究间歇性溪流凋落叶分解过程中胞外酶活性变化规律。结果表明：(1)间歇性溪流凋落叶分解过程中酸性磷酸酶、β-葡萄糖苷酶、β-N-乙酰氨基葡萄糖苷酶和脲酶活性总体高于地表,低于溪流。(2)通过分析胞外酶化学计量比和矢量特征,发现三种生境凋落叶分解过程中微生物群落受碳和磷的共同限制。分解初期,间歇性溪流凋落叶分解过程中微生物群落相对碳限制程度高于其他两个生境,但相对磷限制低于地表,高于溪流;随着分解的进行,间歇性溪流凋落叶分解过程中微生物群落相对磷限制程度逐渐减弱,相对碳限制程度逐渐加强。(3)统计分析表明,间歇性溪流中大气温度是凋落叶分解过程中胞外酶活性的主控因子,而地表凋落叶分解过程中胞外酶活性与大气温度、地表温度和土壤含水量关系更为密切,溪流凋落叶分解过程中胞外酶活性主要受水体温度、溪流深度和气温等因子的影响。研究结果为全面认识亚热带森林生态系统物质迁移与循环过程提供了新思路和科学依据。     

叶呼吸作用实验的简易方法

叶呼吸作用实验大多以盆栽植物为材料,但这种材料找起来不方便.我采用生长旺盛的蔬菜(菠菜、莴苣等阔叶菜)或阔叶野草(如车前草、牛儿大黄等)的叶,实验效果很好.方法是:上课前一天,摘取阔叶植物叶片放人适宜的无     

智利小植绥螨饲养释放初报

1976年我们对从瑞典(1975年)引入的棉叶螨天敌——智利小植绥螨Phytoseiulus persimilts进行了饲养及释放试验,所得结果如下。 一、饲养方法 1.室内 在直径90、高20毫米培养皿里放塑料纱网,下衬湿纱布,网上放新鲜大豆叶片。将捕食螨与     

低温对高等植物叶组织生物电位的影响

在程序降温过程中,玉米、高粱和小麦叶组织分界电位都出现负电性变化,同种植物叶组织分界电位变化的波形和波谷温度相同,玉米叶组织静息电极性的变化波形与其分界电位的变化波形相同。叶组织分界电位负电性变化过程中,叶组织电阻及其相对电解质渗出率都没有出现相应的变化。不同类型的代谢抑制剂处理叶片后,能使降温过程中叶组织分界电位的负电性变化消失。叶组织分界电位的负电性变化与植物细胞的能量代谢及膜电位有关。     

高寒森林不同生境对凋落叶分解灰分动态的影响

灰分是凋落叶的重要组成部分,其浓度直接关系到凋落叶的分解过程及有机组分的动态特征,且可能受生境和分解时期的影响,然而有关凋落叶分解过程中灰分动态的研究鲜有报道。采用凋落袋法,以岷江上游高寒森林4种代表性植物康定柳(Salix paraplesia)、高山杜鹃(Rhododendron lapponicum)、方枝柏(Sabina saltuaria)和四川红杉(Larix mastersiana)凋落叶为研究对象,研究了高寒森林凋落叶在3种不同环境条件下(林下、溪流、河岸带)分解过程中灰分的动态特征。结果表明,灰分量随凋落叶的分解整体呈现降低的趋势,且不同环境条件和不同物种之间存在明显的差异。与之相反,经过两年的分解,除溪流中康定柳凋落叶灰分浓度略有下降外(-0.99%),林下和河岸带中康定柳凋落叶及其它物种凋落叶中灰分浓度在所有环境条件下均表现出了增加的趋势(5.86%—72.15%)。凋落叶分解过程中灰分浓度变异量在不同分解时期存在明显或显著的差异,且受物种和环境因子的调控。这些结果表明,传统上认为凋落叶分解过程中灰分浓度比较稳定的观点是不准确的,且以凋落叶分解过程中灰分浓度不变的前提下采用无灰分质量损失(ash free mass loss)而计算凋落叶质量损失的方法存在一定的不准确性。研究为认识凋落叶分解过程中灰分的动态特征及凋落叶质量损失的测定方法提供了一定的参考。     

Leaf orientation and distribution in a Phaseolus vulgaris L. crop and their relation to light microclimate

Changes in canopy structure parameters (leaflet orientation, leaflet inclination and leaf area index) were measured in crops of beans (Phaseolus vulgaris L.) in the field as the canopy developed between July and October. These changes were compared with the corresponding changes in seasonal light transmission. The beans showed clear heliotropic behaviour, with preferential orientation of leaflets towards the sun’s beam, especially on sunny days. Nevertheless a significant proportion of the leaves pointed in other directions, with as much as 20% oriented towards the north. The highest proportion of leaf inclinations was in the range 30–40° on cloudy days and between 40° and 50° on sunny days. Two methods were compared for assessing changes in light transmission: (a) the use of a Sunfleck Ceptometer and (b) the use of continuous records obtained with sensors installed in the canopy. Over the growth period studied, the total of the leaf plus stem area indices (L _S) increased from 0.26 to 5.2 with the transmission coefficient (τ) for photosynthetic photon flux density (PPFD), obtained using the Ceptometer, correspondingly decreasing from 0.72 to 0.05, and the canopy extinction coefficient decreasing from 1.4 to 0.62. The continuous records of light transmission gave generally similar estimates of τ. Some contrasting leaf angle distribution functions were compared for estimation of L _S from the light measurements. The best leaf angle function to predict L _S from the observed light transmission was a conical function corrected by the degree of heliotropism. Received: 27 January 1999 / Accepted: 11 June 1999     

Responses to light changes in tropical deciduous woody seedlings with contrasting growth rates

We evaluated the responses in growth, biomass allocation, photosynthesis and stomatal conductance, to changes in light in woody seedlings from the tropical deciduous forest in Mexico, which shows a highly seasonal rain pattern. We studied ten species, which differed by 30-fold in relative growth rate (RGR). We analyzed plant growth in two contrasting light levels during 52 days and two transfers: from high to low (HL) and from low to high (LH) light intensity, and the respective controls in high (HH) and low (LL) light for another 52 days. The photosynthetic capacity (A _max) and stomatal conductance were measured at the day of the transfer between light conditions and at the end of the experiment. Species with high RGR showed the largest changes in RGR in response to contrasting light conditions (HH/LL ratio), and species with low RGR showed low responses. The fast-growing species were the most plastic, followed by species with intermediate growth rates, with the slow-growing species being the least plastic. Fast-growing species achieved higher maximum photosynthetic capacities (A _max) and stomatal conductance and higher response to light than slow-growing species. Species with high RGR showed a low RGR HH/LH ratio, suggesting a large response of L plants when transfered to H. The RGR of the species were associated with species specific leaf area and with the response in the leaf area, net assimilation rate and leaf weight ratio, suggesting the importance of the leaf area produced and the leaf characteristics rather than root:shoot ratio in determining RGR. Considering that seed germination is expected at the beginning of the rainy period, seedlings of most of the species will experience high-light conditions during its early growth. There are large annual variations in the time required for canopy closure (35–75 days). The influence of these variations may have different effect on the species studied. Species with intermediate growth rate and intermediate response to light changes were less affected by light reduction than fast-growing species. The intermediate-RGR species Caesalpiniaeriostachys is the most abundant and widely distributed species, perhaps this could be in part due to its ability to acclimate to both light increases and decreases. The fast-growing species studied here can be found in open sites in the forest and in areas cleared for pasture growth. These fast-growing species eventually reach the canopy, although this may require several canopy openings during their lives, which implies juvenile shade tolerance. In the tropical deciduous forest juvenile pioneer trees also benefit from the temporary high light available caused by the dry period during the rainy season. The slow-growing species Celaenodendronmexicanum forms small patches of monospecific forest; the adult trees are not completely deciduous, and they retain their old leaves for a long time period before shedding. Thus seedlings of this species may receive lower levels of light, in agreement with its shade tolerance and its lower response to light increases. Received: 14 April 1997 / Accepted: 29 July 1997     

Ground monitoring the light–shadow windows of a tree canopy to yield canopy light interception and morphological traits

Monitoring the light–shadow windows of a tree via a grid system on the ground was performed on sunny summer days at high spatial resolution using a custom‐built, inexpensive scanner. The measurements were taken with two goals: (1) to quickly and remotely quantify the overall, short‐wave solar radiation (300–1100 nm) intercepted by the tree canopy, and (2) to yield such crown geometric traits as shape, size and the number of theoretical canopy leaf layers (leaf layer index, LLI) in relation to the section orthogonal to sunbeam direction (sun window). The ground readings at each measurement over the day were used to project a digitized shadow image. Image processing was applied and the intercepted radiation was calculated as the difference from the corresponding incoming radiation above the canopy. Tree‐crown size and shape were profiled via computer imaging by analysing the different shadow images acquired at the various solar positions during the day. It is notable that these combined images yielded the crown features without having to parameterize such canopy characteristics as foliage extension and spatial distribution.     

Ecophysiological controls over the net ecosystem exchange of mountain spruce stand. Comparison of the response in direct vs. diffuse solar radiation

Cloud cover increases the proportion of diffuse radiation reaching the Earth's surface and affects many microclimatic factors such as temperature, vapour pressure deficit and precipitation. We compared the relative efficiencies of canopy photosynthesis to diffuse and direct photosynthetic photon flux density (PPFD) for a Norway spruce forest (25‐year‐old, leaf area index 11 m² m⁻²) during two successive 7‐day periods in August. The comparison was based on the response of net ecosystem exchange (NEE) of CO₂ to PPFD. NEE and stomatal conductance at the canopy level (G_canopy) was estimated from half‐hourly eddy‐covariance measurements of CO₂ and H₂O fluxes. In addition, daily courses of CO₂ assimilation rate (A_N) and stomatal conductance (G_s) at shoot level were measured using a gas‐exchange technique applied to branches of trees. The extent of spectral changes in incident solar radiation was assessed using a spectroradiometer. We found significantly higher NEE (up to 150%) during the cloudy periods compared with the sunny periods at corresponding PPFDs. Prevailing diffuse radiation under the cloudy days resulted in a significantly lower compensation irradiance (by ca. 50% and 70%), while apparent quantum yield was slightly higher (by ca. 7%) at canopy level and significantly higher (by ca. 530%) in sun‐acclimated shoots. The main reasons for these differences appear to be (1) more favourable microclimatic conditions during cloudy periods, (2) stimulation of photochemical reactions and stomatal opening via an increase of blue/red light ratio, and (3) increased penetration of light into the canopy and thus a more equitable distribution of light between leaves. Our analyses identified the most important reason of enhanced NEE under cloudy sky conditions to be the effective penetration of diffuse radiation to lower depths of the canopy. This subsequently led to the significantly higher solar equivalent leaf area compared with the direct radiation. Most of the leaves in such dense canopy are in deep shade, with marginal or negative carbon balances during sunny days. These findings show that the energy of diffuse, compared with direct, solar radiation is used more efficiently in assimilation processes at both leaf and canopy levels.     

利用多光谱扫描仪测定空心莲子草冠层光谱的影响因素

【背景】太阳光的入射辐射是影响多光谱扫描仪测定植物冠层光谱反射率的主要因素。本研究旨在探讨不同测定条件对空心莲子草冠层光谱特征值的影响,确定应用多光谱扫描仪测定空心莲子草冠层光谱特征的适宜环境条件。【方法】采用多光谱扫描仪,在不同天气条件、仪器探头高度、太阳高度角、叶片湿度等外界因素条件下,测定空心莲子草冠层光谱反射率的变化。【结果】天气条件、仪器探头高度、太阳高度角、叶片湿度4个因素对空心莲子草冠层在绿光区560nm、黄光区660nm和近红外光区810nm3个特征波段处的光谱反射率均有显著影响。【结论与意义】利用多光谱扫描仪测定空心莲子草冠层光谱数据,应选择晴朗无云的天气,仪器探头距离冠层1.3m,适宜的数据采集时间为10：00～14：00,以保障适度的太阳高度角和干燥的叶面,从而保持稳定的光谱测量结果。本研究可为完善多光谱扫描评价技术提供理论依据。     

Use of Interactive Computer Graphics for Simulation of Radiation Interception and Photosynthesis for Canopies of Kiwifruit Vines with Heterogeneous surface Shape and Leaf Area Distribution

A method incorporating interactive computer graphics to simulatespatially variable interception and canopy photosynthesis isdescribed. The method presents a graphical interface to a conventionalmodel of radiation interception and canopy photosynthesis. Includedis the capacity to consider a large number of positions withinthe canopy, thus providing a rapid and convenient representationof the dynamics of photosynthesis while also overcoming limitationsof one-dimensional models applied to complex plant canopies.The method was applied to examine spatial variability of photosynthesiswithin canopies of kiwifruit (Actinidia deliciosa) vines growingon two trellis types. The diurnal integral of simulated canopyphotosynthesis, assuming sunny conditions, for a vine trainedon a horizontal 'Pergola' trellis was 14% higher than that fora vine with similar leaf area distribution trained on a 'T-bar'trellis with inclined surfaces. Simulations of photosynthesisfor vines on a T-bar trellis, assuming spatially variable leafarea distributions as measured under filed conditions, indicateddisproportionate contributions from different regions of thecanopy. Canopy regions inclined to the east or the west wereusually the major sites for photosynthesis immediately aftersunrise and before sunset respectively, while regions near thecordon were the most important overall. For any day, the maximumsimulated photosynthetic rate generally declined with distancefrom the cordon and, at any distance from the cordon, increasedwith leaf index. For a vine with an average leaf area indexof 2·7, diurnal integrals of photosynthesis on a sunnyday in late summer ranged from 1·0 mol CO₂ m^-2 near thecordon to 0·5 mol CO₂ m^-2 at 1·5 m from the cordon.Within-canopy shading was more important on sunny days thanon cloudy days, while the spatial distribution of leaf areawas especially important on cloudy days. Comparison of simulationswith direct measurements of canopy photosynthesis indicatedthat a numerical integral of simulated photosynthesis, basedon a large number of canopy positions, provided a reasonableestimate of total canopy photosynthesis.Copyright 1993, 1999Academic Press Actinidia deliciosa, kiwifruit, interactive computer graphics, mathematical modelling, photosynthesis, radiation interception, spatial heterogeneity     

夏玉米群体光合速率特性及其与冠层结构、生态条件的关系

研究结果表明：高产夏玉米群体光合速率日变化呈单峰曲线。在水肥充足栽培条件下,光照强度是影响玉米群体光合速率的主导因素,最大自然光强下群体光合未测到光饱和点。群体光合速率随CO2浓度(50—900ppm范围)的增加而提高。土壤呼吸释放的CO2量占群体光合速率的11.68%。高产群体所形成的独特环境对单叶光合速率影响很大,群体生长下的单株,在8×104一9×104Lx光下的单叶光合速率为果穗叶高于下部和上部叶,品种、密度间差异不大;冠层自然状态下的单位叶面积光合速率上部叶却高于中、下部叶,高密度下,紧凑型品种高于平展型品种,低密度下则相反。     

沿林冠开度梯度的银杉幼树对光的适应性

用气体交换技术测定了四川省金佛山生长在一个典型林隙(林隙面积约为100 m²)不同位置的银杉(Cathaya argyrophylla)幼树叶片的部分光合生理生态指标,用改进的鱼眼镜头法测定了所测叶片的林冠开度(CO),并测定了这些银杉幼树个体的生长状况。研究了沿林冠开度梯度银杉幼树对光的适应性。银杉幼树在林隙边缘表现出较好的适应性,包括当年生树高生长速率(HG)、平均地茎生长速率(DG)和当年冠幅生长速率(CG)。随林冠开度的增加,单位叶面积的最大净光合速率(P_narea)、暗呼吸速率(R_darea)和单位叶面积的叶片干物质重(比叶重,SLM)明显增加,且相关显著。随林冠开度的增加,单位叶面积(LA)和单位叶干物质重的暗呼吸速率(R_dmass)略有降低,而单位叶片干物质重的最大净光合速率(P_nmass)和单位叶片干物质重(LM)略有升高,但相关不显著。沿林冠开度的银杉幼树的形态可塑性要略低于生理生态可塑性,但差异不显著。     

钾肥对灌桨期冬小麦群体内叶片光合特性的影响

通过在连续6年施钾与不施钾处理的试验区内,对冬小麦(Triticum aestivum)灌浆期群体内旗叶叶片光合特性的研究表明,施用钾肥时,最大净光合速率(Pmax)增加,光饱和点(LSP)和光补偿点(LcP)提高,表观量子效率(α)降低,表观暗呼吸速率(Rd)略有上升;施钾与不施钾处理的净光合速率(Pn)日变化,晴天和阴天均呈单峰曲线,晴天午前与午后及阴天各时刻的瞬间净光合速率(Pn)下降的主要原因是“气孔因素”,而晴天中午前后则更主要是由于“非气孔因素”作用。     

钾肥对灌浆期冬小麦群体内叶片光合特性的影响

通过在连续6年施钾与不施钾处理的试验区内,对冬小麦(Triticum aestivum)灌浆期群体内旗叶叶片光合特性的研究表明,施用钾肥时,最大净光合速率(Pmax)增加,光饱和点(LSP)和光补偿点(LCP)提高,表观量子效率(α)降低,表观暗呼吸速率(Rd)略有上升;施钾与不施钾处理的净光合速率(Pn)日变化,晴天和阴天均呈单峰曲线,晴天午前与午后及阴天各时刻的瞬间净光合速率(Pn)下降的主要原因是“气孔因素”,而晴天中午前后则更主要是由于“非气孔因素”作用.