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1.
2.
The efficiency of photosystem II antenna complexes (LHCs) in higher plants must be regulated to avoid potentially damaging
overexcitation of the reaction centre in excess light. Regulation is achieved via a feedback mechanism known as non-photochemical
quenching (NPQ), triggered the proton gradient (ΔpH) causing heat dissipation within the LHC antenna. ΔpH causes protonation
of the LHCs, the PsbS protein and triggers the enzymatic de-epoxidation of the xanthophyll, violaxanthin, to zeaxanthin. A
key step in understanding the mechanism is to decipher whether PsbS and zeaxanthin cooperate to promote NPQ. To obtain clues
about their respective functions we studied the effects of PsbS and zeaxanthin on the rates of NPQ formation and relaxation
in wild-type Arabidopsis leaves and those overexpressing PsbS (L17) or lacking zeaxanthin (npq1). Overexpression of PsbS was found to increase the rate of NPQ formation, as previously reported for zeaxanthin. However,
PsbS overexpression also increased the rate of NPQ relaxation, unlike zeaxanthin, which is known decrease the rate. The enhancement
of PsbS levels in plants lacking zeaxanthin (npq1) by either acclimation to high light or crossing with L17 plants showed that the effect of PsbS was independent of zeaxanthin.
PsbS levels also affected the kinetics of the 535 nm absorption change (ΔA535), which monitors the formation of the conformational
state of the LHC antenna associated with NPQ, in an identical way. The antagonistic action of PsbS and zeaxanthin with respect
to NPQ and ΔA535 relaxation kinetics suggests that the two molecules have distinct regulatory functions. 相似文献
3.
The dynamics of the xanthophyll cycle relative to non-photochemical quenching (NPQ) were examined in tobacco plants overexpressing violaxanthin de-epoxidase (VDE), PsbS and PsbS+VDE for effects on NPQ and violaxanthin (V) de-epoxidation over a range of light intensities. Induction of de-epoxidation and NPQ increased in overexpressed VDE and PsbS plants, respectively. Surprisingly, under low light, overexpressing PsbS enhanced de-epoxidation in addition to NPQ. The effect was hypothesized as due to PsbS binding zeaxanthin (Z) or inducing the binding of Z within the quenching complex, thus shifting the equilibrium toward higher de-epoxidation states. Studies in model systems show that Z can stereospecifically inhibit VDE activity against violaxanthin. This effect, observed under conditions of limiting lipid concentration, was interpreted as product feedback inhibition. These results support the hypothesis that the capacity of the thylakoid lipid phase for xanthophylls is limited and modulates xanthophyll-cycle activity, in conjunction with the release of V and binding of Z by pigment-binding proteins. These modulating factors are incorporated into a lipid-matrix model that has elements of a signal transduction system wherein the light-generated protons are the signal, VDE the signal receptor, Z the secondary messenger, the lipid phase the transduction network, and Z-binding proteins the targets. 相似文献
4.
The prasinophycean alga Mantoniella squamata uses in vivo an incomplete violaxanthin cycle. Although the violaxanthin cycle in Mantoniella is capable of converting violaxanthin to zeaxanthin, in intact cells only antheraxanthin accumulates during periods of strong
illumination. Antheraxanthin enhances non-photochemical quenching of chlorophyll fluorescence. Inhibition of antheraxanthin
synthesis by the de-epoxidase inhibitor dithiothreitol abolishes increased thermal energy dissipation. Antheraxanthin-dependent
non-photochemical quenching, like zeaxanthin-mediated non-photochemical quenching in higher plants, is uncoupler-sensitive.
Mantoniella squamata cells cultivated at high light intensities contain higher amounts of violaxanthin than cells grown at low light. The increased
violaxanthin-cycle pool size in high-light-grown Mantoniella cells is accompanied by higher de-epoxidation rates in the light and by a greater capacity to quench chlorophyll fluorescence
non-photochemically. Antheraxanthin-dependent amplification of non-photochemical quenching is discussed in the light of recent
models developed for zeaxanthin- and diatoxanthin-mediated enhanced heat dissipation.
Received: 4 September 1997 / Accepted: 22 December 1997 相似文献
5.
The effect of salt stress on polyamine biosynthesis and content in mung bean plants and in halophytes 总被引:9,自引:0,他引:9
The activity of L-arginine decarboxylase (EC 4.1.1.19) and L-ornithine decarboxylase (EC 4.1.1.17), polyamine content, and incorporation of arginine and ornithine into polyamines, were determined in mung bean [Vigna radiata (L.) Wilczek] plants subjected to salt (hypertonic) stress (NaCl at 0.51–2.27 MPa). Changes in enzyme activity in response to hypotonic stress were determined as well in several halophytes [Pulicaria undulata (L.), Kostei, Salsola rosmarinus (Ehr.) Solms-Laub, Mesembryanthemum forskahlei Hochst, and Atriplex halimus L.]. NaCl stress, possibly combined with other types of stress that accompanied the experimental conditions, resulted in organ-specific changes in polyamine biosynthesis and content in mung bean plants. The activity of both enzymes was inhibited in salt-stressed leaves. In roots, however, NaCl induced a 2 to 8-fold increase in ornithine decarboxylase activity. Promotion of ornithine decarboxylase in roots could be detected already 2 h after exposure of excised roots to NaCl, and iso-osmotic concentrations of NaCl and KCl resulted in similar changes in the activity of both enzymes. Putrescine level in shoots of salt-stressed mung bean plants increased considerably, but its level in roots decreased. The effect of NaCl stress on spermidine content was similar, but generally more moderate, resulting in an increased putrescine/spermidine ratio in salt-stressed plants. Exposure of plants to NaCl resulted also in organ-specific changes in the incorporation of both arginine and ornithine into putrescine: incorporation was inhibited in leaf discs but promoted in excised roots of salt-stressed mung bean plants. In contrast to mung bean (and several other glycophytes), ornithine and arginine decarboxylase activity in roots of halophytes increased when plants were exposed to tap water or grown in a pre-washed soil—i.e. a hypotonic stress with respect to their natural habitat. NaCl, when present in the enzymatic assay mixture, inhibited arginine and ornithine decarboxylase in curde extracts of mung bean roots, but did not affect the activity of enzymes extracted from roots of the halophyte Pulicaria. Although no distinct separation between NaCl stress and osmotic stress could be made in the present study, the data suggest that changes in polyamines in response to NaCl stress in mung bean plants are coordinated at the organ level: activation of biosynthetic enzymes concomitant with increased putrescine biosynthesis from its precursors in the root system, and accumulation of putrescine in leaves of salt-stressed plants. In addition, hypertonic stress applied to glycophytes and hypotonic stress applied to halophytes both resulted in an increase in the activity of polyamine biosynthetic enzymes in roots. 相似文献
6.
The xanthophyll cycle pool size controls the kinetics of non-photochemical quenching in Arabidopsis thaliana 总被引:1,自引:0,他引:1
Arabidopsis plants overexpressing beta-carotene hydroxylase 1 accumulate over double the amount of zeaxanthin present in wild-type plants. The final amplitude of non-photochemical quenching (NPQ) was found to be the same in these plants, but the kinetics were different. The formation and relaxation of NPQ consistently correlated with the de-epoxidation state of the xanthophyll cycle pool and not the amount of zeaxanthin. These data indicate that zeaxanthin and violaxanthin antagonistically regulate the switch between the light harvesting and photoprotective modes of the light harvesting system and show that control of the xanthophyll cycle pool size is necessary to optimize the kinetics of NPQ. 相似文献
7.
Effect of NaCl and Proline on Bean Seedlings Cultured in vitro 总被引:3,自引:0,他引:3
Effects of NaCl (150 mM), proline (10 mM) and their combination on growth and contents of chlorophyll, proline and protein of bean (Phaseolus vulgaris cv. Kizilhaç) seedlings in vitro were investigated. NaCl decreased seedling growth. Proline added to control seedlings did not change seedling growth but decreased chlorophyll and increased protein contents. When proline added to NaCl-treated seedlings growth was increased in comparison with NaCl-treated only. Thus, proline alleviated salinity stress in bean seedlings. 相似文献
8.
Highly time-resolved photoacclimation patterns of the chlorophyte microalga Dunaliella tertiolecta during exposure to an off–on–off (block) light pattern of saturating photon flux, and to a regime of consecutive increasing
light intensities are presented. Non-photochemical quenching (NPQ) mechanisms unexpectedly responded with an initial decrease
during dark–light transitions. NPQ values started to rise after light exposure of approximately 4 min. State-transitions,
measured as a change of PSII:PSI fluorescence emission at 77 K, did not contribute to early NPQ oscillations. Addition of
the uncoupler CCCP, however, caused a rapid increase in fluorescence and showed the significance of qE for NPQ. Partitioning
of the quantum efficiencies showed that constitutive NPQ was (a) higher than qE-driven NPQ and (b) responded to light treatment
within seconds, suggesting an active role of constitutive NPQ in variable energy dissipation, although it is thought to contribute
statically to NPQ. The PSII connectivity parameter p correlated well with F′, F
m
′ and NPQ during the early phase of the dark–light transients in sub-saturating light, suggesting a plastic energy distribution
pattern within energetically connected PSII centres. In consecutive increasing photon flux experiments, correlations were
weaker during the second light increment. Changes in connectivity can present an early photoresponse that are reflected in
fluorescence signals and NPQ and might be responsive to the short-term acclimation state, and/or to the actinic photon flux. 相似文献
9.
Md. Ashaduzzaman Siddikee Puneet S. Chauhan Tongmin Sa 《Journal of Plant Growth Regulation》2012,31(2):265-272
The present study was carried out to understand the mechanism of salt stress amelioration in red pepper plants by inoculation
of 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase-producing halotolerant bacteria. In general, ethylene production,
ACC concentration, ACC synthase (ACS), and ACC oxidase (ACO) enzyme activities increased with increasing levels of salt stress.
Treatment with halotolerant bacteria reduced ethylene production by 47–64%, ACC concentration by 47–55% and ACO activity by
18–19% in salt-stressed (150 mmol NaCl) red pepper seedlings compared to uninoculated controls. ACS activity was lower in
red pepper seedlings treated with Bacillus aryabhattai RS341 but higher in seedlings treated with Brevibacterium epidermidis RS15 (44%) and Micrococcus yunnanensis RS222 (23%) under salt-stressed conditions as compared to uninoculated controls. A significant increase was recorded in red
pepper plant growth under salt stress when treated with ACC deaminase-producing halotolerant bacteria as compared to uninoculated
controls. The results of this study collectively suggest that salt stress enhanced ethylene production by increasing enzyme
activities of the ethylene biosynthetic pathway. Inoculation with ACC deaminase-producing halotolerant bacteria plays an important
role in ethylene metabolism, particularly by reducing the ACC concentration, although a direct effect on reducing ACO activity
was also observed. It is suggested that growth promotion in inoculated red pepper plants under inhibitory levels of salt stress
is due to ACC deaminase activity present in the halotolerant bacteria. 相似文献
10.
Non-photochemical quenching (NPQ) is a mechanism protecting photosynthetic organisms against excessive irradiation. Here, we analyze a unique NPQ mechanism in the alga Chromera velia, a recently discovered close relative of apicomplexan parasites. NPQ in C. velia is enabled by an operative and fast violaxanthin de-epoxidation to zeaxanthin without accumulation of antheraxanthin. In C. velia violaxanthin also serves as a main light-harvesting pigment. Therefore, in C. velia violaxanthin acts as a key factor in both light harvesting and photoprotection. This is in contrast to a similar alga, Nannochloropsis limnetica, where violaxanthin has only light-harvesting function. 相似文献
11.
Based on our recent findings that in the diatom Phaeodactylum tricornutum, chlororespiration in periods of prolonged darkness leads to the accumulation of diatoxanthin (DT), we have elaborated in detail the interdependence between the chlororespiratory proton gradient and the activation of diadinoxanthin de-epoxidase (DDE). The data clearly demonstrates that activation of DDE in Phaeodactylum occurs at higher pH-values compared to activation of violaxanthin de-epoxidase (VDE) in higher plants. In thylakoid membranes as well as in enzyme assays with isolated DDE, the de-epoxidation of diadinoxanthin (DD) is efficiently catalyzed at pH 7.2. In comparison, de-epoxidation of violaxanthin (Vx) in spinach thylakoids is observed below pH 6.5. Phaeodactylum thylakoids isolated from high light grown cells, that also contain the pigments of the violaxanthin cycle, show violaxanthin de-epoxidation at higher pH-values, thus suggesting that in Phaeodactylum, one de-epoxidase converts both diadinoxanthin and violaxanthin. We conclude that the activation of DDE at higher pH-values can explain how the low rates of chlororespiratory electron flow, that lead to the build-up of a rather small proton gradient, can induce the observed accumulation of diatoxanthin in the dark. Furthermore, we show that dark activation of diadinoxanthin de-epoxidation is not restricted to Phaeodactylum tricornutum but was also found in another diatom, Cyclotella meneghiana 相似文献
12.
Photoinhibition of photosynthesis at low temperatures was investigated in two species of subalpine eucalypt, Eucalypts nitens (Deane and Maiden) Maiden and E. pauciflora Sieb. ex Spreng. Imposition of an artificial cold-hardening treatment increased the frost tolerance of leaf tissue and increased
tolerance to excess light. Cold-hardened seedlings of both species had a higher photosynthetic capacity than non-hardened
seedlings at 6 and 16°C and lower levels of non-photochemical quenching (NPQ) at 20 and 5°C. Furthermore, hardened seedlings
had faster rates of NPQ development at 5 and −3.5°C. An increase in minimal fluorescence, which indicates slowly reversible
photoinhibition, was evident in all seedlings at −1.5 and −3.5°C but was less pronounced in hardened seedlings, with a threefold
faster rate of development of NPQ, at −3.5°C than non-hardened seedlings. Hardened seedlings also recovered faster from photoinhibition
at −3.5°C. Thus cold hardening increased tolerance to high light in these species. Differences between E. nitens and E. pauciflora in their response to excess light were small and significant only at −3.5°C. Faster recovery from photoinhibition of E. pauciflora was consistent with its occurrence in colder habitats than E. nitens.
Received: 27 April 1997 / Accepted: 9 September 1997 相似文献
13.
A. A. Ivanov 《Russian Journal of Plant Physiology》2010,57(6):770-777
Sensitivity of wheat (Triticum aestivum L.) seedlings to salt stress was investigated as dependent on light conditions of plant growing. In two-week-old seedlings
grown on salt-free medium, aboveground organs were detached from the roots and subjected to a brief stress at different concentrations
of NaCl. The extent of salt stress effect expressed as a decrease in the rate of the photosynthetic release of oxygen and
the relative content of water and chlorophyll in the leaves greatly depended on light conditions of growing. The plants grown
at low light intensity were notable for a greater sensitivity to NaCl in the medium. Plant responses to salt stress were different
at low and high salt concentrations. At low NaCl concentrations (0.05–0.10 M) in the solution, in plants grown at low light
intensity, the rate of photosynthesis calculated per unit of chlorophyll increased. This effect was not observed in plants
grown at the higher light intensity. At high NaCl concentrations (0.2–0.4 M) in the medium, the rate of photosynthesis rapidly
decreased in all the types of treatment, with the effect being most pronounced in plants grown at low light intensity. The
obtained results suggest a narrow range of NaCl concentrations with an optimum at 0.1 M positively affecting the wheat seedlings
physiological state upon salt stress development depending on light conditions of plant growing. 相似文献
14.
The importance of grana stacking for xanthophyll cycle-dependent NPQ in the thylakoid membranes of higher plants 总被引:1,自引:0,他引:1
In the present study we have examined the effects of grana stacking on the rate of violaxanthin (Vx) de-epoxidation and the extent of non-photochemical quenching of chlorophyll a fluorescence (NPQ) in isolated thylakoid membranes of spinach. Our results show that partial and complete unstacking of thylakoids in reaction media devoid of sorbitol and MgCl2 did not significantly affect the efficiency of Vx de-epoxidation. Under high light (HL) illumination we found slightly higher values of Vx conversion in stacked membranes, whereas in thylakoids incubated at pH 5.2 in the dark, representing the pH-optimum of Vx de-epoxidase, de-epoxidation was slightly increased in the unstacked membranes. Partial and complete unstacking of grana membranes, however, had a dramatic effect on the HL-induced NPQ. High NPQ values could only be achieved in stacked thylakoid membranes in the presence of MgCl2 and sorbitol. In unstacked membranes NPQ was drastically decreased. The effects of grana stacking on the xanthophyll cycle-dependent component of NPQ were even more pronounced, and complete unstacking of thylakoid membranes led to a total loss of this quenching component. Our data imply that grana stacking in the thylakoid membranes of higher plants is of high importance for the process of overall NPQ. For the xanthophyll cycle-dependent component of NPQ it may even be essential. Possible effects of grana stacking on the mechanism of zeaxanthin-dependent quenching are discussed. 相似文献
15.
The effects of temperature on the dark relaxation kinetics of nonradiative energy dissipation in photosystem II were compared in lettuce (Lactuca sativa L.) chloroplasts and leaves of Aegialitis annulata R. Br. After high levels of violaxanthin de-epoxidation in the light, Aegialitis leaves showed a marked delay in the dark relaxation of nonradiative dissipation, measured as non-photochemical quenching (NPQ) of photosystem II chlorophyll a fluorescence. Aegialitis leaves also maintained a moderately high adenylate energy charge at low temperatures during and after high-light exposure, presumably because of their limited carbon-fixation capacity. Similarly, dark-sustained NPQ could be induced in lettuce chloroplasts after de-epoxidizing violaxanthin and light-activating the ATP synthase. The duration and extent of dark-sustained NPQ were strongly enhanced by low temperatures in both chloroplasts and leaves. Further, the NPQ sustained at low temperatures was rapidly reversed upon warming. In lettuce chloroplasts, low temperatures sharply decreased the ATP-hydrolysis rate while increasing the duration and extent of the resultant trans-thylakoid proton gradient that elicits the NPQ. This was consistent with a higher degree of energy-coupling, presumably due to reduced proton diffusion through the thylakoid membrane at the lower temperatures. The chloroplast adenylate pool was in equilibrium with the adenylate kinase and therefore both ATP and ADP contributed to reverse coupling. The low-temperature-enhanced NPQ quenched the yields of the dark level (Fo) and the maximal (Fm) fluorescence proportionally in both chloroplasts and leaves. The extent of NPQ in the dark was inversely related to the efficiency of photosystem II, and very similar linear relationships were obtained over a wide temperature range in both chloroplasts and leaves. Likewise, the dark-sustained absorbance changes, caused by violaxanthin de-epoxidation (A508nm) and energy-dependent light scattering (A536nm) were strikingly similar in chloroplasts and leaves. Therefore, we conclude that the dark-sustained, low-temperature-stimulated NPQ in chloroplasts and leaves is apparently directly dependent on lumen acidification and chloroplastic ATP hydrolysis. In leaves, the ATP required for sustained NPQ is evidently provided by oxidative phosphorylation in the mitochondria. The functional significance of this quenching process and implications for measurements of photo-protection versus photodamage in leaves are discussed.Abbreviations and Symbols A
antheraxanthin
- Chl
chlorophyll
- DPS
de-epoxidation state of the xanthophyll cycle, ([Z+A]/[V+A+Z])
- F, F
steady-state fluorescence in the absence, presence of thylakoid energization
- Fo, Fo
dark fluorescence level in the absence, presence of thylakoid energization
- Fm, Fm
maximal fluorescence in absence, presence of thylakoid energization
- NPQ
nonphotochemical quenching (Fm/Fm)–1
- V
violaxanthin
- Z
zeaxanthin
- NRD
nonradiative dissipation
- PFD
photon flux density
-
[2ATP+ADP]
- pH
trans-thylakoid proton gradient
- S
pH-dependent light scattering
- PSII
(Fm–F)/Fm, photon yield of PSII photochemistry at the actual reduction state in the light or dark
-
[ATP+ADP+AMP]
We thank Connie Shih for skillful assistance in growing plants and for conducting HPLC analyses. Support from an NSF/USDA/DOE postdoctoral training grant to A.G. is gratefully acknowledged. A.G. also wishes to thank Prof. Govindjee for valuable discussions. C.I.W.-D.P.B. Publication No. 1197. 相似文献
16.
We studied carotenoid composition and chlorophyll fluorescence in two-year-old needles from Siberian spruce (Picea obovata (L.) Karst.), Siberian fir (Abies sibirica L.), and common juniper (Juniperus communis L.). The highest values of maximum PSII photochemical activity (F
v/F
m) equaling 0.82–0.85 were observed in July–September. The decrease in F
v/F
m in December–March was more pronounced in juniper (down to 0.15) than in spruce and fir (0.45–0.50). In May, we observed a
nearly complete recovery in maximum PSII photochemical activity in fir and spruce (0.72–0.77), while in juniper, the F
v/F
m value was notably lower (0.65–0.67). The amount of thermal dissipation of energy absorbed by PSII LHC did not exceed 30%
in summer and equaled 60–90% in winter and early spring. The carotenoid pool consisted mainly of xanthophylls, among which
lutein (70%), neoxanthin (7–10%), and a violaxanthin cycle (VXC) component — violaxanthin (3–15%) were constantly present.
The accumulation of two other VXC pigments—zeaxanthin and antheraxanthin, was noted in December–March. In July, these xanthophylls
were not identified. We discovered a direct connection between VXC pigment de-epoxidation level and light energy thermal dissipation
in boreal conifer leaves. Such association reflects the non-species-specific character of the mechanism for quenching zeaxanthin-dependent
nonphotochemical chlorophyll fluorescence in PSII LHC in winter and spring. 相似文献
17.
Y. C. Qi W. Q. Liu L. Y. Qiu S. M. Zhang L. Ma H. Zhang 《Russian Journal of Plant Physiology》2010,57(2):233-240
The Suaeda salsa glutathione S-transferase gene (GST) was introduced into arabidopsis under the control of the cauliflower mosaic virus 35S
promoter. Transformants were selected for their ability to grow on medium containing kanamycin. Southern and northern blot
analyses confirmed that GST was transferred into the arabidopsis genome, and the GST and GPX activities in transgenic plants
(GT) were much higher than in wild-type plants (WT). There were no obvious morphological or developmental differences between
transgenic and wild-type plants. One transgenic homozygous line (GT6–8) and WT plants were evaluated for salt tolerance and gene expression. Seed germination and seedling salt tolerance were improved
after overexpression of GST in arabidopsis; the photosynthesis rate and the fresh weight of the GT6–8 line were distinctly higher than those of WT plants after NaCl treatment. Glutathione content increased substantially in
salt-stressed arabidopsis plants of both genotypes, and the glutathione pool in GT6–8 plants was more oxidized than in WT plants under both control and stressful conditions. The MDA content, an indicator of
lipid peroxidation, increased in WT plants but was not affected distinctly in GT6–8 seedlings after NaCl treatment. Results from different tests indicated that the expression of the GST gene promoted a higher
level of salt tolerance in vivo in transgenic arabidopsis plants. 相似文献
18.
A nonphotochemical-quenching-deficient mutant of Arabidopsis thaliana possessing normal pigment composition and xanthophyll-cycle activity 总被引:1,自引:0,他引:1
Higher-plant chloroplasts alter the distribution of absorbed radiant energy between photosynthesis and heat formation in
response to changing illumination level or environmental stress. Fluorescence imaging was used to screen 62 yellow-green T-DNA
insertion mutant lines of Arabidopsis thaliana (L.) Heynh. for reduced photoprotective nonphotochemical quenching (NPQ) capacity. Pulse-modulation fluorometry was employed
to characterize one line (denoted Lsr1−) that exhibited an approximately 50% reduction in NPQ compared to the wild type (WT). The loss in NPQ capacity was associated
with the ΔpH-dependent phase of quenching (qE). Under the growth conditions employed, pigment composition and levels of the
six photosystem-II light-harvesting chlorophyll a/b proteins were identical in mutant and WT. Changes in the in-vivo levels of the xanthophyll pigments violaxanthin, antheraxanthin,
and zeaxanthin in excess light were the same for mutant and WT. However, use of the violaxanthin de-epoxidase inhibitor dithiothreitol
indicated that a zeaxanthin-dependent component of NPQ was specifically reduced in the mutant. The mutant exhibited diminished
suppression of minimum fluorescence yield (F
o
) in intense light suggesting an altered threshold in the mechanism of response to light stress in the mutant. The NPQ-deficient
phenotype was meiotically transmissible as a semidominant trait and mapped near marker T27K12 on chromosome 1. The results
suggest that the mutant is defective in sensing the transthylakoid ΔpH that reports exposure to excessive illumination.
Received: 26 May 1999 / Accepted: 17 June 1999 相似文献
19.
The influence of chilling (8 °C, 5 d) at two photon flux densities [PFD, L = 200 and H = 500 μmol(photon) m−2 s−1] on the gas exchange and chlorophyll fluorescence was investigated in chilling-tolerant and chilling-sensitive maize hybrids
(Zea mays L., K383×K130, K185×K217) and one cultivar of field bean (Vicia faba L. minor, cv. Nadwiślański). The net photosynthetic rate (P
N) for the both studied plant species was inhibited at 8 °C. P
N of both maize hybrids additionally decreased during chilling. Changes in the quantum efficiency of PS2 electron transport
(ΦPS2) as a response to chilling and PFD were similar to P
N. Measurements of ΦPS2/ΦCO2 ratio showed that in field bean seedlings strong alternative photochemical sinks of energy did not appear during chilling.
However, the high increment in ΦPS2/ΦCO2 for maize hybrids can indicate reactions associated with chill damage generation. At 8 °C the non-photochemical quenching
(NPQ) increased in all plants with chilling duration and PFD. The appearance of protective (qI,p) and damage (qI,d) components of qI and a decrease in qE (energy dependent quenching) took place. NPQ components of field bean and maize hybrids differed from each other. The amount
of protective NPQ (qE + qI,p) components as part of total NPQ was higher in field bean than in maize hybrids at both PFD. On 5th day of chilling, the sum of qE and qI,p was 26.7 % of NPQ in tolerant maize hybrids and 17.6 % of NPQ in the sensitive one (averages for both PFD). The increased
PFD inhibited the ability of all plants to perform protective dissipation of absorbed energy. The understanding of the genotypic
variation of NPQ components in maize may have implications for the future selection of plants with a high chilling tolerance. 相似文献
20.
Trigonelline (TRG) is known as a compatible solute in response to stress as well as a cell cycle regulator, and is more concentrated
in legumes than other non-legume dicots. Four Glycine max L. genotypes (Essex, ExF 67, Forrest and Stressland) were used to examine TRG concentration in seeds and seedlings exposed
to 30 or 100 mM NaCl, and to determine the association of TRG concentrations in seedlings with seedling growth. Seed germination
across genotypes was inhibited by elevated salinity (71–91 %) in ExF 67 and Forrest and by accelerated aging (77–92 %) in
Forrest. Length of seedlings in most genotypes stressed with NaCl apparently decreased. The TRG content in mature seeds of
four genotypes was 44.4–74.6 μg g−1(d.m.). TRG content significantly increased during early young seedling development, but remained or significantly reduced
in some genotypes stressed with NaCl. 相似文献