By using a wild-type rice (Oryza sativa L. cv. Norin No. 8) and the chlorophyll (Chl) b-deficient mutant derived from Norin No. 8 (chlorina 11), the present study monitored the oxygen evolution, contents of Chl a and b, β-carotene, and lutein in leaf and the contents of cytochrome f, and the reaction centres of photosystem I (PSI) and photosystem II (PSII) in thylakoids. The oxygen evolution, maximal quantum yield of PSII (Fv/Fm) and Chl concentration remained constant in both Norin No. 8 and chlorina 11 under 5 and 2% of full sunlight for six days. On the other hand, on the thylakoid level, the PSII reaction centre of chlorina 11 was more stable even under high irradiance, while approximately 40% decrease in levels of the PSII reaction centre occurred under 2% of full sunlight for six days. However, under such conditions, by regulating the stoichiometry of active PSII and PSI centres, the light absorption balance in both rice types was adjusted between the two photosystems. The present study attempted to examine whether the light absorption balance between PSII and PSI is altered to effectively conduct photosynthesis in the wild-type and Chl b-deficient mutant rice seedlings. and J. Yamazaki.
Changes in the pools of carotenoids and protochlorophyll(ide) were investigated in etiolated cucumber cotyledons treated with norflurazon (NF) and an experimental herbicide KC 6361 (KC). Both the NF- and the KC-treated tissues considerably accumulated the colourless carotenes phytoene and phytofluene with a concomitant depletion of the coloured carotenoids lutein and β-carotene in darkness. However, the profiles of changes in chlorophylls (Chls) and carotenoids were different for the two herbicides. The plants were also influenced by the photosynthetic photon flux densities (PPFD's), with a more pronounced decline of Chl under high PPFD than under low PPFD. The ratios of protochlorophyll (PChl)/protochlorophyllide (PChlide) were greatly altered due to a decrease and an increase of PChl in the NF- and the KC-treated etiolated tissues, respectively, whereas the PChlide content was not significantly influenced by the inhibitors. Large increase of PChls in the KC-treated tissues seems to derive from the binding of accumulated geranylgeraniol (GG) equivalents, through carotenogenic inhibition, to PChlide. Therefore, the alterations of PChl and PChlide occurring under disturbed carotenogenesis may suggest an interaction between the biosynthetic pathways of Chls and carotenoids. In addition, the great proportion of PChl GG and PChl dihydro-GG in the KC-treated tissues implies that PChl formation is regulated at the level of hydrogenation. and S. Jung ... [et al.].
Chloroplast polypeptide composition of rice plants {Oryza sativa L. cv. Safari) exposed for 30 d to increasing Cu ion concentrations in a hydroponie growth medium was analyised. The conventional discontinuous SDS-aerylamide gel electrophoretic systém, the SDS PhastGel (Pharmacia Fine Chemicals) gradient 10-15 and tíie 5-8 pH range polyaciylamide isoelectric focusing of the PhastSystem separation and development technique were ušed. With Cu levels greater than 0.25 g m'^ die polypeptide bands with apparent molecular masses of 42/41, 33/32, 21/20 and 19/18 kDa deereased in the PhastSystem separation and development systém, whereas with the conventional discontinuous SDS buffer systém gel electrophoresis all these bands disappeared except the 33/32 kDa band. Also, under the latter systém excess Cu deereased the 56/55, 55/54, 26 and 22 kDa bands which was not shown by the PhastSystem separation and development technique. Furthermore, in the discontinuous SDS-PAGE high Cu levels induced the disappearance of the 16.5, 14.5 and 12 kDa bands, which were again not shown by the PhastSystem separation and development technique; yet the opposite oceurred with the 49 kDa band of the gel profiles. Polyacrylamide isoelectric focusing of thyiakoid membranes showed in all Cu treatments two major bands at pl 7.7 and <5 and a minor one at pl 6.48. At Cu concentrations lower than 1.25 g m'^ two additional smáli bands appeared (pl 5.5 and 5.18); and at Cu concentrations greater than 0.25 g m'^ these smáli bands were replaced by four different ones (pl 6.7, 6.05, 5.35, 5.25).
A comparison between maximum quantum yield of PSII photochemistry (Fv/Fm) and chlorophyll fluorescence decrease ratio (Rfd) for low and high temperature resistance was assessed in a seasonal study of the acclimation in Pterocephalus lasiospermus. Analyzing the regression adjustment of both parameters and the lethal temperatures (LT50), Rfd resulted in being a more sensitive indicator for low and high temperature treatments, since the thermic resistance estimated with Rfd parameter was never higher than those estimated with Fv/Fm. Furthermore, the use of Fv/Fm led to an overestimation of the acclimation phenomena, with 6ºC of a maximum difference between both parameters. Using Rfd as the indicator parameter, P. lasiospermus acclimated to low temperatures but it kept on being a sensitive species (the lowest LT50 values only achieved -9.9 ± 0.3ºC). However, no heat acclimation was observed (LT50 around 43.5ºC). Thus, according to Rfd evaluation of the thermic threshold, this species could be in risk of damage at low temperatures in this alpine ecosystem., A. V. Perera-Castro, P. Brito, A. M. González-Rodríguez., and Obsahuje bibliografii
French bean (Phaseolus vulgaris L.) cotyledons lost most of their reserve substances during several early days of germination and turned green. In cotyledon mesophyll cells of one-week-old seedlings, plastids were represented predominantly by amyloplasts (starch grains) and chloroamyloplasts, and the cells appeared to be metabolically highly active. Cell heterogeneity associated with distance of the cells from cotyledon vascular bundles was evident. Only mesophyll cells near to the bundles were rich in plastids. In two-weeks-old intact bean plants, the cotyledons were yellow and shrunken, and their cells were nearly "empty". The plastids in them were represented by senescent plastids (gerontoplasts) only. In the gerontoplasts as well as freely in cytosol, fluorescent lipoid inclusions were accumulated. This cotyledon development was more or less independent of irradiance. In "decapitated" bean plants, senescence of mesophyll cells and plastids was slowed down considerably, and the life span of the cotyledons was prolonged. and J. Kutík, N. Wilhelmová, J. Snopek.
Chlorophyll (Chl) fluorescence technique was ušed to monitor Cu damage in photosynthetic process in intact leaves of a Cu-tolerant {Silene conipacla) and a non- Cu-tolerant {Thlaspi ochroleucum) species. The initial fluorescence level (Fq) increased whereas the variable fluorescence (Fy) decreased in T. ochroleucum under low and high Cu-dose, suggesting injuries both in reaction centie level and in photooxidizing side of photosystem 2 (PS2). The photochemistiy activity of PS2, Fy/Fp, revealed a slight increase under 8 pM Cu in both species, while at 160 pM of Cu a strong inhibition in T. ochroleucum was observed. The Fp/F() ratio appeared to increase under low Cu dose, however the high Cu dose in nutrient solution resulted in damage to the thylakoid structure affecting the PS2 donor and acceptor side, mainly in T. ochroleucum. The slow part of the Chl fluorescence induction cuiwe was affected more by Cu stress, than the fast one. At low Cu concentration the Rfd value increased in S. compacla but decreased in T. ochroleucum. Fligh Cu dose induced an almost complete inhibition of this parameter, that was more severe in the non-tolerant plants. Yet, low Cu dose enhanced the Chl content in S. compacla but on exposure to 160 pM Cu the symptoms of chlorosis were more visible in T. ochroleucum. Thus, excess of Cu has direct negative effects on the photosynthetic electron transport that may be accounted for by the destruction of the photosynthetic pigments.
Water availability is a major limiting factor in desert ecosystems. However, a winter snowfall role in the growth of biological soil crusts is still less investigated. Here, four snow treatments were designed to evaluate the effects of snow depth on photosynthesis and physiological characteristics of biological soil crusts. Results showed that snow strongly affected the chlorophyll fluorescence properties. The increased snow depth led to increased contents of photosynthetic pigments and soluble proteins. However, all biological soil crusts also exhibited a decline in malondialdehyde and soluble sugar contents as snow increased. Results demonstrated that different biological soil crusts exhibited different responses to snow depth treatment due to differences in their morphological characteristics and microhabitat. In addition, interspecies differentiation in response to snow depth treatment might affect the survival of some biological soil crusts. Further, this influence might lead to changes in the structural composition and functional communities of biological soil crusts., R. Hui, R. M. Zhao, L. C. Liu, Y. X. Li, H. T. Yang, Y. L. Wang, M. Xie, X. Q. Wang., and Obsahuje bibliografii
Photosynthesis in iron-deficient soybean and maize leaves decreased drastically. The quantum yield of photosystem 2 (PS2) electron transport (ΦPS2), the efficiency of excitation energy capture by open PS2 reaction centres (Fv'/Fm'), and photochemical quenching coefficient (qP) under high irradiance were lowered significantly by iron deficiency, but non-photochemical quenching (NPQ) increased markedly. The analysis of the polyphasic rise of fluorescence transient showed that iron depletion induced a pronounced K step both in soybean and maize leaves. The maximal quantum yield of PS2 photochemistry (Φpo) decreased only slightly, however, the efficiency with which a trapped exciton can move an electron into the electron transport chain further than QA (Ψ0) and the quantum yield of electron transport beyond QA (ΨEo) in iron deficient leaves decreased more significantly compared with that in control. Thus not only the donor side but also the acceptor of PS2 was probably damaged in iron deficient soybean and maize leaves. and Chuang-Dao Jiang, Hui-Yuan Gao, Qi Zou.
Influence of drought (D) on changes of leaf water potential (Ψ) and parameters of gas exchange in D-resistant and D-sensitive genotypes of triticale and maize was compared. Soil D (from -0.01 to -2.45 MPa) was simulated by mannitol solutions. At -0.013 MPa significant differences in Ψ, net photosynthetic rate (PN), transpiration rate (E), stomatal conductance (gs), and internal CO2 concentration (Ci) of D-resistant and D-sensitive triticale and maize genotypes were not found. Together with the increase in concentration of the mannitol solution the impact of D on E and gs for D-sensitive genotypes (CHD-12, Ankora) became lower than for the D-resistant ones (CHD-247, Tina). Inversely, impact of D on Ψ was higher in D-sensitive than D-resistant genotypes. From 1 to 3 d of D, a higher decrease in PN was observed in D-resistant genotypes than in the D-sensitive ones. Under prolonged D (5-14 d) and simultaneous more severe D the decrease in PN was lower in D-resistant than in D-sensitive genotypes. Changes in Ψ, PN, E, and gs caused by D in genotypes differing in the drought susceptibility were similar for triticale and maize. Compared to control plants, increase of Ci was different for triticale and maize genotypes. Hence one of the physiological reasons of different susceptibility to D between sensitive and resistant genotypes is more efficient protection of tissue water status in resistant genotypes reflected in higher decrease in gs and limiting E compared to the sensitive ones. Other reason, observed in D-resistant genotypes during the recovery from D-stress, was more efficient removal of detrimental effects of D. and M. T. Grzesiak, S. Grzesiak, A. Skoczowski.
Liriodendron tulipifera was exposed to gradually elevated ozone concentrations of 100-300 μg kg-1 in the naturally irradiated environment chamber. During 15 d of exposure to O3, net photosynthetic rate (PN) decreased and there was large difference between the control (C) and treatment with ozone (OT), while there was no significant difference in water use efficiency. Total chlorophyll content as well as the value of fluorescence parameter Fv/Fm decreased, while antioxidant enzyme activities related to ascorbate-glutathione cycle increased after 15 d of OT. Unchanged contents of ascorbate and glutathione indirectly suggest that the species hastened the antioxidant's oxidization/reduction cycle using enzymes instead of expanding their pool against oxidative stress. and S. Z. Ryang ... [et al.].