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1.
Winter wheat is a grass species widely planted in northern and central China, where the increase of aerosols, air pollutants
and population density are causing significant reduction in solar irradiance. In order to investigate the adaptation of winter
wheat (Triticum aestivum L., cv. Yangmai 13) to low irradiance conditions occurring in the downstream plain of the Yangtze River (China), plants were
subjected to four solar irradiance treatments (100%, 60%, 40%, and 20% of environmental incident solar irradiance). Significant
increases in chlorophyll (Chl) and xanthophyll (Xan) pigments, and decreases in Chl a/b and Xan/Chl ratios were observed in plants under low light. Light-response curves showed higher net photosynthetic rates
(P
N) in fully irradiated plants, that also showed a higher light-compensation point. Shaded plants maintained high values of
minimal fluorescence of dark-adapted state (Fo) and maximum quantum efficiency of PSII photochemistry (Fv/Fm) that assess a lower degree of photoinhibition under low light. Reduced irradiance caused decreases in effective quantum
yield of PSII photochemistry (ΦPSII), electron transport rate (ETR), and nonphotochemical quenching coefficient (qN), and the promotion of excitation pressure of PSII (1 − qP). The activities of the antioxidant enzymes superoxide dismutase and peroxidase were high under reduced light whereas no
light-dependent changes in catalase activity were observed. Thiobarbituric acid reactive species content and electrolyte leakage
decreased under shaded plants that showed a lower photooxidative damage. The results suggest that winter wheat cv. Yangmai
13 is able to maintain a high photosynthetic efficiency under reduced solar irradiance and acclimates well to shading tolerance.
The photosynthetic and antioxidant responses of winter wheat to low light levels could be important for winter wheat cultivation
and productivity. 相似文献
2.
Chlorophyll (Chl) fluorescence of warm day/cool night temperature exposed Phalaenopsis plants was measured hourly during 48 h to study the simultaneous temperature and irradiance response of the photosynthetic
physiology. The daily pattern of fluorescence kinetics showed abrupt changes of photochemical quenching (qP), non-photochemical quenching (NPQ) and quantum yield of photosystem II electron transport (ΦPSII) upon transition from day to night and vice versa. During the day, the course of ΦPSII and NPQ was related to the air temperature pattern, while maximum quantum efficiency of PSII photochemistry (Fv/Fm) revealed a rather light dependent response. Information on these daily dynamics in fluorescence kinetics is important with
respect to meaningful data collection and interpretation. 相似文献
3.
Chang-Ming Zhao Gen-Xuan Wang Xiao-Ping Wei Jian-Ming Deng Dong-Liang Cheng 《Trees - Structure and Function》2007,21(1):55-63
Physiological and photosynthetic responses were investigated at three different depths of groundwater (DGW: 1.4, 2.4, and
3.4 m) in Elaeagnus angustifolia L., a locally adapted tree to the arid region in northwest China. Predawn leaf water potential and chlorophyll content declined
gradually with the increasing DGW, whereas there was little effect on predawn variable-to-maximum chlorophyll fluorescence
ratio F
v/F
m and leaf carotenoid compositions (xanthophyll cycle pool, neoxanthin, lutein, and β-carotene). Net photosynthetic rate (P
n), quantum yield of PSII electron transport (ΦPSII), stomatal conductance (Gs), and intercellular CO2 concentration (Ci) declined obviously; however, P
n decreased more than ΦPSII at deeper DGW. The photoinhibition of PSII at all three DGW occurred at midday in summer and increased as DGW increased.
The ΔpH-dependent thermal dissipation and the level of de-epoxidation of the xanthophyll cycle at all three DGW reached their
maxima at midday with the increase of light intensity. However, the fraction of functional PSII and light intensity at deeper
DGW (2.4, 3.4 m) showed a negative correlation. This correlation suggested that most of violaxanthin was converted into zeaxanthin
at midday, and the reversible inactivation of partial PSII reaction centers took place at deeper DGW. These results together
suggest that both the xanthophyll cycle-dependent thermal dissipation and the reversible inactivation of partial PSII might
have played important roles in avoiding the excess light-induced energy damage in leaves of this tree species at deeper DGW. 相似文献
4.
F.Gevaert A.Creach D.Davoult A.-C.Holl L.Seuront & Y.Lemoine 《Plant, cell & environment》2002,25(7):859-872
Laminaria saccharina (Lamouroux) form the largest, most abundant and conspicuous seaweed populations along the French coast of the eastern English Channel. As they are located in the intertidal zone, they are exposed to considerable irradiance variations, mainly related to tidal cycles. The response of these macro‐algae to light variations over a simulated daily tidal cycle was investigated in the laboratory during spring, autumn and winter using chlorophyll fluorescence and pigment analysis. The maximum quantum yield of photosystem II (PSII) photochemistry (Fv/Fm) and the operating PSII efficiency (ΦPSII) showed clear daily cycles according to the irradiance variation throughout the 12 h simulated tidal cycle, whereas the pattern of the relative photosynthetic electron transport rate (rETR) was not so obvious. The algae reacted to the light increase by developing photoprotective mechanisms able to dissipate the excess energy reaching PSII by the de‐epoxidation of violaxanthin into zeaxanthin. Because of their better acclimation to strong irradiance, spring populations were less affected by this light treatment than were winter populations. In particular, L. saccharina showed more pigments of the xanthophyll cycle in spring to cope with strong irradiance exposure. Alternatively, they developed their antenna complexes in winter to harvest a maximum of light. 相似文献
5.
Chill-induced inhibition of photosynthesis was alleviated by 24-epibrassinolide pretreatment in cucumber during chilling and subsequent recovery 总被引:4,自引:0,他引:4
To investigate whether brassinosteroids (BRs) could be used to alleviate chill-induced inhibition of photosynthesis in cucumber
(Cucumis sativus L) during chilling and subsequent recovery, the effects of exogenously applied 24-epibrassinolide (EBR) on gas exchange,
chlorophyll fluorescence parameters, and antioxidant enzyme activity were studied. Cucumber plants were exposed to chilling
under low light (12/8°C and 100 μmol m−2 s−1 PPFD) for 3 days and then recovered under normal temperature and high irradiance (28/18°C and 600 μmol m−2 s−1 PPFD) for 6 days. Chilling significantly decreased the net photosynthetic rate (P
N) and stomatal conductance (g
s), and increased rate of O2
·− formation and H2O2 and malondialdehyde (MDA) content in cucumber leaves, but did not influence the optimal quantum yield of PSII (Fv/Fm). Chilling also decreased the effective quantum yield of PSII photochemistry (ΦPSII) and photochemical quenching (qP), but induced an increase in nonphotochemical quenching (NPQ), and the activities of superoxide dismutase (SOD) and ascorbate
peroxidase (APX). High irradiance (600 μmol m−2 s−1) further aggravated the decrease in P
N, g
s, ΦPSII and qP, and enhanced the increase in reactive oxygen species (ROS) generation and accumulation in the first day of recovery after
chilling. However, high irradiance induced a sharp decrease in Fv/Fm and NPQ, as well as the activities of SOD and APX on the first day of recovery. EBR pretreatment significantly alleviated
chill-induced inhibition of photosynthesis during chilling stress and subsequent recovery period, which was mainly due to
significant increases in g
s, ΦPSII, qP and NPQ. EBR pretreatment also reduced ROS generation and accumulation, and increased the activities of SOD and APX during
chilling and subsequent recovery. Those results suggest that EBR pretreatment alleviates the chill reduction in photosynthesis
and accelerated the recovery rate mainly by increasing of the stomatal conductance, the efficiency of utilization and dissipation
of leaf absorbed light, and the activity of the ROS scavenging system during chilling and subsequent recovery period. 相似文献
6.
The photosynthetic performances of regenerated protoplasts of Bryopsis hypnoides, which were incubated in seawater for 1, 6, 12, and 24 h, were studied using chlorophyll (Chl) fluorescence and oxygen measurements.
Results showed that for the regenerated protoplasts, the pigment content, the ratios of photosynthetic rate to respiration
rate, the maximal photosystem II (PSII) quantum yield (Fv/Fm), and the effective PSII quantum yield (ΦPSII) decreased gradually along with the regeneration progress, indicated that during 24 h of regeneration there was a remarkable
reduction in PSII activity of those newly formed protoplasts. We assumed that during the cultivation progress the regenerated
protoplasts had different photosynthetic vigor, with only some of them able to germinate and develop into mature thalli. The
above results only reflected the photosynthetic features of the regenerated protoplasts at each time point as a whole, rather
than the actual photosynthetic activity of individual aggregations. Further investigation suggested a relationship between
the size of regenerated protoplasts and their viability. The results showed that the middle-sized group (diameter 20–60 μm)
retained the largest number of protoplasts for 24 h of growth. The changes in Fv/Fm and ΦPSII of the four groups of differently sized protoplasts (i.e. < 20, 20–60, 60–100, and > 100 μm) revealed that the protoplasts 20–60 μm in diameter had the highest potential activity
of the photosynthetic light energy absorption and conversion for several hours. 相似文献
7.
This work aimed to evaluate if gas exchange and PSII photochemical activity in maize are affected by different irradiance
levels during short-term exposure to elevated CO2. For this purpose gas exchange and chlorophyll a fluorescence were measured on maize plants grown at ambient CO2 concentration (control CO2) and exposed for 4 h to short-term treatments at 800 μmol(CO2) mol−1 (high CO2) at a photosynthetic photon flux density (PPFD) of either 1,000 μmol m−2 s−1 (control light) or 1,900 μmol m−2 s−1 (high light). At control light, high-CO2 leaves showed a significant decrease of net photosynthetic rate (P
N) and a rise in the ratio of intercellular to ambient CO2 concentration (C
i/C
a) and water-use efficiency (WUE) compared to control CO2 leaves. No difference between CO2 concentrations for PSII effective photochemistry (ΦPSII), photochemical quenching (qp) and nonphotochemical quenching (NPQ) was detected. Under high light, high-CO2 leaves did not differ in P
N, C
i/C
a, ΦPSII and NPQ, but showed an increase of WUE. These results suggest that at control light photosynthetic apparatus is negatively
affected by high CO2 concentration in terms of carbon gain by limitations in photosynthetic dark reaction rather than in photochemistry. At high
light, the elevated CO2 concentration did not promote an increase of photosynthesis and photochemistry but only an improvement of water balance due
to increased WUE. 相似文献
8.
Influence of bacterial leaf blight on the photosynthetic characteristics of resistant and susceptible rice 总被引:1,自引:0,他引:1
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Hao Hu Li Sheng Guangzhi Zhang Qing Gu Kefeng Zheng 《Journal of Phytopathology》2018,166(7-8):547-554
The effect of crop disease on photosynthetic characteristics is important for disease control. Two varieties, Shenzhou 98 and Neiwuyou 8015 with resistance and susceptibility to bacterial leaf blight (BLB), respectively, were selected, and the responses of the net photosynthetic rate (PN) to active photon flux density (PPFD) and intercellular carbon dioxide concentration (Ci), as well as chlorophyll fluorescence, pigments and stomatal resistance (SR), were measured. The results showed that BLB infection greatly decreased the maximum photosynthetic rate (Pmax), light saturation point (LSP), carboxylation efficiency (CE), maximal fluorescence (Fm) and actual photochemical efficiency of PSII ( Φ PSII) but increased the light compensation point (LCP) and dark respiratory rate (RD), which suggested that the performance of rice photosynthesis was decreased by BLB infection. The BLB infection had a lower effect on resistant rice Shenzhou 98 than on susceptible rice Neiwuyou 8015. The reduction of pigment and increased SR caused by BLB infection may have resulted in the decline in the photosynthetic rate. Significant effects of the BLB infection were observed on chlorophyll fluorescence Fm and ΦPSII in resistant and susceptible rice. These parameters may be useful for noninvasive monitoring of plant disease considering the negative effect caused by other stresses. 相似文献
9.
Photochemical efficiency of PSII of Ctenanthe setosa was investigated to understand the photosynthetic adaptation mechanism under drought stress causing leaf rolling. Stomatal
conductance (g
s), the levels of photosynthetic pigments and chlorophyll (Chl) fluorescence parameters were determined in leaves that had
four different visual leaf rolling scores from 1 to 4, opened after re-watering and mechanically opened at score 4. g
s value gradually decreased in adaxial and abaxial surfaces in relation to scores of leaf rolling. Pigment contents decreased
until score 3 but approached score 1 level at score 4. No significant variations in effective quantum yield of PSII (ΦPSII), and photochemical quenching (qp) were found until score 3, while they significantly decreased at score 4. Non-photochemical quenching (NPQ) increased at
score 2 but then decreased. After re-watering, the Chl fluorescence and other physiological parameters reached to approximately
score 1 value, again. As for mechanically opened leaves, g
s decreased during drought period. The decrease in adaxial surface was higher than that of the rolled leaves. NPQ was higher
than that of the rolled leaves. ΦPSII and qp significantly declined and the decreases were more than those of the rolled leaves. In conclusion, the results indicate that
leaf rolling protects PSII functionality from damage induced by drought stress. 相似文献
10.
Effects of exogenous putrescine on gas-exchange characteristics and chlorophyll fluorescence of NaCl-stressed cucumber seedlings 总被引:1,自引:0,他引:1
The effects of 10 mM putrescine (Put) treated by spraying on leaves on growth, chlorophyll content, photosynthetic gas-exchange
characteristics, and chlorophyll fluorescence were investigated by growing cucumber plants (Cucumis sativus L. cv. ChangChun mici) using hydroponics with or without 65 mM NaCl as a salt stress. Salt stress caused the reduction of
growth such as leaf area, root volume, plant height, and fresh and dry weights. Furthermore, net photosynthesis rate (P
n), stomatal conductance (g
s), intercellular CO2 concentration (C
i), and transpiration rate (T
r) were also reduced by NaCl, but water use efficiency (WUE; P
n/T
r) showed a tendency to be enhanced rather than reduced by NaCl. However, Put alleviated the reduction of P
n by NaCl, and showed a further reduction of C
i by NaCl. The reduction of g
s and T
r by NaCl was not alleviated at all. The enhancement of WUE by NaCl was shown to have no alleviation at day 1 after starting
the treatment, but after that, the enhancement was gradually reduced till the control level. Maximum quantum efficiency of
PSII (F
v/F
m) showed no effects by any conditions based on the combination of NaCl and Put, and in addition, kept constant values in plants
grown in each nutrient solution during this experimental period. The efficiency of excitation energy capture by open photosystem
II (PSII) (F
v′/F
m′), actual efficiency of PSII (ΦPSII), and the coefficient on photochemical quenching (qP) of plants with NaCl were reduced with time, and the reduction was alleviated
till the control level by treatment with Put. The F
v′/F
m′, ΦPSII, and qP of plants without NaCl and/or with Put showed no variation during the experiment. Non-photochemical quenching of
the singlet excited state of chlorophyll a (NPQ) showed quite different manner from the others as mentioned above, namely, continued to enhance during the experiment. 相似文献
11.
Strawberry (Fragaria ananassaDuch. cv. Fengxiang) plantlets were cultured under two in vitroenvironments for rooting, and then acclimatized under two ex vitroirradiance conditions. At the end of rooting stage plant height, fresh weight and specific leaf area of T1-plants grown under high sucrose concentration (3 sucrose), low photosynthetic photon flux density (30 mol m–2 s–1) and normal CO2 concentration (350–400 l l–1) were significantly higher than those of T2-plantlets grown under low sucrose concentration (0.5), high photosynthetic photon flux density (90 mol m–2 s–1) and elevated CO2 concentration (700–800 l l–1). But T2-plantlets had higher net photosynthetic rate (Pn), effective photochemical quantum yield of PSII (PSII), effective photosynthetic electron transport rate (ETR), photochemical quenching (qP) and ratio of chlorophyll fluorescence yield decrease (Rfd). After transfer, higher irradiance obviously promoted the growth of plantlets and was beneficial for the development of photosynthetic functions during acclimatization. T2-plantlets had higher fresh weight, leaf area, PSII and ETR under higher ex vitroirradiance condition. 相似文献
12.
Wild and cultivated varieties of Camellia oleifera Abel. were studied for the response of their photosynthetic apparatus to Al toxicity and low-P stress in pot experiments
with medium of acidic red soil. The effect was measured using physiological processes (growth, photosynthesis, chlorophyll
a fluorescence), and pigment contents. The results showed that Al toxicity and low-P stress affected the seedlings’ growth
and leaves’ photosynthesis, and the differences could be found between the two varieties. Lime plus P fertilizer treatment
led to higher increase in the net photosynthetic rate (Pn) in the cultivar than in the wild variety. Pn increase was positively
related to the increase of stomatal conductance (gs) and negatively correlated to intercellular CO2 concentration (Ci) in both varieties. The maximum PSII quantum yield (Fv/Fm), the efficiency of excitation energy capture
by open PSII reaction centers (Fv’/Fm’), the photochemical quenching (qP) and the efficiency of open PSII centers (ΦPSII) significantly increased almost in all the treatment groups of both varieties, with the exception of an insignificant change
in qP value for P1Al1 group of cultivar. The insensitive qP and lower Pn for cultivar indicate a higher photosynthetic efficiency for the wild
variety, though the ΦPSII was not significant between the two varieties. The pigment contents of oil tea seedlings under treatments changed significantly
when lime and P were added, especially the Car/Chl ratio, suggesting carotenoid plays the role of photoprotection under high-Al
and low-P stresses. 相似文献
13.
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(Gs)是幼叶较低净光合速率(Pn)的限制因素, 从而直接导致其光系统II (PSII)实际光化学效率(ΦPSII)和光化学猝灭系数(qP)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(Fv/Fm)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(Pr)、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。 相似文献
14.
The effect of strong irradiance (2000 micromole photons per square meter per second) on PSII heterogeneity in intact cells of Chlamydomonas reinhardtii was investigated. Low light (LL, 15 micromole photons per square meter per second) grown C. reinhardtii are photoinhibited upon exposure to strong irradiance, and the loss of photosynthetic functioning is due to damage to PSII. Under physiological growth conditions, PSII is distributed into two pools. The large antenna size (PSIIα) centers account for about 70% of all PSII in the thylakoid membrane and are responsible for plastoquinone reduction (Qb-reducing centers). The smaller antenna (PSIIβ) account for the remainder of PSII and exist in a state not yet able to photoreduce plastoquinone (Qb-nonreducing centers). The exposure of C. reinhardtii cells to 60 minutes of strong irradiance disabled about half of the primary charge separation between P680 and pheophytin. The PSIIβ content remained the same or slightly increased during strong-irradiance treatment, whereas the photochemical activity of PSIIα decreased by 80%. Analysis of fluorescence induction transients displayed by intact cells indicated that strong irradiance led to a conversion of PSIIβ from a Qb-nonreducing to a Qb-reducing state. Parallel measurements of the rate of oxygen evolution revealed that photosynthetic electron transport was maintained at high rates, despite the loss of activity by a majority of PSIIα. The results suggest that PSIIβ in C. reinhardtii may serve as a reserve pool of PSII that augments photosynthetic electron-transport rates during exposure to strong irradiance and partially compensates for the adverse effect of photoinhibition on PSIIα. 相似文献
15.
Response of the Photosynthetic Apparatus in Dunaliella salina (Green Algae) to Irradiance Stress 总被引:9,自引:7,他引:2
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Smith BM Morrissey PJ Guenther JE Nemson JA Harrison MA Allen JF Melis A 《Plant physiology》1990,93(4):1433-1440
The response of the photosynthetic apparatus in the green alga Dunaliella salina, to irradiance stress was investigated. Cells were grown under physiological conditions at 500 millimoles per square meter per second (control) and under irradiance-stress conditions at 1700 millimoles per square meter per second incident intensity (high light, HL). In control cells, the light-harvesting antenna of photosystem I (PSI) contained 210 chlorophyll a/b molecules. It was reduced to 105 chlorophyll a/b in HL-grown cells. In control cells, the dominant form of photosystem II (PSII) was PSIIα(about 63% of the total PSII) containing >250 chlorophyll a/b molecules. The smaller antenna size PSIIβ centers (about 37% of PSII) contained 135 ± 10 chlorophyll a/b molecules. In sharp contrast, the dominant form of PSII in HL-grown cells accounted for about 95% of all PSII centers and had an antenna size of only about 60 chlorophyll a molecules. This newly identified PSII unit is termed PSIIγ. The HL-grown cells showed a substantially elevated PSII/PSI stoichiometry ratio in their thylakoid membranes (PSII/PSI = 3.0/1.0) compared to that of control cells (PSII/PSI = 1.4/1.0). The steady state irradiance stress created a chronic photoinhibition condition in which D. salina thylakoids accumulate an excess of photochemically inactive PSII units. These PSII units contain both the reaction center proteins and the core chlorophyll-protein antenna complex but cannot perform a photochemical charge separation. The results are discussed in terms of regulatory mechanism(s) in the plant cell whose function is to alleviate the adverse effect of irradiance stress. 相似文献
16.
Nan Liu Zhi-Fang Lin Anna Van Devender Gui-Zhu Lin Chang-Lian Peng Xiao-Ping Pan Shao-Wei Chen Qun Gu 《Plant Growth Regulation》2009,58(1):73-84
Pigment combinations are regulated during leaf ontogenesis. To better understand pigment function, alterations in chlorophyll,
carotenoid and anthocyanin concentrations were investigated during different leaf development stages in six subtropical landscape
plants, namely Ixora chinensis Lam, Camellia japonica Linn, Eugenia oleina Wight, Mangifera indica L., Osmanthus fragrans Lowr and Saraca dives Pierre. High concentrations of anthocyanin were associated with reduced chlorophyll in juvenile leaves. As leaves developed,
the photosynthetic pigments (chlorophyll and carotenoid) of all six species increased while anthocyanin concentration declined.
Chlorophyll fluorescence imaging of ΦPSII (effective quantum yield of PSII) and of NPQ (non-photochemical fluorescence quenching) and determination of electron transport
rate-rapid light curve (RLC) showed that maximum ETR (leaf electron transport rate), ΦPSII and the saturation point in RLC increased during leaf development but declined as they aged. Juvenile leaves displayed higher
values of NPQ and Car/Chl ratios than leaves at other developmental stages. Leaf reflectance spectra (400–800 nm) were measured
to provide an in vivo non-destructive assessment of pigments in leaves during ontogenesis. Four reflectance indices, related
to pigment characters, were compared with data obtained quantitatively from biochemical analysis. The results showed that
the ARI (anthocyanin reflectance index) was linearly correlated to anthocyanin concentration in juvenile leaves, while a positive
correlation of Chl NDI (chlorophyll normalized difference vegetation index) to chlorophyll a concentration was species dependent. Photosynthetic reflectance index was not closely related to Car/Chl ratio, while a structural-independent
pigment index was not greatly altered by leaf development or species. Accordingly, it is suggested that the high concentration
of anthocyanin, higher NPQ and Car/Chl ratio in juvenile leaves are important functional responses to cope with high radiation
when the photosynthetic apparatus is not fully developed. Another two leaf reflectance indices, ARI and Chl NDI, are valuable
for in vivo pigment evaluation during leaf development. 相似文献
17.
18.
Comparison of photosynthetic damage from arthropod herbivory and pathogen infection in understory hardwood saplings 总被引:2,自引:0,他引:2
Aldea M Hamilton JG Resti JP Zangerl AR Berenbaum MR Frank TD Delucia EH 《Oecologia》2006,149(2):221-232
Arthropods and pathogens damage leaves in natural ecosystems and may reduce photosynthesis at some distance away from directly injured tissue. We quantified the indirect effects of naturally occurring biotic damage on leaf-level photosystem II operating efficiency (ΦPSII) of 11 understory hardwood tree species using chlorophyll fluorescence and thermal imaging. Maps of fluorescence parameters and leaf temperature were stacked for each leaf and analyzed using a multivariate method adapted from the field of quantitative remote sensing. Two tree species, Quercus velutina and Cercis canadensis, grew in plots exposed to ambient and elevated atmospheric CO2 and were infected with Phyllosticta fungus, providing a limited opportunity to examine the potential interaction of this element of global change and biotic damage on photosynthesis. Areas surrounding damage had depressed ΦPSII and increased down-regulation of PSII, and there was no evidence of compensation in the remaining tissue. The depression of ΦPSII caused by fungal infections and galls extended >2.5 times further from the visible damage and was ∼40% more depressed than chewing damage. Areas of depressed ΦPSII around fungal infections on oaks growing in elevated CO2 were more than 5 times larger than those grown in ambient conditions, suggesting that this element of global change may influence the indirect effects of biotic damage on photosynthesis. For a single Q. velutina sapling, the area of reduced ΦPSII was equal to the total area directly damaged by insects and fungi. Thus, estimates based only on the direct effect of biotic agents may greatly underestimate their actual impact on photosynthesis. 相似文献
19.
L. Vitale P. di Tommasi C. Arena M. Oliva T. Bertolini S. Ranucci A. Virzo de Santo V. Magliulo 《Photosynthetica》2011,49(3):330-338
A mixture of ryegrass (Lolium italicum A. Braun) and clover (Trifolium alexandrinum L.) was sown in Eboli (Salerno, Southern Italy) in September 2007. Crop growth, leaf and canopy gas exchange and ecophysiological
traits were monitored throughout the growth cycle. The gross primary production (GPP) was not affected by air temperature
(T
air); on the contrary the ecosystem respiration (R
eco) decreased as T
air decreased while net ecosystem CO2 exchange (NEE) increased. When was normalized with leaf area index (LAI), GPP decreased with T
air, a likely response to cold that down-regulated canopy photosynthesis in order to optimize the light use at low winter temperatures.
Net photosynthetic rates (P
N), the effective quantum yield of PSII (ΦPSII) and photosynthetic pigment content were higher in clover than ryegrass, in relation to the higher leaf N content. The lower
ΦPSII in ryegrass was linked to lower photochemical quenching coefficient (qP) values, due to a reduced number of reaction centres, in agreement with the lowest Chl a content. This behaviour can be considered as an adaptive strategy to cold to avoid photooxidative damage at low temperature
rather than an impairment of PSII complexes. 相似文献
20.
Janusz Ko cielniak Władysław Filek Jolanta Biesaga-Ko cielniak 《Acta Physiologiae Plantarum》2006,28(2):149-158
The effects of drought on photochemical efficiency of PSII in leaves of 22 hybrids of Festuca pratensis × Lolium multiflorum and Festuca pratensis × Lolium perenne and of Festuca pratensis cv. Skra were investigated. A significant decrease of electron transport efficiency (about 25%) in PSII (ΦPSII) was not found before 9 days of seedling growth in hydroponics with water potential (Ψw) equal to −0.8 MPa (simulated “soil drought”). The decrease of ΦPSII was similarly related to that of excitation energy capture by open PSII reaction centre (Fv’/Fm’) and also to the decrease
of the proportion of oxidized to reduced QA (photochemical fluorescence quenching, qp). According to the drought prolongation, variation of all parameters of fluorescence between genotypes significantly increased.
The seedlings of some genotypes were able to recover electron transport efficiency in PSII after increasing water potential
in nutrient solution (removing the “soil drought”).
When plants grew in containers with soil and 4 genotypes with the highest sensitivity of electron transport to drought (S)
as well as 4 genotypes with the highest tolerance (T) were compared 17 days after watering ceased, Ψw in leaves considerably decreased, but the differences between S and T genotypes were often not significant in this respect.
The differences between S and T genotypes, as values of Fv/Fm were concerned, also appeared small (about 5%), similarly as
that of Fv’/Fm’ (5%), qp (12%) and ΦPSII (about 15%).
Drought stress increased non-photochemical quenching of chlorophyll fluorescence (NPQ) 15 to 47% and this could protect the
PSII reaction centres from damages because of energy excess. The increase of NPQ was not closely connected with drought resistance
of plants because it was similar in some genotypes tolerant to dehydration as well as in sensitive ones.
The results of the experiments suggest that resources of genetic variability in Festulolium may be sufficient for revealing differences between genotypes on the basis of measurement of chlorophyll a fluorescence, as far as their tolerance to soil drought is concerned. As the tolerance of PSII against drought is high, the
determinations of fluorescence should be performed rather under severe stress. Such methods seem to be useful for selection
of genotypes with high drought tolerance as well as with the ability to at least partial repairing of PSII after drought. 相似文献