南亚热带森林几种乔木种子萌发和幼苗生长观察

本文对香椿（Ｔｏｏｎａｓｉｎｅｎｓｉｓ（Ａ．Ｊｕｓｓ．）Ｒｏｅｍ．）、木蝴蝶（Ｏｒｏｘｙｌｕｍｉｎｄｉｃｕｍ（Ｌ．）Ｖｅｎｔ．）、扁斗青冈（ＱｕｅｒｃｕｓｈｕｉＣｈｕｎ）、泡桐（Ｐａｕｌｏｗｎｉａｆｏｒｔｕｎｅｉ（Ｓｅｅｍ．）Ｈｅｍｓｌ）罗浮柿（ＤｉｏｓｐｙｒｏｓｍｏｒｒｉｓｉａｎａＨａｎｃｅ）、枳（ＢｅｒｃｈｅｍｉａｄｕｌｃｉｓＴｈｕｎｂ．）等南亚热带森林乔木种子萌发和幼苗生长进行观察．香椿、扁斗青冈、罗浮柿种子在轻阴（５５％光）条件下萌发率最高,分别为７０％、９０％、３０％,木蝴蝶种子在重阴（３８％光）条件下萌发率最高,为８０％,枳种子在光照条件下萌发率最高,为１５％．阳性树种香椿、木蝴蝶、泡桐、枳幼苗生长速度较快,属速生型树种,其幼苗在光照条件下生长速度最快,森林中树种扁斗青冈、罗浮柿幼苗生长速度较慢,属慢生型树种,其幼苗在轻阴条件下生长较好．随着施肥量的增加,幼苗生长速度明显提高．     

缙云山大头茶幼苗种群构件结构及与环境因子的多元分析

基于构件理论,采用灰色关联度分析技术,对四川缙云山１９８９年风灾迹地林窗内大头茶（Ｇｏｒｄｏｎｉａａｃｕｍｅｎａｔａ）幼苗种群构件结构及其与环境因子的关系进行了研究。结果表明,四川缙云山大头茶幼苗种群构件结构主要分为一级枝、二级枝、当年生枝、空间结构、叶片等几大部分,分别可以以一级枝数或茎粗或长度、二级枝数或基粗或长度、当年生枝数、３年生一级枝数、总叶数等的变化特征来表达其动态特点。前四者间的相关性亦很高,后者（包括主茎上叶面积）和主茎上第一一级枝离地面高、主茎上第一叶距地高为比较稳定的特征,受其它生态因子作用影响不十分显著。相对而言,土壤全Ｎ、全Ｐ、全Ｋ、有机质含量及其ｐＨ值是比较关键的环境因子;而海拔高度和林自大小及地形坡度却比较次要。灰色关联度分析不失为一种比较简捷而有效的分析植物种群构件结构特征间及与环境因子间关系的方法。关键词     

不同光环境下胡桃楸幼苗的形态可塑性及其响应研究

为了探求不同光环境对胡桃楸幼苗生长的影响,对全光照（100%光照）、中光照（60%光照）、低光照（30%光照）3种光环境下胡桃楸幼苗的生长、形态特征、生物量分配和水分特征开展研究。结果表明：胡桃楸幼苗的形态在不同光环境下存在明显的可塑性变化,生物量分配和水分特征均表现出不同程度的差异。低光照条件下,胡桃楸幼苗生长快,株高、地径分别为全光照的1.14、1.18倍;冠幅大,是全光照的1.40倍;叶片宽大,叶长和叶宽分别是全光照的1.25和1.36倍;分枝数明显少于全光照。3种光环境下胡桃楸幼苗地上部分生物量存在显著差异,地下部分差异不显著。叶片相对含水量随着光照的降低呈现逐渐增加的趋势;全光照条件下叶片饱和持水量与叶片干鲜比明显大于遮阴条件;3种光照条件下叶绿素含量差异显著。胡桃楸幼苗为适应不同光环境,在形态和生理方面都做出适应性调整,适当的遮阴处理有利于胡桃楸幼苗生长。     

缙云山四川大头茶种群繁殖适应性的数量特征研究

在对缙云山３种含有四川大头茶种群的不同群落调查测定,研究四川大头茶种群年龄结构,繁殖分配,编制静态生命表的基础上,研编了四川大头茶种群的生殖力表,生殖表。对诸生殖参数进行了综合分析,剖析了构成四川大头茶繁殖对策的几个重要组成部分。结果表明：四川大头茶种群在常绿阔叶林中的繁殖寿命最长,适合度最大;四川大头茶种群的生殖值（Ｖｘ）,现时生殖值（ｂｘ）,剩余生殖值（ＲＲＶ）,累积剩余生殖值（ＳＲＲＶ）以及整个生活史的总生殖值（ＴＲＶ）是时间的函数,并受环境制约,诸指标综合反映了遗传特性与环境因素相互作用对四川大头茶特定年龄个体繁殖能力影响的方式和强度,反映了四川大头茶种群繁殖动态规律;存活率ｌｘ与ｂｘ的负相关关系,ＳＲＲＶ与ｂｘ的负相关关系以及生命期望与生殖投资策略的负相关关系进一步反映了较大的生殖投入与较大的死亡概率之间的定量关系。     

不同邻体大头茶幼苗的适应特征

 在亚热带常绿阔叶林自然林窗下,以大头茶幼苗为基株,分别以马尾松、川灰木和大头茶幼苗为邻体。研究不同邻体如何改变可利用资源,影响大头茶幼苗基株生长动态和形态、树冠结构和生物量效应,并探讨影响基株生长的邻体的主导因素。结果表明,不同邻体的生长和截光效应差异明显;基株生长特征与邻体的树高、叶生物量、总生物量和树冠距地表10cm处截光量相关极小,却与邻体树冠距地表30cm处截光量相关极大,故影响基株生长的邻体主导因素是遮挡基株树冠的邻体的可利用光资源;基株生长动态,如树高、叶数、叶面积和叶大小,树冠结构和生物量显著受到不同邻体的影响,并且基株树高及增长量、叶面积、冠幅和生物量均为大头茶单株(GNO)>大头茶+川灰木(GNS)>大头茶+马尾松(GNP)>大头茶+大头茶(GNG)。大头茶幼苗种内竞争明显强于种间竞争。     

光强因子对少花桂幼苗形态和生理指标及精油含量的影响

光是影响植物生长的重要因子之一。它不仅能够影响植物的光合作用,同时,光还以环境信号的形式作用于植物,通过光敏色素等作用途径调节植物生长、发育和形态建成,使植物更好地适应外界环境。除此之外,光还可以影响植物的初生代谢过程和次生代谢。因此提高植物体内重要次生代谢产物,光的因素不可忽视。少花桂(Cinnamomum pauciflorum)是樟科樟属多年生常绿小乔木,其体内含有精油,鲜叶含油量可达3．5％,比黄樟树根含油量高出1倍左右,精油中黄樟油素纯度高达95％以上。以少花桂为材料,采用人工模拟不同生境的光照条件,探讨光强因子对少花桂生长及精油含量的影响,以求对其生产提供理论指导。通过窗纱遮荫实现对其生境光的控制,研究了光强因子对少花桂幼苗形态结构、水分状况、光合指标、生物量、香桂油含量和纯度的影响。结果表明：随生境相对光照强度的减弱,叶片厚度、叶片上表皮厚度、下表皮厚度、栅栏组织、海绵组织厚度、根冠比等都呈现降低的趋势;而平均单叶面积却呈现出增加的趋势;株叶面积在61．5％的全光照下有所增加,而在33．8％和15．4％全光照条件下大幅度减小;遮荫条件下生长的少花桂幼苗根系相对不发达,根冠比小;生境的光照强度会影响植株的水分蒸腾,从而影响含水量。在同样光照下,全光照条件下生长的少花桂幼苗保水能力最强,其次是61．5％全光照,最差的是15．4％全光照。少花桂幼苗的光饱和点、光补偿点随生境中的光强减弱而降低。过度遮荫条件下生长的少花桂幼苗CO2补偿点明显高于自然条件下生长的少花桂幼苗;随生境中的光强度的减弱其光呼吸速率升高,单位叶面积的叶绿素含量增加．Chla／Chlb值减小。遮荫处理后,不同光照条件下生长的少花桂幼苗的质量增加存在显著差异。遮荫过程中61．5％、33．8％和15．4％全光照条件下生长的少花桂幼苗叶片鲜质量的增长速率分别为全光照的1．6倍、1．2倍和0．77倍。香桂油含量以61．5％和33．8％全光照为多,均比全光照高出5％左右,而15．4％全光照叶片含油量又较全光照少5％左右。香桂油中黄樟油素纯度,以33．8％、15．4％全光照生境下的少花桂幼苗叶片为高。少花桂幼苗轻微遮荫(61．5％全光照)栽培．能获得较高的枝叶产量和香桂油产率．重度遮荫(33．8％、15．4％全光照)能获得纯度较高的黄樟油素。     

四川大学气候生态类型的多元分析及SDA判别分析

应用数量分类（ＣＡ）和排序（ＰＣＡ,ＣＯＡ）方法分析了四川大头茶７个地理种群２３个性状特征,并用判别分析（ＳＤＡ）检验分类排序的正确性。结果表明,四川大头茶不同地理种群可划分为３个气候生态类型：云南文山型即Ｉ型,广西型邓Ⅱ型,四川型即Ⅲ型;同时据其判别分析之判别轴图可知,没有位点被错划。通过比较地理气候因子对各类型的贡献率,得知光照     

缙云山大头号茶幼苗种群构件结构及与环境因子的多元分析

 基于构件理论,采用灰色关联度分析技术,对四川缙云山1989年风灾迹地林窗内大头茶(Gordonia acumenata)幼苗种群构件结构及其与环境因子的关系进行了研究。结果表明,四川缙云山大头茶幼苗种群构件结构主要分为一级枝、二级枝、当年生枝、空间结构、叶片等几大部分。分别可以以一级枝数或茎粗或长度、二级枝数或茎粗或长度、当年生枝数、3年生一级枝数、总叶数等的变化特征来表达其动态特点。前四者间的相关性亦很高,后者(包括主茎上叶面积)和主茎上第一级枝离地面高、主茎上第一叶距地高为比较稳定的特征,受其它生态因子作用影响不十分显著。相对而言,土壤全N、全P、全K、有机质含量及其pH值是比较关键的环境因子;而海拔高度和林窗大小及地形坡度却比较次要。灰色关联度分析不失为一种比较简捷而有效的分析植物种群构件结构特征间及与环境因子间关系的方法。     

四川大头茶繁殖分配及其环境适应性的关联度研究

 本文研究了四川缙云山亚热带常绿阔叶林不同群落类型中四川大头茶的繁殖分配(RA),并将植物种群的繁殖提高到种群适应对策的高度来分析,探索了应用灰色关联度分析、灰色动态模型研究四川大头茶繁殖分配的环境适应性。结果表明四川大头茶的RA随群落类型、年龄而发生变化,其每年繁殖分配所占比例为13.6％～20.0％,不同群落类型中四川大头茶RA大小顺序为大头茶纯林>针阔叶混交林>常绿阔叶林。关联度分析指出,10个环境生态因子中对四川大头茶繁殖分配影响较大的环境因素是群落土壤pH值、群落内的热状况和肥、水条件。繁殖分配与环境因子间相互作用的灰色关联时间动态模型方程为dy/dt+0.42y＝0.07x1–4.26x2–6.38x3+15.54x4–7.46x5+4.72x6+1.97x7–0.66x8+0.57x9–0.20x10     

四川大头茶气候生态类型的多元分析及SDA判别分析

应用数量分类（ＣＡ） 和排序（ＰＣＡ、ＣＯＡ） 方法分析了四川大头茶７ 个地理种群２３ 个性状特征,并用判别分析（ＳＤＡ） 检验分类排序的正确性．结果表明,四川大头茶不同地理种群可划为３ 个气候生态类型：云南文山型即Ⅰ型、广西型即Ⅱ型、四川型即Ⅲ型;同时据其判别分析之判别轴图可知,没有位点被错划．通过比较地理气候因子对各类型的贡献率,得知光照对３ 类生态类型的形成分化起主导作用     

Why is it better to produce coffee seedlings in full sunlight than in the shade? A morphophysiological approach

The coffee plant is native to shaded environments and its seedlings are often produced in shaded nurseries. However, some nursery managers, in an effort to improve the acclimation of seedlings to field conditions after transplantation, produce seedlings in full sun exposure. In this study, the morphological and physiological parameters of arabica coffee (Coffea arabica) seedlings produced in full sun (T1) and in shade (T2) were examined. The biomass accumulation and relative growth rate of T1 and T2 seedlings were similar. The T1 seedlings had less biomass allocation to shoots, a lower leaf mass ratio and a lower leaf area ratio; however, they had a greater net assimilation rate (rate of increase in plant mass per unit leaf area), which was associated with a greater net photosynthetic rate. There were no alterations in the concentrations of total chlorophylls or in the chlorophyll a/b ratio when comparing T1 and T2 seedlings. No indications of photoinhibition or photooxidative damage were observed in the T1 plants, which were shown to have a more robust antioxidant system than the T2 plants. Seedlings transferred from shade to full sun (T3) were not capable of utilising the incident extra light to fix CO₂. These seedlings showed a remarkable nocturnal retention of zeaxanthin and a significantly increased deepoxidation state of the xanthophyll cycle, even at predawn, but the activity of antioxidant enzymes was lower than in the T1 and T2 plants. Despite the acclimation capacity of T3 seedlings to the new light environment, they exhibited chronic photoinhibition and considerable photooxidative damage throughout the seven days following the transfer to full sun exposure. We further discuss the practical implications of producing coffee seedlings in full sunlight and under shade.     

Biomass allocation, shade tolerance and seedling survival of the invasive species

Berberis darwinii (Berberidaceae) is a serious environmental weed in New Zealand, capable of invading a range of different light environments from grazed pasture to intact forest. According to optimal partitioning models, some plants optimise growth under different environmental conditions by shifting biomass allocation among tissue types (e.g. roots, shoots) to maximise the capture of limiting resources (e.g. water, light). We examined patterns of growth, biomass allocation, and seedling survival in Berberis darwinii to determine whether any of these factors might be contributing to invasion success. Growth and biomass allocation parameters were measured on seedlings grown for 7 months in five natural light environments in the field. Survival was high in the sunniest sites, and low in the shadiest sites. Seedlings grown in full sun were an order of magnitude taller and heavier, had five times as many leaves, and proportionally more biomass allocated to leaves than seedlings grown in other light environments. In the shade, leaves were bigger and thinner, and leaf area as a proportion of total plant biomass increased, but the proportion of above- to below-ground biomass was similar across all light and soil moisture environments. In summary, although leaf traits were plastic, patterns of biomass allocation did not vary according to optimal partitioning models, and were not correlated with patterns of seedling survival. Implications for the management of this invasive species are discussed.     

朱砂根幼苗在不同光照强度下的形态和生理响应

通过人工遮荫模拟不同生境光强(100%、52%、33%、15%和6%的相对光照)的方法,对朱砂根(Ardisia crenata Sims)幼苗形态、生物量和生理指标的变化特征进行了分析。研究结果显示,朱砂根单株生物量在52%相对光照处理下显著高于其他光照处理,在15%～52%相对光照处理下分配给叶片的生物量比例高于全光照(100%)和极弱(6%)光照处理,但根冠比不受光强影响,其结构可塑性相对较低。硝酸盐含量随遮荫强度的增加而增大,且在6%相对光照处理下显著增加,硝酸盐还原酶的活性同硝酸盐含量变化规律一致,表明朱砂根主要通过改变叶面积和比叶面积等形态指标,以及调整生物量的分配和光合色素含量来适应不同的光环境。叶绿体超微结构分析结果显示,在15%～52%相对光照处理下,叶绿体数量较多且细胞结构较完整,而100%和6%光照处理下的叶绿体数量明显减少,且细胞结构严重受损发生质壁分离现象。因此,朱砂根适宜生长的光照条件为15%～52%,尤其是33%～52%的相对光照条件更佳。     

Effects of light regime on the growth,leaf morphology,and water relations of seedlings of two species of tropical trees

An experiment was conducted with Heliocarpus appendiculatus, a pioneer or large gap species of tropical moist forest in Costa Rica, and Dipteryx panamensis, a small gap species. Seedlings were grown in full sun, partial (80%) shade, and full (98%) shade. After one month of growth they were switched between environments and grown for two more months. Growth in height of Heliocarpus was greatly affected by irradiance, being increased in response to full shade and decreased in full sun. Height of Dipteryx was unaffected by irradiance level. Survival of Heliocarpus seedlings was only 49% in full shade, whereas Dipteryx had 100% survival. Biomass of Heliocarpus was not significantly greater in full sun than in partial shade whereas it was for Dipteryx. The response of root: shoot ratio was similar for both species. They were lowest in full shade and highest in full sun. Heliocarpus exhibited greater changes in leaf thickness, specific leaf weight, and stomatal density than did Dipteryx. Stomatal conductance of both species was lower in full shade and full sun than in partial shade. The results of the experiment indicate that growth of Heliocarpus is more plastic than that of Dipteryx in response to changes in irradiance. Previous environment did not affect the response to the present environment in either species. Both species responded positively to increases in irradiance.     

Variations in leaf morpho‐anatomy and photosynthetic traits between sun and shade populations of Eurya japonica (Pentaphylacaceae) whose seeds are dispersed by birds across habitats

Eurya japonica occurs in diverse light environments through seed dispersal by birds. As the seed size is extremely small, we hypothesized that newly germinated seedlings with restricted depth of roots and length of the hypocotyl would suffer high mortality due to increased transpiration in sunny habitats and low light in shady habitats. We also expected that surviving seedlings would differ in leaf traits between habitats as a result of selection. We aimed to determine how photosynthetic traits differ between habitats and how leaf structure is related to this difference. We examined photosynthesis and leaf morpho‐anatomy for plants cloned from cuttings collected from the forest understory (shade population) and neighboring roadsides and cut‐over areas (sun population) and then grown under two irradiances (18.5% and 100% sunlight) in an experimental garden. Under growth in 100% sunlight, cloned plants from the sun population exhibited significantly greater area‐based photosynthetic capacity compared to cloned plants from the shade population at a comparable stomatal conductance, which was attributable to a higher area‐based leaf nitrogen concentration. On the other hand, mean values of photosynthetic capacity did not significantly differ between the two populations. Cloned plants from the sun population had significantly thicker leaf laminas and spongy tissue and lower stomatal density compared to cloned plants from the shade population. Thickened leaf lamina might have increased leaf tolerance to physical stresses in open habitats. The variation in leaf morpho‐anatomy between the two populations can be explained in terms of the economy of leaf photosynthetic tissue.     

光强对喜树幼苗叶片次生代谢产物喜树碱的影响

喜树碱是我国特有树种——喜树中所含的重要次生代谢产物 ,在人工控制条件下观察了光强对喜树幼苗叶片喜树碱含量的影响。喜树幼苗叶片的喜树碱含量随着遮荫程度的增加 (光照强度降低 )而增加 ,但严重遮荫的 (光强为全光照的 2 0 % )在处理后期 (75 d)喜树碱含量降低。叶片的喜树碱产量 (喜树碱含量与叶片生物量乘积 )在处理初期 (30 d)随光强减弱而缓慢地略有增加 ,处理后期 (45 d以后 )随光强的减弱而有明显增加 ,但光强低于全光照的 6 0 %以后喜树碱产量迅速下降。喜树碱的增加可能是喜树幼苗通过次生代谢过程对不良环境 (遮荫 )的一种适应性反应     

Acclimation responses to high light by Guazuma ulmifolia Lam. (Malvaceae) leaves at different stages of development

• The re‐composition of deforested environments requires the prior acclimation of seedlings to full sun in nurseries. Seedlings can overcome excess light either through the acclimation of pre‐existing fully expanded leaves or through the development of new leaves that are acclimated to the new light environment. Here, we compared the acclimation capacity of mature (MatL, fully expanded at the time of transfer) and newly expanded (NewL, expanded after the light shift) leaves of Guazuma ulmifolia Lam. (Malvaceae) seedlings to high light.
• The seedlings were initially grown under shade and then transferred to full sunlight. MatL and NewL were used for chlorophyll fluorescence and gas exchange analyses, pigment extraction and morpho‐anatomical measurements.
• After the transfer of seedlings to full sun, the MatL persisted and acclimated to some extent to the new light condition, since they underwent alterations in some morpho‐physiological traits and maintained a functional electron transport chain and positive net photosynthesis rate. However, long‐term exposure to high light led to chronic photoinhibition in MatL, which could be related to the limited plasticity of leaf morpho‐anatomical attributes. However, the NewL showed a high capacity to use the absorbed energy in photochemistry and dissipate excess energy harmlessly, attributes that were favoured by the high structural plasticity exhibited by these leaves.
• Both the maintenance of mature, photosynthetically active leaves and the production of new leaves with a high capacity to cope with excess energy were important for acclimation of G. ulmifolia seedlings.

     

Photosynthetic acclimation in eastern hemlock [Tsuga canadensis (L.) Carr.] seedlings following transfer of shade-grown seedlings to high light

 We studied photosynthetic acclimation of eastern hemlock [Tsuga canadensis (L.) Carr.] seedlings in the first month after sudden exposure of shade-grown seedlings to full sunlight. In a greenhouse experiment, seedlings were grown under full sun or 80% shade, and after 7 months, a sample of the shaded trees was transferred to full sun in the greenhouse. Photosynthetic responses of shaded, transferred, and sun trees were followed over the course of 26 days to track short to medium-term acclimation responses. A partial acclimation of photosynthesis at high light occurred in pre-existing (formed in the previous environment) and new foliage of transferred seedlings. This was associated with non-stomatal limitations to photosynthesis. Pre-existing foliage of transferred plants had a prolonged reduction in the ratio of variable to maximal fluorescence, and a limited capacity to adjust photochemical quenching or photosystem II quantum yield in the light to increasing light intensity compared to sun foliage, and apparently had some difficulty sustaining non-photochemical quenching. Seedling survival was only 58% among transferred seedlings, compared to 80% and 100% in the shade or sun groups, respectively. Photosystem II quantum yield in the light, and photochemical and non-photochemical quenching were similar between newly formed foliage of transferred and sun plants. These findings indicate that eastern hemlock depends strongly on the production of new foliage for photosynthetic adjustments to high light, and that development of photosynthetic competence may be a gradual process that occurs over successive foliar production cycles. Received: 12 May 1998 / Accepted: 27 July 1998     

Photosynthetic responses to light in seedlings of selected Amazonian and Australian rainforest tree species

Summary Seedlings of the Caesalpinoids Hymenaea courbaril, H. parvifolia and Copaifera venezuelana, emergent trees of Amazonian rainforest canopies, and of the Araucarian conifers Agathis microstachya and A. robusta, important elements in tropical Australian rainforests, were grown at 6% (shade) and 100% full sunlight (sun) in glasshouses. All species produced more leaves in full sunlight than in shade and leaves of sun plants contained more nitrogen and less chlorophyll per unit leaf area, and had a higher specific leaf weight than leaves of shade plants. The photosynthetic response curves as a function of photon flux density for leaves of shade-grown seedlings showed lower compensation points, higher quantum yields and lower respiration rates per unit leaf area than those of sun-grown seedlings. However, except for A. robusta, photosynthetic acclimation between sun and shade was not observed; the light saturated rates of assimilation were not significantly different. Intercellular CO₂ partial pressure was similar in leaves of sun and shade-grown plants, and assimilation was limited more by intrinsic mesophyll factors than by stomata. Comparison of assimilation as a function of intercellular CO₂ partial pressure in sun- and shade-grown Agathis spp. showed a higher initial slope in leaves of sun plants, which was correlated with higher leaf nitrogen content. Assimilation was reduced at high transpiration rates and substantial photoinhibition was observed when seedlings were transferred from shade to sun. However, after transfer, newly formed leaves in A. robusta showed the same light responses as leaves of sun-grown seedlings. These observations on the limited potential for acclimation to high light in leaves of seedlings of rainforest trees are discussed in relation to regeneration following formation of gaps in the canopy.