基于叶绿素荧光成像及荧光参数分布特征的叶片光合异质性定量分析

植物叶片光合作用具有高度的空间异质性,叶绿素荧光成像技术为叶片光合异质性的研究提供了便利,但叶片光合异质性的定量分析并没有得到广泛应用。本文利用Imaging PAM叶绿素荧光成像系统,获得中亚热带地区越冬期小叶榕(Ficus microcarpa)阳生叶和阴生叶的叶绿素荧光参数图像,并利用仪器的分析软件对其进行分析,定量比较了阳生叶和阴生叶的光合异质性特征。研究发现：越冬期小叶榕阳生叶的光合异质性和光抑制程度明显高于阴生叶,变异系数可作为光合异质性的定量指标。低温强光导致阳生叶坏死率(P_LN)达4.30%,并有53.30%的区域处于严重光抑制(0v/F_m<0.627),但仍有42.27%的区域仅为轻度光抑制(0.627≤F_v/F_m<0.800)。而低温弱光并未造成阴生叶坏死和严重光抑制。通过对光系统Ⅱ(PSⅡ)的实际光合效率(Y(Ⅱ))、调节性能量耗散的量子产额(Y(NPQ))和非调节性能量耗散的量子产额(Y(NO))荧光参数异质性的定量分析表明,阳生叶...     

Effects of shading on photosynthetic characteristics and chlorophyll fluorescence parameters in leaves of Hydrangea macrophylla

Aims The objectives were to investigate the effects of different light intensities on photosynthetic characteristics and chlorophyll fluorescence parameters, to clarify the physiological responses and photo-protective mechanisms of Hydrangea macrophylla to changes in light regimes in view of the distribution of energy absorbed and photosynthetic characteristics.Methods Three light regimes including natural and shade (shading rate 50% and 75% of natural light) were applied to plants for 60 days. After the treatment, the gas-exchange, chlorophyll a fluorescence and photosynthesis-light curves were measured by a portable leaf gas exchange system (LI-6400).Important findings The results showed that the weak light intensity treatment reduced dark respiration rate, light compensation point and light saturation point of plant, but increased apparent quantum yield, suggesting that plants had the physiological strategy to utilize the weakening light by reducing respiration. The net photosynthetic rate, intercellular CO₂ concentration, transpiration rate and water use efficiency of plants grown below 50% of natural light showed significant difference compared with natural and shading rate 75% of natural light. There were significant difference between natural and shade treatments in the maximal quantum efficiency of PSII (F_v/F_m), as indicated that it was significantly less at full light than that at 50% of natural light. Initial fluorescence intensity (F_o) of plants was higher at full light than that at 50% of natural light, suggesting that photoinhibition occurred in natural light. The non-photochemical quenching (NQP) decreased with the aggravation of shade stress, indicating that shading decreased the efficiency of photochemical reaction by reducing the fraction of incident light in photochemical energy utilization and decreased thermal dissipation through regulating energy distribution in photosystem II (PSII) in the leaves of Hydrangea macrophylla. In general, the 70% of incident light in photochemical energy utilization was distributed to thermal dissipation, 20% was distributed to non-regulated energy dissipation and 4% was distributed to effective photochemical reaction. In conclusion, responses of plants to increased irradiance are governed by strategy: to utilize a high fraction of incident light in photochemistry and regulate energy dissipation in PSII and weaken the accumulation of excess excitation energy in PSII to protect the photosynthetic apparatus in the leaves of H. macrophylla under saturated radiation.     

玉米花生间作和磷肥对间作花生光合特性及产量的影响

揭示玉米(Zea mays)和花生(Arachis hypogaea)间作提高花生对弱光利用能力的光合特点及磷(P)肥效应, 对阐明间作花生适应弱光的光合机理和提高间作花生的产量具有重要意义。该试验于2011-2012年在河南科技大学试验农场分析了间作花生功能叶的叶绿素含量与构成、光响应曲线和CO₂响应曲线特点和荧光参数。结果表明: 与单作花生相比, 施P与不施P条件下玉米和花生间作显著(p < 0.01)提高了花生功能叶的叶绿素b含量, 降低了叶绿素a/b, 显著提高了光系统II最大光化学效率(F_v/F_m)、实际光化学效率(Φ_PSII)、光化学猝灭系数(q_P)、表观量子效率(AQY)和弱光时的光合速率, 显著降低了气孔导度、二磷酸核酮糖羧化酶羧化速率(V_cmax)、电子传递速率(J_max)和磷酸丙糖利用速率(TPU); 与不施P相比, 施P有利于提高间作花生功能叶的叶绿素含量, 显著提高了Φ_PSII、q_P、V_cmax、J_max和TPU, 说明间作花生通过提高功能叶的叶绿素b含量, 改变叶绿素构成, 提高了光系统II的F_v/F_m、Φ_PSII和q_P, 增强了对光能的捕获和转化能力, 提高了对弱光的利用能力, 而并非提高了对CO₂的羧化固定能力; 施P有利于提高间作花生对弱光的利用能力和产量, 土地当量比提高了6.2%-9.3%。     

The irreversible photoinhibition of the photosystem II complex in leaves of Vicia faba under strong light

Exposure of the photosynthetic machinery to strong light causes the photoinhibition of the photosystem II complex. The recovery from the photoinhibition in vivo was characterized by monitoring the ratio of variable to maximum fluorescence (F_v/F_m) in detached leaves of broad bean (Vicia faba). The changes in the ratio were explained in terms of three components, namely, two saturating exponential components with half rise-times of about 15 and 120 min, respectively, and a non-recovery component. The non-recovery component increased gradually as the exposure to strong light was prolonged. Our results suggest that this irreversible component of the photoinhibition of the photosystem II complex was caused by severe stress due to strong light under which repair of the photosystem II complex was insufficient to allow full recovery. The irreversible photoinhibition is discussed in terms of both the physiology and ecology of plants.     

邻苯二甲酸二丁酯对绿色巴夫藻的生长毒性和干扰效应

采用批次培养的方法研究了邻苯二甲酸二丁酯(DBP)对绿色巴夫藻(Pavlova viridis)的生长毒性和干扰效应。实验设置了0 mg·L^-1、2.5 mg·L^-1、3.0 mg·L^-1、3.5 mg·L^-1、4.0 mg·L^-1、5.0 mg·L^-1和7.5 mg·L^-1 共7个质量浓度梯度的DBP暴露处理组,测定了绿色巴夫藻的细胞密度、光合色素含量、叶绿素荧光特性及丙二醛(MDA)含量等指标,试图揭示DBP对绿色巴夫藻的生态毒性影响规律及机制。结果表明:DBP暴露对绿色巴夫藻的生长具有显著抑制作用,高质量浓度(5.0 mg·L^-1和7.5 mg·L^-1)DBP暴露下绿色巴夫藻细胞10 d内全部死亡;随着DBP暴露质量浓度增加,藻细胞叶绿素a和类胡萝卜素含量均显著降低;DBP暴露使光系统Ⅱ(PSⅡ)的最大光能转化效率(F_v/F_m)、潜在光化学活性(F_v/F_o)、实际光能转化效率(Yield)和光合电子传递速率(ETR)等指标也显著降低;DBP暴露还能够使绿色巴夫藻的细胞MDA含量显著增加。该研究进一步证实了DBP污染物对微藻光系统和酶类生理生化过程的干扰作用。     

光强对三七光合能力及能量分配的影响

通过研究生长于不同环境光强(29.8%、9.6%、5.0%、1.4%和0.2%全日照)下的2年生三七光合作用对光照强度、CO₂浓度、模拟光斑的响应及叶绿素荧光和能量分配特征,研究光照强度对阴生植物三七光合特征及光适应的影响.结果表明: 29.8%全日照(FL)下三七表观量子效率(AQY)、光系统Ⅱ(PSⅡ)潜在的量子效率(F_v/F_m)、PSⅡ潜在活性(F_v/F_o)较低,最大净光合速率(P_{n max})、最大电子传递速率(J_max)、实际光化学量子效率(F/F_m′)、电子传递速率(ETR)、光化学淬灭系数(q_P)和光能分配到光化学途径的比例(Φ_PSⅡ)较高,但非光化学淬灭系数(NPQ)并不是最高.9.6% FL和5.0% FL处理P_{n max}、光补偿点(LCP)、光饱和点(LSP)、暗呼吸速率(R_d)无显著差异,但它们的AQY、羧化效率(CE)、最大羧化速率(V_{c max})、F_v/F_m、F_v/F_o较高,NPQ也相对较高.生长环境光强低于5.0%FL时,P_{n max}、CE、V_{c max}、J_max、ETR、F/F_m′、q_P、NPQ和Φ_PSⅡ均随生长环境光强的降低呈下降趋势,而捕获的光能分配到荧光耗散的比例(Φ_f,D)逐渐增加.在500 μmol·m^-2·s^-1光斑诱导下,生长环境光强大于5.0%FL下的三七Φ_PSⅡ随诱导时间的延长缓慢增加,1.4%FL和0.2%FL下Φ_PSⅡ迅速达到饱和,且Φ_f,D迅速增加.三七在受到长期高光胁迫的环境下,通过适度的PSⅡ光抑制和保持较高光合电子传递速率,从而提高光能的利用来保护光合机构遭受不可修复的氧化伤害;适度的遮荫能够有效保持较高的非光化学热耗散能力;但过度遮荫会使其光合能力明显降低,捕获的光能更多地通过非光化学的途径耗散,且在接受到高光照射时较容易引发光氧化伤害.     

Photosynthetic responses of seven tropical seagrasses to elevated seawater temperature

This study uses chlorophyll a fluorescence to examine the effect of environmentally relevant (1–4 h) exposures of thermal stress (35–45 °C) on seagrass photosynthetic yield in seven tropical species of seagrasses. Acute response of each tropical seagrass species to thermal stress was characterised, and the capacity of each species to tolerate and recover from thermal stress was assessed. Two fundamental characteristics of heat stress were observed. The first effect was a decrease in photosynthetic yield (F_v / F_m) characterised by reductions in F and F_m′. The dramatic decline in F_v / F_m ratio, due to chronic inhibition of photosynthesis, indicates an intolerance of Halophila ovalis, Zostera capricorni and Syringodium isoetifolium to ecologically relevant exposures of thermal stress and structural alterations to the PhotoSystem II (PSII) reaction centres. The decline in F_m′ represents heat-induced photoinhibition related to closure of PSII reaction centres and chloroplast dysfunction. The key finding was that Cymodocea rotundata, Cymodocea serrulata, Halodule uninervis and Thalassia hemprichii were more tolerant to thermal stress than H. ovalis, Z. capricorni and S. isoetifolium. After 3 days of 4 h temperature treatments ranging from 25 to 40 °C, C. rotundata, C. serrulata and H. uninervis demonstrated a wide tolerance to temperature with no detrimental effect on F_v / F_m′ qN or qP responses. These three species are restricted to subtropical and tropical waters and their tolerance to seawater temperatures up to 40 °C is likely to be an adaptive response to high temperatures commonly occurring at low tides and peak solar irradiance. The results of temperature experiments suggest that the photosynthetic condition of all seagrass species tested are likely to suffer irreparable effects from short-term or episodic changes in seawater temperatures as high as 40–45 °C. Acute stress responses of seagrasses to elevated seawater temperatures are consistent with observed reductions in above-ground biomass during a recent El Niño event.     

Susceptibility of CAM Dendrobium leaves and flowers to high light and high temperature under natural tropical conditions

Responses of CAM Dendrobium Sonia leaves and flowers to high light and high temperature were studied in shade-grown plants after exposure to intermediate and full sunlight under natural conditions. Photosynthetic O₂ evolution decreased in leaves after exposure to full sunlight for 2 weeks while leaves exposed to intermediate sunlight showed an increase in photosynthesis as compared to those leaves maintained in the shade. On the first day of treatment, the changes of F_v/F_m in both leaves and petals grown in the shade were negligible during the day. However, there was a steep decrease in F_v/F_m in both leaves and petals with an increase in incident light during midday after exposure to full sunlight. When exposed to intermediate sunlight, there were no significant changes in F_v/F_m in leaves. The F_v/F_m values of petals, however, decreased during midday. Temperature of thin petals was higher than that of thick leaves during midday under full and intermediate sunlight while that of petals and leaves were similar when grown in the shade. Over the 2-week treatment period, lowered chlorophyll and sustained decreases in F_v/F_m were observed in both leaves and flowers (sepals and petals) when exposed to full sunlight, indicative of ‘chronic photoinhibition'. Photoinhibition was prevented in leaves but occurred in flowers when exposed to intermediate sunlight. It was assumed that photodamage to both leaves and flowers were partially due to the higher temperature. The higher susceptibility of flowers to high light as compared to that of leaves was due to its higher temperature during midday. This was further supported by the findings that more severe damage occurred in flowers at higher temperature of 38°C than 28°C under a higher PFD of 1500 μmol m⁻² s⁻¹.     

UV-B对设施桃叶片光合功能及叶绿体超微结构的影响

对温室栽培的油桃中油5号(Prunus persica var. nectarina cv.‘Zhongyou5’)适量补充UV-B,分析其对桃叶片光合功能及叶绿体超微结构的影响。结果表明,UV-B处理下各色素含量均有不同程度的增加,其中叶绿素b的含量和净光合速率(P_n)提升幅度较大。相较于未补充UV-B的桃树(对照), UV-B处理的F_v/F_m无显著变化, F_v’/F_m’比值、光化学猝灭系数(qP)、非光化学猝灭系数(qN)以及PSII实际光化学量子效率(Φ_PSII)均有显著或极显著升高。透射电镜结果显示,UV-B处理下叶绿体基质片层空隙小,堆叠紧密,叶绿体外膜边缘清晰。可见,温室内适量补充UV-B可快速改善叶片叶绿体的超微结构,提升叶绿素分子捕获光能及向PSII传递的能力,增大PSII反应中心的开放程度,提高实际光能转化效率和PSII电子传递量子效率,提高叶片的光合功能。该研究为设施果树光合性能改善和UV-B合理利用提供了理论依据。     

枸杞岛海藻场6种大型海藻光合荧光特性比较

海藻光合荧光特性研究对分析藻类光合作用和固碳能力具有重要的作用.利用水下调制荧光仪(DIVING-PAM)测定了枸杞岛后头湾夏季常见6种大型海藻孔石莼、斯氏刚毛藻、舌状蜈蚣藻、鼠尾藻、多管藻和羊栖菜的量子产量、快速光曲线(RLC)相关参数.结果显示: 6种常见海藻孔石莼、斯氏刚毛藻、舌状蜈蚣藻、鼠尾藻、多管藻和羊栖菜最大量子产量(F_v/F_m)分别为0.702、0.704、0.457、0.618、0.421、0.567,各物种的开放PSⅡ反应中心原初光能捕获效率(F_v′/F_m′)的大小依次是斯氏刚毛藻>孔石莼>鼠尾藻>羊栖菜>舌状蜈蚣藻>多管藻,且孔石莼、斯氏刚毛藻、羊栖菜的F_v′/F_m′与其他5种大型海藻的差异均达到显著水平;在快速光响应曲线中,羊栖菜、鼠尾藻和孔石莼的最大相对电子传递速率与初始斜率α较高,证明其具有较强的光合能力和捕光能力;舌状蜈蚣藻较高的RLC初始斜率α和较低的I_k表明其有较强的耐弱光能力.3种门类大型海藻之间光合特性有较为显著的差异,其中褐藻门的羊栖菜、鼠尾藻与绿藻门的孔石莼拥有极高的光合活性和抗强光能力,研究结果可为藻场保护工作和大型海藻固碳能力评估提供理论依据.     

Green plastids, maximal PSII photochemical efficiency and starch content of inner stem tissues of three Mediterranean woody species during the year

Wood and pith of 1–2-year-old stems of three woody species with different life strategies common in the Mediterranean basin were studied during the year regarding (i) the occurrence of green plastids, (ii) their maximal photosystem II photochemical efficiency (F_v/F_m) and (iii) their starch content. Green plastids were identified from the red chlorophyll auto-fluorescence under epi-fluorescence microscope, F_v/F_m was estimated using imaging-PAM fluorometry and starch content was recorded under bright field microscope after iodine staining. The evergreen sclerophyll Nerium oleander, the summer deciduous Euphorbia acanthothamnos and the winter deciduous species Platanus orientalis were selected for the study.

Epi-fluorescence microscopy revealed that (i) all species possess abundant green plastids in their wood ray and pith cells throughout the year. In the winter deciduous species chlorophyll fluorescence was found to be strong during the leafless period. By contrast, in the evergreen and the summer deciduous species chlorophyll fluorescence was found uniformly bright during the year; (ii) F_v/F_m value variation during the year seems to be species-specific: in the wood of N. oleander it remains unchanged whereas in the pith it is low during spring–summer; in both tissues of E. acanthothamnos F_v/F_m value reaches maximal value during spring and in P. orientalis during autumn; (iii) in N. oleander and E. acanthothamnos starch is accumulated during spring, whereas in P. orientalis starch content is high during winter.

The scanning electron microscopy (SEM) investigation revealed that the stem epidermis of all three species lacks stomata and formation of lenticels is delayed. Provided that gas exchange is therefore minimized and that PSII photochemical efficiency of inner stem tissues is relatively high, it is further supported that green plastids of wood ray and pith cells may help toward the re-fixation of the internally respired CO₂.     

乡土风箱果和紫叶风箱果叶片光合特性对土壤干旱的响应

研究叶片光合气体交换参数和叶绿素荧光参数对土壤干旱的响应,分析濒危的乡土风箱果和引种紫叶风箱果的抗旱能力及其差异.结果表明: 土壤干旱第7天时,紫叶风箱果叶片明显失水萎蔫,而乡土风箱果却有较高的叶片含水率和水分利用效率.土壤干旱降低了2种风箱果叶片的净光合速率、气孔导度和蒸腾速率,紫叶风箱果降低幅度明显大于乡土风箱果.土壤干旱7 d时,紫叶风箱果叶片的胞间CO₂浓度(C_i)高于未干旱处理,而乡土风箱果C_i低于未干旱处理.乡土风箱果叶片的电子传递速率(ETR)和光化学淬灭系数(q_P)明显降低,而PSⅡ反应中心光能捕获效率(F_v′/F_m′)没有发生明显变化;但是紫叶风箱果叶片的F_v′/F_m′、ETR和q_P均明显降低,并且其降低幅度大于乡土风箱果.土壤干旱7 d时,乡土风箱果叶片OJIP曲线上J点的相对可变荧光(V_J)没有发生明显变化,而紫叶风箱果叶片V_J明显增加.紫叶风箱果的叶片碳同化能力和PSⅡ功能对土壤干旱的敏感性明显大于乡土风箱果,土壤干旱降低乡土风箱果光合能力的原因以气孔因素限制为主,而紫叶风箱果以非气孔因素限制为主.     

Effects of wind erosion and sand burial on water relations and photosynthesis in Alhagi sparsifolia in the southern edge of the Taklimakan Desert

塔克拉玛干沙漠南缘风沙活动十分频繁, 风蚀和沙埋是该地区自然植被生长发育的重要影响因子。该文以塔克拉玛干沙漠南缘策勒绿洲-沙漠过渡带为研究区, 以该区域主要建群种植物骆驼刺(Alhagi sparsifolia)为研究对象, 对一次强沙尘天气过后沙丘表面5种不同风蚀沙埋状况的骆驼刺植物进行标定(包括10 cm风蚀、5 cm风蚀、不蚀不积、10 cm沙埋、30 cm沙埋), 天晴后测定其叶水势、叶片含水量、光合参数和叶绿素荧光等参数, 分析研究自然环境条件下风蚀和沙埋对骆驼刺水分和光合作用的影响。结果表明: (1)风蚀显著降低了骆驼刺叶水势和叶片含水量, 进而导致植物气孔导度降低, 并引起植物光合速率和蒸腾速率的下降。风蚀的植物水分利用效率低于沙埋, 特别是在10 cm风蚀深度明显降低。 (2)沙埋增加了骆驼刺的叶水势、叶片含水量和气孔导度, 并引起植物光合速率和蒸腾速率的上升, 水分利用效率也得到提升。(3)风蚀条件下骆驼刺所受胁迫增加, 但可以通过增加活性反应中心的数量和光化学效率来抵消胁迫造成的不利影响。沙埋条件下骆驼刺受胁迫减轻, 反应中心吸收的光能和用于光化学反应的能量随着沙埋程度增加而减小, 这是骆驼刺适应风沙环境的一种生存策略。(4)与5 cm风蚀以及10 cm沙埋相比, 10 cm风蚀显著抑制骆驼刺的生长, 30 cm沙埋则会显著促进骆驼刺的生长。     

苗期干旱及复水条件下不同花生品种的光合特性

为探索不同花生(Arachis hypogaea)品种的旱后恢复能力, 研究花生品种耐旱性与光合特性的关系, 通过盆栽土壤水分控制实验, 测定了12个花生品种苗期对干旱胁迫与复水过程的光合响应特征, 并讨论了所测各性状参数与抗旱性强弱的关系, 包括对水分胁迫伤害的修复能力。结果表明, 根据苗期生物量抗旱系数, ‘山花11号’、‘如皋西洋生’、‘A596’、‘山花9号’、‘农大818’的抗旱性较强, 且复水后植株产生超补偿生长效应, 补偿生长能力与抗旱性呈极显著正相关。叶片净光合速率(P_n)、气孔导度(G_s)、胞间CO₂浓度(C_i)、最大光化学效率(F_v/F_m)、实际光化学效率(Φ_PSII)、光化学猝灭系数(q_P)随干旱进程逐渐降低, 复水后逐渐增加, 抗旱性强的花生品种变幅较小。干旱7天, 大多数花生品种的光合参数值未有显著性差异。干旱14天, 抗旱性越强的花生品种光合参数值越高, 不同抗旱性花生品种的光合参数值有显著差异。‘山花11号’、‘如皋西洋生’、‘A596’、‘山花9号’的P_n、G_s、Φ_PSII、F_v/F_m、q_P在复水5天时恢复至对照水平, 复水10天时超过对照, ‘79266’、‘ICG6848’、 ‘白沙1016’、‘花17’在复水10天时仍未达到对照水平, 复水过程中抗旱性强的品种的光合参数显著高于抗旱性弱的品种。相关分析表明, 干旱胁迫14天和复水5天后, 花生的P_n、Φ_PSII、F_v/F_m、q_P与品种抗旱性呈极显著正相关。因此, 可在苗期用40%土壤相对含水量胁迫14天及复水5天时花生的P_n、Φ_PSII、F_v/F_m、q_P鉴定品种的干旱伤害程度及修复能力, ‘山花11号’可作为强干旱适应性鉴定的标准品种。     

遮阴对闽楠叶绿素含量和光合特性的影响

为探讨闽楠对不同光环境的光合适应机制,以2年生闽楠幼苗为材料,设置3个光照处理(全光照、遮光率50%和遮光率78%),适应6个月后,测定其叶绿素含量、气体交换和叶绿素荧光同步数据,研究不同光环境处理对闽楠叶片叶绿素含量、叶绿素荧光参数和光合特性的影响.结果表明: 3种光照处理下,闽楠叶片叶绿素a、叶绿素b、叶绿素(a+b)和类胡萝卜素含量大小次序为78%遮光率>50%遮光率>全光照,但不同光照处理对闽楠叶绿素a/b值没有显著影响.遮阴条件下,闽楠叶片光补偿点(LCP)降低,光饱和点(LSP)和表观量子效率(AQY)升高,说明遮阴条件下闽楠叶片对弱光和强光的利用能力均有所提高;最大净光合速率(P_{n max})、光下暗呼吸速率(R_d)和最大电子传递速率(J_max)均增大.在不同处理间,闽楠叶片净光合速率(P_n)、CO₂气孔导度(g_sc)、胞间CO₂浓度(C_i)和叶肉导度(g_m)均存在显著差异.P_n和g_m的大小顺序为: 78%遮光率>50%遮光率>全光照.78%遮光率处理下g_sc显著大于全光照.50%遮光率条件和78%遮光率条件下C_i均显著小于全光照.78%遮光率条件下PSⅡ实际光量子产量(F_v′/F_m′)、PSⅡ光化学效率(Φ_PSⅡ)和电子传递速率(J)均显著大于50%遮光率条件和全光照.由此可知,在遮阴条件下闽楠可以通过增加叶绿素含量、AQY、J、g_sc和g_m来增大光合能力.     

环境强光诱导玉簪叶片光抑制的机制

为进一步阐述光抑制的强光诱导和发生机制, 该文以喜阴植物玉簪(Hosta spp.)为材料研究其光抑制发生规律及其与环境光强的关系。结果表明, 全日照和遮阴条件下玉簪叶片发育分别形成适应强光和弱光的形态特征; 与遮阴处理相比, 强光下生长的玉簪光合速率和叶绿素含量较低, 但两种处理叶片最大光化学效率差异很小, 证明强光下植株可以正常生长且光合机构未发生严重的光抑制。将遮阴处生长的植株转移到全日照下, 光合速率和最大光化学效率急剧下降; 荧光诱导动力学曲线发生明显改变, 而且光系统II供体侧和受体侧荧光产量的变化幅度分别达到24.3%和34.2%, 表明玉簪由弱光转入强光后光系统II发生不可逆失活, 且受体侧受到的伤害较供体侧更严重。因此, 作者认为环境光强骤然提高并超过玉簪生长光强时很容易诱导其光合机构发生严重的光抑制。该研究对于理解植物适应光环境的策略以及喜阴植物的优质栽培有重要意义。     

NaCl处理下两种引进红树的光合及抗氧化防御能力

在长期盐胁迫(28天, NaCl浓度从100 mmol·L^-1升至400 mmol·L^-1)下, 比较研究了引进的无瓣海桑(Sonneratia apetala)和拉关木(Laguncularia racemosa)幼苗叶片的气体交换、叶绿素含量、最大光化学效率(F_v/F_m)、O₂^-_· 产生速率以及抗氧化酶的活性, 探讨了两种红树幼苗光合、抗氧化防御能力的差异与耐盐性的关系。结果显示: NaCl处理没有明显地影响两种红树幼苗的生长, 表明盐生植物对盐环境的适应性, 但两种红树的生理反应对NaCl处理存在较大的差异。在实验的第28天(苗木的NaCl累计处理浓度递增到400 mmol·L^-1)时, 与对照相比, 无瓣海桑叶片的净光合速率、水分利用效率增加, 气孔导度、蒸腾速率和胞间CO₂浓度/大气CO₂浓度(C_i/C_a)相应降低; 然而, 拉关木叶的净光合速率、蒸腾速率和水分利用效率均回落到对照的水平, 而气孔导度和C_i/C_a均增加, 表明同样的NaCl浓度处理对拉关木叶的净光合速率影响大于无瓣海桑。在NaCl处理期间, 无瓣海桑F_v/F_m一直保持在0.8以上, 而拉关木的F_v/F_m为0.75以下, 说明无瓣海桑具有高于拉关木的潜在最大光合能力。在实验的第7天(NaCl浓度为100 mmol·L^-1)和14天(苗木的NaCl累计处理浓度递增到200 mmol·L^-1)时, 两种红树O₂^-_· 产生速率迅速增加, 在实验的第28天(苗木的NaCl累计处理浓度递增到400 mmol·L^-1)时, 无瓣海桑O₂^-_· 产生速率是对照的5.3倍, 差异极显著, 此时, 拉关木叶中O₂^-_· 产生速率已降低到低于对照的水平。盐处理诱导了两种红树叶中抗氧化酶(超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)、谷胱甘肽还原酶(GR)、过氧化物酶(POD))活性增加, 但拉关木增加的幅度大于无瓣海桑, 表明拉关木能响应盐胁迫并上调抗氧化酶活性, 降低盐诱导的膜脂过氧化, 提高耐盐的能力, 无瓣海桑通过提高水分利用效率来保持体内的水分, 同时, 保持PSII的最大光化学量子产量, 使得无瓣海桑在高盐处理时仍能保持高于对照水平的光合速率。     

超声波对铜绿微囊藻与蛋白核小球藻生理特征及竞争生长的影响

铜绿微囊藻是常见的水华蓝藻,常常在湖泊中与蛋白核小球藻共存或竞争生长。超声波可用于藻华即时治理,能够降低藻类生理活性,影响藻类生长,还可能改变藻类种间竞争关系。为了探究超声胁迫(35 kHz,0.035 W·cm^-3)对铜绿微囊藻与蛋白核小球藻的生理特征及种间竞争的影响,本研究设置纯藻组和1:1混合组(细胞浓度比)进行试验。结果表明: 铜绿微囊藻对超声胁迫更加敏感。超声处理600 s后,铜绿微囊藻的光合活性(F_v/F_m)和酯酶活性存在显著变化,纯藻组和混合组的F_v/F_m分别降低了51.8%和64.7%。而各组中蛋白核小球藻的光合活性变化较小。同时,铜绿微囊藻释放的荧光溶解性有机物(类色氨酸、类酪氨酸、类富里酸物质)含量多于蛋白核小球藻。两种藻的细胞浓度对超声波的响应也不同,蛋白核小球藻变化较小,而铜绿微囊藻的细胞浓度出现不同程度的下降。尤其是600 s超声处理大幅降低了混合组中铜绿微囊藻的细胞浓度(-42.6%),在超声胁迫解除后的8 d内蛋白核小球藻占优势,种间关系由铜绿微囊藻单边抑制蛋白核小球藻转变为两者互相抑制。在超声处理后,铜绿微囊藻的活性能够逐渐恢复,为了提高控藻效果的持久性,建议在一周后再次进行超声处理。     

根区缓冲降温处理对葡萄叶片冻害的影响

为探索根区降温条件对葡萄(Vitis vinifera)叶片冻害的影响,以1年生美乐葡萄(V.vinifera cv.‘Merlot’)幼苗为试材,设置根区正常降温和缓冲降温2种降温条件,人工模拟霜冻,分析了叶片冻害指数和叶片的荧光参数。结果表明,根区正常降温会导致根系受冻,同时叶片发生严重的冻害,冻害指数达74.36%;根区缓冲降温使根区温度保持在0°C以上,叶片冻害指数降低53.29%,仅有21.07%的叶片遭受了冻害。根区缓冲降温处理能有效提高叶片霜冻恢复过程中光化学淬灭系数(qP)和天线色素转化效率(F_v~'/F_m~'),加快PSII光合电子传递量子效率(Φ_(PSII))的恢复,提高热耗散能力(NPQ),减轻霜冻后的光抑制(F_v/F_m),有利于叶片霜冻后的恢复。     

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。