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1.
The effects of water deficit on photochemical parameters and activities of superoxide dismutase, catalase, ascorbate peroxidase
and glutathione reductase were investigated in two olive cultivars differing in drought tolerance — ‘Chemlali’ and ‘Chetoui’.
After 30 days without irrigation, leaf water potential fell to −5.5 MPa that was accompanied by a marked decrease in net photosynthesis
in ‘Chetoui’ olive cultivar. Maximal efficiency of PSII photochemistry (Fv/Fm) decreased slightly in ‘Chemlali’ (28 %) and substantially in ‘Chétoui’ (47 %). Both cultivars showed a similar decline (about
25 %) in the photochemical quenching coefficient, but only the drought-sensitive olive cultivar exhibited an enhancement (31
%) of non-photochemical fluorescence quenching under water deficit conditions. The quantum yield of electron transport decreased
in both olive cultivars. ‘Chemlali’ showed a higher protection against oxidative stress, as judged from the lower levels of
the malondialdehyde production. Catalase activity was higher in ‘Chetoui’. Glutathione reductase activity was increased similarly
in both olive cultivars under water stress. Ascorbate peroxidase activity was enhanced in ‘Chemlali’ under water stress, but
was unaffected in ‘Chetoui’. While, superoxide dismutase activity was inhibited in both cultivars under water stress, but
higher activity was detected in ‘Chemlali’. Thus, the ability to increase ascorbate peroxidase and a higher superoxide dismutase
activity might be an important attribute linked to the drought tolerance in ‘Chemlali’ olive cultivar. 相似文献
2.
In this study, the gas exchange, chlorophyll fluorescence, and antioxidant activity in eight tall fescue cultivars were investigated
under aluminum stress. The results showed that the net photosynthetic rate (P
N) and stomatal conductance (g
s) were decreased, while the intercellular CO2 concentration (Ci) was stable or increased under Al stress conditions. The efficiency of excitation capture by open PSII reaction centers (F′v/F′m), the maximum quantum yield of PSII photochemistry (F
v/F
m), the quantum yield of PSII electron transport (ΦPSII), and the photochemical quenching (qP) were also decreased after Al stress, while the non-photochemical quenching (NPQ) was
increased. Moreover, Al stress increased the antioxidant activities and MDA contents in each tall fescue cultivars. However,
there was a lot genotype differences between the Al-tolerant and Al-sensitive cultivars. Cv. Barrington was the most sensitive
cultivar and cv. Crossfire 2 was the most tolerant cultivar. The excessive excitation energy could not be dissipated efficiently
by antenna pigments, and reactive oxygen species could not be scavenged efficiently, thereby resulting in membrane lipid peroxidation
in cv. Barrington under Al stress conditions. 相似文献
3.
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
4.
In this study, the effects of lanthanum were investigated on contents of pigments, chlorophyll (Chl) fluorescence, antioxidative enzymes, and biomass of maize seedlings under salt stress. The results showed that salt stress significantly decreased the contents of Chl and carotenoids, maximum photochemical efficiency of PSII (Fv/Fm), photochemical quenching (qP), and quantum efficiency of PSII photochemistry (ΦPSII), net photosynthetic rate (PN), and biomass. Salt stress increased nonphotochemical quenching (qN), the activities of ascorbate peroxidase, catalase, superoxide dismutase, glutathione peroxidase, and the contents of malondialdehyde and hydrogen peroxide compared with control. Pretreatment with lanthanum prior to salt stress significantly enhanced the contents of Chl and carotenoids, Fv/Fm, qP, qN, ΦPSII, PN, biomass, and activities of the above antioxidant enzymes compared with the salt-stressed plants. Pretreatment with lanthanum also significantly reduced the contents of malondialdehyde and hydrogen peroxide induced by salt stress. Our results suggested that lanthanum can improve salt tolerance of maize seedlings by enhancing the function of photosynthetic apparatus and antioxidant capacity. 相似文献
5.
Koblížek M. Ciscato M. Komenda J. Kopencký J. Šiffel P. Masojídek J. 《Photosynthetica》1999,37(2):307-323
The dark-adapted cells of the green alga Spongiochloris sp. were exposed to "white light" of 1000 μmol(photon) m−2 s−1 for 2 h and then dark adapted for 1.5 h. Changes of photochemical activities during photoadaptation were followed by measurement
of chlorophyll (Chl) fluorescence kinetics, 77 K emission spectra, photosynthetic oxygen evolution, and pigment composition.
We observed a build-up of slowly-relaxing non-photochemical quenching which led to a decrease of the Fv/Fm parameter and the connectivity. In contrast to the depression of Fv/Fm (35 %) and the rise of non-photochemical quenching (∼ 1.6), we observed an increase in effective absorption cross-section
(20 %), Hill reaction (30 %), photosynthetic oxygen evolution (80 %), and electron transport rate estimated from the Chl fluorescence
analysis (80 %). We showed an inconsistency in the presently used interpretation schemes, and ascribe the discrepancy between
the increase of effective absorption cross-section and the photosynthetic activities on one side and the effective non-photochemical
quenching on the other side to the build-up of a quenching mechanism which dissipates energy in closed reaction centres. Such
a type of quenching changes the ratio between thermal dissipation and fluorescence without any effect on photochemical yield.
In this case the Fv/Fm ratio cannot be used as a measure of the maximum photochemical yield of PS2.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
Role of calcium ion in protection against heat and high irradiance stress-induced oxidative damage to photosynthesis of wheat leaves 总被引:8,自引:0,他引:8
Cross stress of heat and high irradiance (HI) resulted in the accumulation of active oxygen species and photo-oxidative damage
to photosynthetic apparatus of wheat leaves during grain development. Pre-treatment with calcium ion protected the photosynthetic
system from oxidative damage by reducing O-.
2 production, inhibiting lipid peroxidation, and retarding electrolyte leakage from cell. Therefore, high Fv/Fm [maximal photochemical efficiency of photosystem 2 (PS2) while all PS2 reaction centres are open], Fm/F0 (another expression for the maximal photochemical efficiency of PS2), ΦPS2 (actual quantum yield of PS2 under actinic irradiation), qP (photochemical quenching coefficient), and P
N (net photosynthetic rate) were maintained, and lower qNP (non-photochemical quenching coefficient) of the leaves was kept under heat and HI stress. EGTA (a chelant of calcium ion)
and LaCl3 (a blocker of Ca2+ channel in cytoplasmic membrane) had the opposite effect. Thus Ca ion may help protect the photosynthetic system of wheat
leaves from oxidative damage induced by the cross stress of heat and HI. 相似文献
7.
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
8.
Plant growth, chlorophyll (Chl) content, photosynthetic gas exchange, ribulose-1,5-bisphosphate carboxylase (RuBPCO) enzyme
activity, and Chl fluorescence in radish (Raphanus sativus var. longipinnatus) plants were examined after turnip mosaic virus (TuMV) infection. Plant fresh mass, dry mass, Chl content, net photosynthetic
rate (P
N), transpiration rate (E), stomatal conductance (g
s), and RuBPCO activity were significantly lower in infected plants after 5 weeks of virus infection as compared to healthy
plants. The 5-week virus infection did not induce significant differences in intercellular CO2 concentration (C
i, photochemical efficiency of photosystem 2, PS2 (Fv/Fm), excitation capture efficiency of open PS2 reaction centres (Fv'/Fm'), effective quantum efficiency of photosystem 2 (ΔF/Fm'), and photochemical quenching (qP), but non-photochemical quenching (qN) and alternative electron sink (AES) were significantly enhanced. Thus the decreased plant biomass of TuMV-infected plants
might be associated with the decreased photosynthetic activity mainly due to reduced RuBPCO activity. 相似文献
9.
Agronomic traits, photosynthetic pigments, gas exchange, and chlorophyll (Chl) fluorescence parameters of red stem buckwheat
(Fagopyrum dibotrys Hara) mutants induced by γ-radiation were compared with green control at seedling stage. Plant height, number of first-class
branches, and rhizome biomass were inhibited significantly (p<0.01). Chl a, Chl b, and Chl a+b contents decreased with elevated dose of γ-rays, while increasing carotenoid content indicated that buckwheat was capable
of adjusting to the radiation damage. Decrease in net photosynthetic rate was the result of both stomatal and non-stomatal
limitations. Fluorescence parameters, such as F0, Fm, Fv/Fm, Fv/F0, ΦPS2, electron transport rate, and photochemical quenching declined significantly (p<0.01) as compared with control due to photoinhibition, while non-photochemical quenching increased to enhance thermal dissipation.
Lower parameters implied that leaf tissue was damaged significantly by high dose of γ-radiation and therefore leaf senescence
was accelerated. 相似文献
10.
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
11.
为评价日本荚蒾(Viburnum japonicum)的耐盐雾能力,对4 a生实生苗用不同盐雾浓度处理(盐雾NaCl质量浓度分别为0%、1%、2%、3%),测定叶片净光合速率、最大光化学效率(Fv/Fm)和叶绿素含量(Chl)等指标的变化。结果表明,1%盐雾处理的日本荚蒾植株能够存活,但生长不良,大于2%的盐雾处理的植株全部死亡。随着浓度的升高,日本荚蒾叶片的最大光合速率、Fv/Fm及Chl含量下降,而光饱和点及光补偿点总体呈上升趋势。这说明盐雾胁迫通过伤害光系统Ⅱ反应中心、改变植物可利用光能范围及降低叶绿素含量影响植物的光合作用。 相似文献
12.
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
13.
The chlorophyll (Chl) fluorescence imaging technique was applied to cashew seedlings inoculated with the fungus Lasiodiplodia theobromae to assess any disturbances in the photosynthetic apparatus of the plants before the onset of visual symptoms. Two-month-old cashew plants were inoculated with mycelium of L. theobromae isolate Lt19 or Lt32. Dark-adapted and light-acclimated whole plants or previously labelled, single, mature leaf from each plant were evaluated weekly for Chl fluorescence parameters. From 21 to 28 days, inoculation with both isolates resulted in the significantly lower maximal photochemical quantum yield of PSII (Fv/Fm) than those for control samples, decreasing from values of 0.78 to 0.62. In contrast, the time response of the measured fluorescence transient curve from dark-acclimated plants increased in both whole plants and single mature leaves in inoculated plants compared with controls. The Fv/Fm images clearly exhibited photosynthetic perturbations 14 days after inoculation before any visual symptoms appeared. Additionally, decays in the effective quantum yield of PSII photochemistry and photochemical quenching coefficient were also observed over time. However, nonphotochemical quenching increased during the evaluation period. We conclude that Fv/Fm images are the effective way of detecting early metabolic perturbations in the photosynthetic apparatus of cashew seedlings caused by gummosis in both whole plants and single leaves and could be potentially employed in larger-scale screening systems. 相似文献
14.
Photosynthetic rate (PN) and chlorophyll (Chl) fluorescence induction of source leaves in response to a low sink demand created by girdling the branch
(GB) between the root-tuber-system and the leaves were studied in Dahlia pinnata L. cv. Rigolet during the stage of rapid tuber growth in the greenhouse. GB resulted in significantly lower values of PN, stomatal conductance (gs), and transpiration rate (E), but in higher leaf temperature (Tl) compared with those of controls. With exception of maximum quantum yield of photosystem 2 (PS 2) photochemistry (Fv/Fm) and maximum ratio of quantum yields of photochemical and concurrent non-photochemical processes in PS 2 (Fv/F0), no significant differences were observed in Chl fluorescence parameters between girdled and control leaves on days 1 and
2 after GB, indicating no apparent damage in the photosynthetic apparatus. However, longer girdling duration resulted in higher
non-photochemical Chl fluorescence quenching (NPQ), but lower Fv/F0, actual efficiency of energy conversion in PS 2 under steady-state conditions (ΦPS2), and photochemical quenching coefficient (qP) in comparison with controls from 10:00 to 16:00 or 15:00 on days 4 and 5,
respectively, indicating reversible injury in the photosynthetic apparatus. 相似文献
15.
Changes in pigment composition and chlorophyll (Chl) fluorescence parameters were studied in 20 year-old Scots pine (Pinus sylvestris L.) trees grown in environment-controlled chambers and subjected to ambient conditions (CON), doubled ambient CO2 concentration (EC), elevated temperature (ambient +2−6 °C, ET), or a combination of EC and ET (ECT) for four years. EC did
not significantly alter the optimal photochemical efficiency of photosystem 2 (PS2; Fv/Fm), or Chl a+b content during the main growth season (days 150–240) but it reduced Fv/Fm and the Chl a+b content and increased the ratio of total carotenoids to Chl a+b during the ‘off season’. By contrast, ET significantly enhanced the efficiency of PS2 in terms of increases in Fv/Fm and Chl a+b content throughout the year, but with more pronounced enhancement in the ‘off season’. The reduction in Fv/Fm during autumn could be associated with the CO2-induced earlier yellowing of the leaves, whereas the temperature-stimulated increase in the photochemical efficiency of PS2
during the ‘off season’ could be attributed to the maintenance of a high sink capacity. The pigment and fluorescence responses
in the case of ECT showed a similar pattern to that for ET, implying the importance of the temperature factor in future climate
changes in the boreal zone.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
16.
In Leymus chinensis, mild water stress (soil moisture 60–65 % of field capacity) had no significant effects on nitrogen metabolism, photosynthesis, and chlorophyll fluorescence. Severe water stress (35–40 %) significantly decreased the activities of nitrate reductase, glutamine synthetase, and glutamate dehydrogenase, net photosynthetic rate, stomatal conductance, transpiration rate, maximal efficiency of photosystem 2 photochemistry (Fv/Fm), actual quantum yield, and photochemical quenching, but increased the endopeptidase activity and malondialdehyde contents. The adverse effects on photosynthesis and N metabolism were markedly greater in reproductive shoots than in vegetative shoots. 相似文献
17.
低温弱光胁迫及恢复对切花菊光合作用和叶绿素荧光参数的影响 总被引:15,自引:4,他引:11
以切花菊品种‘神马’为试材,在偏低温弱光(16℃/12℃,PFD100μmol.m-2.s-1)和临界低温弱光(12℃/8℃,PFD60μmol.m-2.s-1)下分别胁迫11d,然后转入正常条件(22℃/18℃,PFD450μmol.m-2.s-1)恢复11d,研究不同低温弱光强度及恢复对菊花光合作用和叶绿素荧光参数的影响.结果表明:低温弱光导致菊花叶片的净光合速率(Pn)和气孔限制值(Ls)下降,而胞间CO2浓度(Ci)上升.偏低温弱光胁迫下菊花叶片暗适应下最大光化学效率(Fv/Fm)和初始荧光(Fo)无明显变化,但光适应下最大光化学效率(Fv′/Fm′)在处理前期略有下降,后期则有所回升;而临界低温弱光处理的Fo明显升高,Fv/Fm和Fv′/Fm′显著降低.PSⅡ光合电子传递量子效率(ΦPSⅡ)、光化学猝灭系数(qP)和表观光合电子传递速率(ETR)均随着低温弱光胁迫程度的增加和时间的延长而降低;偏低温弱光处理植株在解除胁迫后能迅速恢复到对照水平,而临界低温弱光处理植株回升速度较慢;同时,低温弱光胁迫下吸收光强用于分配光化学反应部分(Prate)的比例减少,而天线热耗散(Drate)和反应中心的能量耗散(Ex)比例上升,但天线热耗散为过剩光能的主要分配途径. 相似文献
18.
Photosynthetic parameters were measured in two invasive weeds, Mikania micrantha and Chromolaena odorata, grown in soil under full, medium, and low irradiance and full, medium, and low water supply. Both species showed significantly
higher net photosynthetic rate, quantum yield of PS 2 photochemistry and photochemical quenching coefficient under high than
low irradiance. For M. micrantha, low irradiance caused decreased chlorophyll content (Chl), Chl a/b ratio and maximum photochemical efficiency of PS 2 (Fv/Fm), while drought decreased Chl content and Fv/Fm and increased nonphotochemical quenching (NPQ). However, these parameters were much less affected in C. odorata except that Chl content and NPQ slightly increased under drought and high irradiance. High irradiance increased xanthophyll
pools in both species, especially M. micrantha under combination with drought. 相似文献
19.
This contribution is a practical guide to the measurement of the different chlorophyll (Chl) fluorescence parameters and gives
examples of their development under high-irradiance stress. From the Chl fluorescence induction kinetics upon irradiation
of dark-adapted leaves, measured with the PAM fluorometer, various Chl fluorescence parameters, ratios, and quenching coefficients
can be determined, which provide information on the functionality of the photosystem 2 (PS2) and the photosynthetic apparatus.
These are the parameters Fv, Fm, F0, Fm′, Fv′, NF, and ΔF, the Chl fluorescence ratios Fv/Fm, Fv/F0, ΔF/Fm′, as well as the photochemical (qP) and non-photochemical quenching coefficients (qN, qCN, and NPQ). qN consists of three components (qN = qE + qT + qI), the contribution of which can be determined via Chl fluorescence relaxation kinetics measured in the dark period after the induction kinetics. The above Chl fluorescence
parameters and ratios, many of which are measured in the dark-adapted state of leaves, primarily provide information on the
functionality of PS2. In fully developed green and dark-green leaves these Chl fluorescence parameters, measured at the upper
adaxial leaf side, only reflect the Chl fluorescence of a small portion of the leaf chloroplasts of the green palisade parenchyma
cells at the upper outer leaf half. Thus, PAM fluorometer measurements have to be performed at both leaf sides to obtain information
on all chloroplasts of the whole leaf. Combined high irradiance (HI) and heat stress, applied at the upper leaf side, strongly
reduced the quantum yield of the photochemical energy conversion at the upper leaf half to nearly zero, whereas the Chl fluorescence
signals measured at the lower leaf side were not or only little affected. During this HL-stress treatment, qN, qCN, and NPQ increased in both leaf sides, but to a much higher extent at the lower compared to the upper leaf side. qN was the best indicator for non-photochemical quenching even during a stronger HL-stress, whereas qCN and NPQ decreased with progressive stress even though non-photochemical quenching still continued. It is strongly recommended
to determine, in addition to the classical fluorescence parameters, via the PAM fluorometer also the Chl fluorescence decrease ratio RFd (Fd/Fs), which, when measured at saturation irradiance is directly correlated to the net CO2 assimilation rate (P
N) of leaves. This RFd-ratio can be determined from the Chl fluorescence induction kinetics measured with the PAM fluorometer using continuous saturating
light (cSL) during 4–5 min. As the RFd-values are fast measurable indicators correlating with the photosynthetic activity of whole leaves, they should always be
determined via the PAM fluorometer parallel to the other Chl fluorescence coefficients and ratios. 相似文献
20.
In order to investigate the photoprotective function of photorespiration in grapevine under water stress, potted grapevines
(Vitis vinifera L. cv. Cabernet Sauvignon) were randomly divided into three uniform groups for well-watered [watered every morning to keep
the relative water content (RWC) of soil over 70 %], water-stress adapted (drought-adapted at 30 % relative soil water content
for 30 days), and water stress without adaptation treatment (water-stressed to 30 % relative soil water content for 3 days).
Net assimilation rate (A
N), stomatal conductance (g
s), substomatal CO2 concentration (C
i), transpiration rate (E), actual photochemical efficiency of PSII (ΦPSII), and maximum photochemical efficiency of PSII (Fv/Fm) were recorded by combining measurements of gas exchange and chlorophyll fluorescence. Gross photorespiration (Pr), photosynthetic electron partitioning (JC/JT), photochemical quenching coefficient (qP), and non-photochemical quenching (NPQ) were also calculated. The ratio of net
assimilation rate to transpiration rate (A
N/E) was used as an indicator of water use efficiency (WUE). A
N, apparent Pr, ΦPSII, Fv/Fm, qp, and g
s decreased, NPQ increased, and gross Pr sustained at a high level under water stress. This suggests that both photorespiration and energy dissipation play important
roles in protecting photosynthetic apparatus against photoinhibition. C
i in water-stressed plants without adaptation treatment increased, which indicates the leaves suffered a non-stomatal limitation,
while the water-stress adaped plants only suffered a stomatal limitation indicated by low C
i. 相似文献