Camellia nitidissima is shadetolerant and has a limited photosynthetic potential of acclimating high light. The effects of different shading levels (8%, 25%, 50% and 100% of full sunlight) on the growth, biomass, chlorophyll fluorescence parameters of C.nitidissima seedlings were examined in order to know the growth and physiological responses of C.nitidissima to strong light. The growth of C.nitidissima seedlings were inhibited under different strong light stress. As the strong light stress was enhanced, the color of C.nitidissima seedlings leaves turned into light green and yellow green from dark green, leaf burning was getting worse, time of shooting was delayed and the shoots grew poor, the death rate increased. The biomass of root, stem, leaf and total plant significantly decreased with the strengthened stress. The strong light stress had the most influence on leaf biomass, followed by root biomass, and then the stem biomass. With the increasing strong light stress, the contents of total chlorophyll (Chl), chlorophyll a (Chla) and chlorophyll b (Chlb) in leaves of C.nitidissima seedlings significantly decreased, while Chla/Chlb and Car/Chl increased. The chlorophyll fluorescence parameters F o , F m , F v , F v / F o , F v / F m all decreased under strong light stress, which indicated that with the increasing of strong light stress, the reaction center of PSⅡ was destroyed, photosynthetic electron transform capability was weakened and photosynthesis was restrained.

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。

Net photosynthetic rate(Pn) and apparent quantum yield(AQY) were measured with Li-6200 portable photosynthesis system in parallel with superoxide dismutase(SOD) activity determined with UV-754 ultraviolet spectrophotometer in attached leaves of poplar clone seedlings. It was found that Pn decreased, and photosynthesis depression phenomenon occurred at noon. At this conditions Pn was limited by non-stomatal factors, and the decline of Pn had no relations with the closure of stomata. AQY in attached leaves of poplar clone seedlings decreased and photoinhibition of photosynthesis occurred evidently under stressful conditions. SOD could protect photosynthesis. The inhibitor of SOD could intensified, while antioxidant could alleviated, photoinhibition of photosynthesis. The conclusion was that photoinhibition of photosynthesis in attached leaves of poplar clone seedlings had intrinsic relations with the accumulation of reactive oxygen species.

为更多地了解自然条件下活体叶片的光抑制, 以LI-6200 便携式光合系统测定了杨树无性系幼苗叶片叶的净光合速率(Pn)、表观量子产量(AQY)等, 比色法测定了超氧化物歧化酶(SOD)活性。结果表明, 中午Pn 降低, 出现光合"午休"现象, 此时Pn 受非气孔因素限制, Pn 的降低与气孔关闭关系不大。低湿、高温、强光条件下杨树无性系幼苗叶片AQY 降低, 发生了明显的光抑制。SOD 对光合作用具有保护作用, SOD 抑制剂使光抑制加剧, 抗氧化剂使光抑制得到缓解, 表明光抑制的发生可能与活性氧的积累有关。

摘　要： 概述了植物光合作用光抑制的研究进展,包括造成光抑制和光氧化的活性氧的产生和作用机理,光抑制的作用部位,以及光保护机制等,着重从三个方面讨论了植物抗光抑制的保护机理:与光系统Ⅱ天线以及叶黄素循环相关的热耗散途径,包括光呼吸、H2O-H2O循环和环式电子传递在内的电子传递途径,以及活性氧清除机制等.

摘　要： 对光抑制的作用机制与光合器官中活性氧代谢的概况及相关的研究进展作了综述。

为了探明弱光条件下东方百合的生长发育及光合特性,为我国北方地区东方百合切花的耐弱光品种选育提供依据,以东方百合品种'Marcopolo'、'Tiber'、'Constanta'和'Acapulco'为试验材料,在整个生长季对其进行不同遮光处理(正常光照、50%遮光、75%遮光),测定不同光强下各品种光合参数及生长发育指标.结果表明:75%遮光条件下东方百合各品种的净光合速率(Pn)、光补偿点(LCP)、光饱和点(LSP)、暗呼吸速率(Rd)降低,表观量子效率(AQY)下降,叶绿素含量增高,叶绿素a与叶绿素b的比值降低,比叶质量减小,叶面积增大,切花观赏品质有所下降;不同百合品种的耐弱光性不同,弱光下'Marcopolo'的LCP、Rd较低,比叶质量较小,AQY变化幅度小,表现出较强的耐弱光性;相反地,'Acapulco'则对弱光较敏感.

在高温强光条件下,研究了外源水杨酸对黄瓜叶片叶绿素荧光参数和叶黄素循环的影响.结果表明,在高温强光胁迫前2 d用50~400μmol.L-1水杨酸处理叶片,抑制了高温强光下原初光能转换效率(Fv/Fm)、光合电子传递量子效率(ΦPSⅡ)、最大荧光(Fm)和光化学猝灭系数(qP)的下降,分别比对照提高了16.1%~30.2%、11.9%~33.0%、7.2%~41.0%和27.2%~160.8%,促进了非光化学猝灭系数(NPQ)的升高,比对照提高了13.1%~62.9%,而对初始荧光(Fo)影响不大.水杨酸处理可减小高温强光下叶黄素循环库的下降幅度,使(A+Z)/(V+A+Z)升高,分别比对照高29.5%和24.6%.这些结果说明,水杨酸可通过提高非辐射能量耗散,对高温强光引起的黄瓜叶片光合机构的破坏具有保护作用.

Two types of cabbage cultivars ( heat-sensitive and heat-tolerant) were used asmaterial to study the difference of photosynthesis under short-term high temperature stress with high light. Results showed that photosynthetic rate of‘Daniuxin’was app roximately 30% higher than that of‘Wufen 8’under 1200 mol·m - 2 ·s - 1 PFD when leaf temperature was 40℃. Compared with at 28℃, their photosynthetic rates decreased 7% and 24%, respectively. Under 40℃, the quantum yield of PSII electron transport (ΦPSII) and maximal photochemical efficiency of PSII in the light ( Fvp/Fmp) decreased with the increase of light, but non-photochemical quenching (NPQ) increased continuously, its slow-component ( q I) remained app roximately 10% of NPQ, the increase of fast component ( qf) is the main factor leading to the increase of NPQ, indicating that xanthophyll cycle2dependent‘high energy’quenching was the main mechanism for effectively dissipating the excess excitation energy. However, there were no significant differences inΦPSII, Fv'/Fm', NPQ, qf, qI between two types of cabbage cultivars. In addition, no significant difference was observed in maximal photochemical efficiency of PSII (Fv/Fm) , intercellular CO2 concentration (Ci) , photoresp iratory rate (Pr). Therefore,the difference of photosynthetic rates between two cultivars under short-term high temperature stresswith the high lightmight result from non-stomatal limitation which had no relation with photoreaction process.

以耐热性不同的两个甘蓝( Brassica oleracea L. var. capitata ) 品种为材料, 对短期高温强光胁迫下光合作用的差异做了初步探讨, 结果表明: 在叶温40℃, 1 200μmol·m - 2 ·s - 1 的光强下, ‘大牛心’净光合速率比‘无粉8号’高出约30% , 与28℃叶温下光合速率结果相比较, 两品种分别降低7%和24% , 高温下, 大牛心的光合速率显示较强的耐热性。40℃预处理后随着光强的升高, 光系统II ( PSII)的电子传递效率(ΦPSII) 和PSII的激发能捕获效率( Fv'/Fm') 持续下降, 而非光化学猝灭(NPQ) 持续增加, 慢组分( qI) 一直维持在NPQ的10%左右, NPQ的增加主要是快组分( qf) 的迅速增加。可见高温强光胁迫下依赖于叶黄素循环的高能态猝灭是甘蓝幼苗叶片耗散过剩激发能的主要方式。然而两品种之间ΦPSII、Fv'/Fm'、NPQ及其qf和qI均无显著性差异, 且最大光化学效率( Fv/Fm) , 细胞间隙CO 2 浓度(Ci) , 光呼吸速率( Pr) 也无显著性差异。因此在短期高温强光胁迫下两品种净光合速率差异主要取决于与光反应无关的非气孔限制。

摘　要： 为了探讨切花月季在滇中地区的高产优质栽培措施，对黑魔术、沃蒂、帕里欧3个月季品种在设施 条件下的光合特性及叶绿素含量进行了研究。结果表明，无论在什么季节和生育期，3个品种的叶片光合作用日变化皆表现出明显的光合“午休”现象，最大光合速 率出现在上午10：00～11：00。植株中部叶片的净光合速率最高，其次是上位叶，下位叶最低，而不同位置叶片的叶绿素含量变化趋势是中位叶〉下位叶〉 上位叶。在滇中地区，月季中午光合速率的降低主要与温室中高温有关，而不同叶位光合速率的变化与光环境、叶绿素含量及叶龄有关。根据研究结果，讨论了滇中 地区设施条件下切花月季的一些栽培措施。

采用盆栽试验,研究了不同水分条件下月季和大叶黄杨的光合生理特性.结果表明:(1)随着水分胁迫的加重(W1→W2→W3),月季和大叶黄杨的主要光合参数净光合速率(Pn)、蒸腾速率(Tr)日均值均呈逐渐降低趋势;大叶黄杨的WUE逐渐降低,月季先升高后降低;月季的气孔导度(Gs)逐渐降低,大叶黄杨在中度控水处理(W2)时的Gs高于轻度控水处理(W1);月季的胞间CO2浓度(Ci)先降后升,而大叶黄杨有逐渐增加的趋势.(2)水分胁迫下,两植物叶绿素荧光参数Fo升高,最大荧光(Fm),可变荧光(Fv),Fv/Fm,Fv/Fo降低,但大叶黄杨的参数变幅均大于月季.(3)两植物主要光合参数的日变化曲线有明显不同,CK和W1时,月季的Pn和Tr为"双峰"型,大叶黄杨为"单峰"型.(4)水分胁迫下,各荧光参数和光合作用参数变化均表明,大叶黄杨对土壤水分胁迫更为敏感.

Diurnal variation of photosynthesis under natural conditions and shading treatment in summer in the leaves of field Tree Peony( Paeonia suffruticosa ) was studied using the technology of gas exchange and analyzing chlorophyll fluorescence. The results indicated that the curve of diurnal variation of net photosynthetic rate ( P n ) was demonstrated single peak in spring,two peaks in clear days in summer,with midday depression of photosynthesis. The apparent quantum yield ( AQY ) and the carboxylation efficiency ( CE ) displayed significant midday decline. The maximal PSⅡ efficiency ( F v / F m ) and maximal fluorescence ( F m ) demonstrated reverse single peaks, which decreased obviously in the midday. Through shading treatment in summer, the curve of diurnal variation of P n was demonstrated single peak. Photosynthetic active radiation (PAR) and limit of stomatal ( L s ) decreased, but stomatal conductance ( G s ) and the internal leaf CO 2 pressure ( C I ) increased compared with those in sun-light. And the decreased amplitude of F v / F m and F m declined obviously. Shading treatment hardly affected the F o . These results showed that PSⅡ reaction center exhibited a dynamic change on revisable inactivation; PSⅡ function exhibited obviously down-regulation and photoinhibition under strong midday light in summer. Shading treatment in summer can improve photosynthetic function and accelerate products by abating photoinhibition.

利用气体交换和叶绿素荧光分析技术,研究大田牡丹叶片在自然光照和夏季遮荫处理下光合作用日变化。结果表明:自然光下夏季牡丹叶片的净光合速率( P n )明显低于春季,2个生长季节 P n 日变化差异明显,即春季的 P n 日变化呈“单峰型”曲线,夏季的 P n 日变化为“双峰型”曲线,有明显的光合“午休”;羧化效率( CE )变化趋势与 P n 相似;表观量子效率(AQY)中午降低,下午逐渐回升;光系统Ⅱ(PSⅡ)最大光化学效率 F v / F m 和最大荧光 F m 日变化为倒“单峰型”曲线,中午明显降低;与夏季自然光下相比,夏季遮荫处理(遮光50%)的牡丹叶片 P n 、AQY、CE升高;气孔限制值( L s )和叶温( t l )降低; F v / F m 和 F m 中午下降幅度显著减小。这些结果说明:夏季晴天中午高温、强光下,牡丹叶片PSⅡ反应中心发生了可逆失活,PSⅡ功能下调,光合作用的光抑制明显发生,遮荫可减轻光抑制,改善光合功能以增加光合产物积累。

This paper studied the effects of different shading (light transmittance 20%, 40%, 60%, and 100%) on the photosynthesis characteristics of two ornamental foliage plants Photinia × frasery and Aucuba japonica var. variegata . After shading for six weeks, the  net photosynthesis rates of two plants measured ex situ under natural light enhanced, compared to those measured in situ , and, with the increase of shading degree, the net photosynthetic rates had an increasing trend, with the maximum being 9.7 μmol·m -2 ·s -1 for Photinia × frasery and 8.3μmol·m -2 ·s -1 for Aucuba japonica var. variegata . In the meantime, the transpiration rates of the two plants increased significant\ly. Shading increased the chlorophyll a, b, and a+b contents and the chlorophyll/carotenoids ratio, decreased the chlorophyll a/b, but less affected the carotenoids content. The phenotypic plasticity index (PPI) of net photosynthesis rate and transpiration rate of Photinia × frasery and Aucuba japonica var. variegate was 2.08 and 3.21, and 0.55 and 1.60, respectively. The chlorophyll and carotenoids contents of the two plants were relatively stable, indicating the minor influence of external environment factors on pigments. Aucuba japonica var. variegata had a higher shading tolerance than Photinia × frasery .

研究不同遮荫处理(透光率分别为20%、40%、60%、100%)对红叶石楠和洒金桃叶珊瑚两种观叶植物光合特性的影响.结果表明：遮荫处理6周后,与遮荫状态下原位测定相比,自然状态下两种植物异位测定的光合作用增强,随着遮荫程度的增强, 叶片净光合速率呈增大趋势, 红叶石楠和洒金桃叶珊瑚的最大值分别为9.7和8.3 μmol·m -2 ·s -1 ；两种植物的蒸腾速率显著提高.遮荫处理不同程度地提高了两种植物叶片叶绿素a、b含量、叶绿素a+b总量及叶绿素/类胡萝卜素值，降低了叶绿素a/b值,但类胡萝卜素含量无显著变化.在自然状态下,红叶石楠净光合速率和蒸腾速率的表型可塑性指数(PPI)分别为2.08和3.21；洒金桃叶珊瑚的相应指标仅为0.55和1.60.两种植物的叶绿素和类胡萝卜素含量相对稳定,受外界环境因子影响相对较小.洒金桃叶珊瑚的耐荫性高于红叶石楠.

The experiments took Clematis manshurica Rupr. a medicinal plant, as material, studied the effects of five different shading levels (Shading of 0, 30%, 50%, 70% and 90%) on its growth and photosynthetic characteristics, and it is essential for its normalized cultivation in Jilin Province, Northeast China. The photosynthetic parameters, dry matter accumulation as well as chlorophyll contents in the leaves of C. manshurica were measured. The results indicated that the contents of total chlorophyll, chlorophyll a and chlorophyll b in leaves under the shading conditions were significant higher than under the full daylight; the chlorophyll contents increased with the increasing of shading levels, and it reached the top point under the shading of 90%. However, the variation trend of chlorophyll a/b was contrary. The specific leaf area of C. manshurica increased with the weakening of light intensity, so the accumulation of photosynthetic products was produced by increasing the total photosynthetic area under lower light intensity. The diurnal changes in the net photosynthetic rate of C. manshurica in full light could be expressed as two-hump curves, reflecting a significant middy depression at noon, but the middy depression was not obvious in the shading of 30%; the effects of shading treatments on transpiration rate and stomatal conductance were different significantly, and the values of transpiration rate and stomatal conductance of C. manshurica decreased with the increasing of shading levels; the diurnal average of net photosynthetic rate and module biomass of C. manshurica were increased firstly, and then decreased along the shading gradient. There were significant effects of shading on the net photosynthetic rate, the biomass of the root and rhizomes, stems and leaves of C. manshurica. A sharp increase dry matter accumulation of C. manshurica was observed in the shading of 30% compared with the other levels. The light intensity and the canopy temperature were markedly reduced in the shading of 30%, but the relative humidity was increased. Consequently, the temperatures of leaf surface were decreased, which can improved canopy microclimate conditions and eliminated the phenomenon of “midday depression” effectively. At the same time it increased the net photosynthetic rate and the module biomass of C. manshurica, in other words, appropriate shading was conducive to its matter production. But the net photosynthetic rate and the total accumulation of photosynthetic products of C. manshurica were decreased with the increasing of shading levels. The stems were short, the biomass of the root, rhizomes, stems and leaves were decreased. The diurnal changes in the net photosynthetic rate in the shading of 50%, 70% and 90% could be expressed as the single peak curve, and the overhead shading could effectively overcome the harm caused by high temperature and strong light, but the photosynthetic efficiency of C. manshurica was deceased because of lower light. The excess shading significantly decreased the photosynthesis and module biomass, and it could bring unfavorable effects to the growth of C. manshurica. In conclusion, the above experiment showed that appropriate shading was propitious to increase the net photosynthetic rate of C. manshurica in the practical production, which is the important measure to increase the output of C. manshurica.

遮荫处理对东北铁线莲生长发育和光合特性的影响

Aims Although Phellodendron amurense is generally recognized as a shade-intolerant tree species, it has been reported to have some shade tolerance and be able to regenerate in both full sunshine and shade in New York, USA, where it is invasive. Our objective was to investigate shade tolerance of P. amurense . Methods We planted 2-year-old P. amurense seedlings in two plantation plots, one with full natural light and the other with 15% of full natural light. After one year we observed the parameters of gas ex-chang, including maximum net photosynthetic rate ( P max ), apparent quantum yield ( AQY ), dark respira-tion rate ( R d ), light compensation point ( LCP ) and light use efficiency ( LUE ), using a Li-6400 (Li-Cor, USA). We also determined chlorophyll ( Chl ) contents per unit leaf area and per unit mass and specific leaf weight ( SLW ). Important findings There were no significant differences ( p >0.05) between sun and shade treatments for P max , AQY and R d . However, plants in the shade treatment had significantly lower LCP and SLW , but higher Chl content per unit mass and leaf area. These results indicated that P. amurense seedlings effectively used weak light by decreasing LCP and R d , and enhanced the ability of capturing light by de-creasing SLW and increasing leaf area and relative content of chlorophyll b, which made LUE increase in weak light condition. Therefore, P. amurense seedlings are shade tolerant.

一直以来黄波罗( Phellodendron amurense )被认为是不耐阴树种, 然而引入美国纽约后, 发现它具有一定的耐阴性, 在全光和林下均能更新, 在纽约已经成为生物入侵种。为了探讨黄波罗的耐阴性问题, 通过设置自然光与遮阴(15%自然光)两种光环境, 观测了三年生黄波罗幼苗(遮阴1 a后)光合生理参数、光能利用效率、叶绿素和比叶重的变化。结果表明, 与自然光处理相比, 遮阴处理的黄波罗幼苗最大光合速率、表观量子效率和暗呼吸速率略有下降, 但差异不显著( p >0.05), 光补偿点下降显著( p p >0.05), 而单位干重叶绿素含量显著升高, 比叶重显著下降, 叶面积显著增大( p <0.05)。上述结果说明: 遮阴的黄波罗幼苗通过降低光补偿点和暗呼吸速率利用环境中的弱光, 同时通过减小比叶重、增大叶面积和提高叶绿素b相对含量来增强对光的捕获, 使其在弱光时的光能利用效率提高。由此推断, 黄波罗幼苗能适应一定程度的遮阴。

用Ｌｉ-６４００光合测定系统测定了不同光照下蝴蝶花的光合特性，结合蝴蝶花的生长发育状况，探讨了蝴蝶花在不同光照下的适应性。结果显示，随植株上层光强的降低，蝴蝶花的Ｃｈｌａ／Ｃｈｌｂ、净光合速率、气孔导度、蒸腾速率、胞间ＣＯ ２ 浓度均呈降低趋势，Ｃｈｌｂ含量、蒸汽压亏缺、气孔限制呈增加趋势；光补偿点、暗呼吸速率、ＣＯ ２ 补偿点、表观量子效率下降，羧化效率增加，揭示了蝴蝶花对光照减低的生理适应机制；蝴蝶花的光补偿点在５．１８～ １２．０５μｍｏｌ／ｍ ２ ·ｓ，光饱和点在１０００μｍｏｌ／ｍ ２ ·ｓ左右，说明其对光的适应范围较宽。ＣＯ ２ 补偿点在５４．８４～５８．４５μｍｏｌ／ｍｏｌ、ＣＯ ２ 饱和点在９７０μｍｏｌ／ｍｏｌ左右。结合蝴蝶花生长发育状况分析，竹林下植株的叶面积最大、开花状况最佳，生长最好。但３种环境下植株均能生长。

Aims Our objective was to investigate the effects of different light intensities on leaf morphology, photosynthetic capacity, heat dissipation and antioxidant enzyme activities in seedlings of Alnus formosana and A. cremastogyne from a hilly region near Lingyan Mountain in northwestern Sichuan Province in China. We also discuss photosynthetic acclimation and photoprotection strategies in seedlings of the two species Methods Three light regimes of 100%, 56.2% and 12.5% of natural light were simulated to match forest openings, forest gaps and forest canopies, respectively. After more than three months, we measured the parameters of gas exchange, including maximum net photosynthetic rate ( P max ), light saturation point ( LSP ), light compensation point ( LCP ), net photosynthetic rate ( P n ), stomatal conductance ( G s ), transpiration rate ( T r ), intercellular CO 2 concentration ( C i ), fluorescent non-photochemical quenching ( NPQ ), maximum efficiency of PSII photochemistry ( F v / F m ) and light use efficiency ( LUE ), using a LI-6400 in seedling leaves. We also determined pigment contents per unit leaf area, lamina mass per unit area ( LMA ) and activity of antioxidant enzymes (superoxide dismutase, catalase and ascorbate peroxidase). Important findings LMA , carotenoid content (Cars), ratio of carotenoid to total chlorophyll (Car/Chl) and activities of superoxide dismutase, catalase and ascorbate peroxidase in leaves increased with the increase of light intensities. P max , LSP , LCP and NPQ tended to increase, while the chlorophyll content (Chl) and LUE decreased. However, the C i decreased with the increase of P n , G s and stomatal limitation value ( L s ). We speculated that non-stomatal limitation was the main factor that inhibited P n . Seedlings of the two alder species could acclimate to different light regimes in this study through changing of physiological and morphological traits. Under all light regimes, diurnal photoinhibition of photosynthesis, as judged by F v / F m , was significantly more severe in A. cremastogyne than in A. formosana . The acclimation capacity to high light regime was stronger in A. formosana than in A. cremastogyne . With the increase of light intensities, P max and antioxidant enzyme activities increased significantly, but not NPQ in A. formosana . The opposite trends occurred in A. cremastogyne . At the same light intensity, thermal dissipation was much lower, but P max was much higher in A. formosana than in A. cremastogyne . These results indicated that A. formosana seedlings might adapt resistance to photoinhibition through improving the use of solar energy by higher P max and antioxidant enzyme system, while A. cremastogyne seedling avoided photoinhibition mainly through converting excess light energy to heat energy in the form of non-radiative dissipation through the antenna system.

通过搭建荫棚设置3种不同的光强, 模拟森林幼苗生长的旷地(砍伐迹地)、林窗和林下光照环境(分别为100%、56.2%和12.5%的全光照), 比较研究了外来种台湾桤木( Alnus formosana )和乡土种桤木( A. cremastogyne )幼苗的叶形态、光合能力、热耗散和抗氧化酶的活性, 探讨了两树种幼苗对光强的适应及光保护策略。结果表明: 在3种光强下, 一定光强范围内随着光强的增加, 两种桤木幼苗的比叶重( LMA )、类胡萝卜素(Cars)、类胡萝卜素/叶绿素(Cars/Chl)和抗氧化酶(超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX))活性升高, 最大净光合速率( P max )、光饱和点( LSP )、光补偿点( LCP )和非光化学猝灭系数( NPQ )具有升高的趋势; Chl含量和瞬时光能利用效率( LUE )降低; 净光合速率( P n )、气孔导度( G s )、气孔限制值( L s )升高, 胞间CO 2 浓度( C i )降低, 推测 P n 降低的主要因素是非气孔限制, 表明两种桤木幼苗均能适应不同的生长光强。生长在相同光强下, 桤木幼苗光抑制现象比台湾桤木幼苗严重, 台湾桤木幼苗对光强适应能力较强。随着光照强度的增加, 台湾桤木幼苗 NPQ 增加不显著, 热耗散较少, 相同光强下 P max 和抗氧化酶活性显著高于桤木幼苗, 而桤木幼苗随着光强的增加热耗散显著, 表明在光抑制时, 台湾桤木幼苗主要是通过提高 P max 利用光能和抗氧化酶系统进行保护性调节, 桤木幼苗则通过天线系统非辐射耗散将过剩的光能以热能的形式消耗掉。