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1.
Photoinhibition was examined in four co-occurring Mediterranean evergreen tree species during two consecutive winters. In response to low temperatures and saturating light, Juniperus phoenicea L., Pinus halepensis Mill., Quercus coccifera L. and Q. ilex ssp. ballota (Desf.) Samp. exhibited marked chronic photoinhibition, indicated by low predawn maximal photochemical efficiency of photosystem II (PSII) (Fv/Fm). Low Fv/Fm values were correlated with high concentrations of xanthophyll cycle components (VAZ) and with the maintenance of high concentrations of zeaxanthin overnight (DPSpd). In all species, however, chronic photoinhibition was enhanced as the winter progressed in the absence of changes in DPSpd, suggesting cumulative damage toward the end of winter. Photoinhibition differed among species: P. halepensis always displayed significantly higher Fv/Fm values; and Q. coccifera had the lowest Fv/Fm values, showing a high sensitivity to the combination of high light and low temperatures. Differences among species were not fully explained by differences in the xanthophyll pool or its de-epoxidation state. Chronic photoinhibition overlapped with a dynamic photoinhibition as shown by the low values of photochemical efficiency of the open reaction centers of PSII at midday. Winter photoprotective strategies differed among species and may involve photoprotective mechanisms in addition to those associated with xanthophylls. The observed species-specific differences matched results obtained for the same species in summer; however, comparison of the two seasons suggests that the higher VAZ concentration observed in winter has an additional structural photoprotective role. 相似文献
2.
Populations of cork oak (Quercus suber L.) were assessed for seasonal and inter-population variability in, and temperature responses of, the ratio between light-induced variable and maximum fluorescence of chlorophyll, Fv/Fm, considered a surrogate for the maximum photochemical efficiency of photosystem II (PSII). Seedlings from 10 populations throughout the distribution range of Q. suber in the Mediterranean basin were grown in a common garden in central Spain. The Fv/Fm ratio of dark-adapted leaves was measured at dawn every month for 2 years. Air temperature was recorded at a nearby climatic station. During the summer, when maximum air temperatures reached 40 degrees C, there were no significant differences in Fv/Fm among populations, but significant differences were seen during the winter. In colder months, Fv/Fm ranged in all populations between 0.5-0.6 and 0.2-0.3 in 2001 and 2002, respectively. The variance explained by the population effect was greatest during winter months, especially in 2002, reaching a peak value of 10% when minimum air temperature was below -10 degrees C. Populations originating from warmer sites showed the largest decline in Fv/Fm between the end of 2001 and the beginning of 2002. Thus, a negative linear relationship was established between mean annual temperature at the population source and population mean Fv/Fm recorded in the coldest month in 2002 and normalized by the Fv/Fm spring measurement. 相似文献
3.
Plants in the neotropical savannas of central Brazil are exposed to high irradiances, high air temperatures and low relative humidities. These conditions impose a selection pressure on plants for strong stomatal regulation of transpiration to maintain water balance. Diurnal adjustments of non-photochemical energy dissipation in photosystem II (PSII) provide a dynamic mechanism to reduce the risk of photoinhibitory damage during the middle of the day when irradiances and leaf temperatures are high and partial closure of the stomata results in considerable reductions in internal CO(2) concentration. At the end of the dry season, we measured diurnal changes in gas exchange, chlorophyll fluorescence parameters and carotenoid composition in two savanna tree species differing in photosynthetic capacity and in the duration and extent of the midday depression of photosynthesis. Non-photochemical quenching and its quantum yield were tightly correlated with zeaxanthin concentrations on a total chlorophyll basis, indicating that the reversible de-epoxidation of violaxanthin to antheraxanthin and zeaxanthin within the xanthophyll cycle plays a key role in the regulation of thermal energy dissipation. In both cases, a single linear relationship fitted both species. Although efficient regulation of photochemical and non-photochemical quenching and adjustments in the partitioning of electron flow between assimilative and non-assimilative processes were operating, these trees could not fully cope with the rapid increase in irradiance after sunrise, suggesting high vulnerability to photoinhibitory damage in the morning. However, both species were able to recover quickly. The effects of photoinhibitory quenching were largely reversed by midday, and zeaxanthin rapidly converted back to violaxanthin as irradiance decreased in late afternoon, resulting in the maximal quantum yield of PSII of around 0.8 just before sunrise. 相似文献
4.
Effects of chilling-dependent photoinhibition on gas exchange, chlorophyll fluorescence, growth and nutrition of Eucalyptus nitens (Deane and Maiden) Maiden seedlings were assessed for 70 weeks after transplanting 9-month-old seedlings in early winter. One month before transplanting, the seedlings were assigned to fertilized or nutrient-deprived treatments. Immediately after transplanting, half the seedlings in each nutrient treatment were placed in shadecloth tree shelters. The experimental site was at an altitude of 700 m, which is considered marginal for the establishment of E. nitens plantations in Tasmania because of low mean annual minimum temperatures. Overnight frosts followed by sunny morning conditions in the first 20 weeks after transplanting (early June to early October) caused severe photoinhibition. Predawn maximal photochemical efficiency (Fv/Fm) and maximum net photosynthesis (Amax) were depressed in nutrient-deprived seedlings compared with fertilized seedlings, although shading partially alleviated this difference. Neither Fv/Fm nor Amax recovered to values observed before transplanting until > 20 weeks after transplanting. During this period, non-photochemical quenching (NPQ) was high in seedlings in all treatments, although NPQ was lower in shaded, fertilized seedlings than in seedlings in the other treatments. Total foliar nitrogen (N) concentration increased up to 42 weeks after transplanting in the nutrient-deprived seedlings in parallel with increasing relative growth rate (RGR). Fractionation of N- and phosphorus (P)-containing compounds indicated that differences in protein N accounted for the treatment differences in total seedling N. Nucleic acid P increased and inorganic P decreased during growth periods, although total seedling P remained constant. Among treated seedlings, height growth was greatest in shaded seedlings: this was probably a result of apical dominance effects because RGR was higher in unshaded seedlings than in shaded seedlings. Thus, the shade treatment alleviated chilling-dependent photoinhibition and maximized growth during winter, but limited growth during warmer periods and therefore overall growth. 相似文献
5.
以冷驯化的两种梁山慈竹(Dendrocalamus farinosus)体细胞突变体植株及梁山慈竹实生植株为材料,研究了梯度降温处理(依次为4、0、?5、?10和?15℃)对其叶绿素荧光参数的影响。结果表明,实生植株在?5℃胁迫下死亡,而突变体植株No.101-1b和No.101-1c直到?15℃胁迫下才出现死亡。低温胁迫后,突变体植株和实生植株的最大光化学效率(Fv/Fm)、光系统Ⅱ有效光量子产量(YⅡ)和光化学淬灭系数(qP)均有降低,下降幅度排序为实生植株>No.101-1b>No.101-1c。非光化学猝灭系数(NPQ)显著高于胁迫前,以No.101-1c表现最为突出。品系和温度2个因素及两者交互作用对叶绿素荧光的影响均达到显著水平。总结得出,突变体植株No.101-1c具有较高的耐寒性,本研究可为耐寒梁山慈竹体细胞突变体植株的筛选提供科学依据。 相似文献
6.
GAO Jian PENG Zhen-hua 《林业研究》2006,17(4):269-272
Introduction Salinity is a major factor in inhibiting plant growth and decreasing forest productivity. Up to 1997, the total area affected by salinity in the world had amounted to 930 million hm2 (FAO), and is still increasing. A global study of land use … 相似文献
7.
Photoinhibition of photosynthesis and photosynthetic recovery were studied in detached needles of cypress (Cupressus sempervirens L.) Clones 52 and 30 under controlled conditions of high irradiation (about 1900 micromol m(-2) s(-1) for 60 min; HL treatment), followed by 60 min in darkness. The degree of photoinhibition was determined based on the ratio of variable to maximum chlorophyll fluorescence (Fv/Fm), which is a measure of the potential efficiency of photosystem II (PSII), and on electron transport measurements. The Fv/Fm ratio declined in needles of both clones in response to the HL treatment. Minimal fluorescence (Fo) increased in HL-treated needles of both clones. The HL treatment decreased rates of whole-chain and PSII activity of isolated thylakoids more in Clone 52 than in Clone 30. In needles of both clones, PSI activity was less sensitive to photoinhibition than PSII activity. In the subsequent 60-min dark incubation, fast recovery was observed in needles of both clones, with PSII efficiencies reaching similar values to those in non-photoinhibited needles. The artificial exogenous electron donors diphenyl carbazide (DPC), hydroxylamine (NH2OH) and manganese chloride (MnCl2) failed to restore the HL-induced loss of PSII activity in needles of Clone 30, whereas DPC and NH2OH significantly restored PSII activity in photoinhibited needles of Clone 52. Quantification of the PSII reaction center protein D1 and the 33-kDa protein of the water-splitting complex following HL treatment of needles revealed pronounced differences between Clone 52 and Clone 30. The large decrease in PSII activity in HL-treated needles was caused by the marked loss of D1 protein and 33-kDa protein in Clone 30 and Clone 52, respectively. 相似文献
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9.
不同桉树无性系幼苗叶片形态、生理特征的差异性比较 总被引：1，自引：0，他引：1
以8个无性系桉树幼苗为试验材料,对其叶片形态、生理特征的差异性进行比较.结果表明:叶片形态特征、叶绿素含量和PSII电子传递最大潜力差异显著;PSII反应中心最大光能转换效率及实际光化学转换效率差异极显著.DH32-26、DH32-28幼苗叶片保水力和维持水分平衡能力中等,原生质耐脱水能力较好;DH33-27、GL-UG9叶片的保水力和维持水分平衡能力强,原生质忍耐脱水能力较差;DH184-1、GL-U4、GL-WC3幼苗叶片的保水力、维持水分平衡能力以及原生质耐脱水能力均为中等;DH201-2的保水力和维持水分平衡能力较差,原生质耐脱水能力中等.从叶片形态和生理特征方面综合评定DH184-1、GL-U4、GL-WC3为较优无性系. 相似文献
10.
水分胁迫对美国山核桃叶绿素荧光参数的影响 总被引：1，自引：0，他引：1
研究水分胁迫对美国山核桃叶绿素荧光参数的影响,以探究水分胁迫损伤光合作用的机理.结果表明:在离体快速干旱水分胁迫处理方式下,美国山核桃叶片F o、Fm、F v/Fm、F v/F o、qP在离体6 h时均下降,但降低幅度不大;Y ield和qN在离体6 h时分别显著下降和上升,此说明美国山核桃苗遭遇水分胁迫时,叶片的PS II反应中心电子传递活性受到了一定程度的影响,但影响不大;光合电子传递速率明显下降,PS II反应中心耗散过剩光能的能力增强,其可作为品种耐旱能力的鉴定指标. 相似文献
11.
Susceptibility to low-temperature photoinhibition in three conifers differing in successional status 总被引：1，自引：0，他引：1
Robakowski P 《Tree physiology》2005,25(9):1151-1160
Susceptibility to photoinhibition of the evergreen conifers Abies alba Mill., Picea abies (L.) Karst. and Pinus mugo Turra was investigated in an unheated greenhouse during winter and spring 2003. Photosynthetic performance of the seedlings was assessed by chlorophyll a fluorescence and analyses of chlorophyll and total carotenoid concentrations in needles. During winter months, maximum quantum yield of PSII photochemistry (ratio of variable to maximum fluorescence, Fv/Fm) was significantly greater in A. alba than in P. abies and P. mugo. Abies alba also sustained higher maximum apparent electron transport rate (ETRmax) than P. abies and P. mugo. Total concentrations of chlorophyll and carotenoids in needles decreased during the winter in P. mugo and P. abies, but remained stable in A. alba. For all species, Fv/Fm decreased from December until February and then increased to a maximum in April. Photoinhibition was greatest (Fv/Fm < 0.80) in all seedlings in February, the month with the lowest mean temperature. Saturating photosynthetic photon flux (PPFsat) and ETRmax were positively related to air temperature. All species had lower values of ETRmax and PPFsat in winter than in spring. Non-photochemical quenching of chlorophyll fluorescence (NPQ) was highest at low air temperatures. Differences among species in susceptibility to winter photoinhibition resulted from their specific light preferences and led to different mechanisms to cope with photoinhibitory stress. The more shade-tolerant A. alba sustained a higher photosynthetic capacity in winter than P. abies and P. mugo. Winter photoinhibition in P. abies, P. mugo and, to a lesser extent, in A. alba may reflect adaptive photoprotection of the photosynthetic apparatus in winter. 相似文献
12.
To clarify the changes in plant photosynthesis and mechanisms underlying those responses to gradually increasing soil drought stress and reveal quantitative relationships between photosynthesis and soil moisture,soil water conditions were controlled in greenhouse pot experiments using 2-year-old seedlings of Forsythia suspensa(Thunb.) Vahl. Photosynthetic gas exchange and chlorophyll fluorescence variables were measured and analyzed under 13 gradients of soil water content. Net photosynthetic rate(PN), stomatal conductance(gs), and water-use efficiency(WUE) in the seedlings exhibited a clear threshold response to the relative soil water content(RSWC). The highest PNand WUEoccurred at RSWCof51.84 and 64.10%, respectively. Both PNand WUEwere higher than the average levels at 39.79% B RSWCB 73.04%. When RSWCdecreased from 51.84 to 37.52%,PN, gs, and the intercellular CO2 concentration(Ci)markedly decreased with increasing drought stress; the corresponding stomatal limitation(Ls) substantially increased, and nonphotochemical quenching(NPQ) also tended to increase, indicating that within this range of soil water content, excessive excitation energy was dispersed from photosystem II(PSII) in the form of heat, and the reduction in PNwas primarily due to stomatal limitation.While RSWCdecreased below 37.52%, there were significant decreases in the maximal quantum yield of PSII photochemistry(Fv/Fm) and the effective quantum yield of PSII photochemistry(UPSII), photochemical quenching(qP), and NPQ; in contrast, minimal fluorescence yield of the dark-adapted state(F0) increased markedly. Thus,the major limiting factor for the PNreduction changed to a nonstomatal limitation due to PSII damage. Therefore, an RSWCof 37.52% is the maximum allowable water deficit for the normal growth of seedlings of F. suspensa, and a water content lower than this level should be avoided in field soil water management. Water contents should be maintained in the range of 39.79% B RSWCB 73.04% to ensure normal function of the photosynthetic apparatus and high levels of photosynthesis and efficiency in F.suspensa. 相似文献
13.
In the context of climate change, an increased frequency of drought stresses might occur at a regional scale in boreal forests. To assess photosynthetic responses to drought treatment, seedlings of 12 open-pollinated families of white spruce (Picea glauca (Moench) Voss) differing in their growth performance were grown in a controlled environment. Gas exchange and chlorophyll fluorescence parameters as well as shoot xylem water potential (WP) were measured for 21 successive days after watering was stopped. Net photosynthesis decreased as stomatal conductance decreased. Net photosynthesis was not affected by drought until WP reached –2.0 MPa when stomata were closed. Initial fluorescence (F and basic fluorescence after induction (F00) were not affected by drought. A progressive decrease in maximal (Fm) and variable fluorescences (Fv), maximum photosystem II (PS II) efficiency (Fv = Fm), effective quantum yield of PS II (FII), photochemical efficiency of open PS II (Fp), and photochemical quenching (qP) was observed at WP < - 1.0 MPa, whereas non-photochemical quenching (qN) remained high throughout the drought treatment. White spruce families with inferior growth performance showed higher values of Fm, Fv, Fv = Fm, Fp, and qN at WP< - 2.0MPa. The results indicated that chlorophyll fluorescence variables can be used as drought markers in relation to present or predicted climate conditions. These could be used for selecting planting stock adapted to drought periods or dry environments. These markers showed that slow-growing genotypes are better adapted to drought conditions than intermediate or fast-growing genotypes in present and predicted drought conditions. 相似文献
14.
Changes in photosystem II (PSII) thermotolerance during drought and recovery were studied under controlled conditions in three Mediterranean cedar species (Cedrus brevifolia Henry, C. libani Loudon and C. atlantica Manetti). The temperature at which the quantum yield of PSII photochemistry was reduced by 15% of its value at 25 degrees C was 3 to 4 degrees C higher in drought-treated plants than in well-watered plants. The drought-induced increase in PSII thermotolerance was already evident 8 days after water had been withheld from the seedlings, when net CO(2) assimilation was still at 80% of its initial value, and was visible for up to 12 days after re-watering. When seedlings of the three species were exposed to temperatures above 45 degrees C for 5 h, both maximal quantum yield of PSII photochemistry and net CO(2) assimilation rate were significantly reduced in unconditioned seedlings, whereas drought-preconditioned seedlings were almost unaffected by the heat treatment. Drought-preconditioned seedlings still exhibited a higher tolerance to heat stress than unconditioned seedlings 60 days after re-watering, although the transient, drought-induced osmotic adjustment had fully disappeared. Among species, C. atlantica was the most heat sensitive, whereas the heat treatment had no significant effect on the parameters measured in C. brevifolia. 相似文献
15.
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
16.
以加勒比松(Pinus caribaea)16个种源、湿地松(P.elliottii)4个种源2.5 a生营养袋苗木为材料,定期开展生长调查,于2016年7—8月、2017年2月开展叶绿素荧光参数的测定,分析加勒比松、湿地松针叶叶绿素荧光参数对树种、种源、不同测量时间的响应.结果表明,不同种源加勒比松/湿地松的株高、地径生长均存在显著差异(P<0.01);测量时间与树种对最大PSⅡ的光能转换效率(Fv/Fm)有显著影响(P<0.01),二者互作效应不显著,与7、8月相比,测量值均在第2年2月显著提高;两个树种的实际量子产量(ΦPSⅡ)、光化学淬灭(qP)与表观量子传递速率(ETR)对测量时间的响应模式相反;加勒比松与湿地松叶绿素荧光参数受种源影响不显著;相关性分析表明,加勒比松与湿地松的株高和地径生长与2月Fv/Fm、PSⅡ有效光化学效率(Fv′/Fm′)测量值呈一定的负相关关系;高光强抑制了湿地松、加勒比松的叶绿素荧光参数,但抑制效果与生长无明显相关关系;低温造成的胁迫主要抑制了加勒比松的光化学反应,并与其生长表现有一定的负相关关系.可考虑将2月份测量的叶绿素荧光参数作为加勒比松耐寒个体的筛选指标. 相似文献
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18.
以少穗竹为研究对象,利用IMAGING-PAM对其进行了荧光成像诱导等研究,结果表明:①:从荧光诱导曲线,Y、qP和rETR值均很低,后均逐渐达到稳态.其中Y、rETR、qP均为一直升高并达到稳态变化趋势一致,NPQ则有一个先升高再降低逐步达到稳态的过程.②根据快速光曲线的拟合可以得到少穗竹Ik=145.273 4、α=0.200312、rETRmax=29.1.③少穗竹各荧光参数存在着大小不一的异质性,除PSII最大量子产量Fv/Fm、吸光系数Abs以外,其他参数均存在较大的异质性.其中PSII实际量子产量Y、光化学淬灭qP和相对电子传递速率PS/5O的变化基本一致,而非光化学淬灭NPQ/4的变化与前三者相反. 相似文献
19.
不同光强下红锥幼苗叶绿素荧光参数的日变化 总被引：1，自引：0，他引：1
测定分布在不同光照强度（全光照、遮荫下光强分别相当于自然光照的80％、30％和20％）的红锥（Castanopsis hystrix）盆栽幼苗叶绿素荧光参数的日变化过程,以探讨红锥幼苗生长对光强的适应性.结果显示,4种生境光强下的叶绿素荧光参数日变化趋势基本一致;低光强下（30％和20％光强）的有效光化学量子产量（Fv＇/Fm＇）、光化学淬灭系数（qP）和最大光能转化效率（Fv/Fm）显著高于高光强下（全光照和80％光强）的对应值,且三者均表现为中午较低,傍晚最高的趋势;相对表观电子传递速率（ETR）和非光化学淬灭系数（NPQ）表现为随生境光强的增加而升高的趋势,低光强下显著低于高光强下的对应值,且两者均表现为傍晚最低.研究表明,红锥盆栽幼苗对低光强的适应性很强,适当遮光有利于提高红锥苗的光合能力. 相似文献
20.
5种红山茶叶绿素荧光特性的比较研究 总被引：34，自引：3，他引：34
在大四条件下，通过对五种红山茶的叶绿素荧光特性研究，结果表明，不同亚组、同一亚组不同系之间的叶绿素荧光参数值存在差异．且亚组间大于亚组内。初始荧光(FO)、最大荧光(Fm)、RSⅡ最大光化学效率(Fv／Fm)、PSⅡ实际光化学效率(Yield／ΦPSⅡ)、表观电子传递速率(ETR)的日变化与光强有关．其中，Fm、Fv／Fm、Yield随光强的变化呈相同的变化趋势，呈单谷曲线；而ETR则相反呈单峰曲线；FO呈双峰曲线。不同树种的荧光参数日变化幅度存在差异。 相似文献