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1.
There are no previous records about planting bamboo in Changli, Hebei Province, north China. Since they were introduced in 2004, the propinquity bamboo (Phyllostachys propinqua McClure) has demonstrated good adaptability to the cold climate in Changli. The overwintering status of the bamboo and some of its physiological changes after the winter have been studied to ascertain the adaptability of the bamboo to the cold weather in Changli and to establish a firm basis for growing the plants in larger areas in northern China. The bamboo lived through the winter without any protection. The leaves of windward bamboos growing at various intervals have been studied for their viability and health after the winter. The changes in some physiological indices of the leaves were measured in the following spring. Results showed that the bamboo is partly green even at a temperature as low as -22.3℃in Changli. During the winter, some leaves died and some partly died. Leaves are light in color and turn gradually to a dark green when the temperature increases in the following spring. As new leaves develop, the contents of chlorophyll and water and the ratio of free and bound water in the old leaves increase as does transpiration. At the same time the contents of free amino acid, proline, soluble sugar, malondialdehede (MDA), permeability of the membrane, superoxide dismutase (SOD) and peroxidase (POD) activities decrease. The direction of these physiological indices changes when the new leaves begin to sprout. The old leaves reduce their rate of photosynthesis, their blade functions decline gradually and the leaves fall off towards the middle of June. The cold wind affects the survival of bamboo leaves in winter, but has little effect on new leaves growing at the start of the following year. The results indicate that the propinquity bamboo can survive the winter in Changli quite well.  相似文献   

2.
A study was conducted to determine the fitting soil moisture for the normal growth of two-year-old W. sinensis （Sims） Sweets by using gas exchange technique. Remarkable threshold values of net photosynthetic rate （Pn）, transpiration rate （Tr） and water use efficiency （WUE） were observed in the W. sinensis leaves treated by various soil moisture and photosynthetic available radiation （PAR）. The fitting soil moisture for maintaining a high level of Pn and WUE was in range of 15.3%-26.5% of volumetric water content （VWC）, of which the optimal VWC was 23.3%. Under the condition of fitting soil moisture, the light saturation point of leaves occurred at above 800μmol.m^2.s^-1, whereas under the condition of water deficiency （VWC, 11.9% and 8.2%） or oversaturation （VWC, 26.5%）, the light saturation point was below 400μmol.m^-1.s^-1. Moreover, the light response curves suggested that a special point of PAR occurred with the increase in PAR. This special point was considered as the turning point that indicated the functional transition from stomatal limitation to non-stomatal limitation. The turning point was about 600, 1000, 1000 and 400 μmol.m^-2.s^-1, respectively, at VWC of 28.4%, 15.3%, 11.9% and 8.2%. In conclusion, W. sinensis had higher adaptive ability to water stress by regulating itself physiological function.  相似文献   

3.
As one of the three major five-leaved pines in the northern hemisphere, Pinus koraiensis is the most important dominant tree species in the natural mixed-broadleaved Korean pine forests. However, the regeneration of P koraiensis under the canopy of secondary forest stands is poor because of the light limitation. This study was conducted to understand how P koraiensis seedlings adapt to different light intensities and what would be the optimum light level for their establishment and growth. Three repetition plots with four light intensities （15%, 30%, 60% and 100% of the natural incident irradiances, achieved by suspending layers of black nylon net above and surrounding the plots） were set up under natural climate conditions in a montane region in eastern Liaoning Province, Northeast China. A total of 80 P koraiensis seedlings with similar height and root collar diameter were transplanted into four plots. After one year of acclimation to the specific light conditions, the seasonal variations of the photosynthetic variables and needle traits of the current and one-year-old needles, and the growth parameters were observed under four light intensities. The results indicated that： （1） The seedling at 60% treatment exhibited the greatest growth, which agreed with the response of the light-saturated photosynthetic rates （Amax） and the dark respiration rate （Rd） in the current and one-year-old needles, i.e., Rd at 60% treatment was significantly lower than that at 100% treatment, but Amax did not differ between the seedlings at 100% and 60% treatments. （2） The P. koraiensis seedlings have a certain photosynthetic plasticity to adapt the light conditions by adjusting their needle traits and regulating the physiological processes, because Amax, Rd, light saturation point and compensation point, the needle mass area, needle nitrogen and chlorophyll contents were significantly （p〈0.05） correlated with the light intensities. Especially, Am,x at 100% and 60% treatments was significantly higher （p〈0.05） than that at 30% and 15% treatments for both current and one-year-old needles. （3） The needles of different ages played a commutative role during the growing season, i.e., the one-year-old needles played a major role for the photosynthesis in the early growing season; the current year needles did in the later growing season. This ensured the effective photosynthesis throughout the growing season. These findings suggest that P. koraiensis is the in-between heliophilous and shade-tolerant tree species at least for the seedlings up to 8 years.  相似文献   

4.
Available light under forest canopies includes two components, diffuse light and direct light (sunflecks), and is characterized as low and highly dynamic. Understory habitats under different forest types experience different light conditions.Sunflecks as a critical resource for understory plants have great importance on carbon gain of understory plants. Under the light-limiting habitat, understory plants exhibit a high light utilization efficiency attributed by a post-illumination CO2 uptake. Although different species have different photosynthetic responses, shade plants appear to be acclimated to respond more quickly and efficiently to sunflecks. This acclimation includes a faster induction, relatively lower rate of induction loss, lower photosynthetic compensation point, and higher water use efficiency. The process that shade plants harvest light energy is not .well known. Studies of photosynthetic responses to sunflecks in natural conditions are rare. Little is known about constraints on sunfleck utilization, which may change seasonally. Extensive field studies in conjunction with laboratory investigations will be needed to further understand potential and actual constraints on sunfleck utilization. Most studies on photosynthetic responses to fluctuating light condition were done in the level of leaves. Fluctuating light utilization on the basis of whole plants and populations presents future challenges to ecologists.  相似文献   

5.
This paper deals with the photosynthetic properties of Eucalyptue camphoia. E. camaldulenaia. E. gunni-i. E. viminalia. E. giandia. E. dunii and E. maidenii. including the daily bariations of photosynthetic and respiratory rates, the comparison of the photosynthetic rates of various Eucalyriua spp. measured,the relationship between photo-synthetic rate and chlorophyll content, as well as the light saturation point.  相似文献   

6.
Plants distributed in riparian regions experience frequent episodes of flooding and drought between years, and hence, riparian plants need to be floodand drought-tolerant. Riparian plants possess various traits to survive flooding, while their sensitivity to drought has received less attention. To investigate the growth and photosynthetic responses of a riparian species (Bolboschoenus planiculmis) to flooding and drought, plants of this species were subjected to 60-d flooding or drought stress under greenhouse conditions. Growth and photosynthetic traits were measured at the end of the treatments. As well, we determined the efficiency of photosynthetic apparatus in mature leaves. Plants of B. planiculmis adequately adjusted their growth and photosynthetic traits under both flooding and drought conditions. Flooding did not affect the above-ground growth of B. planiculmis. Increased growth of roots and rhizomes and the generation of new tubers suggested a high ability of below-ground lateral growth by capturing resources under flooding conditions. Enhanced photosynthetic capacity, retained leaf pigment concentrations and chlorophyll a fluorescence capacity indicated photosynthetic adaptation to flooding. In contrast, drought significantly decreased the above-ground growth of B. planiculmis, especially the leaves, thereby minimizing water loss due to transpiration. Its increased root to shoot ratio and "phalanx" asexual propagation pattern might enhance soil water uptake ability. Although the functional leaves of B. planiculmis could retain their leaf pigment concentrations, as well as photosynthesis and chlorophyll a fluorescence, the total biomass of plants decreased, which may be a consequence of the reduced leaf area, suggesting adverse effects by drought. Therefore, both growth and photosynthetic responses of B. planiculmis are likely to contribute to the ability of this species to thrive in riparian regions, but remain susceptive to drought.  相似文献   

7.
Soil moisture is a major limiting factor for plant growth on shell ridge islands in the Yellow River Delta.However, it is difficult to carry out situ experiment to study dominant plant photosynthesis physiological on the shell ridge islands under extreme soil water stress. To evaluate the adaptability of plants to light and moisture variations under extreme soil moisture conditions present on these islands, we measured photosynthetic gas exchange process,chlorophyll fluorescence, and stem sap flow variables for3-year-old trees of Tamarix chinensis Lour, a restoration species on these islands, subjected to three types of soilwater levels: waterlogging stress(WS), alternating dry–wet(WD), and severe drought stress(SS) to inform decisions on its planting and management on shell ridge islands. Gas exchange, chlorophyll fluorescence, and stem sap flow in T.chinensis were then measured. Net photosynthetic rate(PN), transpiration rate(E), and water use efficiency(WUE)were similar under WS and alternating dry–wet conditions,but their mean E and WUEdiffered significantly(P \ 0.05).Under SS, the PN, E and WUEof T. chinensis leaves varied slightly, and mean PN, E and WUEwere all low. Apparent quantum efficiency(AQY), light compensation point(LCP),light saturation point(LSP), and maximum net photosynthetic rate(PNmax) of leaves were not significantly different(P [ 0.05) under WS and dry–wet conditions; however,under extreme drought stress, compared with the dry–wet conditions, LCPwas higher, LSPwas lower, and AQYand PNmaxwere both at the lowest level. Therefore, drought stress weakened light adaptability of leaves, and the efficiency of light transformation was poorer.(3) Maximum photochemical efficiency(Fv/Fm) and the actual photochemical efficiency(UPSII) were similar under waterlogged stress and dry–wet conditions, indicating a similar healthy photosynthetic apparatus and photosynthetic reaction center activity, respectively. Under SS, Fv/Fmwas 0.631, and the coefficient of non-photochemical quenching(NPQ) was0.814, which indicated that while the photosynthetic mechanism was damaged, the absorbed light energy was mainly dissipated in the form of heat, and the potential photosynthetic productivity was significantly reduced. The daily cumulants of sap flow of T. chinensis under dry–wet alternation and severe drought stress were 22.25 and63.97% higher, respectively, than under waterlogging stress. Daily changes in sap flow velocity for T. chinensis differed under the three soil water levels. Stem sap flow was weak at night under severe drought stress. Under dry–wet alternation, daytime average stem sap flow velocity was the highest, and night stem flow accounted for 10.26%of the day cumulants, while under waterlogged stress, the average nightly stem flow velocity was the highest,accounting for 31.82% of the day cumulants. These results provide important information for regional vegetation restoration and ecological reconstruction.  相似文献   

8.
We investigated the combined effects of soil moisture and light intensity on the growth, development and ecophysiological characteristics of one-year old Amorpha fruticosa seedlings. Soil moisture and light intensity influenced the ecophysiological characteristics of Amorpha fruticosa seedlings. Soil moisture resulted in the decreases of growth rate, individual size, net photosynthetic rate, transpiration rate, leaf water loss rate (WLR), and biomass accumulation of plant parts, and led to increased leaf water saturation deficit (WSD). Under water stress, more photosynthetic products were allocated to root growth. With decreasing light intensity, net photosynthetic rate, transpiration rate, chla/b, water saturation deficit, water use efficiency, water loss rate and biomass accumulation declined, while Chla, Chlb, Chla+b and carotenoids (Car) increased and more photosynthetic products were allocated to stem and leaf growth. Maximum growth vigor, net photosynthetic rate and total biomass accumulation in Amorpha fruticosa seedlings was recorded at 75 80% soil water-holding capacity and 100% light density in greenhouse environments.  相似文献   

9.
光皮桦种子千粒重、寿命及生命力研究   总被引：13，自引：0，他引：13  
祝小科  朱守谦 《林业科学》2003,39(4):168-172
The thousand-seed weight, germination rate and vitality of seeds for Betula luminifera were studied. The results showed that the thousand-seed weight was different in various habitats, and varied with the age and the part of crown and fruit. The seed had a longevity of 32—37 days in general and with a characteristic of the rapid germination. The seed had a high germination rate during the early stage or perk stage of seed dispersal, and a lower germination rate during the end stage. The germination rate and vitality of mature seed reduced with the increase of the storing time, the change in seed ger-mination was significantly different at the various ages and habitats.  相似文献   

10.
Since the generation of full-sib artificial triploid families, rapid clone establishment and genetic improvements have been needed. Here, we report an in vitro method of direct shoot regeneration of a triploid hybrid poplar[(Populus simonii × P. nigra 'Italica')×(P. × 'popularis')]. Using different randomized block designs, we selected one triploid to evaluate the explant type, optimal concentrations of plant growth regulators and agar, and culture time under light or dark conditions over 60 days. The highest rate of shoot induction, 80.0%, was obtained using Murashige and Skoog(MS) medium supplemented with 0.2 mg/L benzyladenine, 0.04 mg/L naphthaleneacetic acid(NAA), and 5.5 g/L agar for the first 30 days in the dark,then 3 g/L agar for the next 30 days in light. This last medium yielded the best rate of shoot induction(6.32 shoots/explant). These three media were also used to evaluate the influence of the genotypes of the parents and hybrid triploids on regeneration. Two parents and three of the four full-sib triploids were regenerated successfully;different genotypes and explant types significantly affected the rate of shoot induction and average number of shoots.Leaves but not petioles were a suitable explant. One genotype produced the highest rate of shoot induction of 96.67%.Half-strength MS medium supplemented with 0.2 mg/L indole butyric acid and 0.04 mg/L NAA was the most effective for rooting; rooting rate was 96.67%, survival rate of transplants was 73.33%, and rooting frequency surpassed 85% for each genotype. Overall, this in vitro regeneration system will be useful for the propagation and genetic modification of triploid poplars.  相似文献   

11.
绿竹 (Dendrocalamopsisoldhamii)属禾本科竹亚科绿竹属 ,原产我国 ,集中分布浙江南部、台湾、福建及广西、广东等省 (区 )。在浙江、台湾、福建三省普遍栽培 ,是亚热带地区优良速生的笋材两用的丛生竹种之一。绿竹笋味鲜美 ,清凉解暑 ,同时具有降压、降脂、增强消化系统功能的作用 ,是夏秋两季深受群众喜爱的美味佳肴。绿竹竹材易降解 ,是应用前景广阔的造纸原料。近年来 ,以笋用林为主要经营目的的绿竹林发展很快 ,并取得不少的经验 (张文燕等 ,1 999;郑文汉等 ,1 997;董建文 ,2 0 0 0 )。叶片作为最主要的同化器官在竹林生长发育过程中起着重要作用 ,研究竹叶片生理生化特性 ,揭示叶片生长发育规律 ,对指导竹林栽培具有重要意义。当前对竹子叶片生理生化特性的研究已有过不少报道 ,如毛竹(Phyllostachysheterocyclacv .pubescens) (郑郁善等 ,1 998;黄启胜等 ,1 989)、麻竹 (Dendrocalamuslatiflorus)(邱尔发等 ,2 0 0 1 ;2 0 0 2 )、雷竹 (Phyllostachyspraecoxf.pre...  相似文献   

12.
在毛竹丰产林中 ,设置 4块标准地 ,1 996年 1 1月注射毛竹营养液 ,1 997年夏在各注射和未注射营养液的标准地中取 1 992～ 1 997年生毛竹枝叶测定光合速率、光呼吸、暗呼吸、CO2 补偿点、光补偿点等光合性状。结果表明 ,施用毛竹营养液后叶质重、叶绿素含量明显提高 ,净光合速率增大 ,暗呼吸有所提高 ,光呼吸速率减小 ,CO2 补偿点和光补偿点明显下降 ,这些指标的改变有利于提高光合作用、增加有机质积累 ,有利于培养高产稳产竹林。  相似文献   

13.
绿竹开花生理生化特性研究   总被引：9，自引：2，他引：9  
绿竹 (Ｄｅｎｄｒｏｃｌａｍｏｐｓｉｓｏｌｄｈａｍｉ)属禾本科竹亚科绿竹属 ,原产我国。集中分布浙江南部、台湾、福建及广西、广东等省。在浙江、台湾、福建 3省普遍栽培 ,是亚热带地区优良速生的笋材两用的丛生竹种之一。具有生长迅速、成林快、轮伐期短、笋体大、笋期长、产量高、营养丰富等优点。绿竹笋味鲜美 ,清凉解暑 ,同时具有降压、降脂、增强消化系统功能的作用 ,是夏秋两季深受群众喜爱的美味佳肴。绿竹竹材易降解 ,是应用前景广阔的造纸原料。近年来 ,以笋用林为主要经营目的的绿竹林发展很快 ,并取得丰富的经验 (郑郁善等 ,1…  相似文献   

14.
海南岛簕竹属5个竹种雨季光合特性与叶片形态结构性状   总被引：1，自引：0，他引：1  
【目的】通过对簕竹属5个竹种雨季光合生理特性的研究,探究热带地区不同竹种雨季光合能力差异性,掌握不同竹种栽培特性,为竹种高效培育及园林应用提供理论依据。【方法】以海南岛簕竹属5个竹种作为研究材料,利用Li-6400便携式光合仪测定日变化、光响应曲线、CO2响应曲线,分析不同因子的影响及叶片形态结构性状与光合作用的相关性。【结果】1)不同竹种之间净光合速率存在较大差异,5个竹种净光合速率日变化规律呈现“双峰”曲线;2)各竹种光响应曲线在5—6月净光合速率较高,8—10月净光合速率较低,最大净光合速率(Pmax)、光饱和点(LSP)、暗呼吸速率(Rd)之间存在差异;青秆竹、粉单竹Pmax、LSP值高、Rd值低,光合能力较强;3)5个竹种CO2响应曲线均在5—8月净光合速率较高,9—10月净光合速率较低;相较于潜在最大净光合速率(Amax)、CO2饱和点(CSP),CO2补偿点(CCP)、光呼吸速率(Rp)、羧化速率(CE)之间存在差异;4)雨季中5个竹种Pn主要受气孔导度(Gs)、蒸腾速率(Tr)、气温(Ta)、光合有效辐射(PAR)、胞间CO2浓度(Ci)、大气CO2浓度(Ca)等因子制约;5个竹种叶片形态结构性状研究表明:佛肚竹、黄金间碧竹叶面积(LA)显著高于青秆竹、崖州竹、粉单竹(P<0.05),佛肚竹、青秆竹、黄金间碧竹叶厚度(LT)显著高于崖州竹、粉单竹(P<0.05),比叶面积(SLA)则相反;而5个竹种叶干物质含量(LDMC)差异不显著(F=0.691,P=0.615),不同竹种Pmax、Amax与LA、LT、LDMC、SLA相关性有所差异,与LA相关性较大。【结论】簕竹属5个竹种光合特征参数与叶片形态结构性状不同,竹种生理特性与叶片形态结构性状存在一定相关性。在竹类植物保存与利用中,叶面积可作为竹类植物筛选的主要性状指标。在园林配置中,青秆竹栽培区域较广、佛肚竹栽培区域较窄、崖州竹可在阴生条件下栽培、粉单竹适宜光照充足地区生长、黄金间碧竹介于青秆竹与崖州竹之间。  相似文献   

15.
为了选筛选出不同光效水平的油茶种质,利用LI-6400便携式光合仪对6个进入盛果期的油茶品种的光合日变化、光响应曲线和CO2响应曲线进行了研究,同时检测了叶片中叶绿素含量和成熟后种籽与果实含油率等经济性状,分析了油茶果实生长期光合特性与经济性状的相关性。结果表明,不同油茶品种间各光合特性参数、叶绿素含量和经济性状指标等均存在差异,‘国油13’和‘湘林210’由于具有较好的光能和CO2利用率、较高的叶绿素含量和含油率等,以及较低的暗呼吸速率,表现出较高的光合效率。最大净光合速率、表观量子效率、羧化效率、光呼吸速率和CO2饱和点与含油率等经济性状呈显著正相关,暗呼吸速率、光补偿点和光饱和点与含油率等经济性状呈显著负相关。  相似文献   

16.
绿竹开花生理生化特性研究   总被引：10，自引：0，他引：10  
通过对开花与未开花一年生 (1a)、二年生 (2 a)绿竹叶质重、叶绿素含量、光合速率、呼吸速率及不同器官 N、P、K元素浓度等指标的测定 ,结果表明 :1a、2 a开花绿竹与未开花绿竹相比 ,就平均值而言 ,叶质重、叶绿素总量分别减少 12 .75 %和 2 1.79%,净光合速率、光合系数分别降低10 .36 %、2 7.5 2 %,光呼吸、暗呼吸速率分别提高 6 4 .5 2 %、17.90 %,说明开花绿竹较未开花绿竹同化能力降低 ,而异化能力增强 ;各器官 N、P、K元素浓度以地下部分差异比较明湿 ,与未开花绿竹相比 ,根部 N、P、K元素浓度分别减少 17.0 2 %、 33.76 %、 2 9.84 %;竹蔸分别减少 2 7.4 3%、6 6 .6 3%、5 1.17%;而地上部分秆、枝、叶 N、P、K元素浓度开花绿竹较未开花绿竹有升高趋势。这是由绿竹生殖生长的特殊生理特性决定的。  相似文献   

17.
We examined the effects of elevated CO2 concentration ([CO2]) on leaf demography, late-season photosynthesis and leaf N resorption of overstory sweetgum (Liquidambar styraciflua L.) trees in the Duke Forest Free Air CO2 Enrichment (FACE) experiment. Sun and shade leaves were subdivided into early leaves (formed in the overwintering bud) and late leaves (formed during the growing season). Overall, we found that leaf-level net photosynthetic rates were enhanced by atmospheric CO2 enrichment throughout the season until early November; however, sun leaves showed a greater response to atmospheric CO2 enrichment than shade leaves. Elevated [CO2] did not affect leaf longevity, emergence date or abscission date of sun leaves or shade leaves. Leaf number and leaf area per shoot were unaffected by CO2 treatment. A simple shoot photosynthesis model indicated that elevated [CO2] stimulated photosynthesis by 60% in sun shoots, but by only 3% in shade shoots. Whole-shoot photosynthetic rate was more than 12 times greater in sun shoots than in shade shoots. In senescent leaves, elevated [CO2] did not affect residual leaf nitrogen, and nitrogen resorption was largely unaffected by atmospheric CO2 enrichment, except for a small decrease in shade leaves. Overall, elevated [CO2] had little effect on the number of leaves per shoot at any time during the season and, therefore, did not change seasonal carbon gain by extending or shortening the growing season. Stimulation of carbon gain by atmospheric CO2 enrichment in sweetgum trees growing in the Duke Forest FACE experiment was the result of a strong stimulation of photosynthesis throughout the growing season.  相似文献   

18.
为给高州油茶种质资源创新及辐射诱变育种提供技术参考,研究了在不同剂量60Co-γ射线照射条件下高州油茶的光合特性及与其相关的细胞结构等指标的变化情况。结果表明:经10~70 Gy辐照处理后的高州油茶叶片各组织结构厚度都有增厚的趋势,而以80 Gy辐照处理的叶片各组织结构的厚度均未改变甚至有减小的趋势;不同剂量的辐照处理后高州油茶叶片的Pn值呈现出不同的变化规律,剂量在10~80 Gy内的辐照处理均能促进高州油茶的光合作用,其中以20 Gy辐照处理的高州油茶其利用弱光的能力最强,以60 Gy处理的油茶其利用强光的能力最强;不同剂量辐照处理下高州油茶的光响应曲线之间存在差异,辐照对其光补偿点、暗呼吸速率的影响均显著;不同剂量的辐照处理对高州油茶净光合速率、水分利用效率、光合利用效率、胞间二氧化碳浓度等光合指标均有显著影响,且在不同的季节其影响的程度不同。  相似文献   

19.
【目的】为探究不同造林密度条件下西南桦Betula alnoides幼林冠层光合生理特征,进而为西南桦造林密度和修枝强度的合理配置提供理论依据。【方法】以6年生西南桦无性系密度试验林为对象,每个密度处理选取3株优势木,将每个单株6 m以下树冠按每段1 m划分为2~4个冠层(2~3m、3~4m、4~5m、5~6m),每个冠层选择一位于阳面中间位置的平均枝,测定位于枝近顶端的4片发育完满叶光响应曲线。【结果】1)西南桦幼林冠层间最大光合速率、光饱和点和光补偿点均差异显著(P<0.05),这些指标均随冠层的升高而显著增大,表明上部冠层光合能力较强,且对强光的利用能力高。2)西南桦幼林冠层暗呼吸速率随冠层上升虽有降低趋势,但不同冠层间未达显著差异水平(P≥0.05)。3)相同冠层条件下,造林密度显著影响西南桦幼林冠层的表观量子效率、最大光合速率及光饱和点,三者均随造林密度增加呈显著下降趋势,特别是冠层3~4 m和5~6 m规律更明显。但是造林密度对于西南桦幼光补偿点和树暗呼吸速率无显著的影响。【结论】总体而言,西南桦幼林上部树冠表现出更大的光合潜力,冠层对于西南桦幼林光合能力的影响要高于造林密度,且两者存在明显的交互作用。研究将为珍贵树种通过合理修枝调控林木生长提供理论支撑。  相似文献   

20.
Naturally regenerated 20-25-year-old Scots pine (Pinus sylvestris L.) trees were grown in open-top chambers in the presence of an elevated temperature or CO(2) concentration, or both. The elevated temperature treatment was administered year-round for 3 years. The CO(2) treatment was applied between April 15 and September 15 for 2 years. The photosynthetic responses of 1- and 2-year-old needles to varying photon flux densities (0-1500 micro mol m(-2) s(-1)) and CO(2) concentrations (350, 700 and 1400 micro mol mol(-1)) during measurement were determined. The CO(2) treatment alone increased maximum photosynthetic rate and light-use efficiency, but decreased dark respiration rate, light compensation and light saturation regardless of needle age. In contrast, the temperature treatment decreased maximum photosynthetic rate and photosynthetic efficiency, but increased dark respiration rate, light compensation and light saturation. The aging of needles affected the photosynthetic performance of the shoots; values of all parameters except photosynthetic efficiency were less in 2- than in 1-year-old needles. The CO(2) treatment decreased and the temperature treatment enhanced the reduction in maximum photosynthesis due to needle aging.  相似文献   

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