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1.
Effects of foliar application of nitrogen on the photosynthetic performance and growth of two fescue cultivars under heat stress 总被引:1,自引:0,他引:1
The effects of nitrogen fertilization on the growth, photosynthetic pigment contents, gas exchange, and chlorophyll (Chl)
fluorescence parameters in two tall fescue cultivars (Festuca arundinacea cv. Barlexas and Crossfire II) were investigated under heat stress at 38/30 °C (day/night) for two weeks. Shoot growth rate
of two tall fescue cultivars declined significantly under heat stress, and N supply can improved the growth rates, especially
for the Barlexas. Chl content, leaf net photosynthetic rate, stomatal conductance, water use efficiency, and the maximal efficiency
of photosystem 2 photochemistry (Fv/Fm) also decreased less under heat stress by N supply, especially in Crossfire II. Moreover, cultivar variations in photosynthetic
performance were associated with their different response to heat stress and nitrogen fertilization, which were evidenced
by shoot growth rate and photosynthetic pigment contents. 相似文献
2.
The phytotoxic aluminum species (Al3+) is considered as the primary factor limiting crop productivity in over 40 % of world’s arable land that is acidic. We evaluated the responses of two wheat cultivars (Triticum aestivum L.) with differential Al resistance, cv. Yecora E (Al-resistant) and cv. Dio (Al-sensitive), exposed to 0, 37, 74 and 148 μM Al for 14 days in hydroponic culture at pH 4.5. With increasing Al concentration, leaf Ca2+ and Mg2+ content decreased, as well as the effective quantum yield of photosystem II (PSII) photochemistry (Φ PSII ), while a gradual increase in leaf membrane lipid peroxidation, Al accumulation, photoinhibition (estimated as F v /F m ), and PSII excitation pressure (1 ? q p ) occurred. However, the Al-resistant cultivar with lower Al accumulation, retained larger concentrations of Ca2+ and Mg2+ in the leaves and kept a larger fraction of the PSII reaction centres (RCs) in an open configuration, i.e. a higher ratio of oxidized to reduced quinone A (QA), than plants of the Al-sensitive cultivar. Four times higher Al concentration in the nutrient solution was required for Al-resistant plants (148 μM Al) than for Al-sensitive (37 μM Al), in order to establish the same closed RCs. Yet, the decline in photosynthetic efficiency in the cultivar Dio was not only due to closure of PSII RCs but also to a decrease in the quantum yield of the open RCs. We suggest that Al3+ toxicity may be mediated by nutrient deficiency and oxidative stress, and that Al-resistance of the wheat cultivar Yecora E, may be due at least partially, from the decreased Al accumulation that resulted to decreased reactive oxygen species (ROS) formation. However, under equal internal Al accumulation (exposure Al concentration: Dio 74 μM, Yecora E 148 μM) that resulted to the same oxidative stress, the reduced PSII excitation pressure and the better PSII functioning of the Al-resistant cultivar was probably due to the larger concentrations of Ca2+ and Mg2+ in the leaves. We propose that the different sensitivities of wheat cultivars to Al3+ toxicity can be correlated to differences in the redox state of QA. Thus, chlorophyll fluorescence measurements can be a promising tool for rapid screening of Al resistance in wheat cultivars. 相似文献
3.
Photosynthetic gas exchange, vegetative growth, water relations and fluorescence parameters as well as leaf anatomical characteristics
were investigated on young plants of two Olea europaea L. cultivars (Chemlali and Zalmati), submitted to contrasting water availability regimes. Two-year-old olive trees, grown
in pots in greenhouse, were not watered for 2 months. Relative growth rate (RGR), leaf water potential (ΨLW) and the leaf relative water content (LWC) of the two cultivars decreased with increasing water stress. Zalmati showed higher
values of RGR and LWC and lower decreased values of ΨLW than Chemlali, in response to water deficit, particularly during severe drought stress. Water stress also caused a marked
decline on photosynthetic capacity and chlorophyll fluorescence. The net photosynthetic rate, stomatal conductance, transpiration
rate, the maximal photochemical efficiency of PSII (F
v/F
m) and the intrinsic efficiency of open PSII reaction centres (F′
v/F′
m) decreased as drought stress developed. In addition, drought conditions, reduced leaf chlorophyll and carotenoids contents
especially at severe water stress. However, Zalmati plants were the less affected when compared with Chemlali. In both cultivars,
stomatal control was the major factor affecting photosynthesis under moderate drought stress. At severe drought-stress levels,
the non-stomatal component of photosynthesis is inhibited and inactivation of the photosystem II occurs. Leaf anatomical parameters
show that drought stress resulted in an increase of the upper epidermis and palisade mesophyll thickness as well as an increase
of the stomata and trichomes density. These changes were more characteristic in cv. ‘Zalmati’. Zalmati leaves also revealed
lower specific leaf area and had higher density of foliar tissue. From the behaviour of Zalmati plants, with a smaller reduction
in relative growth rate, net assimilation rate and chlorophyll fluorescence parameters, and with a thicker palisade parenchyma,
and a higher stomatal and trichome density, we consider this cultivar more drought-tolerant than cv. Chemlali and therefore,
very promising for cultivation in arid areas. 相似文献
4.
Influence of water stress on leaf photosynthetic characteristics in wheat cultivars differing in their susceptibility to drought 总被引:11,自引:1,他引:10
A gradual reduction in leaf water potential (Ψleaf), net photosynthetic rate (P
N), stomatal conductance, and transpiration rate was observed in two drought tolerant (C 306 and K 8027) and two susceptible
(RW 893 and 899) genotypes subjected to water stress. The extent of reduction was lower in K 8027 and C 306 and higher in
RW 893 and RW 899. Rewatering the plants after 5 d of stress restored P
N and other gas exchange traits in all four cultivars. Water stress had no significant effect on variable to maximum fluorescence
ratio (Fv/Fm) indicating that water stress had no effect on primary photochemistry of photosystem 2 (PS2). However, water stress reduced
the efficiency of excitation energy transfer (F′v/F′m) and the quantum yield of electron transport (ΦPS2). The reduction was more pronounced in susceptible cultivars. Water stress had no significant effect on photochemical quenching,
however, the non-photochemical quenching increased by water stress. 相似文献
5.
Z. Shu L. Shao H. -Y. Huang X. -Q. Zeng Z. -F. Lin G. -Y. Chen C. -L. Peng 《Photosynthetica》2009,47(4):548-558
In the present study, we investigated the antioxidative potential in leaves of the chromatic (CC) versus green (GC) Amaranthus tricolor L. under moderate high-temperature stress at 45°C. Before heat stress, CC had significantly higher levels of betacyanins
[about 3.2 mg g−1(FM)] than the green [1.8 mg g−1(FM) (p<0.01), while similar chlorophyll (Chl) content [about 2 mg g−1(FM)] was observed between both cultivars. After exposure to high temperature (45°C) for 6 days, betacyanins in leaves of
CC were remarkably increased (about 2 times of that in control samples grown at 30°C). In contrast, betacyanins in GC significantly
decreased by 56% in comparison with that of the control. Chl level in CC was higher than that in GC after heat stress for
6 days. Flavonoids and total phenolics in both cultivars were increased, but much more in CC. Significantly less H2O2 accumulation was observed in the leaves and stems of CC than in those of GC under heat stress. Interestingly, much stronger
circadian oscillation in fluorescence was observed in both cultivars after treatment at 45°C, which suggested that heat stress
stimulates endogenous rhythms of photosystem II (PSII). Under moderate high-temperature stress, Chl fluorescence parameters
Fv/Fm (maximum quantum yield of PSII), qP (coefficient of photochemical quenching), ΦPSII (effective PSII quantum yield), and ETR (electron transport rate) exhibited a gradual decrease, NPQ (nonphotochemical quenching)
showed a slight increase followed by a gradual decline, whereas Fo (minimum fluorescence of a dark-adapted leaf) increased continuously. In contrast to GC, after 120 h of high-temperature
treatment, CC exhibited significantly lower Fo level, and higher levels of Fv/Fm and NPQ. It is clear that PSII in CC was more stable than that in GC. The results indicate that betacyanins are an effective
antioxidant, and probably contribute greatly to the higher thermal stability of PSII and higher tolerance to heat stress. 相似文献
6.
Yellow-green foliage cultivars of four vegetables grown outdoors, i.e., Chinese mustard (Brassica rapa), Chinese kale (Brassica oleracea var. alboglabra), sweet potato (Ipomoea batatas) and Chinese amaranth (Amaranthus tricolor), had lower chlorophyll (Chl) (a+b) (29–36% of green cultivars of the same species), total carotenoids (46–62%) and ascorbate (72–90%) contents per leaf area.
Furthermore, yellow-green cultivars had smaller photosystem II (PSII) antenna size (65–70%) and lower photosynthetic capacity
(52–63%), but higher Chl a/b (107–156%) and from low (60%) to high (129%) ratios of de-epoxidized xanthophyll cycle pigments per Chl a content. Potential quantum efficiency of PSII (Fv/Fm) of all overnight dark-adapted leaves was ca. 0.8, with no significant difference between yellow-green and green cultivars of the same species. However, yellow-green
cultivars displayed a higher degree of photoinhibition (lower Fv/Fm after illumination) when they were exposed to high irradiance.
Although vegetables used in this study are of either temperate or tropical origin and include both C3 and C4 plants, data from all cultivars combined revealed that Fv/Fm after illumination still showed a significant positive linear regression with xanthophyll cycledependent energy quenching
(qE) and a negative linear regression with photoinhibitory quenching (qI). Fv/Fm was, however, not correlated with nonphotochemical quenching (NPQ). Yet, a higher degree of photoinhibition in yellow-green
cultivars could recover during the night darkness period, suggesting that the repair of PSII in yellow-green cultivars would
allow them to grow normally in the field. 相似文献
7.
Effect of phosphorus deficiency on the photosynthetic characteristics of rice plants 总被引:1,自引:0,他引:1
The effects of phosphorus deficiency on the photosynthetic characteristics were studied in rice seedlings (Oryza sativa L.) every 8 days after treatment. P deficiency caused a significant reduction in the net photosynthesis rate (P
N) in rice plants. During the first 16 days of P deficiency, the maximum efficiency of PSII photochemistry (F
v/F
m), the effective PSII quantum yield (ϕPSII), the electron transport rate (ETR) as well as photochemical quenching (qP) in the P-limited rice plants kept close to the control, but the excitation energy capture efficiency of PSII reaction centers
(F′v/F′m) was significantly declined in the P-deficient rice leaves. Meanwhile, in the stressed leaves, we also found a significant
increase in nonphotochemical quenching (NPQ) as well as in the activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX). It was indicated that a series
of photoprotective mechanisms had been initiated in rice plants in response to short-term P deficiency. Therefore, PSII functioning
was not affected significantly under such stress. As P deficiency continued, the excess excitation energy was accumulated
in excess of the capacity of photoprotection systems. When the rice suffered from P deficiency more than 16 days, ϕPSII, ETR, and qP were decreased more rapidly than that in the control plants, although NPQ still kept higher in the stressed plants. These results were also consistent with the data on the distribution of excitation
energy. The excess energy induced the generation of reactive oxygen species, which might lead to the further damage to PSII
functioning.
This text was submitted by the authors in English. 相似文献
8.
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
9.
Stresses imposed on the cyanobacterium Synechocystis sp. PCC 6803 by various compounds present during silica sol–gel encapsulation, including salt, ethanol (EtOH), polyethylene
glycol (PEG), glycerol, and glycine betaine, were investigated. Viability of encapsulated cells and photosynthetic activity
of cells stressed by immediate (2 min) and 24-h exposure to the five stress-inducing compounds were monitored by pulse amplitude
modulated fluorometry. Cells of Synechocystis sp. PCC 6803 readily survive encapsulation in both alkoxide-derived gels and gels from aqueous precursors and can remain
active at least 8 weeks with slight degradation in PSII efficiency. Post-encapsulation survival was improved in gels containing
no additive when compared with gels containing PEG or glycerol. Glycerol was shown to have a detrimental effect on Synechocystis sp. PCC 6803, reducing ϕPSII and F
v′/F
m′ by as much as 75%, possibly a result of disrupting excitation transfer between the phycobilisomes and photosystems. PEG
was similarly deleterious, dramatically reducing the ability to carry out a state transition and adequately manage excitation
energy distribution. EtOH stress also hindered state transitions, although less severely than PEG, and the cells were able
to recover nearly all photosynthetic efficiency within 24 h after an initial drop. Betaine did not interfere with state transitions
but did reduce quantum yield and photochemical quenching. Finally, Synechocystis sp. PCC 6803 was shown to recover from salt stress. 相似文献
10.
Ming Diao Long Ma Jianwei Wang Jinxia Cui Aifei Fu Hui-ying Liu 《Journal of Plant Growth Regulation》2014,33(3):671-682
Tomato (Lycopersicon esculentum Miller) cv. Jiahe No. 9 (a salinity-resistant cultivar) and cv. Shuangfeng 87-5 (a salinity-sensitive cultivar) were used as experimental materials to investigate the effects of exogenous selenium (Na2SeO3 0.05 mM) on plant growth, chlorophyll fluorescence, photosynthetic rate, and antioxidative metabolism of chloroplasts in tomato seedlings under NaCl (100 mM) stress. Salt stress significantly inhibited plant growth, net photosynthetic rate (P n), maximum quantum yield of PSII (F v/F m), actual photochemical efficiency of PSII (Φ PSII), photochemical quenching coefficient (q P), and non-photochemical quenching coefficient (q N) of both cultivars, whereas application of Se reversed the negative effects of salt stress. Furthermore, application of Se significantly decreased the levels of hydrogen peroxide (H2O2) and malondialdehyde. Application of Se increased the activities of superoxidase dismutase, glutathione reductase, dehydroascorbate reductase, monodehydroascorbate reductase, glutathione peroxidase, and thioredoxin reductase, and the contents of ascorbate, glutathione (GSH) and NADPH, and the ratios of GSH/GSSH, AsA/DHA, and NADPH/ NADP+ in the salt-stressed chloroplasts of both cultivars. These results suggest that Se alleviates salt-induced oxidative stress through regulating the antioxidant defense systems in the chloroplasts of tomato seedlings, which is associated with the improvement of the photochemical efficiency of PSII, thereby maintaining higher photosynthetic rates. In addition, the salt tolerance of Jiahe No. 9 is closely related with high reactive oxygen species scavenging activity and reducing power levels in the chloroplasts. 相似文献
11.
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
12.
Congming Lu Nianwei Qiu Qingtao Lu Baoshan Wang Tingyun Kuang 《Physiologia plantarum》2003,118(2):173-182
Kalanchoë daigremontiana, a CAM plant grown in a greenhouse, was subjected to severe water stress. The changes in photosystem II (PSII) photochemistry were investigated in water‐stressed leaves. To separate water stress effects from photoinhibition, water stress was imposed at low irradiance (daily peak PFD 150 μmol m?2 s?1). There were no significant changes in the maximal efficiency of PSII photochemistry (Fv/Fm), the traditional fluorescence induction kinetics (OIP) and the polyphasic fluorescence induction kinetics (OJIP), suggesting that water stress had no direct effects on the primary PSII photochemistry in dark‐adapted leaves. However, PSII photochemistry in light‐adapted leaves was modified in water‐stressed plants. This was shown by the decrease in the actual PSII efficiency (ΦPSII), the efficiency of excitation energy capture by open PSII centres (Fv′/Fm′), and photochemical quenching (qP), as well as a significant increase in non‐photochemical quenching (NPQ) in particular at high PFDs. In addition, photoinhibition and the xanthophyll cycle were investigated in water‐stressed leaves when exposed to 50% full sunlight and full sunlight. At midday, water stress induced a substantial decrease in Fv/Fm which was reversible. Such a decrease was greater at higher irradiance. Similar results were observed in ΦPSII, qP, and Fv′/Fm′. On the other hand, water stress induced a significant increase in NPQ and the level of zeaxanthin via the de‐epoxidation of violaxanthin and their increases were greater at higher irradiance. The results suggest that water stress led to increased susceptibility to photoinhibition which was attributed to a photoprotective process but not to a photodamage process. Such a photoprotection was associated with the enhanced formation of zeaxanthin via de‐epoxidation of violaxanthin. The results also suggest that thermal dissipation of excess energy associated with the xanthophyll cycle may be an important adaptive mechanism to help protect the photosynthetic apparatus from photoinhibitory damage for CAM plants normally growing in arid and semi‐arid areas where they are subjected to a combination of water stress and high light. 相似文献
13.
Chilling stress and chilling tolerance of sweet potato as sensed by chlorophyll fluorescence 总被引:2,自引:0,他引:2
We studied changes in the chlorophyll (Chl) fluorescence components in chilling-stressed sweet potato (Ipomoea batatas L. Lam) cv. Tainung 57 (TN57, chilling-tolerant) and cv. Tainung 66 (TN66, chilling-susceptible). Plants under 12-h photoperiod
and 400 μmol m−2 s−1 irradiance at 24/20 °C (day/night) were treated by a 5-d chilling period at 7/7 °C. Compared to TN66, TN57 exhibited a significantly
greater basic Chl fluorescence (F0), maximum fluorescence (Fm), maximum fluorescence yield during actinic irradiation (Fm′ ), and the quantum efficiency of electron transport through photosystem 2, PS2 (ΦPS2). Chilling stress resulted in decrease in the potential efficiency of PS2 (Fv/Fm), ΦPS2, non-photochemical fluorescence quenching (NPQ), non-photochemical quenching (qN), and the occurrence of chilling injury in TN66. Chilling increased the likelihood of photoinhibition, characterized by a
decline in the Chl fluorescence of both cultivars, and photoinhibition during low temperature stress generally occurred more
rapidly in TN66. 相似文献
14.
15.
To investigate how excess excitation energy is dissipated in a ribulose-1,5-bisphospate carboxylase/oxygenase activase antisense
transgenic rice with net photosynthetic rate (P
N) half of that of wild type parent, we measured the response curve of P
N to intercellular CO2 concentration (C
i), electron transport rate (ETR), quantum yield of open photosystem 2 (PS2) reaction centres under irradiation (Fv′/Fm′), efficiency of total PS2 centres (ΦPS2), photochemical (qP) and non-photochemical quenching (NPQ), post-irradiation transient increase in chlorophyll (Chl) fluorescence (PITICF), and
P700+ re-reduction. Carboxylation efficiency dependence on C
i, ETR at saturation irradiance, and Fv′/Fm′, ΦPS2, and qP under the irradiation were significantly lower in the mutant. However, NPQ, energy-dependent quenching (qE), PITICF, and P700+ re-reduction were significantly higher in the mutant. Hence the mutant down-regulates linear ETR and stimulates cyclic electron
flow around PS1, which may generate the ΔpH to support NPQ and qE for dissipation of excess excitation energy. 相似文献
16.
Xiang-sheng Zhou Dian-xing Wu Sheng-quan Shen Jun-wei Sun Qing-yao Shu 《Photosynthetica》2006,44(2):316-319
Comparative analysis revealed that a xantha rice mutant (cv. Huangyu B) had higher ratios of chlorophyll (Chl) a/b and carotenoids/Chl, and higher photosynthetic efficiency than its wild type parent (cv. II32 B). Unexpectedly, the mutant
had higher net photosynthetic rate (P
N) than II32 B. This might have resulted from its lower non-photochemical quenching (qN) but higher maximal photochemical efficiency (FV/FM), higher excitation energy capture efficiency of photosystem 2 (PS2) reaction centres (FV′/FM′), higher photochemical quenching (qP), higher effective PS2 quantum yield (ΦPS2), and higher non-cyclic electron transport rate (ETR). This is the first report of a chlorophyll mutant that has higher photosynthetic
efficiency and main Chl fluorescence parameters than its wild type. This mutant could become a unique material both for the
basic research on photosynthesis and for the development of high yielding rice cultivars. 相似文献
17.
In a glasshouse, Bemisia tabaci infestation largely reduced response of photosynthesis to irradiance and CO2 concentration of Mikania micrantha compared with the non-infested control (C) ones. The maximum irradiance-saturated photosynthetic rate (P
max) and saturation irradiance (SI) of the infested M. micrantha were only 21.3 % and 6.5 % of the C-plants, respectively. B. tabaci infestation led to the reduction of contents of chlorophyll and carotenoids in M. micrantha, which was accompanied with the decrease of actual photosystem 2 (PS2) efficiency (ΦPS2), efficiency of excitation energy capture by open PS2 reaction centres (Fv′/Fm′), electron transport rate (ETR), and photochemical quenching (qP). Moreover, superoxide dismutase and catalase activities significantly decreased while proline and glutathione contents significantly
increased in infested M. micrantha. Hence B. tabaci infestation not only induced direct damage of photosynthetic apparatus but also altered the antioxidant enzymes activities
in M. micrantha, which might as consequences accelerate senescence of this weed. 相似文献
18.
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
19.
Xanthophyll cycle and light stress in nature: uniform response to excess direct sunlight among higher plant species 总被引:73,自引:0,他引:73
Photosystem II (PS II) efficiency, nonphotochemical fluorescence quenching, and xanthophyll cycle composition were determined in situ in the natural environment at midday in (i) a range of differently angled sun leaves ofEuonymus kiautschovicus Loesener and (ii) in sun leaves of a wide range of different plant species, including trees, shrubs, and herbs. Very different degrees of light stress were experienced by these leaves (i) in response to different levels of incident photon flux densities at similar photosynthetic capacities amongEuonymus leaves and (ii) as a result of very different photosynthetic capacities among species at similar incident photon flux densities (that were equivalent to full sunlight). ForEuonymus as well as the interspecific comparison all data fell on one single, close relationship for changes in intrinsic PSII efficiency, nonphotochemical fluorescence quenching, or the levels of zeaxanthin + antheraxanthin in leaves, respectively, as a function of the actual level of light stress. Thus, the same conversion state of the xanthophyll cycle and the same level of energy dissipation were observed for a given degree of light stress independent of species or conditions causing the light stress. Since all increases in thermal energy dissipation were associated with increases in the levels of zeaxanthin + antheraxanthin in these leaves, there was thus no indication of any form of xanthophyll cycle-independent energy dissipation in any of the twenty-four species or varieties of plants examined in their natural environment. It is also concluded that transient diurnal changes in intrinsic PSII efficiency in nature are caused by changes in the efficiency with which excitation energy is delivered from the antennae to PSII centers, and are thus likely to be purely photoprotective. Consequently, the possibility of quantifying the allocation of absorbed light into PSII photochemistry versus energy dissipation in the antennae from changes in intrinsic PSII efficiency is explored.Abbreviations A
antheraxanthin
- F
actual level of fluorescence
- Fa, F
o
minimal fluorescence in the absence, presence of thylakoid energization
- Fm, F
m
maximal fluorescence in the absence, presence of thylakoid energization
- Fm, - F)/F
m
actual PSII efficiency ( = percent of absorbed light utilized in PSII photochemistry)
- Fv/Fm, F
v
/Fm/
PSII efficiency of open centers in the absence, presence of thylakoid energization
- NPQ
nonphotochemical fluorescence quenching
- Fm/F
m
- 1; qp
quenching coefficient for photochemical quenching
- V
violaxanthin
- Z
zeaxanthin 相似文献
20.
Seedlings (70-d-old) of two tall fescue (Festuca arundinacea Schreb.) genotypes, heat-tolerant Jaguar 3 and heat-sensitive TF 66, were exposed to a high temperature stress of 35/30 °C
(day/night) for 20 d and both light-saturated and CO2-saturated leaf stomatal conductance decreased, especially in TF 66. Higher reductions of quantum efficiency, carboxylation
efficiency and maximum photochemical efficiency of photosystem 2 in dark adapted leaves (measured as Fv/Fm) occurred in TF 66 than in Jaguar 3. High temperature stress increased photorespiration in the two plants, but more in TF
66. Moreover, high temperature stress also reduced the growth, chlorophyll content and caused cell membrane injuries in the
two cultivars, the changes were again more pronounced in TF 66 than in Jaguar 3. 相似文献