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1.
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
2.
Caragana korshinskii seedlings maintain positive photosynthesis during short-term,severe drought stress 总被引:1,自引:0,他引:1
Seedling performance may determine plant distribution, especially in water-limited environments. Plants of Caragana korshinskii commonly grow in arid and semiarid areas in northwestern China, and endure water shortage in various ways, but little is
known about their performance when water shortage occurs at early growth stages. The water relations, photosynthetic activity,
chlorophyll (Chl) content and proline accumulation were determined in 1-year-old seedlings growing in a 1:1 mixture of Loess
soil and Perlite and subjected to (1) a water deficit for 20 days and (2) kept adequately watered throughout. The water deficit induced low (−6.1 MPa) predawn leaf water potentials (LWP), but did
not induce any leaf abscission. Stomatal conductance (g
s), leaf transpiration rate (E), and net photosynthetic rate (P
N) decreased immediately following the imposition of the water deficit, while the maximal photochemical efficiency of photosystem
II (PSII) (Fv/Fm) and the effective quantum yield of PSII (ΦPSII) decreased 15 days later. An early and rapid decrease in g
s, reduced E, increased Chl (a+b) loss, increased the apparent rate of photochemical transport of electrons through PSII (ETR)/P
N, as well as a gradual increase in non-photochemical quenching of fluorescence (NPQ) and proline may have contributed to preventing
ΦPSII from photodamage. C. korshinskii seedlings used a stress-tolerance strategy, with leaf maintenance providing a clear selective advantage, considering the
occasional rainfall events during the growing season. 相似文献
3.
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
4.
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
5.
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
6.
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
7.
The effect of four different NaCl concentrations (from 0 to 102 mM NaCl) on seedlings leaves of two corn (Zea mays L.) varieties (Aristo and Arper) was investigated through chlorophyll (Chl) a fluorescence parameters, photosynthesis, stomatal conductance, photosynthetic pigments concentration, tissue hydration and
ionic accumulation. Salinity treatments showed a decrease in maximal efficiency of PSII photochemistry (Fv/Fm) in dark-adapted leaves. Moreover, the actual PSII efficiency (ϕPSII), photochemical quenching coefficient (qp), proportion of PSII centers effectively reoxidized, and the fraction of light used in PSII photochemistry (%P) were also
dropped with increasing salinity in light-adapted leaves. Reductions in these parameters were greater in Aristo than in Arper.
The tissue hydration decreased in salt-treated leaves as did the photosynthesis, stomatal conductance (g
s) and photosynthetic pigments concentration essentially at 68 and 102 mM NaCl. In both varieties the reduction of photosynthesis
was mainly due to stomatal closure and partially to PSII photoinhibition. The differences between the two varieties indicate
that Aristo was more susceptible to salt-stress damage than Arper which revealed a moderate regulation of the leaf ionic accumulation. 相似文献
8.
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
9.
Effects of water stress and high temperature on gas exchange and chlorophyll fluorescence in Triticum aestivum L. 总被引:1,自引:0,他引:1
I. A. Hassan 《Photosynthetica》2006,44(2):312-315
Wheat plants grown in controlled growth chambers were exposed to drought stress (DS) and high temperature (HT) singly and
in combination (DS+HT). The effects of these two stresses on net photosynthetic rate (P
N), stomatal conductance (g
s), intercellular CO2 concentration (C
i), quantum efficiency of photosystem 2 (ΦPS2), variable to maximum chlorophyll (Chl) fluorescence (Fv/Fm), photochemical (qp) and non-photochemical (NPQ) Chl fluorescence, and yield were investigated. Grain yield was decreased by 21 % due to DS,
while it was increased by 26 % due to HT. P
N, g
s, C
i, and Chl fluorescence were dramatically reduced to DS, HT, and their interaction, except NPQ which showed an increase due
to HT. 相似文献
10.
Protective mechanism of desiccation tolerance in <Emphasis Type="Italic">Reaumuria soongorica</Emphasis>: Leaf abscission and sucrose accumulation in the stem
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Reaumuria soongorica (Pall.) Maxim., a perennial semi-shrub, is widely found in semi-arid areas in northwestern China and can survive severe desiccation
of its vegetative organs. In order to study the protective mechanism of desiccation tolerance in R. soongorica, diurnal patterns of net photosynthetic rate (Pn), water use efficiency (WUE) and chlorophyll fluorescence parameters of
Photosystem II (PSII), and sugar content in the source leaf and stem were investigated in 6-year-old plants during progressive
soil drought imposed by the cessation of watering. The results showed that R. soongorica was characterized by very low leaf water potential, high WUE, photosynthesis and high accumulation of sucrose in the stem
and leaf abscission under desiccation. The maximum Pn increased at first and then declined during drought, but intrinsic WUE
increased remarkably in the morning with increasing drought stress. The maximal photochemical efficiency of PSII (Fv/Fm) and
the quantum efficiency of noncyclic electric transport of PSII(ΦPSII) decreased significantly under water stress and exhibited an obvious phenomenon of photoinhibition at noon. Drought stressed
plants maintained a higher capacity of dissipation of the excitation energy (measured as NPQ) with the increasing intensity
of stress. Conditions of progressive drought promoted sucrose and starch accumulation in the stems but not in the leaves.
However, when leaf water potential was less than −21.3 MPa, the plant leaves died and then abscised. But the stem photosynthesis
remained and, afterward the plants entered the dormant state. Upon rewatering, the shoots reactivated and the plants developed
new leaves. Therefore, R. soongorica has the ability to reduce water loss through leaf abscission and maintain the vigor of the stem cells to survive desiccation. 相似文献
11.
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
12.
13.
A. Pavlovič 《Photosynthetica》2011,49(2):253-258
Australian carnivorous pitcher plant Cephalotus follicularis Labill. produces two types of leaves. During the spring time, the plant produces a foliage type of noncarnivorous leaf called
lamina. Later, the second type of leaf is produced — carnivorous pitcher. Using simultaneous measurements of gas exchange
and chlorophyll (Chl) fluorescence photosynthetic efficiency of these two distinct forms of leaves were compared. In addition
stomatal density, an important component of gas exchange, and Chl concentration were also determined. Pitcher trap had lower
net photosynthetic rate (P
N) in comparison to noncarnivorous lamina, whereas the rate of respiration (R
D) was not significantly different. This was in accordance with lower stomatal density and Chl concentration in the pitcher
trap. On the other hand maximum quantum yield of PSII (Fv/Fm) and effective quantum yield of photochemical energy conversion in PSII (ΦPSII) was not significantly different. Nonphotochemical quenching (NPQ) was significantly higher in the lamina at higher irradiance.
These data are in accordance with hypothesis that changing the leaf shape in carnivorous plants to make it a better trap generally
makes it less efficient at photosynthesis. However, the pitcher of Cephalotus had much higher P
N than it was expected from the data set of the genus Nepenthes. Because it is not possible to optimize for contrasting function such as photosynthesis and carnivory, it is hypothesized
that Cephalotus pitchers are less elaborated for carnivorous function than the pitchers of Nepenthes. 相似文献
14.
X. K. Yuan 《Photosynthetica》2016,54(3):475-477
In order to investigate the effect of day/night temperature difference (DIF) on photosynthetic characteristics of tomato plants (Solanum lycopersicum, cv. Jinguan 5) at fruit stage, an experiment was carried out in climate chambers. Five day/night temperature regimes (16/34, 19/31, 25/25, 31/19, and 34/16°C) with respective DIFs of -18, -12, 0, +12, and +18 were used and measured at mean daily temperature of 25°C. The results showed that chlorophyll (Chl) a, Chl b, net photosynthetic rate (PN), stomatal conductance (gs), maximum quantum yield of PSII photochemistry (Fv/Fm), effective quantum yield of PSII photochemistry (?PSII), and photochemical quenching (qp) significantly increased under positive DIF, while they decreased with negative DIF. In contrast, the Chl a/b ratio and nonphotochemical quenching (NPQ) decreased under positive DIF, while increased with negative DIF. Chl a, Chl b, PN, gs, Fv/Fm, ?PSII, and qp were larger under +12 DIF than those at +18 DIF, while Chl a/b and NPQ showed an opposite trend. 相似文献
15.
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
16.
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
17.
Z. -M. Ge X. Zhou S. Kellomäki K. -Y. Wang H. Peltola P. J. Martikainen 《Photosynthetica》2011,49(2):172-184
The effects of elevated growth temperature (ambient + 3.5°C) and CO2 (700 μmol mol−1) on leaf photosynthesis, pigments and chlorophyll fluorescence of a boreal perennial grass (Phalaris arundinacea L.) under different water regimes (well watered to water shortage) were investigated. Layer-specific measurements were conducted
on the top (younger leaf) and low (older leaf) canopy positions of the plants after anthesis. During the early development
stages, elevated temperature enhanced the maximum rate of photosynthesis (P
max) of the top layer leaves and the aboveground biomass, which resulted in earlier senescence and lower photosynthesis and biomass
at the later periods. At the stage of plant maturity, the content of chlorophyll (Chl), leaf nitrogen (NL), and light response of effective photochemical efficiency (ΦPSII) and electron transport rate (ETR) was significantly lower under elevated temperature than ambient temperature in leaves
at both layers. CO2 enrichment enhanced the photosynthesis but led to a decline of NL and Chl content, as well as lower fluorescence parameters of ΦPSII and ETR in leaves at both layers. In addition, the down-regulation by CO2 elevation was significant at the low canopy position. Regardless of climate treatment, the water shortage had a strongly
negative effect on the photosynthesis, biomass growth, and fluorescence parameters, particularly in the leaves from the low
canopy position. Elevated temperature exacerbated the impact of water shortage, while CO2 enrichment slightly alleviated the drought-induced adverse effects on P
max. We suggest that the light response of ΦPSII and ETR, being more sensitive to leaf-age classes, reflect the photosynthetic responses to climatic treatments and drought
stress better than the fluorescence parameters under dark adaptation. 相似文献
18.
Mutants with altered leaf morphology are useful as markers for the study of genetic systems and for probing the leaf differentiation
process. One such mutant with deficient greening and altered development of the leaf mesophyll appeared in an inbred line
of sunflower (Helianthus annuus L.). The objectives of the present study were to determine the inheritance of the mutant leaf trait and its morphological
characterisation. The mutation, named mesophyll cell defective1 (mcd1), has pleiotropic effects and it is inherited as a monogenic recessive. The structure and tissue organization of mcd1 leaves are disrupted. In mcd1 leaves, the mesophyll has prominent intercellular spaces, and palisade and spongy tissues are not properly shaped. The mutant
palisade cells also appear to be more vacuolated and with a reduced number of chloroplasts than the wild type leaves of equivalent
developmental stage. The lamina thickness of mcd1 leaves is greatly variable and in some areas no mesophyll cells are present between the adaxial and abaxial epidermis. The
leaf area of the mcd1 mutant is extremely reduced as well as the stem height. A deficient accumulation of photosynthetic pigments characterizes
both cotyledons and leaves of the mutant. In mcd1 leaves, chlorophyll (Chl) fluorescence imaging evidences a spatial heterogeneity of leaf photosynthetic performance. Little
black points, which correspond to photosystem II (PSII) maximum efficiency (Fv/Fm) values close to zero, characterize the mcd1 leaves. Similarly, the lightadapted quantum efficiency (ΦPSII) values show a homogeneous distribution over wild type leaf lamina, while the damaged areas in mcd1 leaves, represented by yellow zones, are prominent. In conclusion, the loss of function of the MCD1 gene in Helianthus annuus is correlated with a variegated leaf phenotype characterized by a localized destruction of mesophyll morphogenesis and defeat
of PSII activity. 相似文献
19.
Reaumuria soongorica (Pall.) Maxim., a perennial semi-shrub, is widely found in semi-arid areas in northwestern China and can survive severe desiccation
of its vegetative organs. In order to study the protective mechanism of desiccation tolerance in R. soongorica, diurnal patterns of net photosynthetic rate (Pn), water use efficiency (WUE) and chlorophyll fluorescence parameters of
Photosystem II (PSII), and sugar content in the source leaf and stem were investigated in 6-year-old plants during progressive
soil drought imposed by the cessation of watering. The results showed that R. soongorica was characterized by very low leaf water potential, high WUE, photosynthesis and high accumulation of sucrose in the stem
and leaf abscission under desiccation. The maximum Pn increased at first and then declined during drought, but intrinsic WUE
increased remarkably in the morning with increasing drought stress. The maximal photochemical efficiency of PSII (Fv/Fm) and
the quantum efficiency of noncyclic electric transport of PSII(ΦPSII) decreased significantly under water stress and exhibited an obvious phenomenon of photoinhibition at noon. Drought stressed
plants maintained a higher capacity of dissipation of the excitation energy (measured as NPQ) with the increasing intensity
of stress. Conditions of progressive drought promoted sucrose and starch accumulation in the stems but not in the leaves.
However, when leaf water potential was less than −21.3 MPa, the plant leaves died and then abscised. But the stem photosynthesis
remained and, afterward the plants entered the dormant state. Upon rewatering, the shoots reactivated and the plants developed
new leaves. Therefore, R. soongorica has the ability to reduce water loss through leaf abscission and maintain the vigor of the stem cells to survive desiccation.
Supported by the Program of the Research of Vegetation Restoration in Arid Areas of Lanzhou (Grant No. 03-2-27) and the National
Natural Science Foundation of China (Grant No. 30270243) 相似文献
20.
Limitations to photosynthesis inCoffea canephoraas a result of nitrogen and water availability 总被引:1,自引:0,他引:1
Fbio M. DaMatta Rodolfo A. Loos Emerson A. Silva Marcelo E. Loureiro 《Journal of plant physiology》2002,159(9):975
Plants of C. canephora grown in pots under low nitrogen (LN) or high nitrogen (HN) applications were submitted to either cyclic water stress or daily irrigation. Water deficit led to marked decreases in net carbon assimilation rate (A) and, to a lesser extent, in stomatal conductance (gs), regardless of the N treatments. In well-watered plants, A appreciably increased in HN plants relative to LN plants without significant changes in gs. As a whole, changes in internal CO2 concentration predominantly reflected changes in A rather than in gs. Under irrigated conditions, A, but not gs, correlated with leaf N concentration in a curvilinear way. Photosynthetic nitrogen-use efficiency was considerably low, and decreased with increasing leaf N concentration. Limited N, but not water, slightly decreased the maximum photochemical efficiency of photosystem II (PSII). Under continuous irrigation, LN plants had a smaller quantum yield of electron transport (PSII) through slight decreases of photochemical quenching (qp) and capture efficiency of excitation energy by open PSII reaction centres, and increases in Stern-Volmer non-photochemical quenching. Under water-stressed conditions, changes in PSII photochemistry were apparent only in HN plants, with a 25 % decrease in PSII, due mainly to variations in qp. Biochemical constraints, rather than stomatal or photochemical limitations, provoked the decreases in A under limited supply of either N or water. 相似文献