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1.
以东北山樱桃实生幼苗为试材,利用Hansatch PEA,采用叶绿素荧光诱导动力学理论和JIP-test数据分析方法,研究对羟基苯甲酸对叶片叶绿素荧光参数的影响。结果表明:幼苗在不同浓度对羟基苯甲酸(0.1、1、10 mmol·L-1)处理下的叶片光合性能指数、捕获的激子将电子传递到电子传递链中QA-下游的其他电子受体的概率、用于电子传递的量子产额和单位面积有活性的反应中心数目较对照均有所下降;PSⅡ最大量子效率、单位面积有活性的反应中心数目几乎没有变化;而PSⅡ受体侧的电子受体库容量则高于对照,且呈"上升—下降"趋势。天线色素吸收的能量在低浓度下有小幅升高,反应中心捕获的能量、用于电子传递的能量及用于热耗散的能量则无明显变化。可见,对羟基苯甲酸对东北山樱桃叶片光合结构的不同部位产生影响,进而降低光合性能,影响光合作用。  相似文献   

2.
为了掌握植物叶片中花色素苷含量对植物叶片PSⅡ功能的影响情况,以土庄绣线菊Spiraea pubescens、金焰绣线菊S.×bunmalba cv.Goldflame和金山绣线菊S.×bunmalba cv.Goldmound为试验材料,利用叶绿素荧光技术研究了花色素苷在绣线菊叶片光合机构中的作用。结果表明:三种绣线菊的完全展开叶片(即成熟叶片)中的花色素苷含量较低,叶绿素含量以及叶绿素荧光参数之间的差异较小;而在三种绣线菊的伸展叶片(生长叶片)中,金焰绣线菊和金山绣线菊叶片中花色素苷含量明显高于土庄绣线菊,而其叶绿素含量却明显低于土庄绣线菊。金焰绣线菊和金山绣线菊伸展叶片的初始荧光(Fo)、最大荧光(Fm)和单位反应中心吸收的光能(ABS/RC)均明显低于土庄绣线菊,说明较高含量的花色素苷降低了绣线菊叶片对光能的吸收,但是PSⅡ最大光化学效率(Fv/Fm)、PSⅡ潜在光化学活性(Fv/Fo)、电子传递速率(ETR)和实际光化学效率(ФPSⅡ)却明显高于土庄绣线菊。土庄绣线菊伸展叶片的有活性的PSⅡ反应中心数量明显低于金焰绣线菊和金山绣线菊,而单位反应中心吸收的光能(ABS/RC)、单位反应中心捕获的用于还原QA的能量(TRo/RC)、单位反应中心捕获的用于电子传递的能量(ETo/RC)和单位反应中心耗散掉的能量(DIo/RC)均明显高于金焰和金山绣线菊,且土庄绣线菊伸展叶片失活反应中心的比例较高。花色素苷不但改变了金焰绣线菊和金山绣线菊伸展叶片对光能的吸收,而且改变了光合电子的传递速率和能量分配参数,影响了绣线菊伸展叶片的PSⅡ功能。  相似文献   

3.
以3年生金叶风箱果为试材,通过对其进行不同遮阴(0%、30%、50%和80%)处理,探究不同遮阴条件下快速叶绿素荧光诱导动力学曲线及快速叶绿素荧光参数,旨在阐明遮阴对金叶风箱果快速叶绿素荧光特性的影响。结果表明,随遮阴度的增加,金叶风箱果叶片的最大荧光值(Fm)、最大光化学效率(Fv/Fm)以及PSII潜在活性(Fv/Fo)的值均显著增大;遮阴处理下,PSII反应中心用于电子传递的量子比率(φEo)提高,而用于热耗散的量子比率(φDo)降低;随遮阴度上升,反应中心吸收的光能(ABS/RC)下降,用于电子传递的能量(ETo/RC)显著上升,而用于热耗散的能量(DIo/RC)显著下降。可见,遮阴后金叶风箱果叶片吸收的光能减少,但为适应弱光环境,可通过提高PSII电子传递效率及降低热耗散的能量,进而提高对光能的利用。  相似文献   

4.
为阐明糠椴(Tilia mandshurica Rup et Maxim.)对不同光环境的光合特性,以2 a生糠椴实生苗为试验材料,设定4个遮光度,分别为透光率100%(CK)、透光率70%(轻度遮光,LS)、透光率40%(中度遮光,MS)、透光率10%(重度遮光,SS)。研究处理后叶片净光合速率日变化、光响应参数、叶绿素含量等的变化。结果表明:(1)随着遮光度的增加,幼苗净光合速率、气孔导度、蒸腾速率和水分利用率先升高后降低,胞间CO_2浓度先降低后升高;(2)轻度遮光处理下,幼苗光响应参数表观量子效率(AQY)、光补偿点(LCP)、最大净光合速率(P_(max))显著提升,光饱和点(LSP)和暗呼吸速率(Rd)降低;(3)轻度遮光处理下的最大光化学效率(Fv/Fm)、能量分配比例参数中吸收的光能被反应中心捕获的量子产量(φPo)、激子被反应中心捕获后促进电子传递到电子传递链中超过QA的电子受体的激子与促进QA还原激子的比值(Ψo)、单位反应中心所捕获的应用到电子传递的能量(ETo/RC)的值显著增加。(4)糠椴叶绿素b和叶绿素总量随遮光度的升高而增加。叶绿素a/b随遮光度的增加而降低。综合各指标分析认为:轻度遮光环境有利于提升糠椴幼苗的光合特性,促进幼苗生长。  相似文献   

5.
温度对植物的光合作用和地理分布范围均具有重要影响,因此,研究温度变化对南极假山毛榉光合系统的影响,对引种培育具有重要意义。通过人工模拟温度变动(-5、5、15、25、30、35和40℃),对南极假山毛榉1年生苗的叶绿素荧光、快速光响应曲线和叶绿素含量进行了分析。结果表明:1)随着高、低温胁迫的加剧,叶片性能指数(PI_(ABS))、PSⅡ用于光化学反应的能量比例(P)和光能利用效率(α)均呈下降趋势,非光化学猝灭系数(qN)呈持续上升趋势,说明胁迫导致叶片吸收的光能相对过剩;叶绿素荧光动力学曲线出现明显的K点和L点,单位反应中心捕获的用于电子传递的能量(ET_o/RC)持续显著下降,说明胁迫主要干扰PSⅡ的放氧复合体和电子传递途径。2)高温40℃胁迫导致非光化学反应耗散能量比例(E)、PSI荧光强度(F1)和PSⅡ单位面积反应中心数量(RC/CS)分别比25℃时增加了110.0%(P 0.01)、178.1%(P 0.01)和6.9%,低温-5℃胁迫导致RC/CS和E分别比25℃时增加了12.8%和43.3%(P 0.01),说明增加叶片荧光散射强度和PSⅡ单位面积反应中心的数量是南极假山毛榉应对高低温胁迫的保护性反应。3)所有测量参数中ET_o/RC对温度变化最敏感,非线性拟合显示南极假山毛榉光合作用的最适温度为23.83℃。  相似文献   

6.
为了探明间伐对乔化‘红富士’苹果叶片光合、荧光特性的影响,以甘肃中部地区盛果期富士苹果树体为试材,通过对隔株间伐及CK的冠层不同部位叶片光合及荧光参数的比较研究,结果表明:与CK相比,同一冠层中,间伐处理的叶片净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)、基础荧光产量(Fo)、最大荧光产量(Fm)、非光化学猝灭系数(qN)、单位反应中心吸收光能(ABS/RC)、单位反应中心捕获的用于电子传递的能量(ETo/RC)、单位反应中心捕获的用于还原Q_A的能量(TRo/RC)等参数显著提高;间伐的树冠中上部、下部外围和下部内堂叶片的Pn显著高于CK,分别较CK提高了9.80%、25.2%和28.0%。可见,间伐处理的不同冠层叶片光合性能均显著优于CK。  相似文献   

7.
【目的】研究黄化对‘赤霞珠’葡萄光合及叶绿素荧光特性的影响情况,为了解黄化对酿酒葡萄的伤害机制提供参考依据。【方法】以出现黄化现象的‘赤霞珠’葡萄植株为材料,分析Ⅰ、Ⅱ、Ⅲ、Ⅳ级黄化等级葡萄叶片的光合色素、光合作用气体交换参数及叶绿素荧光参数的变化特点。【结果】‘赤霞珠’葡萄因受土壤高pH值、低养分等因素的影响发生了叶片黄化现象;与正常植株(CK)相比,黄化等级分别为Ⅰ、Ⅱ、Ⅲ、Ⅳ级的葡萄叶片中的叶绿素总量分别降低了63.91%、70.43%、73.91%、76.52%,而黄化叶片中的类胡萝卜素在色素组成中的比例有所增高;叶片黄化迫使葡萄叶片净光合速率(P_n)、气孔导度(G_s)、蒸腾速率(T_r)均显著降低,Ⅳ级黄化叶片的P_n较对照显著下降85.08%;黄化叶片的叶绿素荧光动力曲线出现明显K点(300μs),ΔV_t和ΔW_t曲线上在100 ms处均出现了明显的凹峰;叶绿素荧光参数PSⅡ最大光化学效率(F_v/F_m)、结构性能指标(PI_(ABS))、原初光化学产额(ψ_o)、用于电子传递量子比率(φ_(Eo))等参数值均显著低于对照,而最小荧光强度(F_o)、单位反应中心吸收光能(ABS/RC)等值均显著高于对照,其PSⅡ潜在的光化学效率、光合电子传递速率、量子效率均显著低于对照。【结论】光合色素的减少,致使葡萄植株叶片黄化,影响了叶片的光合作用,导致叶片受到光抑制与光氧化,致使植株的代谢能力减弱。  相似文献   

8.
为了比较秋季不同衰老时期苹果叶片光合生理特性的差异,以生草覆盖条件下5年生苹果园为对象,研究了不同衰老时期叶片的叶绿素、可溶性蛋白质、超氧阴离子、丙二醛的含量和超氧化物歧化酶活性及光合荧光参数的差异。结果表明,叶片净光合速率(P n)随衰老程度的加剧而显著降低。与衰老初期相比,中后期叶片J相相对可变荧光(V j)显著升高、最大荧光(F m)显著降低,说明PSⅡ的基本结构和功能受到了严重破坏;捕获的激子用来推动电子传递链中超过Q A的激子所占比率(ψo)和用于电子传递的量子产额(φEo)显著降低、PSⅡ最大光化学效率(F v/F m)变化平稳,说明光合机构通过调控F v/F m来维持较高水平的ψo和φEo。在衰老后期,可变荧光F k占F j-F o振幅的比例(W k)和V j急剧升高,初始荧光(F o)、F m、ψo、φEo和F v/F m急剧降低,ψo、φEo和F v/F m分别为初期的29.7%、11.3%和38.0%,说明叶片PSⅡ的基本结构受到了严重破坏,功能基本丧失。  相似文献   

9.
【目的】通过比较分析铁尾矿基质下不同遮荫处理间臭柏实生苗叶片原初光化学反应的差异,揭示臭柏在不同光照条件下的光保护机制,从理论上解释其天然更新过程,为臭柏光胁迫的研究提供理论依据,也为臭柏在铁尾矿废弃地造林提供技术依据。【方法】以唐山迁安铁尾矿为基质,通过盆栽遮荫试验,利用快速叶绿荧光诱导动力学测定与 JIP-test数据分析方法,分别测定0,25%,50%,75%和90%5个遮荫处理下臭柏叶绿素8项荧光参数。【结果】1)全光照条件下Fo 增大,Fm 减小,而叶片光合系统量子产额和能量分配比率(φPo,Ψo和φEo)、单位面积光合机构的比活性参数(Fm,ETo/CSm和 TRo/CSm)和单位面积内反应中心的数量(RC/CSm)均最小,且各个遮荫处理组间差异均达到显著(P＜0.05)或极显著水平(P＜0.01),表明全光照条件下臭柏实生苗反应中心失活,受到光抑制,而全光照下快速叶绿素荧光诱导动力学曲线中 K 点与 J 点明显高于其他遮荫处理,而且光抑制对臭柏叶片PSⅡ的供体侧(OEC)有伤害,造成PSⅡ受体侧(Q －A )的大量积累,阻碍电子传递链向Q －A 下游传递。2)全光照条件下叶片热耗散的量子比率(φDo )和单位面积光合机构的比活性参数( DIo/CSm )均最大,且与其他遮荫处理组间差异也均达到显著(P＜0.05)或极显著水平(P＜0.01),表明全光照条件下臭柏在遭受光抑制后,通过增加天线色素的热耗散,增加非辐射能量耗散等一系列机制来保护光合机构免受过量光能的危害。3)随着遮荫率增加,φPo ,Ψo和φEo,Fm(ABS/CSm),ETo/CSm和TRo/CSm,RC/CSm随之上升,而φDo和Fo(ABS/CSo),DIo/CSm随之下降,90%遮荫处理表现出明显的光捕捉特征,50%遮荫处理 Fm ,PIABS的平均值最大,说明该遮荫条件下臭柏叶片光抑制最小,光合能力最强,其他参数在不同遮荫处理组间无明显差异( P＜0.05)。【结论】臭柏幼苗若无遮荫措施,受到光胁迫,而其通过增加非辐射能量耗散途径达到光抑制防御的机制。因此臭柏天然更新从乌柳灌丛下开始,逐渐脱离乌柳灌丛的保护,完全暴露在全光照条件下,进而实现自身的不断生长、壮大,但在废弃地上植苗造林初期尚需采取一定的遮荫措施,以提高造林成活率。  相似文献   

10.
不同温度下秋茄树幼苗叶绿素荧光参数对光强的响应   总被引：1，自引：0，他引：1  
为了更好地开展秋茄树Kandelia obovata的引种、繁育等工作,以其2年生移植容器苗为材料,设置了昼夜温度分别为A(25/20℃),B(20/15℃),C(15/10℃)和D(10/5℃)共4个处理,研究了电子传递速率(ETR)、光系统Ⅱ(PSⅡ)反应中心的激发能捕获效率(Fv'/Fm')、PSⅡ反应中心电荷分离实际量子效率(Φ_(PSⅡ))、光化学猝灭系数(qP)和非光化学猝灭系数(qN)等参数对光强(PAR)的响应曲线。结果表明,光响应机理模型和双指数模型可以较好地拟合不同温度处理下秋茄树幼苗ETR对PAR的响应,所得结果与实测值较为接近(P0.05);在不同温度下,秋茄树幼苗叶片的饱和PAR有所差异,在1 000～1 400μmol·m~(-2)·s~(-1)之间;以光响应机理模型拟合的结果为例,在A,B,C,D不同处理下,秋茄树叶片的最大电子传递速率(ETR_(max))间均有显著差异(P(27)0.05),分别为124.393,110.812,64.153和33.427μmol·m~(-2)·s~(-1);D处理下的Fv'/Fm',Φ_(PSⅡ),qP和qN均处于最低水平,说明5℃以下低温对秋茄树幼苗的光合影响较大。因此,建议在幼苗阶段,夏季进行适当遮阳,冬季喷施植物生长调节剂或采用其他措施进行保温。  相似文献   

11.
I~uchonRhodho saChaliDensis A. Bor is perennial herbthst b6longs tO Crassulaceae. It mainly distributes inJapan, KOrea, China and Russian. In China it mainlydiSbout6S at the alhtude Of 1 770-2 500 m in Changbei Moudsin Of Jinn Province and ZhangguangcaiMountain Of Heilontoiang Province. It is typical alpineplant (Wu et al. 1987, Qin 1994, Lu et al. 1995) andalso very imPOtent m6dicinal plant. From 1950s a lotOf reseaus with about RhodiOIa plantS had beendone in RuSSian, Ukraine…  相似文献   

12.
A quantitative analysis was applied to the stomatal and biochemical limitations to light-saturated net photosynthesis under optimal field conditions in mature trees and seedlings of the co-occurring evergreen oak, Quercus ilex L., and the deciduous oak, Q. faginea Lam. Stomatal limitation to photosynthesis, maximal Rubisco activity and electron transport rate were determined from assimilation versus intercellular leaf carbon dioxide concentration response curves of leaves that were subsequently analyzed for nitrogen (N) concentration, mass per unit area, thickness and percent internal air space. In both species, seedlings had a lower leaf mass per unit area, thickness and leaf N concentration than mature trees. The root system of seedlings during their third year after planting was dominated by a taproot. A lower leaf N concentration of seedlings was associated with lower maximal Rubisco activity and electron transport rate and with assimilation rates similar to or lower than those of mature trees, despite the higher stomatal conductances and potential photosynthetic nitrogen-use efficiencies of seedlings. Consequently, stomatal limitation to photosynthesis increased with tree age in both species. In both seedlings and mature trees, a lower assimilation rate in Q. ilex than in Q. faginea was associated with lower stomatal conductance, N allocation to photosynthetic functions, maximal Rubisco activity and electron transport rate, and potential photosynthetic nitrogen-use efficiency but greater leaf thickness and leaf mass per unit area. Tree-age-related changes differed quantitatively between species, and the characteristics of the two species were more similar in seedlings than in mature trees. Despite higher stomatal conductances, seedlings are more N limited than adult trees, which contributes to lower biochemical efficiency.  相似文献   

13.
Niinemets U  Kull O 《Tree physiology》2001,21(12-13):899-914
We used chlorophyll fluorescence techniques to investigate responses of Photosystem II (PSII) quantum yield to light availability in the short term (quantum flux density integrated over the measurement day, Qd) and in the long term (Qd averaged over the season, Qs) in a mixed deciduous forest comprising shade-tolerant and water-stress-sensitive Tilia cordata Mill. in the lower canopy and shade-intolerant and water-stress-resistant Populus tremula L. in the upper canopy. In both species, intrinsic efficiency of PSII in the dark-adapted state (Fv/Fm) was lower during the day than during the night, and the difference in Fv/Fm between day and night increased with increasing Qs. Although the capacity for photosynthetic electron transport increased with increasing Qs in both species, maximum quantum efficiency of PSII in the light-adapted state (alpha) decreased with increasing Qs. At a common Qs, alpha was lower in T. cordata than in P. tremula primarily because of a higher fraction of closed PSII centers, and to a smaller extent because of limited, non-radiative, excitation energy dissipation in the pigment bed in T. cordata. Across both species, photochemical quenching (qP), which measures the openness of PSII centers, varied more than fivefold, but the efficiency of excitation energy capture by open PSII centers (Fv'/Fm'), which is an estimate of non-radiative excitation energy dissipation in PSII antennae, varied by only 50%. Chlorophyll turnover rates increased with increasing irradiance, especially in T. cordata, possibly because of increased photodestruction. Diurnal measurements of PSII quantum yields (PhiPSII) indicated that, under similar environmental conditions, PhiPSII was always lower in the afternoon than in the morning, and the fraction of daily integrated photosynthetic electron transport lost because of diurnal declines in PhiPSII (Delta) increased with increasing Qd. At a common Qd, mean daily PSII center reduction state, the fraction of light in excess (1 - fractions of light used in photochemistry and dissipated as heat) and Delta were higher in T. cordata than in P. tremula. This was attributed to greater stomatal closure during the day, which led to a greater reduction in the requirement for assimilative electron flow in T. cordata. Across both species, Delta scaled negatively with the fraction of light utilized photochemically, demonstrating the leading role of PSII center openness in maintaining high PSII efficiency. Because photosynthesis (A) at current ambient carbon dioxide concentration is limited by CO2 availability in high light and mainly by photosynthetic electron transport rates in low light, overall daily down-regulation of PhiPSII primarily influences A in low light. Given that foliar water stress scales positively with Qs in both species, we conclude that the inverse patterns of variation in water and light availabilities in the canopy result in a greater decline in A than is predicted by decreases in stomatal conductance alone.  相似文献   

14.
We assessed clonal variation in morphological variables, mineral nutrition, root growth capacity, net photosynthesis, tannin distribution, and cuticle and epicuticular wax features within four families of white spruce (Picea glauca (Moench) Voss). Seeds were collected from four families obtained through controlled crosses among selected genotypes. For each family, plants were produced either from seeds (zygotic) or by somatic embryogenesis (clones). Each family was therefore represented by its zygotic seedlings and three clones. Within a family and under similar growth conditions, several clones differed significantly from the zygotic seedlings in height, root-collar diameter, needle dry mass, branch density, shoot dry mass, root dry mass, and length of needles. Branch density (number of first-order branches per cm height) of zygotic seedlings and clones varied from 0.8 to 1.4 branches cm(-1) and from 0.6 to 1.3 branches cm(-1), respectively. Mean needle length of zygotic seedlings and clones ranged from 11 to 14 mm and from 11 to 17 mm, respectively. For many variables (height, dry mass of new roots, needle dry mass and branch density), differences among clones were significantly greater than differences among zygotic seedlings within a family. Tannins were more abundant in needles of clones than in needles of zygotic seedlings. In some clones, tannins occurred as a ribbon along the central vacuole, whereas in others they appeared as aggregates dispersed in the vacuole. Within a family, N, P and K showed considerable variations in their use efficiency. Interclonal variations were observed in root growth potential and net photosynthesis. Variations in growth and physiology reflect genetically determined differences among clones within a family.  相似文献   

15.
Cai ZQ  Chen YJ  Bongers F 《Tree physiology》2007,27(6):827-836
We hypothesized that photosynthesis and growth of tropical vegetation at its most northern distribution in Asia (Xishuangbanna, SW China) is adversely affected by seasonal drought and chilling temperatures. To test this hypothesis, we measured photosynthetic and growth characteristics of Zizyphus attopensis Pierre seedlings grown in three contrasting forest microhabitats: the understory, a small gap and a large gap. Photosynthetic capacity (light-saturated photosynthetic rate (A(max)), maximum rate of carboxylation and electron transport rate) and partitioning of leaf nitrogen (N) into carboxylation and electron transport differed significantly among seasons and microhabitats. Specific leaf area (SLA) did not change seasonally, but differed significantly among microhabitats and showed a negative linear relationship with daily integrated photon flux (PPF(i)). In contrast, leaf N concentration per unit area (N(a)) changed seasonally but did not differ among microhabitats. Measurements of maximum PSII photochemical efficiency (F(v)/F(m)) indicated that chronic photoinhibition did not occur in seedlings in any of the microhabitats during the study. Photosynthetic capacity was greatest in the wet season and lowest in the cool season. During the cool and dry seasons, the reduction in A(max) was greater in seedlings grown in the large gap than in in the understory and the small gap. Close logarithmic relationships were detected between PPF(i), leaf N(a) and photosynthetic capacity. Stem mass ratio decreased, and root mass ratio increased, in the dry season. We conclude that seasonal acclimation in growth and photosynthesis of the seedlings was associated with changes in biochemical features (particularly N(a) and partitioning of total leaf N between the different photosynthetic pools) and biomass allocation, rather than with changes in leaf morphological features (such as SLA). Local irradiance is the main factor driving seasonal variations in growth and photosynthesis in the study area, where the presence of heavy fog during the cool and dry seasons limits irradiance, but supplies water to the soil surface layers.  相似文献   

16.
Medlyn BE 《Tree physiology》1998,18(3):167-176
The observation that, for unstressed plants, light use efficiency of a plant canopy, defined as the ratio of net primary productivity (NPP) to absorbed photosynthetically active radiation (APAR), is approximately constant with respect to changes in APAR, implies that NPP can be modeled using a linear relationship with APAR. However, such a linear relationship is counter-intuitive because the relationship between leaf photosynthesis and absorbed light is strongly nonlinear. Three arguments have been advanced to explain the observed linear relationship between NPP and APAR. In this paper, a detailed, physiologically based model of canopy radiation absorption and photosynthesis (MAESTRO) was used to analyze these arguments. The first argument is that the canopy is structured so that radiation is distributed throughout the canopy such that most leaves are exposed to non-saturating quantum flux density, resulting in a linear response of canopy photosynthesis to APAR. Simulations of MAESTRO indicated that this explanation is inadequate, because daily values of canopy photosynthetic light use efficiency calculated with MAESTRO were highly variable regardless of canopy structure. The second argument is that variability in light use efficiency decreases with increasing time scale. The simulations showed that this is true to some extent, although simulated annual canopy photosynthetic light use efficiency still varies across sites with different LAI or light climate. The third argument is that changes in canopy nitrogen content act both to maximize net canopy photosynthesis and to keep light use efficiency constant. This argument could not be tested with the model, but the failure of the first two explanations suggests that this third explanation deserves closer attention.  相似文献   

17.
Eight red maple (Acer rubrum L.) provenances, four each from wet and dry sites, were grown under the same conditions and their physiological responses to soil water availability investigated. Under well-watered conditions, seedlings of wet-site provenances grew faster and had consistently higher net photosynthesis, leaf conductance, maximum carboxylation rate, maximum rate of coupled photosynthetic electron transport, apparent quantum use efficiency, light-saturated photosynthesis and dark respiration than seedlings of dry-site provenances. Under conditions of low soil water availability, only dry-site provenances responded with decreased osmotic potential at full hydration and at the turgor loss point; however, provenances from wet sites showed a smaller reduction in absolute growth rate, a greater reduction in gas exchange and a greater increase in abscisic acid concentrations than dry-site provenances.  相似文献   

18.
An experiment in open-top chambers was carried out in summer 2008 at Curno (Northern Italy) in order to study the effects of ozone and mild water stress on poplar cuttings (Oxford clone). In this experiment direct fluorescence parameters (JIP-test) were measured in leaves from different sections of the crown (L: lower; M: medium; U: upper parts of the crown). The parameters considered were calculated at the different steps of the fluorescence transient, and include maximum quantum yield efficiency in the dark-adapted state (F(v)/F(M)); the L-band, at 100?∝?s, that expresses the stability of the tripartite system reaction centre-harvesting light complex-core antenna; the K-band, at 300?∝?s, that expresses the efficiency of the oxygen-evolving complex; the J-phase, at 2 ms, that expresses the efficiency with which a trapped exciton can move an electron into the electron transport chain from Q(A)(-) to the intersystem electron acceptors; the IP-phase, which expresses the efficiency of electron transport around the photosystem 1 (PSI) to reduce the final acceptors of the electron transport chain, i.e., ferredoxin and NADP; and finally the performance index total (PItot) for energy conservation from photons absorbed by PSII to the reduction flux of PSI end acceptors. The main results are: (i) different dynamics were observed between leaves in the lower section, whose PItot decreased over time, and those in the upper sections in which it increased, with a dynamic connected to the leaf age; (ii) ozone depressed all the considered fluorescence parameters in basal leaves of well-watered plants, while it had little or no damaging effect on medium-level or upper-section leaves; (iii) PItot and IP-phase increased in upper leaves of plants subjected to ozone stress, as well as the net photosynthesis; (iv) water stress increased PItot of leaves in all levels of the crown. The results suggest that ozone-damaged poplar plants compensate, at least partially, for the loss of photosynthesis with higher photosynthetic rates in young leaves (in the upper section of the crown), more efficient to fix carbon.  相似文献   

19.
We analyzed processes limiting photosynthesis in two-year-old, container-grown Pinus pinaster Ait. seedlings subjected to phosphorus (P) deficiency. After withholding P for 3 months, seedlings were supplied P at four relative addition rates (0, 0.005, 0.01 and 0.02 day(-1)) in a nutrient recycling system. At Weeks 12 and 22, responses of photosynthesis to CO(2) and irradiance were measured and the following parameters derived: maximal velocity of carboxylation by Rubisco, V(m); apparent quantum efficiency of electron transport, alpha maximal electron transport rate, J(m); stomatal conductance and relative stomatal limitation of photosynthesis. At Week 22, these measurements were combined with concurrent measurements of chlorophyll fluorescence to determine the quantum yield of PSII, and a theoretical partitioning of total light-driven linear electron flow between fractions used to regenerate carboxylated and oxygenated RuBP. After 12 weeks of treatment, needle P concentrations ranged from 0.04 to 0.15 x 10(-2) g g(DW) (-1), and then remained constant until Week 22. Values of J(m), alpha and V(m) increased with increasing needle P concentration (from 30 to 133 &mgr;mol m(-2) s(-1), 0.02 to 0.25 mol mol(-1) and 13 to 78 &mgr;mol CO(2) m(-2) s(-1) at the lowest and highest needle P concentrations, respectively). Under ambient conditions, net assimilation rates in P-deficient seedlings were limited by V(m) under saturating irradiance, and by J(m) under limiting irradiance, but not by triose-P regeneration. There was no detectable change in the partitioning of total light-driven linear electron flow between the fractions used for carboxylation and oxygenation. Predawn photochemical efficiency of PSII was significantly reduced in seedlings with low P concentrations. Although stomatal conductance tended to decrease with decreasing needle P concentration, relative stomatal limitation was not significantly affected. At Week 22, there was an attenuation of the effects of P nutrition on V(m) and an increase in alpha and J(m) that was probably related to cessation of growth and the seasonal decline in natural irradiance.  相似文献   

20.
Gardiner ES  Krauss KW 《Tree physiology》2001,21(15):1103-1111
Two-year-old cherrybark oak (Quercus pagoda Raf.) seedlings raised in full or partial (27%) sunlight were flooded for 30 days to study the effects of light availability and root inundation on photosynthetic light response. Compared with seedlings receiving full sunlight, seedlings receiving partial sunlight developed leaves with 90% greater blade area, 26% less mass per unit volume, and 35% lower nitrogen (N) concentration per unit area, leading to a 15% reduction in leaf photosynthetic capacity when carbon exchange rates were based on blade area. However, when carbon exchange rates were based on leaf mass, leaves acclimated to partial sunlight exhibited a 15% greater photosynthetic capacity realized primarily through an increased initial slope of the photosynthetic light response (A/PPFD) curve and increased net photosynthesis at leaf saturation (Amax). Short-term flooding increased leaf mass per unit area more than 19%, reduced foliar N concentrations per unit dry mass by 19%, and initiated reductions in Amax and apparent quantum yield (phi) of seedlings in both light regimes. Greatest impairment of Amax (56% area basis, 65% mass basis) and phi (40%) were observed in leaves receiving full sunlight, and the declines were concomitant with a 35% decrease in chlorophyll concentration. Flooding also depressed instantaneous photosynthetic N-use efficiency (PPNUE) such that Amax decreased 54%, and the initial slope of PPNUE/PPFD curves decreased 33 and 50% for leaves acclimated to partial and full sunlight, respectively. The A/PPFD patterns indicated that the magnitude of flood-induced inhibition of the photosynthetic mechanism of cherrybark oak seedlings is determined partly by the light environment.  相似文献   

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