强光胁迫下银杏叶片的光抑制及其防御机制

为探讨强光对银杏叶片光合特性的影响 ,对银杏叶片进行强光 (12 0 0 μmolphotons·m- 2 s- 1 )胁迫 5h ,通过分析叶绿素a荧光参数和叶黄素循环组分研究了强光胁迫下银杏叶片的光抑制以及相关的光破坏防御机制。强光胁迫过程中 ,银杏叶片的PSⅡ最大光化学效率 (Fv Fm)明显下降 ,胁迫结束时 ,Fv Fm 接近 0 3。而初始荧光(Fo)则在整个胁迫过程中呈上升趋势。PSⅡ实际光化学效率 (ФPSⅡ)和表观光合电子传递速率 (ETR)均大幅度下降 ,而非光化学猝灭 (NPQ)和天线热耗散 (HDR)明显上升 ,叶黄素循环关键组分玉米黄质 (Z)的相对含量则随着强光处理时间的延长而增加 ,由处理前的 3%上升到胁迫结束时的 6 6 %。结果表明 ,强光胁迫过程中 ,银杏叶片发生了严重的光抑制 ,依赖于叶黄素循环的非光化学猝灭和天线热耗散起到了有效耗散过剩光能的作用 ,但是PSⅡ反应中心可逆失活是银杏叶片Fv Fm 下降的主要原因。     

西藏3种沙棘属植物光合生理特性的比较

为给西藏地区困难地造林提供参考,以云南沙棘、江孜沙棘和肋果沙棘1年生苗木为材料,采用LI-6400便携式光合仪红蓝光源和荧光叶室测定叶片光响应曲线和叶绿素荧光日变化参数,并进行比较分析。结果表明:云南沙棘最大净光合速率(P_(nmax))和表观量子效率(α)均最大,光饱和点(I_(sat))最高,光补偿点(I_c)最低。3种沙棘属植物叶绿素荧光参数变化趋势一致。电子传递速率先上升,到达最高值后迅速下降;最小初始荧光(F_0)日变化趋势为单峰曲线,整体呈"N"形变化;潜在光化学活性(F_v/F_0)、最大光化学效率(F_v/F_m)、有效光化学效率(F_v′/F_m′)、实际光化学效率(Y_(PSⅡ))先下降后上升;光化学猝灭系数(q_p)呈先降低后升高的趋势;非光化学猝灭系数呈抛物线形先上升后下降趋势。光合有效辐射和温度(T_a)与电子传递速率、非光化学猝灭系数极显著正相关,与F_v′/F_m′、Y_(PSⅡ)、q_p极显著负相关;湿度(H_r)与F_v′/F_m′、Y_(PSⅡ)、q_p显著正相关,与非光化学猝灭系数显著负相关。云南沙棘光适应能力最强,在西藏高原困难地造林时,云南沙棘可作为沙棘属植物的优选树种,江孜沙棘次之。     

模拟酸雨对假俭草叶绿素荧光特性的影响

研究模拟酸雨(pH 2.5、pH 3.0)对假俭草叶绿素荧光特性的影响.结果表明:酸雨6 h胁迫引起假俭草PSⅡ最大光化学效率(Fv/Fm)、PSⅡ潜在活性(Fv/F0)、光化学猝灭系数(qP)、PSⅡ电子传递量子产率(ФPSⅡ)、光合电子传递速率(ETR)和非光化学猝灭系数(NPQ)下降,pH 2.5处理比pH 3.0处理的下降幅度大;酸雨处理停止24 h后, Fv/Fm、Fv/F0、qP、ФPSⅡ、ETR、NPQ回升;酸雨处理停止48 h后,回升至接近对照.研究还表明,利用非损伤的叶绿素荧光技术可快速检测草对环境因子变化的响应.     

河北杨与沙棘的光合生理特性及叶绿素荧光参数比较

河北杨Populus hopeiensis和沙棘Hippophae rhamnoides为黄土丘陵区主要的造林树种,其对生态恢复和保护具有重要作用。为比较两种树种的光合生理生态适应性,分别以吴起县人工栽培林内的河北杨和沙棘为研究对象,测定了两树种的叶片光响应曲线、蒸腾速率Tr、水分利用效率RWUE和叶绿素荧光参数等光合生理指标季节动态变化。结果表明:除5月下旬外,沙棘的最大光化学效率Fv/Fm在不同生育期均显著高于河北杨(P0.05);沙棘在5月下旬、8月上旬和9月中旬的光合电子传递量子效率ΦPSII均显著高于河北杨(P0.05);且不同生育期下沙棘的光化学猝灭qP和非光化学猝灭qNPQ均显著高于河北杨(P0.05),表明沙棘具有相对较高的PSII光化学效率和较强的光保护能力。河北杨和沙棘在整个生育期均具有较高的LSP,且不同生育期下河北杨的RAQE,Pmax,Tr和Rd均显著高于沙棘,但LCP与之相反(P0.05),表明两者均属典型阳性植物且能较适应当地的强光环境,而河北杨相对于沙棘具有较高的叶片光合能力。     

重金属铅对榉树幼树叶绿素荧光参数的影响

以阔叶树种榉树1年生幼树为对象,采用室内盆栽,通过4次连续掺入PbCl_2溶液于土壤中,研究连续Pb处理榉树叶片的光合和光系统Ⅱ(PSⅡ)叶绿素荧光特性,以揭示铅胁迫下榉树抗逆性的机制。结果表明,4次Pb处理下榉树的最大净光合速率(P_n)、蒸腾速率(T_r)、气孔导度(G_s)和气孔阀值(Ls)均表现为P_b处理对照,且差异性显著(P0.05),胞间CO_2(Ci)则表现为Pb处理对照,出现了由非气孔限制引起的P_n下降。4次Pb处理下PSⅡ最大光化学效率(F_v/F_m)、PS_Ⅱ实际光化学效率(Y_Ⅱ)均低于对照,其中YⅡ差异显著(P0.05);光化学猝灭(qP)显著降低,非光化学猝灭(NPQ)显著升高,说明榉树在铅胁迫下发生了明显光抑制现象,但有效地将PSⅡ的过剩光能以热的形式耗散掉。铅对榉树PSⅡ量子产量的转化和分配有影响,Y_Ⅱ(PSⅡ非环式电子传递效率)显著低于对照,Y_(NPQ)(可调节性能量耗散)和Y_(NO)(非调节性能量耗散)高于对照,说明榉树能有效地通过自身调节,将过剩光能以热的形式耗散,使PSII反应中心受伤害的程度降至最低,这进一步说明了榉树幼树对Pb具有较强的抗逆性。     

3种引种杨树和3种乡土杨树苗叶的光合特性比较

在自然条件下,测定了3种引种杨树和3种乡土杨树苗木叶片的光合气体交换参数和叶绿素荧光参数。3种引种杨树为芬兰山杨A21、芬兰山杨16、加杨,3种乡土杨树为小青杨、小叶杨、兴安杨。其测定结果表明,3种引种杨树苗叶的净光合速率(Pn)显著高于3种乡土杨树,同时蒸腾速率(E)、瞬时水分利用效率(WUE)的平均值也高于3种乡土杨树的苗叶。从而说明3种引种杨树的光合能力较强,对吸收的光能和水分的利用效率较高。3种引种杨树苗叶的初始荧光(Fo)、最大荧光(Fm)、PSⅡ光能捕获效率(F′v/F′m)、稳定荧光(Fs)、光适应下最小荧光产量(F′o)、最大荧光产量(F′m)的平均值均高于3种乡土杨树,3种引种杨树的可变荧光(Fv)、PSⅡ最大光能转换效率(Fv/Fm)、可变荧光与初始荧光之比(Fv/Fo)、PSⅡ电子传递量子效率(ΦPSⅡ)、非光化学猝灭系数(NPQ)、光化学猝灭系数(qP)的平均值均低于3种乡土杨树。相关分析表明,Pn与Tr、Tr与Ci、Fm与Fo、Fv/Fo与Fv/Fm、ΦPSⅡ与Fo均呈极显著正相关(P0.01);ΦPSⅡ与Fm、F′v/F′m与Fv/Fo呈显著正相关(P0.05);Fv/Fo与Fo、Fv/Fm与Fo、NPQ与Fv/Fm、NPQ与Fv/Fo均呈极显著负相关(P0.01);qP与F′v/F′m呈显著负相关(P0.05)。     

冷驯化期间4种楸树叶片叶绿素荧光参数变化研究

以南北不同纬度的4种1 a生楸树嫁接苗(滇楸、灰楸、梓楸、金丝楸)为研究对象,研究自然条件下冷驯化期间4种楸树叶片叶绿素荧光参数变化规律。结果表明,冷驯化期间随着自然温度的降低,4种楸树叶片光系统Ⅱ电子传递量子效率(ΦPSⅡ)下降,光系统Ⅱ最大光化学效率(Fv/Fm)、非光化学猝灭(NPQ)和电子传递速率(ETR)先下降、后上升,最终值偏低,其中Fv/Fm与抗寒性存在较高的一致性,可作为楸树叶片抗寒性强弱的鉴定指标。     

不同温度下喷施油菜素内酯对香椿幼苗的影响

为了探究外源油菜素内酯(BR)对不同温度(8、28、38℃)下香椿幼苗生长的调节作用,以盆栽5月龄香椿幼苗为试材,以喷施清水为对照,研究外源油菜素内酯对不同温度下香椿幼苗生物量、叶绿素含量、光合特性、叶绿素荧光特性的影响。结果表明;外源BR处理可提高不同温度下香椿幼苗叶绿素的含量,显著提高香椿幼苗生物量和干物质积累量,使香椿幼苗叶片组织加厚,叶片相对含水率(RWC)提升,并且提高了香椿幼苗的净光合速率(P_n)、气孔导度(Gs)、最大光化学效率(F_v/F_m)、实际光化学效率(ΦPSⅡ)和光化学猝灭系数(qP),降低了胞间CO_2浓度(C_i)、蒸腾速率(T_r)、初始荧光(F_o)、非光化学猝灭系数(qN)。综上所述:喷施油菜素内酯可以促进适温下(28℃)香椿幼苗植株的生长,提高香椿幼苗在温度胁迫下的缓解作用和适应能力。     

紫色土上大叶女贞苗接种丛枝菌根真菌后对干旱胁迫的响应

为探讨紫色土上大叶女贞苗接种不同丛枝菌根真菌(AMF)后对干旱环境的响应,采集紫色土区的大叶女贞种子,以紫色土为基质,先采用盆栽方式育苗,再对幼苗分别接种摩西斗管囊霉(FM)和幼套近明球囊霉(CE)两种AMF,进行干旱胁迫试验,研究两种AMF对紫色土上大叶女贞叶片生长与生理特性的影响。结果表明：干旱胁迫使紫色土上大叶女贞的叶片数显著减少,使叶面积、叶长、平均叶宽等均显著减小,使叶片相对含水量显著降低,但叶干物质含量受干旱胁迫后反而提高了。干旱胁迫使大叶女贞叶片的净光合速率受到抑制,接种AMF后抑制程度减轻;干旱胁迫还显著降低了大叶女贞叶片的气孔导度、胞间CO₂浓度、蒸腾速率、光化学猝灭系数(qP),但提高了大叶女贞叶片的非光化学猝灭系数(NPQ)和SPAD值。接种AMF使大叶女贞叶片数增多、叶面积增大,使叶片相对含水量、水分利用效率、PSⅡ最大光化学效率(Fv/Fm)和SPAD值提高,特别是在干旱胁迫的环境下,促进作用更明显。接种FM对紫色土上大叶女贞的叶片数增多和叶面积、叶长、叶宽增大以及水分利用效率提高等的促进效果都优于接种CE的。     

热胁迫对连翘离体叶圆片光系统Ⅱ活性的影响

【目的】探讨高温对连翘离体叶圆片光系统Ⅱ活性和叶黄素循环脱环化程度的影响,揭示热胁迫下连翘叶片光合机构的行为特征,充实植物光能高效利用研究领域。【方法】以连翘为供试材料,在功能叶片主叶脉两侧打取直径为1 cm的叶圆片,采用热胁迫温度(26,31,34,37,40,43,46,49和52℃)和时间(5,25和45 min)组合处理,之后于26℃室内环境中暗适应30 min,利用叶绿素成像荧光仪( MINI-IMAGING-PAM)和 QE65光谱仪分别进行叶绿素荧光参数和漫反射率的测定。【结果】在5,25,45 min热胁迫下,连翘叶片 PSⅡ光化学活性 Fv/Fm 和实际光化学量子产量 Y(Ⅱ)开始显著降低的温度分别为43,37,37℃和43,31,31℃。随着热胁迫温度和时间的增加,呈现出暗适应下最小荧光 Fo 和光化学荧光猝灭系数 qP 先减后增的变化、暗适应下最大荧光 Fm 大幅度降低、开放的 PSⅡ反应中心的激发能捕获效率 F'v/F'm和 PSII 电子传输活性 Fm/Fo 迅速降低、调节性能量耗散量子产量 Y ( NPQ)与非调节性能量耗散的量子产量 Y( NO)和值的趋饱和增加、PSⅡ与 PSⅠ间的激发能分配不平衡偏离系数β/α－1先增后降的变化趋势。另外,叶黄素循环脱环化程度负相关的 PRI与 Y( NO)呈现相反变化趋势。【结论】在长时间较高的热胁迫温度下,连翘叶片的热胁迫伤害不仅会发生在PSⅡ蛋白复合体的多个位点,也会发生在整个光合机构,还会从暗反应的酶活性衰减转向 PSⅡ活性衰减;同时,对热胁迫伤害的协调保护机制,一方面表现在过剩的激发能量会从以调节性能量耗散 Y( NPQ)为主转向非调节性能量耗散 Y( NO)为主,另一方面也可能会表现在通过调节 PSⅡ与 PSⅠ之间激发能分配平衡性的天线系统的状态转换上。     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week⁻¹ for leaves and from 0.0225 to 0.0633 week⁻¹ for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient enrichment capacity and slower decomposition rates which would minimize leaching losses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Growth of Phlebiopsis gigantea in wood of seven conifer species

Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered.     

Effects of Seed Weight and Seed Type on Early Seedling Growth of Pinus sylvestris under Harsh and Optimal Conditions

The effects of seed weight and seed type on seedling growth of Pinus sylvestris (L.) were studied by seeding individually weighed orchard and stand seed in different mixtures under harsh (direct seeding in field) and optimal (seeding in nursery) conditions. In the nursery experiment an increase in the seed weight from 3 to 7 mg increased the seedling height by 10-27% and total weight by 27-113%, and decreased the height/diameter ratio by 5-6% after 2 yrs. With elimination of seed weight effects, orchard seedlings were 2% taller than stand seedlings in year 2. Without elimination of seed weight effects, orchard seedlings were 7-13% taller. In the field experiment an increase in the seed weight from 3 to 7 mg increased seedling height by 18-65%, stem volume by 81-274% and the number of top-buds by 23-34% in year 5. After elimination of seed weight effects, orchard seedlings were 7-13% taller than stand seedlings and without elimination of seed weight effects 20-21% taller after 5 yrs. Even after elimination of both seed weight and genetic effects orchard seedlings were 3-9% larger than stand seedlings in the field experiment. In conclusion, the influence of seed weight and seed type on growth traits and slenderness is highly significant and the influence seems to be greater in harsh conditions.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral contents and B₁ and B₂ vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B₁ 88 mg 100 g⁻¹, B₂ 187 mg 100 g⁻¹, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations.     

Modelling of adequate pretwist for obtaining straight timber

Abstract

Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic–ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists.