不同光照处理下青藏高原克隆植物黄帚橐吾(Ligulariavirgaurea)种子大小对其幼苗生长的影响

以高寒草甸克隆植物黄帚橐吾为实验材料,通过遮荫网模拟植被遮荫,研究种子大小与萌发及幼苗生长能力的关系和幼苗对光照条件的反应。结果表明：（1）在自然光照下,黄帚橐吾种子大小对种子萌发的影响显著,大种子的萌发率高于小种子。遮荫生境下,大、小种子萌发率有所降低,但遮荫对小种子萌发的影响比大种子显著。小种子的萌发率下降了近1/8,而大种子的萌发率仅下降了1/11。（2）黄帚橐吾种子大小对幼苗生物量积累影响显著,大种子幼苗总生物量（TB）大于小种子幼苗的。但生物量的分配与播种时间相关,播种后60 d,在自然光照条件下,大种子幼苗对根生物量的分配大于小种子幼苗,而对叶生物量的分配则正好相反。在遮荫环境中,大、小种子幼苗普遍对根的生物量分配增加,大种子幼苗根冠比（R/S）大于小种子幼苗。（3）黄帚橐吾种子大小对幼苗的生长也有明显影响。在自然光照下,小种子幼苗的相对生长速率（RGR）较大于大种子幼苗,但叶面积比率（LAR）、叶面积干质量比（SLA）、叶干质量（LWR）差别不明显。在遮荫条件下,幼苗的LAR、SLA、LWR显著增加,但大、小种子幼苗间差异不显著,幼苗的RGR减小,小种子幼苗的减小趋势大于大种子幼苗。     

不同光照对望天树种子萌发和幼苗早期生长的影响

在不同光照梯度的人工遮荫和森林生境中,研究了西双版纳季节雨林标志树种望天树的种子萌发和幼苗早期生长特征.结果表明,裸地上的强光照和深度遮荫均不利于望天树种子的萌发,中等程度的遮荫有利于种子萌发.望天树种子萌发率在林窗中央最大,而且萌发迅速,林窗边缘和林下生境不利于种子萌发.幼苗株高、基径和单株叶面积等生长指标均在部分遮荫处理条件下最大;幼苗根冠比在裸地上最高,且随遮荫程度的增加而降低;幼苗比叶面积在一定光照强度范围内随遮荫程度的增加而增大,在3层遮荫最大.除幼苗根冠比以外的其它生长参数均在林窗中央最大.讨论了环境因子(主要是光照强度和光质)对望天树种子萌发和幼苗生长的影响.     

遮荫对七子花幼苗光合特性和非结构性碳水化合物含量的影响

为探讨不同光环境下濒危植物七子花（Heptacodium miconioides）的生长及适应规律,以2年生七子花幼苗为研究对象,设置全光照、60%遮荫和90%遮荫3种光照强度,研究不同光环境对七子花幼苗的光合特性和非结构性碳水化合物（NSC）含量的影响。结果表明：（1）3种光照处理下,七子花幼苗的净光合速率（P_n）日变化均呈“单峰型”曲线,P_n日均值为全光照>60%遮荫>90%遮荫,90%遮荫下水分利用效率（W_UE）日均值显著低于全光照和60%遮荫。（2）与全光照相比,60%遮荫下七子花幼苗的光补偿点（L_CP）和暗呼吸速率（R_d）显著下降,而光饱和点（L_SP）、最大净光合速率（P_nmax）、最大羧化速率（V_cmax）、最大电子传递速率（J_max）和磷酸丙糖利用率（T_PU）无显著差异;重度遮荫（90%遮荫）导致植株的P_nmax、L_SP、L_CP、R_d、V_cmax、J_max和T_PU显著降低。（3）七子花幼苗叶片的淀粉、可溶性糖和NSC含量在60%遮荫处理中最高,90%遮荫处理下则显著下降。植株的NSC含量与P_n、V_cmax、J_max和T_PU呈显著正相关关系。综上所述,七子花在幼苗期具有一定的喜光性和耐荫能力,适度遮荫下植株可通过降低L_CP、R_d来调整叶片的光合生理,维持较高的NSC含量,从而来提高对弱光的利用率和碳同化能力,但在生产育苗过程中过度遮荫不利于七子花幼苗的生长。     

环境因子对龙脑香科幼苗的生长和存活的影响研究进展

就光照、水分、动物捕食和菌根共生体对龙脑香科(Dipterocarpaceae)植物幼苗生长与死亡的影响进行了综述,并对未来研究的发展方向作一展望。光照是影响龙脑香科植物幼苗生长和存活的最重要的资源条件,林窗中的较强光照有利于幼苗的生长与存活。引起龙脑香科植物幼苗死亡的主要原因是干旱;脊椎动物捕食增加龙脑香科植物幼苗的死亡,昆虫对幼苗叶片捕食造成的死亡只发生在叶片大量损失或幼苗较小的情况下。龙脑香科植物幼苗能通过与真菌形成共生体从成年植株获得营养和水分供应而生长,尤其在资源亏缺的条件下更为明显。     

遮荫对风箱果幼苗光合能力和碳水化合物积累的影响

以1年生风箱果幼苗为材料,采用人工遮荫方式设置CK （全光）、轻度遮荫L1（60%全光）和重度遮荫L2（20%全光）3种光环境,测定不同光环境下风箱果幼苗的光合特性、光合色素含量、非结构性碳水化合物（NSC）积累等,分析风箱果幼苗对不同遮荫环境的适应性。结果表明：风箱果属于阳生树种,对光环境的变化非常敏感;遮荫显著降低了表观量子效率（AQY）、最大净光合速率（P_max）、暗呼吸速率（R_d）、光补偿点（LCP）、光饱和点（LSP）和类胡萝卜素含量（Car）（P<0.05）,显著提高了叶绿素a （Chla）、叶绿素b （Chlb）、总叶绿素（Chl）含量和叶绿素/类胡萝卜素（P<0.05）;遮荫显著减少了根、茎、叶中NSC含量（P<0.05）,尤其是L2时,分别比CK减少了52.5%、44.9%和43.9%。综上所述,风箱果幼苗对于遮荫环境的适应和调节能力较差,生产实践中应栽植在阳光充足的环境中。     

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。     

遮荫处理对芍药幼苗生长和矿质营养积累的影响

遮荫是保护芍药幼苗生长的重要措施。本试验研究了不同遮荫处理对多伦芍药幼苗生长特性和矿质营养积累的影响,以便为多伦芍药幼苗栽培提供指导。采用盆栽试验,研究不遮荫(CK)、出苗一周后20%遮荫、40%遮荫、60%遮荫和80%遮荫5个处理的多伦芍药幼苗生长和矿质营养积累的变化。结果表明:与CK相比,遮荫处理显著提高了幼苗株高,增幅分别为19.9%、31.1%、52.9%、63.7%;显著降低了根生物量比和根冠比,降幅分别为21.5%、23.6%、29.2%、41.8%和40.6%、44.0%、50.9%、63.2%。40%遮荫、60%遮荫和80%遮荫显著提高了比叶面积,增幅分别为77.0%、84.1%、65.2%,显著增加了叶绿素和类胡萝卜素含量,增幅分别为92.3%、128.7%、98.1%和86.9%、113.1%、90.5%,显著降低了根生物量,降幅分别为61.4%、74.3%、78.6%。与CK、20%遮荫、40%遮荫和80%遮荫处理相比,60%遮荫显著提高了根中磷含量,增幅分别为245.7%、65.9%、40.5%、10.3%;60%遮荫处理的根中钾和镁含量显著高于其他处理,比CK、20%遮荫、40%遮荫和80%遮荫处理分别高102.9%、131.7%、57.0%、63.3%和131.3%、55.1%、40.4%、7.7%。本试验条件下,60%遮荫是多伦芍药幼苗生长适宜的光照条件。     

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。     

遮荫处理对秋枫幼苗生理生态特性的影响

为了解遮荫对秋枫(Bischofia javanica)幼苗生长的影响,对夏季1年生秋枫幼苗在4种遮荫(透光率分别为自然光的100%、41.3%、14.6%和3.6%)处理150 d后的生理指标变化进行了研究。结果表明,1年生秋枫幼苗的光补偿点(LCP)、光饱和点(LSP)和暗呼吸速率(Rd)随着遮荫程度加重而减小,表观量子效率(AQY)则增大,净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)和胞间CO_2浓度(Ci)的日变化表明秋枫有明显的"午休"现象,遮荫引起光合速率降低的主要原因是非气孔限制,而全光照条件下则是气孔限制。叶绿素、可溶性糖含量随遮荫程度的增大呈先升后降的变化趋势;相对电导率、丙二醛(MDA)含量、过氧化氢酶(CAT)活性则呈先降后升的趋势,以41.3%透光率的最小;可溶性蛋白质含量、超氧化物歧化酶(SOD)活性随遮荫程度的增大而降低。因此,秋枫幼苗主要通过提高Pn、抗氧化酶活性(SOD和CAT)、叶绿素含量,降低LSP、LCP和Rd,增大AQY来提高弱光利用能力;适度遮荫(41.3%NS)更有利于1年生秋枫幼苗在夏季的生长。     

遮荫条件下黄檗生长和生理响应的性别差异研究

分析遮荫条件下黄檗幼苗形态指标、生理指标和代谢物质性别间差异，探讨其对遮荫的响应策略，为黄檗野生资源保护及造林抚育提供理论依据。以2年生黄檗雌雄株幼苗为试验材料，采用控制实验，设置3个遮荫梯度，自然光为对照，对比研究遮荫条件下黄檗幼苗雌雄植株形态特征、生物量分配、抗氧化防御酶活性、代谢物质的差异，以揭示其遮荫条件下的生存策略。结果表明：遮荫处理更有利于黄檗的生长，轻度遮荫雌株生物量积累大于雄株，重度遮荫后雄株大于雌株；遮荫处理对叶绿素a、总叶绿素含量均有显著影响（P<0.01），性别间差异不显著，遮荫条件有利于促进黄檗幼苗叶绿素积累；遮荫处理对酶活性和MDA含量均有显著影响，性别间差异不显著，SOD酶活性均随遮荫强度的增强而增大，POD和CAT酶活性随遮荫强度的增强而减小，MDA含量在对照处理时最高；遮荫条件下可溶性糖和可溶性淀粉含量下降，性别间差异不显著。黄檗幼苗通过改变构件性状、生物量、抗氧化酶活性及代谢物质含量，适应遮荫环境。研究遮荫对黄檗生长和生理响应的性别差异，以期为遮荫环境下黄檗个体发育、种群形成、适应机制及种群繁衍等研究奠定基础，为雌雄异株植物资源的保护利用提供科学借鉴。     

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。     

遮阴对石笔木苗木生长和保护酶活性的影响

为探讨石笔木Tutcheria championi苗木对遮阴环境的适应性,以全光照(无遮阴覆盖)为对照,研究遮阴30%、50%和70%对2年生石笔木苗生长和生理特性的影响。结果表明,全光照下石笔木苗木生长较为健壮,其苗高、地径生长优于遮阴处理;全光照下石笔木总生物量、根生物量比以及根冠比显著大于遮阴处理(P<0.05);50%遮阴处理苗木叶片叶绿素含量显著高于全光照和70%遮阴处理(P<0.05),叶绿素a/b值在各处理间无显著差异。丙二醛(MDA)含量、超氧化物歧化酶(SOD)活性在各处理间无显著差异(P>0.05);70%遮阴处理的苗木叶片过氧化氢酶(CAT)活性最高,显著高于全光照和50%遮阴。由此表明,充足的光照环境有利于石笔木苗木生长。     

Drought and shade interact to cause fine-root mortality in Douglas-fir seedlings

Summary Both desiccation and depleted carbohydrate reserves have been suggested as causes of fine-root (2 mm in diameter) mortality in trees. In this study, Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] seedlings were subjected to four combinations of shading and watering to determine whether shading increases drough-induced root mortality and, if so, whether this effect is due to reduced levels of carbohydrate reserves or increased susceptibility to desiccation. Two correlated measures of root mortality (counting root tips and weighing roots) showed that significantly more fine roots died only when seedlings were both shaded and unwatered. Concentrations of suberin, a compound synthesized by plant roots to control desiccation, were unaffected by any combination of shading and watering; however, carbohydrate reserves were nearly exhausted in the shaded and unwatered treatment — the treatment with highest root mortality. Water stress may have increased root mortality indirectly by increasing root temperature and maintenance respiration and by inhibiting photosynthate transport to the root system, but massive die-off in response to drought was apparent only when starch and sugar reserves were nearly depleted. Drought cannot be considered directly responsible for death of fine roots. Instead, a root's ability to continue to respire, which in turn depends on the status of its starch and sugar reserves, seems to be the primary physiological control of fine-root mortality.     

Root production is determined by radiation flux in a temperate grassland community

Accurate knowledge of the response of root turnover to a changing climate is needed to predict growth and produce carbon cycle models. A soil warming system and shading were used to vary soil temperature and received radiation independently in a temperate grassland dominated by Holcus lanatus L. Minirhizotrons allowed root growth and turnover to be examined non‐destructively. In two short‐term (8 week) experiments, root responses to temperature were seasonally distinct. Root number increased when heating was applied during spring, but root death increased during autumnal heating. An experiment lasting 12 months demonstrated that any positive response to temperature was short‐lived and that over a full growing season, soil warming led to a reduction in root number and mass due to increased root death during autumn and winter. Root respiration was also insensitive to soil temperature over much of the year. In contrast, root growth was strongly affected by incident radiation. Root biomass, length, birth rate, number and turnover were all reduced by shading. Photosynthesis in H. lanatus exhibited some acclimation to shading, but assimilation rates at growth irradiance were still lower in shaded plants. The negative effects of shading and soil warming on roots were additive. Comparison of root data with environmental measurements demonstrated a number of positive relationships with photosynthetically active radiation, but not with soil temperature. This was true both across the entire data set and within a shade treatment. These results demonstrate that root growth is unlikely to be directly affected by increased soil temperatures as a result of global warming, at least in temperate areas, and that predictions of net primary productivity should not be based on a positive root growth response to temperature.     

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。     

遮荫对峦大杉1年生苗木生长的影响及动态优化

以当年播种的峦大杉(Cunninghamia konishii)幼苗为材料,采用单因素试验设计3个遮荫处理(50%、75%、100%光照),每隔7 d监测地径、苗高等生长进程;应用Logistic方程拟合苗高、地径生长过程并分析其生长节律。结果表明,遮荫显著促进峦大杉幼苗全生长季的苗高、地径生长,以50%光照表现最好;不同生长阶段遮荫对峦大杉苗高、地径生长量的影响有所不同,进行动态优化十分必要。Logistic方程能较好地拟合峦大杉苗木生长动态。50%光照处理显著提高峦大杉苗高、地径的线性生长速率、最大线性生长速率和线性生长量,显著提前苗高线性生长终期、缩短线性生长持续时间,显著推迟地径线性生长始期。峦大杉苗期光照强度动态优化方案：在t≤133 d前阶段宜采用50%光照,在t＞133 d期间宜采用100%光照。     

Suppression of growth and death of meristematic tissues in <Emphasis Type="Italic">Abies sachalinensis</Emphasis> under strong shading: comparisons between the terminal bud,the terminally lateral bud and the stem cambium

The suppression of apical growth and radial trunk growth in trees under shade is a key factor in the competition mechanism among individuals in natural and artificial forests. However, the timing of apical and radial growth suppression after shading and the physiological processes involved have not been evaluated precisely. Twenty-one Abies sachalinensis seedlings of 5-years-old were shaded artificially under a relative light intensity of 5% for 70 days from August 1, and the histological changes of the terminal bud and terminally lateral bud of terminal leader and the cambial zone of the trunk base were analyzed periodically. In shade-grown trees, cell death of the leaf primordia in a terminal bud of terminal leader was observed in one of the three samples after 56 and 70 days of shading, whereas the leaf primordia in a terminal bud of terminal leader in all open-grown trees survived until the end of the experiment. In addition, the leaf primordia of the terminally lateral buds of terminal leader retained their cell nuclei until the end of the experiment. No histological changes were observed in the cambial cells after shading, but the shade-grown trees had less cambial activity than the open-grown trees through the experiment. Strong shading appeared to inhibit the formation and survival of cells in the terminal bud of terminal leader rather than the terminally lateral buds of terminal leader and the cambium. The suppression of the terminal bud growth and elongation of the surviving lateral buds would result in an umbrella-shaped crown under shade.