不同遮荫水平下4个玉簪品种的生长性状分析

研究了4 个玉簪品种(Hosta ‘Golden Edger’, H.‘Antioch’, H.sieboldiana ‘Elegans', H.plantagenea‘Aphrodite')在全日照的50%、30%和5%条件下的生长性状, 结果表明, 4 个玉簪品种的生长性状均受光照强度的影响, 随遮荫程度的加深, 所有供试品种的各生物量增量均表现下降, H.‘GoldenEdger'和H.plantagenea ‘Aphrodite'对光照较H.‘Antioch'和H.sieboldiana ‘Elegans'敏感, 前二者的适合生长光强为全光照的50%以上, 后两者适合生长的光强为全光照的30%~50%;光强对所有供试品种的单株总叶面积和株高均没有显著影响;各品种比叶重随光强减弱而下降;50%以上遮荫不利于芽及花序的产生。遮荫还改变各品种器官间的生物量分配比例, 50%以上遮荫使根生物量比例减少, 叶片生物量增加;随着遮荫程度的加深, 所有供试品种的各器官干重的总体减少程度大于鲜重。     

遮荫对青桐幼苗生长性状与化学计量特征的影响

营养元素含量及化学计量比可反映植物器官营养元素的分配及互作关系,亦可反映其营养利用效率及生长环境的养分限制状况。以青桐(Firmiana platanifolia)幼苗为材料,分析4种不同光强(全光照,50%、75%和95%遮荫)对青桐幼苗生长,C、N、P、K含量及其化学计量特征的影响。结果表明:遮荫对青桐幼苗的生长性状、生物量、元素含量和积累量及化学计量比均有显著影响(P<0.05)。苗高和比叶面积随遮荫强度增加而升高,而地径和粗壮度随遮荫强度增加而减小。总生物量在75%遮荫下最大,在95%遮荫下最小。在各遮荫处理下,叶片C、N、P、K含量均大于根和茎,且N含量顺序为叶>根>茎,K含量顺序为叶>茎>根。C、P、K积累量随遮荫强度增大而增加,在75%遮荫下达到最大值,而在95%遮荫下达到最小值。青桐幼苗C∶N和C∶P呈现出相同的变化趋势,随遮荫强度变大先增加后减小,均在50%遮荫下达最大值。青桐各器官N∶P远低于14,即青桐幼苗在不同遮荫条件下的生长严重受N限制。这些结果说明,遮荫可调节青桐幼苗在不同光环境中的养分积累与分配,进而影响生物量。因此,青桐苗期培育宜选75%遮荫,有助于苗高、比叶面积、生物量、养分含量和积累量的增加,而过度遮荫可抑制幼苗生长发育。     

遮光对马蹄金生物量分配和形态特征的影响

通过盆栽试验研究了透光率在100％、66％、20.5％和9％的4个光照梯度下,马蹄金的生物量分配及形态特征。结果表明：随着遮光程度的增加,单株的生物量表现出先上升后下降的趋势,在66%透光率下生物量达到最高值;单株生物量分配随着遮光度的增加也发生了改变,其中叶生物量比及叶柄生物量比增加,根生物量比下降,茎生物量比表现出先增大后减小的趋势;随着遮光程度的增加,茎节间长度逐渐增加,分枝角度减小,茎长、分枝强度、叶面积、叶柄均呈先增大后减小的变化趋势。综合分析表明,马蹄金对光环境有一定的适应能力,适度遮光有利于马蹄金的生长、构件数量的增加和生物量的积累,强光或严重遮光均不利于其生长发育。     

光强对三种喀斯特植物幼苗生长和光合特性的影响

以块根紫金牛、地枫皮和秀丽海桐的2年生幼苗为材料,通过搭建遮阴棚设置3个光照强度,对其不同光强下的形态结构、生物量分配以及光合特性进行了比较研究,以探讨光强对喀斯特植物幼苗生长和光合特性的影响。结果表明:遮阴促进了3种喀斯特植物幼苗株高、总叶面积和冠面积等形态指标的增长。总体而言,3种植物幼苗的根生物量比和根冠比均随光强的增大而显著增大,叶生物量比、叶面积比和比叶面积均随光强的增大而显著降低。强光显著降低了地枫皮与块根紫金牛的净光合速率(Pn),非气孔限制是其Pn下降的主要因素;秀丽海桐的Pn随光强的升高而显著增大。遮阴显著增加了地枫皮和秀丽海桐的单位面积叶绿素含量,强光显著增加了块根紫金牛的单位面积类胡萝卜素含量、叶绿素a/b和类胡萝卜素/叶绿素比。地枫皮和块根紫金牛在50%遮阴强度下的总生物量最大,秀丽海桐总生物量随光强增大而显著增大。3种喀斯特植物幼苗对不同的光环境表现出较强的适应性,但强光不利于地枫皮和块根紫金牛幼苗的生长,而秀丽海桐幼苗对光的适应性很强。     

不同光强对棱角山矾幼苗生长及光合特性的影响

通过比较不同遮阴处理下棱角山矾幼苗生长及光合特性的差异,以探讨不同光强对棱角山矾生长及光合作用的影响及其适应机制。结果表明：棱角山矾幼苗的生物量分配对光强的反应敏感,在强光处理下,比叶面积减小,总叶面积变小;弱光处理下通过增大叶生物量比、叶面积比,支持结构生物量比,提高捕光能力。但L100、L30、L10处理下总生物量的积累显著小于L50处理,L30、L50、L100光强处理下总叶面积显著高于L10光强处理。并且10%和100%光强下棱角山矾叶片的最大净光合速率（P_max）、光饱和点（LSP）、表观量子效率（AQY）均显著低于30%和50%光强处理;而光补偿点（LCP）则随光强的增大而升高;总叶绿素和类胡萝卜素含量在10%~100%随着光强增大而显著降低（P<0.05）。说明棱角山矾幼苗在不同光环境下具有一定适应性,但过强或过弱的光环境均会对棱角山矾的生长产生负面影响,其中50%光强是棱角山矾幼苗生长的最佳光强;棱角山矾为中性树种,苗木适宜生长在荫蔽的环境下。     

光强对两种入侵植物生物量分配、叶片形态和相对生长速率的影响

 比较研究了不同光强下生长的（透光率分别为12.5%、36%、50%、100%）两种入侵性不同的外来种——紫茎泽兰（Eupatorium adenophorum）和兰花菊三七（Gynura sp.）的生物量分配、叶片形态和生长特性。结果表明: 1）两种植物叶片形态对光环境的反应相似。弱光下比叶面积（SLA）、平均单叶面积（MLS）和叶面积比（LAR）较大,随着光强的升高,SLA、MLS、LAR和叶根比（LARMR）降低。2）100%光强下紫茎泽兰叶生物量比（LMR）、叶重分数（LMF）和叶面积指数高于低光强下的值,也高于兰花菊三七,支持结构生物量比（SBR）则相反。强光下紫茎泽兰叶片自遮荫严重,这可能是其表现入侵性的重要原因之一;兰花菊三七分枝较多,避免了叶片自遮荫,较多的分枝利于种子形成对其入侵有利。3）随生长环境光强的升高,两种植物的净同化速率（NAR）、相对生长速率（RGR）和生长对NAR的响应系数均升高（但100%光强下兰花菊三七RGR降低）,平均叶面积比（LARm）和生长对LARm的响应系数均降低,但不同光强下LARm对生长的影响始终大于NAR。4）随着光强的减弱,两种植物都增加高度以截获更多光能,但它们的生物量分配策略不同,紫茎泽兰根生物量比（RMR）降低,SBR增大,而兰花菊三七SBR降低,RMR增大。紫茎泽兰的生物量分配策略更好的反应了弱光环境中的资源变化情况。结论：紫茎泽兰对光环境的适应能力强于兰花菊三七。     

遮荫对江南油杉幼苗生长和叶绿素荧光参数的影响北大核心CSCD

为探究有利于江南油杉(Keteleeria fortunei var.cyclolepis)幼苗生长发育的最适光照条件,该研究以1.5年生江南油杉幼苗为研究对象,对其进行为期2年不同光照强度(即全光照和遮荫率40%、60%、80%)处理,分析其形态生长、叶绿素含量、叶绿素荧光参数、生物量积累及分配等对不同光环境的适应机制。结果表明：(1)随遮荫程度的增强,江南油杉幼苗的地径生长量、叶片厚度逐渐减小,株高生长量、叶面积和比叶面积逐渐增大,叶片干质量呈先升后降的趋势;(2)遮荫造成叶片的叶绿素含量、初始荧光(Fo)、PSⅡ潜在活性(Fv/Fo)、PSⅡ最大光化学量子产量(Fv/Fm)、PSⅡ实际光化学量子产量[Y(Ⅱ)]、电子传递速率(ETR)均呈现显著增加的趋势;(3)遮荫处理下幼苗的叶、茎、根生物量和总生物量总体表现出随着光照强度的降低而减小的变化趋势,幼苗根生物量比和根冠比均减小,而叶生物量比、茎生物量比以及光合组织与非光合组织生物量比均增大。研究发现,全光照下江南油杉幼苗生长发育受到了抑制,遮荫显著影响江南油杉苗期生长及叶绿素荧光特性,适度遮荫能提高幼苗叶片的光捕获能力、光能利用效率,增强幼苗光合能力,促进生长;江南油杉幼苗在遮荫率为60%的环境下受光胁迫较小,其生长、叶片表观特征、光合能力以及生物量积累与分配等表现最优。     

披针叶茴香对变化光环境的表型可塑性

植物对变化光环境的表型可塑性大小影响其在林下生境中分布、生长和更新。为探讨披针叶茴香在不同光环境下的整体表型可塑性及其适应机制,采用遮荫试验模拟5种光照条件(100%、52%、33%、15%和6%相对光照强度),研究了不同光环境下披针叶茴香叶片形态、生理、解剖结构、根系形态以及生物量分配等的变化。结果表明:叶生物量在5种光照处理之间差异不显著,但叶面积和比叶面积均随光照强度减弱显著增加。遮荫处理增加了叶绿素a、叶绿素b和类胡萝卜素的含量,但叶绿素a/b比值随光照强度减弱而降低。遮荫降低了非结构性碳水化合物(淀粉和可溶性糖)和可溶性蛋白的含量,增加了叶片氮和磷含量,对叶片氮/磷比影响较小。在52%和33%相对光照处理下,叶片中硝酸盐含量最低,而在100%和6%相对光照处理下硝酸盐积累较多。根生物量、细根和粗根的长度、表面积以及比根长和比根表面积在5种光照处理之间均没有显著差异,根系氮含量在低光环境(15%和6%相对光照处理)中显著降低。随光照强度减弱,披针叶茴香采取保守生存策略,并没有增加叶生物量的分配,而是分配较多的生物量给枝条和树干,储存能量。综合来看,披针叶茴香具有较宽的光生态幅,在6%—100%光照强度下均能正常生长,遮荫有利于披针叶茴香地上和总生物量的积累,52%的相对光照条件下生长最佳。变化光环境下根系性状和整体结构的可塑性相对较低,叶片生理性状的可塑性在披针叶茴香适应光环境变化过程中发挥了主要作用。     

不同养分水平对飞机草生长与生物量分配的影响

采用温室盆栽模拟实验研究了不同养分水平对外来入侵植物飞机草(Chromolaena odorata)的生长性状、生物量积累以及生物量分配格局的影响。实验共设置5 种养分浓度处理, 分别为Hoagland 标准营养液的10%、25%、50%、100%和200%溶液。结果表明: 养分水平对飞机草植株的生长性状以及生物量的积累、分配产生显著影响。随着养分水平的增加, 飞机草的总分枝数量、长度以及一级分枝数量、长度持续增加, 并且100%、200%处理还能促进二级分枝的萌发生长。飞机草的叶片数、总叶面积、总生物量以及茎、叶两器官生物量随养分水平的上升显著增加, 但株高、根生物量不受养分浓度变化的影响。根生物量比、根冠比随养分水平的提高显著下降, 叶生物量比则显著上升, 但茎生物量比在各养分浓度保持稳定。叶面积比、叶根比、RGR 亦随养分含量的上升显著增加。说明养分资源丰富的环境将促进飞机草的地上部生长, 而生物量分配格局的变化可能是其在入侵蔓延过程中适应养分异质性生境的重要生态策略。     

光照和氮素对喜旱莲子草形态特征和生物量分配的影响

研究了两个光照梯度和3个土壤氮素水平交互作用对喜旱莲子草(Alternan thera philoxeroides(Mart.)Griseb.)形态特征和生物量分配的影响。结果表明,全光照促进喜旱莲子草总生物量的积累,但在遮荫条件下,喜旱莲子草可以通过增加株高、光合叶面积和改变生物量分配来适应弱光生境。土壤中氮素含量对喜旱莲子草生长有明显影响,总生物量、株高、叶面积、茎生物量比和叶生物量比等随土壤氮素水平增加而增加。光照和氮素的交互作用对总生物量、根生物量比、茎生物量比和叶生物量比也有显著影响。随着氮素水平的增高,遮荫和高光照处理下喜旱莲子草的叶面积、总生物量和叶生物量比之间的差异减小,而株高和根生物量比之间的差异增大。此外,光照强度对茎生物量比的影响具有明显的氮素浓度依赖性,低氮条件下,茎生物量比在高光照处理下显著高于遮荫处理,而在中氮条件下,遮荫处理却显著高于高光照处理,且在高氮处理下其差异进一步加大。这些结果表明喜旱莲子草在高氮素环境下能够通过形态可塑性和生物量分配模式的改变来适应弱光环境所带来的不利影响。研究结果不但可为研究喜旱莲子草对异质生境的入侵机制提供资料,也可为进一步研究喜旱莲子草的入侵和扩散与农业等生态系统中土壤氮素残留的关系提供参考。       

遮阴对地枫皮幼苗生长和生物量分配的影响

为了解光照强度对地枫皮(Illicium difengpi)幼苗生长和生物量分配的影响,对不同等级幼苗在不同遮阴处理下的形态和生物量变化进行了研究。结果表明,遮阴处理下幼苗的株高、冠宽和平均单叶面积均显著高于对照,同时比叶面积均随光强增大而显著降低。除I级苗50%遮阴处理外,全光处理下各等级幼苗的根长均显著高于遮阴处理。随着光照强度的增加,各等级幼苗的根生物量比与根冠比显著增加,叶生物量比显著减少;不同等级幼苗对强光和弱光环境均表现出较强的适应性,但以50%遮阴处理的总生物量最大,全光和85%遮阴处理均较小。遮阴处理的幼苗个体大小与其初始大小呈正相关,其中II级苗与I级苗差别较小,III级苗生长较差。在人工育苗条件下I级苗数量不到10%,较差的种苗质量叠加喀斯特山顶恶劣环境,可能是导致野外幼苗更新限制的重要原因。因此在野外回归和人工栽培过程中宜选用I、II级种苗,光强控制在透光率50%为宜。     

强光胁迫对濒危植物金花茶幼苗生长和叶绿素荧光参数的影响

以当年生盆栽金花茶实生苗为材料,研究不同程度的强光胁迫（25％、50％和100％自然光强,以8%自然光强为对照）对其生长、生物量、叶片光合色素含量、叶绿素荧光参数的影响。结果表明：在不同程度的强光胁迫下,金花茶幼苗的生长均受到抑制,随着胁迫程度的增强,金花茶叶片颜色由深绿变为浅绿、黄绿色,叶片灼伤愈来愈严重;植株抽稍时间推迟,抽稍后长出的新叶长势较差;幼苗死亡率越来越高。幼苗根生物量、茎生物量、叶生物量和总生物量均随胁迫程度的升高而显著降低,强光胁迫对叶生物量的影响最大,根生物量次之,对茎生物量的影响最小。随着胁迫程度的增强,叶片叶绿素总量（Chl）、叶绿素a（Chla）、叶绿素b（Chlb）含量均显著降低,Chla/Chlb和Car/Chl显著升高。叶绿素荧光参数F_o、F_m、F_v、F_v/F_m、F_v/F_o均随胁迫程度的升高降低,强光胁迫使PSⅡ受到了伤害,光合作用原初反应过程受抑制,光合电子传递受到影响,从而抑制植株的正常生长。     

狭叶红景天幼苗对水分及遮阴的生长及生理生化响应

研究植物对水分和遮阴胁迫的响应及其生理机制对制定合理的栽培管理措施十分必要。以红景天属植物为研究对象,设置土壤含水量分别为田间持水量的80%(过湿水分)、70%(正常水分)、60%(轻度干旱)、40%(中度干旱)、20%(重度干旱)5个水分梯度;设置2个遮阴处理,以全光照(遮阴率为0)为对照、黑色遮阴网遮阴(遮阴率为85%),研究狭叶红景天生长及生理生化指标的变化特征。结果表明:在不同水分处理下,与对照相比,叶绿素含量、茎干重和茎重比(SMR)显著增加(P0.05),株高、总生物量、叶面积、叶干重、叶重比(LMR)、比叶面积(SLA)、叶面积比(LAR)和叶面积根干重比(LARMR)增加,根冠比和根重比(RMR)减少;随着干旱程度加剧,丙二醛(MDA)、脯氨酸(Pro)和可溶性糖(Ss)含量增加,超氧化物歧化酶(SOD)活性总体呈先增加后减小的趋势。在遮阴处理下,株高、SMR、SLA、LAR和LARMR显著增加(P0.05),叶绿素SPAD值和叶面积增加,总生物量、根干重、根冠比和LMR显著减少(P0.05),茎干重和叶干重减少,MDA含量显著增加,Pro含量略有下降,Ss含量减少。在水分胁迫下,狭叶红景天中度干旱时通过增加酶活性抵御伤害,重度干旱超过其阈值,SOD活性下降,植物体受到伤害,Ss可能是主要的渗透调节物质。在遮阴处理下,狭叶红景天通过增加SLA避免遮阴伤害。狭叶红景天在受到环境胁迫时会通过形态改变、调节MDA含量、抗氧化酶活性和渗透调节物质来保证自身正常的生长发育。     

Biomass allocation,morphology and photosynthesis of invasive and noninvasive exotic species grown at four irradiance levels

We tested the hypotheses that invasive species had higher irradiance plasticity, capture ability and efficiency than noninvasive species using two invasive aliens – Ageratina adenophora and Chromolaena odorata, and one noninvasive alien – Gynura sp. The three aliens were grown at 4.5%, 12.5%, 36%, 50% and 100% irradiances for 64 days before harvesting. The plastic response of specific leaf area (SLA) contributed to improved light interception at low irradiance, carbon gain and water balance at high irradiance. It was a good predictor for intraspecific irradiance responses of leaf area ratio (LAR), leaf area:root mass ratio, maximum photosynthetic rate (P_max) and net assimilation rate (NAR). Biomass allocation-related traits were species specific and their plasticity to irradiance was low. The high root mass fraction, leaf mass fraction and LAR distinguished the two invaders from Gynura. However, other resource capture-related traits, such as SLA, NAR and P_max, were not always higher for the invaders than for Gynura. Furthermore, plasticity to irradiance was not different between the invasive and noninvasive aliens. With increasing irradiance, Gynura decreased biomass investment to roots and leaves but increased the investment to support structures adversely affecting both low and high irradiance acclimation. Ageratina might invade new habitat successfully through tolerating shading at low irradiance and outshading competitors by forming dense stands when irradiance is increased. The results suggested that both resource capture-related traits and irradiance acclimation conferred competitive advantage to the two invaders and some traits were common for invasive and noninvasive aliens but others were specific for invaders.     

Effects of irradiance on growth,photosynthetic characteristics,and artemisinin content of <Emphasis Type="Italic">Artemisia annua</Emphasis> L.

With an increase in growth irradiance (from 15 to 100 % of full sunlight, I₁₅ to I₁₀₀), the maximum net photosynthetic rate (P _max), compensation (CI) and saturation irradiances of A. annua increased. At full sunlight, A. annua had a high capacity of photosynthesis, while at low irradiance it maintained a relatively high P _max with a low CI. The height and diameter growth, total and leaf biomass, and artemisinin content of A. annua decreased with the decrease in irradiance, which might be connected with lower photosynthesis at lower than at higher irradiance. Irradiances changed biomass allocations of A. annua. The leaf/total mass ratio of A. annua increased with decreasing irradiance, but the root/total mass ratio and root/above-ground mass generally increased with increasing irradiance. Thus A. annua can grow in both weak and full sunlight. However, high yield of biomass and artemisinin require cultivation in an open habitat with adequate sunshine.     

Consequences of phenotypic plasticity vs. interspecific differences in leaf and root traits for acquisition of aboveground and belowground resources

Trade-offs between acquisition capacities for aboveground and belowground resources were investigated by studying the phenotypic plasticity of leaf and root traits in response to different irradiance levels at low nutrient supply. Two congeneric grasses with contrasting light requirements, Dactylis glomerata and D. polygama, were used. The aim was to analyze phenotypic covariation in components of leaf area and root length in response to above- and belowground resource limitation and the consequences of this variation for resource acquisition and plant growth. At intermediate shading (30 and 20% of full sunlight) the plants were able to maintain their total root length, despite a strongly increased total leaf area and a reduced biomass allocation to roots. This was associated with an unaltered or slightly increased nutrient uptake and growth. At 5.5% relative irradiance, growth was severely reduced, especially in the shade-tolerant D. polygama. The results show that constraints on acquisition capacities for aboveground and belowground resources, caused by biomass allocation, may be alleviated by plasticity in other traits such as tissue-mass density and thickness of roots and leaves. The results also suggest different adaptive constraints for phenotypic plasticity and for genetically determined interspecific variation. Phenotypic plasticity tends to maximize resource acquisition and growth rate in the short term, whereas the higher tissue-mass density and the longer leaf life-span of shade-tolerant species indicate reduced loss rates as a more advantageous species-specific adaptation to shade in the long term.     

Increased growth of young citrus trees under reduced radiation load in a semi-arid climate

This study investigated the effects of radiation heat-load reduction by shading on the growth and development of citrus trees in a warm subtropical region. The experiment was conducted from mid-June until late October when daily maximal air temperature averaged 29.3 degrees C. Two-year-old de-fruited Murcott tangor (Citrus reticulata BlancoxCitrus sinensis (L.) Osb.) trees were grown under 30% or 60% shade tunnels, or 60% flat shade (providing midday shade only), using highly reflective aluminized nets. Non-shaded trees were used as the control. Shading reduced direct more than diffuse radiation. Daily radiation was reduced by 35% for the 30% Tunnel and 60% Flat treatments, and by 55% for the 60% Tunnel. Two days of intensive measurement showed that shading increased average sunlit leaf conductance by 44% and photosynthesis by 29%. Shading did not significantly influence root and stem dry weight growth, but it increased the increment in leaf dry weight during the three month period by an average of 28% relative to the control, while final tree height in the 30% Tunnel treatment exceeded the control by 35%. Shoot to root and shoot mass ratios increased and root mass ratio decreased due to shading because of the increase in leaf dry weight. Shading increased starch concentration in leaves while the shadiest treatment, 60% Tunnel, decreased starch concentration in the roots. Carbon isotope ratio (delta(13)C) of exposed leaves that developed under shading was significantly reduced by 1.9 per thousand in the 60% Tunnel, indicating that shading increased CO(2) concentrations at the chloroplasts (C(c)), as would be expected from increased conductance. Substomatal CO(2) concentrations, C(i), computed from leaf net CO(2) assimilation rate and conductance values, also indicate that shading increases internal CO(2) concentrations. Based on tree dry mass, tree height, and total carbohydrates fractions, the 30% Tunnel and the 60% Flat were the optimal shade treatments.     

The effects of irradiance on growth, respiration and nitrate reductase activity of Terminalia ivorensis and Terminalia superba

Controlled-environment experiments were conducted to determine the effect of three irradiance levels obtained by artificial shading (40%, 65% and 100% light) on the growth, distribution of photosynthate, relative growth rate, net assimilation rate, respiration and nitrate reductase activities in the leaves of seedlings of Terminalia ivorensis and Terminalis superba, two important tropical tree species. Total dry weights of both species increased with increasing irradiance level during growth. Shading affected the percentage dry matter in the roots and number of leaves of both species. Relative growth rate, net assimilation rate, respiration and nitrate reductase in the leaves of both species increased with increases in irradiance level during growth. Significant differences between the species were observed in most of the parameters studied.