[Show abstract][Hide abstract] ABSTRACT: Alocasia macrorrhiza is a fast growing and propagating herbaceous species commonly found in South China. To determine its physiological responses to Pb and Cd stresses, the biochemical, histochemical and cytochemical changes under PbAC2 and CdCl2 phytotoxicity were detected using leaf discs as an experimental model. After leaf discs were infiltrated in different concentrations of PbAC2 and CdCl2 solutions (0, 50, 100, 150, 200 microM) for 72 h, the formation of reactive oxygen species (H2O2 and O2-) in plant tissue were found to be exaggerated together with elevated OH concentration and cell death. Changes in chlorophyll fluorescence (Fv/Fm, PhiPSII, qP and NPQ) imaging colours/areas of leaf discs indicated decreased photosystem II functions by both heavy metal treatments and positive reactions of antioxidants under Pb2+ stress. Results showed that fluorescent detection of hydroxylated terephthlate using terephthalic acid as OH trap is a simple, yet valuable and specific method for monitoring OH generation in plant tissue under heavy metal stresses. As compared with Cd2+, Pb2+ was found to be less toxic, indicating that A. macrorrhiza tissue might have a potential tolerance to Pb.
[Show abstract][Hide abstract] ABSTRACT: The effects of long-term (33months) sun/shade acclimation and short-term (within 10h) HSO3
− treatment on leaf photosynthetic apparatus were investigated in three subtropical forest plants, Pinus massoniana, Schima superba, and Acmena acuminatissima. After 33months’ growth in two light environments (100 and 12% sunlight), rapid light curves (RLC), chlorophyll fluorescence
imaging and chloroplast ultrastructures of three tested species were changed to different degrees. When leaf sections were
immersed in 50mM NaHSO3 for 10h, all the RLCs were lowered; chlorophyll fluorescence imaging was inclined to present warmer colors and imaging areas
were decreased. However, changes in chloroplast ultrastructures differed from three species. Our results showed that the photosynthetic
apparatus of a dominant species, A. acuminatissima, in the late succession stage of a subtropical forest in South China, was less sensitive to NaHSO3 under both growing light intensities. Conversely, the chloroplasts of P. massoniana, the pioneer heliophyte species, were most susceptible to NaHSO3. It is deduced that, SO2 pollution may become as a factor to accelerate the succession of subtropical forest.
[Show abstract][Hide abstract] ABSTRACT: Leaf discs of Alocasia macrorrhiza were treated with various stress factors, including two photo-oxidants, methyl viologen (MV) or riboflavin (RB); three pollutants,
sodium bisulphite (NaHSO3), or the heavy metals lead or cadmium; or an osmotic medium, polyethylene glycol 6000. The in situ localisation sites for
− generation were identified using specific dye nitro blue tetrazolium as a probe. The level of superoxide production was determined
by scanning the blue-stained formazan area and was defined as the percentage of pixels from the stained portion versus the
total number of pixels in the entire leaf disc area. All stress factors induced the generation of O2
− in a time- or concentration-dependent pattern. Although superoxide production also was enhanced by longer time periods in
untreated discs (control), the degree to which this occurred was less than that measured in leaves treated with either MV
or RB. Generation sites were primarily found in the chloroplasts of stomatal guard cells and in the plasma membrane of the
epidermis and mesophyll cells, indicating that they were most responsive to stress conditions. Nevertheless, the site of O2
− generation varied among these stress factors.
[Show abstract][Hide abstract] ABSTRACT: 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 (400–800nm) 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.
[Show abstract][Hide abstract] ABSTRACT: The value of intrinsic chlorophyll fluorescence polarization, and the intensity in emission spectrum were investigated in leaf segments of Alocasia macrorrhiza under several stress conditions including different temperatures (25-50 degrees C), various concentrations of NaCl (0-250 mM), methyl viologen (MV, 0-25 microM), SDS (0-1.0%) and NaHSO(3) (0-80 microM). Fluorescence emission spectrum of leaves at wavelength regions of 500-800 nm was monitored by excitation at 436 nm. The value of fluorescence polarization (P value), as result of energy transfer and mutual orientation between chlorophyll molecules, was determined by excitation at 436 nm and emission at 685 nm. The results showed that elevated temperature and concentrations of salt (NaCl), photooxidant (MV), surfactant (SDS) and simulated SO(2) (NaHSO(3)) treatments all induced a reduction of fluorescence polarization to various degrees. However, alteration of the fluorescence spectrum and emission intensity of F(685) and F(731) depended on the individual treatment. Increase in temperature and concentration of NaHSO(3) enhanced fluorescence intensity mainly at F(685), while an increase in MV concentration led to a decrease at both F(685) and F(731). On the contrary, NaCl and SDS did not cause remarkable change in fluorescence spectrum. Among different treatments, the negative correlation between polarization and fluorescence intensity was found with NaHSO(3) treatments only. We concluded that P value being measured with intrinsic chlorophyll fluorescence as probe in leaves is a susceptible indicator responding to changes in environmental conditions. The alteration of P value and fluorescence intensity might not always be shown a functional relation pattern. The possible reasons of differed response to various treatments were discussed.
Journal of Fluorescence 12/2007; 17(6):663-9. DOI:10.1007/s10895-007-0213-1 · 1.93 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The effects of simulated SO 2 treatment (NaHSO 3 with different concentrations) on chlorophyll fluorescence in five subtropical forest plants, namely Pinus massoniana Lamb, Schima superba Gardn., and Champ, Castanopsis fissa R and W, Acmena acuminatissima Bi.merr., and Perry, and Cryptocarya concinna Hance, were investigated. After the leaf sections were immersed in 0, 20, 50, 100 mM NaHSO 3 for 10 h, the low temperature (77 K) chlorophyll fluorescence emission, F PSI /F PSII ratio and chlorophyll fluorescence induction curves of all five woody plants reduced to different extents, while an increase in low temperature fluorescence polarization was found. Short-term treatment of SO 2 damaged PSII, decreased the fluidity of thylakoid membrane, and affected the process of electron transport. Sulfite oxidase activities of five plants grown in three light environments (100, 32, and 12% of natural light intensities) were varied, which showed different resistance to SO 2 pollution. A. acuminatissima and C. concinna, the dominant species in the late succession stage of a subtropical forest in South China, was less sensitive to SO 2 pollution. And P. massoniana, the pioneer heliophyte species was less able to resist NaHSO 3 . It is suggested that SO 2 pollution may accelerate the succession of subtropical forest.
Pakistan Journal of Botany 12/2007; 39(6):1921-1935. · 0.82 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The adaptations and responses of photosynthesis to long-and short-term growth light gradient treatments were investigated in five subtropical forest plants, namely Pinus massoniana Lamb., Schima superba Gardn. et Champ., Castanopsis fissa (Champ. ex Benth.) Rehd. et Wils., Acmena acuminatissima (BI.) Merr et Perry, and Cryptocarya concinna Hance. With diurnal changes in sunlight and air temperature, the de-epoxidation state and lutein content in the five woody plants under three light intensities first increased and then decreased during the day. However, maximal photochemical efficiency (F v /F m ; where F m is the maximum fluorescence yield and F v is variable fluorescence) and the photochemical quantum yields of photosystem (PS) II (Φ Φ Φ Φ Φ PSII) of the species examined changed in the opposite manner, with those in plants grown under 100% natural light changing the most. After long-term treat-ment (21 months), anti-oxidant capacity (1,1-diphenyl-2-picrylhydrazyl radical (DPPH·)-scavenging capacity) and uti-lization of excitation energy showed differences in modulation by different light intensities. It was shown that A. acuminatissima and C. concinna, as dominant species in the late succession stage of a subtropical forest in Dinghu mountain, South China, were better able to adapt to different light environments. However, P. massoniana, the pioneer species of this forest, exhibited less adaptation to low light intensity and was definitely eliminated by the forest succession process.
[Show abstract][Hide abstract] ABSTRACT: The effects of simulated SO2 treatment on the photosynthetic apparatus were investigated in five subtropical forest plants, namely Pinus massoniana Lamb., Schima superba Gardn. et Champ., Castanopsis fissa (Champ. ex Benth.) Rehd. et Wils., Acmena acuminatissima (Bl.) Merr et Perry, and Cryptocarya concinna Hance. After leaf sections had been immersed in 0, 20, 50, and 100 mmol/L NaHSO3 for 20 h, total chlorophyll (Chl) content, Chl a/b, maximal photochemical efficiency, and the photochemical quantum yields of photo-system II of all five woody plants were reduced to different degrees, whereas lutein content (Chl base) was increased. Two protective mechanisms, namely the xanthophyll cycle (deepoxidation) and an anti-oxidant system (1,1-diphenyl-2-picrylhydrazyl radical-scavenging capacity), showed differences in the degree of modulation under simulated SO2 treatment. Compared with control (distilled water treatment), the revised normalized difference vegetation index, a leaf reflectance index, was lowered with increasing concentrations of NaHSO3. Cryptocarya concinna, a dominant species in the late succession stage of subtropical forests in South China, exhibited less sensitivity to NaHSO3. Conversely, Pinus massoniana, the pioneer heliophyte species, was most susceptible to NaHSO3 treatment. It is suggested that SO2 pollution may accelerate the succession of subtropical forest.
(Managing editor: Ping He)
[Show abstract][Hide abstract] ABSTRACT: In the present study, both electron spin resonance (ESR) and chemical detection confirmed that lutein [extracted from alfalfa (Medicago sativa L.)], the most abundant xanthophyll in thylakoids of chloroplasts, could serve as an antioxidant to scavenge reactive oxygen species (ROS) in vitro. Lutein exhibited a greater capacity for scavenging hydroxyl (OH .) and superoxide (O 2 . −) radicals than β-carotene at the same concentration, whereas the opposite trend was observed in the capacity for scavenging singlet oxygen (1 O 2). The capacity of lutein for scavenging ROS from high to low is OH . > O 2 . − > 1 O 2 . We hypothesise that lutein plays an important photoprotective role in scavenging O 2 . − and OH . under severe stress. This hypothesis is consistent with our previous report that the lut2 (lutein-deficient) Arabidopsis mutant is more susceptible to damage than the npq1 (lutein-replete but violaxanthin de-epoxidase-deficient) Arabidopsis mutant under severe stress during exposure to high light intensity at low temperature (Peng and Gilmore 2003).
[Show abstract][Hide abstract] ABSTRACT: Two new yellow rice chlorophyll (Chl) b-less (lack) mutants VG28-1 and VG30-5 differ from the other known Chl b-less mutants with larger amounts of soluble protein and ribulose-1,5-bisphosphate carboxylase/oxygenase small sub-unit and smaller amounts of Chl a. We investigated the altered features of Chl-protein complexes and excitation energy distribution in these two mutants, as compared with wild type (WT) rice cv. Zhonghua 11 by using native mild green gel electrophoresis and SDS-PAGE, and 77 K Chl fluorescence in the presence of Mg2+. WT rice revealed five pigment-protein bands and fourteen polypeptides in thylakoid membranes. Two Chl b-less mutants showed only CPI and CPa pigment bands, and contained no 25 and 26 kDa polypeptides, reduced amounts of the 21 kDa polypeptide, but increased quantities of 32, 33, 56, 66, and 19 kDa polypeptides. The enhanced absorption of CPI and CPa and the higher Chl fluorescence emission ratio of F685/F720 were also observed in these mutants. This suggested that the reduction or loss of the antenna LHC1 and LHC2 was compensated by an increment in core component and the capacity to harvest photon energy of photosystem (PS) 1 and PS2, as well as in the fraction of excitation energy distributed to PS2 in the two mutants. 77 K Chl fluorescence spectra of thylakoid membranes showed that the PS1 fluorescence emission was shifted from 730 nm in WT rice to 720 nm in the mutants. The regulation of Mg2+ to excitation energy distribution between the two photosystems was complicated. 10 mM Mg2+ did not affect noticeably the F685/F730 emission ratio of WT thylakoid membranes, but increased the ratio of F685/F720 in the two mutants due to a reduced emission at 685 nm as compared to that at 720 nm.
[Show abstract][Hide abstract] ABSTRACT: Two yellow rice mutants VG28-1 and VG30-5 were obtained during the tissue culture process from a rice plant (cv. Zhonghua No.11 japonica) with inserted maize Ds transposon element. Absorption spectra and pigment composition showed that two mutants had no chlorophyll (Chl) b and lower Chl a content in comparison to the wild type (WT). Net photosynthetic rate (P
N), total electron transport rate (JF), photochemical quenching (qp), quantum yield of PS2 dependent non-cyclic electron transport (PS2), fraction of Prate, and leaf area were lower but Fv/Fm and apparent quantum yield (AQY) remained at similar levels as in the WT plant. Xanthophyll cycle pool size (V+A+Z) on a Chl basis, and de-epoxidation state were enhanced in the mutants. The mutants had larger amounts of soluble protein and ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO), especially the small subunit of RuBPCO, than WT. The characteristics of two rice mutants differed somewhat from the other common Chl b-less mutants originating from mutagenic agent treatments.
[Show abstract][Hide abstract] ABSTRACT: The daily changes in the behavior of xanthophyll cycle and antioxidant systems in flag leaves of superhigh-yield hybrid rice
were investigated in relation to various developing stages. Dark-adapted Fv/Fm decreased with the increasing incident light
intensity on leaf surface in the morning and then minimized at midday; Deepoxidation State showed an opposed daily pattern
to Fv/Fm at different developing stage. As compared with increased deepoxidation state maximum value, the relative content
of xanthophyll cycle pigments remained almost constant during development. The daily changes in activities of superoxide dismutase,
ascorbate-peroxidase and glutathione reductase and the content of ascorbate and glutathione displayed a similar pattern, where
they increased from 8:00 and reached maximum at midday, however, a lower daily fluctuation of superoxide dismutase activity
was observed in senescent leaves. The enhanced contribution of xanthophyll cycle and Mehler-ascorbate peroxidase reaction
to photoprotection in old leaves could be partially due to the altered leaf posture. In conclusion, daily changes of xanthophyll
cycle and antioxidant systems in leaves of rice at various developing stages were dependent on leaf age, leaf angle and intensity
of solar irridiance.
Acta Physiologiae Plantarum 12/2001; 23(4):391-398. DOI:10.1007/s11738-001-0048-3 · 1.58 Impact Factor