短期环割对塔克拉玛干沙漠南缘两种荒漠植物的生理影响

随着气候条件的改变, 人口和载畜量的日益增加, 塔克拉玛干沙漠南缘策勒绿洲主要植物种群花花柴(Karelinia caspia)和骆驼刺(Alhagi sparsifolia)正遭受日益严重的虫噬、放牧等机械损伤的影响, 干扰因子对花花柴和骆驼刺的影响日趋明显。以塔克拉玛干南缘沙漠策勒绿洲主要建群种花花柴和骆驼刺为材料, 测量了韧皮部环割处理10天后, 光合色素含量和光系统II (PSII)叶绿素荧光的变化。结果表明: (1)在韧皮部半割处理下, 花花柴、骆驼刺的光合色素含量和叶绿素荧光变化都不明显。(2)在韧皮部全割处理下, 花花柴、骆驼刺的光合色素含量和叶绿素荧光各参数变化较大, 在该处理下, 两种植物光合原初反应被抑制, PSII结构和功能遭到损害, 活性降低, 光合器官对光能的吸收、传递、转化和电子捕获等过程被抑制。(3)韧皮部全割对花花柴和骆驼刺各生理状况产生较大影响, 相比而言, 环割对花花柴的影响更为持久。对于单个植株而言, 机械损伤对花花柴的破坏损伤更为显著。(4)在环割对花花柴和骆驼刺光合速率的影响中, 存在着依赖于碳水化合物(carbohydrate-dependent)的机制。     

塔克拉玛干沙漠南缘9种禾本科牧草光系统Ⅱ特性

以新疆塔克拉玛干沙漠南缘策勒绿洲边缘广泛种植的中间偃麦草、新燕麦、无芒雀麦、老芒麦、天山赖草、披碱草、矮生高羊茅、冰草和碱茅等9种牧草为试验对象,测定暗适应20 min后牧草叶片的快速叶绿素荧光诱导曲线,比较光系统Ⅱ(PSⅡ)的特性,分析各牧草对本地区环境的适应能力.结果表明： 天山赖草和披碱草的最大荧光(F_m)、PSⅡ最大光化学效率(F_v/F_m)和单位面积反应中心的数量(RC/CS_o)的值均显著高于矮生高羊茅、冰草和碱茅,而初始荧光(F_o)、单位反应中心吸收的光能(ABC/RC)、单位反应中心捕获的能量(TR_o/RC)、单位反应中心耗散的能量(DI_o/RC)、荧光诱导曲线初始斜率(M_o)值则低于矮生高羊茅、冰草和碱茅;中间偃麦草、新燕麦、无芒雀麦和老芒麦的各值处于中间水平.9种牧草均受到恶劣气候条件的不同程度胁迫,PSⅡ反应中心的活性及电子传递受到抑制,其中,天山赖草和披碱草受到的影响较小,而矮生高羊茅、冰草和碱茅的PSⅡ结构和功能受到比较严重的影响,光合作用受抑制的程度较大.     

樟树幼苗机械损伤叶片对挥发性有机化合物及叶绿素荧光参数的影响

为探讨植物在机械损伤后C₆-C₁₀醛类化合物的释放机理, 及C₆-C₁₀醛类化合物对叶片光系统II (PSII)的影响, 以樟树(Cinnamomum camphora)为材料, 采用动态顶空气体循环法和热脱附/气相色谱/质谱联用技术(TDS-GC-MS), 对樟树幼苗叶片损伤后释放的C₆-C₁₀醛类化合物进行采集与分析, 并同步测定了脂氧合酶活性和损伤叶片的叶绿素荧光动力学参数。结果表明: 樟树幼苗叶片损伤后, 其挥发性有机化合物中己醛、庚醛、辛醛、壬醛和癸醛的释放量比损伤前分别增加了2.47、0.99、1.34、0.91和28.38倍(p < 0.01); 同时新增4种醛类化合物, 分别是: 2-己烯醛、2,4-己二烯醛、(E)-2-辛烯醛和(E)-2-壬烯醛。脂氧合酶活性比损伤前增加1.2倍(p < 0.01)。PSII单位反应中心复合体吸收的能量和被核心捕获的能量分别比损伤前下降12.8%和9.8% (p < 0.01)。单位面积反应中心的数量、电子传递量子产额、捕获激子能导致电子传递效率和叶片性能指数分别比损伤前增加23.3%、24.4%、22.6%和82.7% (p < 0.01)。损伤24 h后, 醛类化合物的种类、释放量、脂氧合酶活性及叶片叶绿素荧光动力学参数基本恢复到损伤前水平。说明机械损伤使PSII供体侧受损、脂氧合酶活性升高, 致使C₆-C₁₀醛类化合物大量释放, 樟树幼苗通过增加单位面积反应中心的数量来提高光合效率应对胁迫。     

深圳7种园林植物叶绿素荧光特性及其对大气SO2浓度的响应

叶绿素荧光信号能快速灵敏地反映植物生理状态及其与环境的关系,是一种理想光系统探针。测定了深圳市7种园林植物叶片的叶绿素荧光参数和叶绿素含量,并对这些生理参数与大气污染物SO₂的相关性进行了分析。结果表明,7种植物叶片的叶绿素含量具有明显的种间差别,生境的差别远小于种间差别。所测定的7种园林植物的F_v/F_m相差不大,平均为0.78,低于理想条件下的最大值,说明存在一定的生长胁迫。叶绿素荧光的光化学淬灭qP的种间差别不明显。非光化学猝灭系数qN的种类差别较大,白兰Michelia alba和短穗鱼尾葵Caryota mitis具有较高的非光化学淬灭能力,说明这两个种具有一定的光保护能力。7种植物中,白兰的ΦpsⅡ要明显地较低于其它植物。深圳大气污染对城区植物的生理生化特性尚未构成不良影响,在深圳市区的环境中,短穗鱼尾葵、勒杜鹃Bougainvillea spectabilis和阴香Cinnamomum burmanii的叶绿素荧光参数可以作为大气污染物的指示指标;大红花Hibiscus rosa-sinensis、九里香Murraga paniculata、白兰和黄叶假连翘Duranta cv Golden Leaves具有相对较高抗污染物的能力。植物的叶绿素荧光参数也在一定程度上受到叶绿素的影响,阴香、短穗鱼尾葵、大红花和九里香的部分叶绿素荧光参数与植物叶片叶绿素含量呈正相关。     

微藻叶绿素荧光值与传统生长指标的关联性研究

利用TD-700型叶绿素荧光仪测定了6种不同海洋和淡水微藻,即锥状斯氏藻(Scrippsiella trochoidea)、球形棕囊藻(Phaeocystis globosa)、三角褐指藻(Phaeodactylum tricornutum)、眼点拟微绿球藻(Nannochloropsis oculata)、四列藻(Tetraselmis tetrethele)和雨生红球藻(Haematococcus pluvialis)的叶绿素荧光值,同时采用经典方法同步测定其细胞密度和叶绿素a含量。统计分析结果显示,微藻细胞密度、叶绿素a含量、叶绿素荧光值三者之间具有显著或极显著的正相关关系。因此,利用叶绿素荧光仪测定微藻生物量的方法是切实可行的,具有快捷方便、灵敏度高的优点。     

铝胁迫对蓼科植物生长和光合、蒸腾特性的影响

采用水培试验,设置5种铝处理浓度,研究了铝对3种蓼科植物酸模叶蓼、杠板归和辣蓼叶片光合、蒸腾和叶绿素荧光参数的影响。结果表明,高铝处理(400μmol.L-1)显著抑制3种蓼科植物地上部和根系生长,并且导致3种蓼科植物叶片叶绿素含量、Chla/Chlb、净光合速率(Pn)、水分利用效率(WUE)、PSII光合电子传递量子效率(φPSII)和光化学猝灭系数(qP)显著下降。中低铝处理(25~100μmol.L-1)时,与对照相比,酸模叶蓼生物量显著增加,杠板归显著减少,辣蓼先增加后减少。其中,酸模叶蓼和辣蓼叶绿素含量、Chla/Chlb、Pn、蒸腾速率(Tr)、胞间CO2浓度(Ci)、PSII最大光化学效率(Fv/Fm)、qP均未发生显著变化,但辣蓼WUE、φPSII和非光化学猝灭系数(NPQ)显著下降,酸模叶蓼无显著变化;而杠板归除Ci、Fv/Fm外,其余叶片光合、蒸腾及叶绿素荧光参数均出现显著下降。上述结果表明,酸模叶蓼在中低铝处理条件下可通过保持较高的叶绿素含量、Chla/Chlb、WUE、Pn、PSII反应中心光化学反应效率以及提高非辐射能量耗散来增强其对铝的耐性。     

具放氧活性的光系统Ⅱ核心复合物的光谱特性和叶绿素蛋白质成分的研究

我们从菠菜叶片分离出一种具有高放氧活性的光系统Ⅱ(PSII)核心复台物.我们对这种PSII核心复合物进行了PSII光化学活性、吸收、荧光光谱特性和叶绿素蛋白质成分的研究.这种PSII核心复合物是一种不含PSI成分,又除去了LHC-Ⅱ的较纯,较小的具有高放氧活性(?)的单位.在文中对PSII反应中心叶绿素的吸收成分和CPa带进行了一些讨论.     

不同光强下高锰对黄瓜光合作用特性的影响

采用营养液培养的方法,研究了不同光强下高锰对黄瓜植株生长、叶绿素含量、叶绿素荧光参数和光合作用的影响.结果表明,高锰处理抑制了黄瓜植株的生长,与弱光处理相比强光下抑制幅度更加显著.强光下,高锰处理显著降低叶绿素含量,但降低光强却增加其含量.强光下,高锰处理显著降低原初光能转换效率(F_v/F_m)、光合电子传递量子效率(ΦPSII)和光化学猝灭系数(qP);弱光下,高锰处理对F_v/F_m和qP无显著影响.高锰处理使净光合速率(P_n)和气孔导度(G_s)下降.尤其是在强光下下降幅度更大.高锰处理使细胞间CO₂浓度(C_i)在强光下升高,而在弱光下则下降.与C_i相反,高锰处理使气孔限制值(L_s)在强光下下降,而在弱光下上升.因此,强光下高锰胁迫使净光合速率下降可能是由非气孔限制引起的,而弱光下高锰处理使净光合速率下降可能是由气孔因子限制引起的.     

不同培养基对发菜细胞生长和光合活性的影响

研究测定了发菜(NostocflagelliformeBorn.etFlah.)细胞在不同培养基中的生长速率、光合作用和叶绿素荧光活性。结果显示培养11d后:Detmer培养基中叶绿素a的含量为1.08mg/L,Kratz-Myers培养基中叶绿素a的含量为1.87mg/L,水生104号培养基中叶绿素a的含量为1.21mg/L,BG11培养基中叶绿素a的含量为2.18mg/L,表明在BG11培养基中培养的细胞具有最高生长速率;与另外4种不同浓度的BG11培养基相比,上述BG11培养基培养的发菜具有最大的光合速率Pm(218.1μmolO2.mg-1chla.h-1)和最高的PSII光化学效率(Fv/Fm=0.349)。实验结果表明,BG11是适合发菜生长的培养基,对其光合作用和叶绿素荧光活性具有显著促进作用。     

青藏高原春小麦叶片光合作用的光抑制及PSII反应中心光化学效率的恢复分析

在青海省都兰县香日德镇东盛村, 以中国科学院西北高原生物研究所培育的春小麦(Triticum aestivum)品种为材料, 主要采用调制叶绿素荧光分析手段, 研究了抽穗期旗叶光合作用的光抑制现象, 并分析了非光化学猝灭组分的光诱导和非光诱导耗散的量子产量变化。结果表明, 高原春小麦各品种间旗叶光合色素含量和比叶重存在差异; 全晴天3个典型时段准确暗适应20 min后的PSII最大光化学效率(F_v/F_m)的比较分析证实, 高原春小麦存在着光合作用的光抑制现象, F_v/F_m的降低是由于PSII反应中心的可逆失活; 稳态作用光下PSII有效光化学效率(F_v′/F_m′)易受持续强光胁迫的影响, 而PSII实际光化学效率(Φ_PSII)在各春小麦品种间的差异略为明显; 上下午间4个春小麦品种的光化学猝灭系数(q_P)和非光化学猝灭系数(NPQ)呈较一致的变化趋势, 显然q_P和NPQ既属品种的内禀特性, 又与强太阳光胁迫的累积密切相关; 非光化学猝灭组分中光诱导的PSII调节性能量耗散的量子产量(Φ_NPQ)所占比例较大, 下午时分Φ_NPQ的上调反映了高原春小麦对青藏高原持续强光胁迫的驯化适应。     

氮调控对盐环境下甜菜功能叶光系统Ⅱ荧光特性的影响

采用盆栽试验方法,以NaCl为盐分模拟不同盐度环境,研究了施氮(N)对盐环境下生长的甜菜(Beta vulgaris)功能叶光系统Ⅱ (PSⅡ)荧光特性的影响及光合色素含量的变化.结果表明:在轻度、中度及重度盐环境下,施N均能增大PSⅡ最大光化学效率(Fv/Fm)、PSⅡ潜在活性(Fv/Fo)、PSⅡ实际光量子产量(Y(Ⅱ))、非调节性能量耗散的量子产量(Y(NO))、相对电子传递速率(ETR)及光化学猝灭系数(qp),且在适宜的施N范围内(0-1.2 g·kg-1)上述参数随施N量的增加而增大.各叶绿素荧光参数光响应的结果表明,随着光强的增加,各处理下调节性能量耗散的量子产量(KNPQ))、ETR及非光化学猝灭系数(NPQ)旱上升趋势,相反,Y(Ⅱ)、Y(NO)及qp则呈下降趋势,在有效的光强范围内(0-1 000 μmol·m-2·s-1)施N提高了甜菜功能叶PSⅡ反应中心的开放程度,并且在高光强下调节PSⅡ耗散掉过剩的光能以避免对其反应中心造成伤害.各盐度环境下施N也显著增加了甜菜功能叶叶绿素与类胡萝卜素含量,增大了叶绿素a/叶绿素b值,且叶绿素与类胡萝卜素含量随施N水平的增加而增加.说明盐环境下施N能够增强甜菜功能叶PSⅡ的活性,提高PSⅡ光能利用率,从而增强其对盐渍环境的适应性.     

Growth,fluorescence, photosynthetic O<Subscript>2</Subscript> production and pigment content of salt adapted cultures of <Emphasis Type="Italic">Arthrospira</Emphasis> (<Emphasis Type="Italic">Spirulina</Emphasis>) <Emphasis Type="Italic">platensis</Emphasis>

The effect of salt concentration (NaCl) on growth, fluorescence, photosynthetic activities and pigment content of the cyanobacterium Arthrospira platensis has been investigated over 15 days. It has been observed that high NaCl concentration induces an increase of the growth, photosynthetic efficiency (α), phycobilin/chlorophyll ratio and a slight decrease of dark respiration and compensation points. Moreover, high NaCl concentration enhances photosystem II (PSII) activity compared to photosystem I (PSI). Results show that the phycobilin-PSII energy transfer compared to the chlorophyll-PSII (F_695,600/F_695,440) increases. However, data obtained about the maximal efficiency of PSII photochemistry are controversial. Indeed, the Fv/Fm ratio decreases in salt adapted cultures, while at the same time the trapping flux per PSII reaction center (TR₀/RC) and the probability of electron transport beyond Q_A (₀) remain unchanged at the level of the donor and the acceptor sites of PSII. This effect can be attributed to the interference of phycobilin fluorescence with Chl a when performing polyphasic transient measurements.     

田间条件下棉花幼叶光合特性及光保护机制

通过比较棉花(Gossypium hirsutum)幼叶和完全展开叶气体交换参数及叶绿素荧光特性的差异, 探讨高光强下幼叶的光抑制程度及明确光保护机制间的协调机理。在田间自然条件下, 以棉花刚展平的幼嫩叶片(幼叶)和面积已达到最大的完全展开叶片为研究对象, 通过测定不同发育阶段叶片气体交换参数及叶绿素a荧光参数的变化, 并运用Dual-PAM100对不同发育阶段的叶片进行快速光响应曲线的拟合。结果表明: 幼叶和完全展开叶片在光合、荧光特性方面表现出明显的差异。与完全展开叶相比, 较低的叶绿素(Chl)含量和气孔导度(G_s)是幼叶较低净光合速率(P_n)的限制因素, 从而直接导致其光系统II (PSII)实际光化学效率(Φ_PSII)和光化学猝灭系数(q_P)的降低。在1800 μmol·m^-2·s^-1光强以下, 完全展开叶具有较强的围绕PSI循环的电子流(CEF), 有利于合成ATP, 是其具有较高光合能力的原因之一。相同光强下, 幼叶较低的光饱和点(LSP)更易受光抑制, 但其PSII原初光化学效率(F_v/F_m)的日变化幅度显著小于完全展开叶, 说明强光下幼叶通过类胡萝卜素(Car)猝灭单线态氧、光呼吸(P_r)、热耗散(NPQ)以及PSI-CEF等光保护机制能有效地耗散过剩的光能, 从而避免其光合机构发生光抑制。     

Water stress induces different levels of photosynthesis and electron transport rate regulation in grapevines

A, net CO₂ assimilation rate
E, leaf transpiration
ETR, electron transport rate
F_s, fluorescence yield at steady state
F_m and F_m', maximal fluorescence levels when all PSII reaction centres are closed in dark- and light-acclimated leaves, respectively
F_o and F_o', initial fluorescence levels when all PSII reaction centres are closed in dark- and light-acclimated leaves, respectively
F_v/F_m, efficiency of excitation capture by open PSII in dark-adapted leaves
ΔF/F_m', actual photochemical efficiency of PSII
g, stomatal conductance
NPQ, non-photochemical quenching of chlorophyll fluorescence
PPFD, photosynthetic photon flux density
Ψ_PD and Ψ_MD, leaf water potential at pre-dawn and midday, respectively
Rl, estimated photorespiration rate
I₁ and I₂, Irrigation treatments
R, Recovery treatment
D₁ and D₂, drought treatments
HD₁ and HD₂, hard drought treatments

Diurnal time courses of chlorophyll fluorescence and gas-exchange rates were measured in young potted grapevines (Vitis vinifera L. cv. Tempranillo) subjected to different conditions of water supply under Mediterranean summer conditions. The irrigated plants exhibited typical diurnal patterns for all measured parameters, showing a correspondence between electron transport rate, net CO₂ assimilation and stomatal conductance. Mild decreases in soil-water availability led to different degrees of down-regulation of photosynthesis and increased nonphotochemical quenching of chlorophyll fluorescence. A good correspondence between electron transport rate and CO₂ assimilation was still maintained, suggesting a coregulation of both photosynthetic processes. In contrast, a severe water deficit induced a drastic down-regulation of photosynthesis and breakage of the above-mentioned link. Both midday net CO₂ assimilation and electron transport rate significantly correlated with pre-dawn water potential (Ψ_PD) (r² = 0·65 and r² = 0·92, P < 0·001, respectively). However, when field data were analysed, the relationship between electron transport rate and Ψ_PD was not maintained, although net CO₂ assimilation was similarly correlated with Ψ_PD. Interestingly, the steady-state chlorophyll fluorescence yield was a good indicator of plant water stress.     

Ozone sensitivity in herbaceous species as assessed by direct and modulated chlorophyll fluorescence techniques

Seven plant species were exposed in open-top chambers to four levels of ozone (O₃) during two growing seasons and screened for treatment effects on the fast chlorophylla(Chl) fluorescence transient kinetics of dark-adapted leaves, and on the fluorescence signals obtained from the same leaves in illuminated steady-state. The aim was to identify the nature of O₃ effects on PSII, and to determine inter-specific differences. In dark-adapted leaves, O₃ caused a reduction in variable fluorescence (F_V : F₀), indicating an overall reduction in the efficiency of primary photochemistry. A large increase in excitation energy dissipation per active reaction centre (DI₀/RC) and a smaller increase in the trapping rate of excitons (TR₀/RC), showed that a fraction of the reaction centres was inactivated while the rest sustained full functionality. The magnitude of the effect increased in the order ofBromus erectusCentaurea jacea Trisetum flavescens Rumex obtusifolius Plantago lanceolataTrifolium pratense Knautia arvensis. The inter-specific variability in PSII responses could not be explained solely by specific differences in modelled O₃ uptake by the leaves. Visible leaf injury was not related to changes in fluorescence emission. In illuminated steady-state, O₃ sensitivity was most expressed in the change in quantum yield of photosynthetic electron transport (Φ_PSII). The ranking of species differed from the ranking obtained in dark-adapted leaves. These results suggest that the mechanistic basis for O₃ effects on PSII is similar in all species, but that inter-specific differences exist in the magnitude of change which cannot be explained solely by different O₃ uptake rates. The observed changes in fluorescence signals are not O₃-specific.     

Effects of salt stress on photosystem II efficiency and CO2 assimilation of two Syrian barley landraces

The photosynthetic activity of two Syrian barley landraces, Arabi (A.) Aswad and A. Abiad, grown under 120 mM NaCl, was studied, using gas exchange and chlorophyll (Chl) a fluorescence transient (OJIP) measurements. Salt treatment of barley seedlings decreased both the rates of photosynthesis and photosystem II (PSII) activity, as evaluated from chlorophyll fluorescence data. However, the noted decrease was dependent on the duration of the salt treatment and the barley cultivar. Several parameters (e.g., light absorption flux per cross section of leaf; time to reach maximum chlorophyll a fluorescence intensity; plastoquinone pool size; yield of heat loss; rate of reaction center closure; and the so-called Performance Index), calculated and inferred from Chl fluorescence measurements, and related to PSII activity, were affected after 24 h of salt application, but these changes were much more pronounced after 7 days of salt treatment. Similar changes were found for measured gas exchange parameters: CO₂ uptake (photosynthetic) rate and stomatal conductance. The photosynthetic apparatus of the cultivar variety (c.v.) Arabi Aswad was found to be much more tolerant to salt treatment, compared with c.v. Arabi Abiad. After 7 days of salt treatment, the latter showed a very high value of the initial (minimal) fluorescence (F_o) and then essentially almost flat fluorescence transient curve; this result may be due to several causes that include structural changes as well as changes in the rate constants of different dissipative processes. The parameters that were most affected, by salt treatment, were: the time needed to reach the maximal chlorophyll fluorescence (F_m), and the inferred oxygen evolving complex activity (F_v/F_o, where F_v, is F_m − F_o), and the calculated Performance Index (PI_ABS) that depends on the efficiency and the yield of energy transfer and primary photochemistry. We suggest that the early reactions of the photosynthetic apparatus of barley plants could play a key role in their tolerance to salt stress. Further, we found that the first stage of salinity effect on photosynthesis of barley plants is related to stomatal conductance limitation rather than to PSII activity reduction. Thus, on the basis of our results on the two barley landraces, we recommend the use of a combination of gas exchange measurements along with the analysis of the OJIP fluorescence transient for the detection of salt stress-induced changes in plants.     

The acceptor side of photosystem II is damaged more severely than the donor side of photosystem II in ‘Honeycrisp’ apple leaves with zonal chlorosis

To investigate the photoinhibition of photosynthesis in ‘Honeycrisp’ apple (Malus domestica Borkh. cv. Gala) leaves with zonal chlorosis, we compared pigments, CO₂ assimilation and chlorophyll (Chl) a fluorescence (OJIP) transient between chlorotic leaves and normal ones. Chl and carotenoids (Car) contents, Chl a/b ratio, and absorptance were lower in chlorotic leaves than in normal ones, whereas Car/Chl ratio was higher in the former. Although CO₂ assimilation and stomatal conductance were lower in chlorotic leaves, intercellular CO₂ concentration did not differ significantly between the two leaf types. Compared with normal leaves, chlorotic ones had increased deactivation of oxygen-evolving complexes (OEC), minimum fluorescence (F _o), dissipated energy, relative variable fluorescence at L-, W-, J- and I-steps, and decreased maximum fluorescence (F _m), maximum quantum yield for primary photochemistry (F _v /F _m or TR_o/ABS), quantum yield for electron transport (ET_o/ABS), quantum yield for the reduction of end acceptors of photosystem I (PSI) (φ_Ro and RE_o/ABS), maximum amplitude of IP phase, amount of active photosystem II (PSII) reaction centers (RCs) per cross section (CS) and total performance index (PI_tot,abs). In conclusion, photoinhibition occurs at both the donor (i.e., the OEC) and the acceptor sides of PSII in chlorotic leaves. The acceptor side is damaged more severely than the donor side, which possibly is the consequence of over-reduction of PSII due to the slowdown of Calvin cycle. In addition to decreasing light absorptance by lowering Chl level, energy dissipation is enhanced to protect chlorotic leaves from photo-oxidative damage.     

Physiological and growth characteristics of Ginkgo biloba L. exposed to open field and shade enclosure during the reproductive stage

The current study compares responses to open field and shade enclosure condition (plastic shading nets were used to imitate a natural shading rate) to test the possible benefit of shading in terms of physiological and growth characteristics in Ginkgo biloba L. during the reproductive stage in summer. Compared with the net shade treated plants (NS-plants), the open-field plants (O-plants) contained lower chlorophyll (Chl) a + b content and Chl a/b ratio, and exhibited a decreased ratio of Chl/Car. Results showed that the chlorophyll fluorescence characteristics including maximum PSII photochemical efficiency (F _v /F _m ), potential electron transport per excited leaf cross-section (ET₀/CS₀), potential electron transport per PSII reaction center (ET₀/RC), dissipation per excited leaf cross-section (DI₀/CS₀), dissipation per PSII reaction center (DI₀/RC), and overall performance index of PSII photochemistry on absorbtion basis (PI_ABS) were altered by the net shade treatment. It was observed that the grana were illegible and difficult to distinguish by transmission electron microscopy, especially, in the cells of O-plants in which phenols were observed in the vacuole. The phenomenon of photoinhibition induced by excessive irradiance was confirmed by the abnormally high levels of the reactive oxygen species. Moreover, antioxidant enzymes activities were induced by high irradiance in the ginkgo leaves. In addition, significant differences were observed in the fresh weight and dry weight of leaves and seeds. Comparison of the variation of underlying physiological and biochemical mechanisms suggested that there was a better efficiency of ginkgo plants under artificial net shade conditions. Therefore, ginkgo plant would be best grown at 30–35 % of natural irradiance in summer months to be more profitably harvested and then meet the increasing demand of leaves and seeds.