An experiment was performed to study gas exchange and chlorophyll fluorescence responses of rice (Oryza sativa L.) to various regimes, such as flooding-midseason drying-flooding (FDF), flooding-midseason drying-saturation (FDS), and flooding-rain-fed (FR) regimes. Compared to FDF, FR resulted in an obvious decrease in net photosynthetic rate (PN), due to the decrease in stomatal conductance and the increase in stomatal limitation. In contrast, FDS plants did not suffer stomatal limitation and had comparable PN with FDF plants. For diurnal light-saturated electron transport rate and saturation irradiance, FDF performed the best, which was followed by FDS and FR successively. FR and FDS plants tended to suffer from midday depression. FDS reduced irrigated water by 17.2% compared to FDF for comparable yields. The results suggested that FDS can be an effective irrigation regime to save water., X. H. Wu, W. Wang, X. L. Xie, C. M. Yin, K. J. Xie., and Obsahuje bibliografii
Cell wall-bound phenolics (CWP) play an important role in the mechanisms of plant acclimation to soil drought. The study involved CWP analyses in 50 strains and 50 doubled haploid (DH) lines of winter triticale exposed to drought at their vegetative and generative stages. CWP in the plants experiencing drought at the generative stage positively correlated with their leaf water contents. The strains and DH lines characterized by high content of CWP showed higher leaf water content and higher activity of photosynthetic apparatus when exposed to drought at the generative stage compared to the strains and DH lines with the low CWP content. Furthermore, when drought subsided at the generative stage, the strains and DH lines richer in CWP demonstrated higher regeneration potential and their grain yield loss was smaller., K. Hura, A. Ostrowska, K. Dziurka, T. Hura., and Obsahuje seznam literatury
The southernmost presence of Rhizophora mangle in the western Atlantic coast occurs in coastal wetlands between 27 and 28°S in the State of Santa Catarina, Brazil. We selected mangrove communities at the estuary of the River Tavares, Florianopolis, and the Sonho Beach, Palhosa, for measurement of photosynthetic performance and intrinsic water-use efficiency of R. mangle and coexisting individuals of Avicennia schaueriana and Laguncularia racemosa, during the spring season. We used gas-exchange techniques and isotopic signatures of C and N to estimate instantaneous water-use and carboxylation efficiency (CE), long-term water-use efficiency, and potential N limitation. Results showed that R. mangle had significantly lower photosynthetic rates but similar conductance values as the other two species resulting in lower intrinsic water use (WUEi) and CE. WUEi and CE were positively correlated in L. racemosa and A. schaueriana, but not in R. mangle. At each site, δ13C values of A. schaueriana were consistently higher than those for the other species, indicating that these species are subjected to contrasting water stress conditions. Leaf concentrations of C were lower, whilst those of N were always higher in A. schaueriana, indicating accumulation of salts and nonprotein N-compounds in leaves. Nitrogen concentrations and moderate positive δ15N values indicated that plant growth at the study sites was not inhibited by nutrient deficiency, and was not influenced by urban residual waters. Lower photosynthetic rates and values of CE of R. mangle compared to the other two species may constitute constraining factors preventing this species from establishing at higher latitudes., M. L. Gomes Soares, M. M. Pereira Tognella, E. Cuevas, E. Medina., and Obsahuje seznam literatury
We investigated the photosynthetic characteristics of Chorispora bungeana under conditions of drought stress caused by different concentrations of polyethylene glycol-6000 (PEG; 0, 5, 20, and 40%) and various concentrations of exogenous glycine (0, 5, 10, and 20 mM) with 20% PEG. We showed that moderate and severe drought stress of PEG reduced the chlorophyll (Chl) content (both Chl a and b), maximal quantum yield of PSII photochemistry (Fv/Fm), actual photochemical efficiency of PSII in light (YII), and quantum yield of regulated energy dissipation (YNPQ), while Chl a/b and quantum yield of nonregulated energy dissipation (YNO) increased. The low and moderate drought stress increased Mg2+ and Fe3+ contents, while a decrease in Mg2+ and Fe3+ was found under severe drought stress. Compared to sole PEG stress, the addition of exogenous 10 mM glycine increased Chl, Mg2+ and Fe3+ contents, Fv/Fm, YII, and YNPQ, and reduced YNO. On the contrary, 20 mM glycine showed an opposite effect, except for YNO. Our results proved that Chl contents and fluorescence parameters are reliable indicators for drought tolerance of C. bungeana. We suggest that a proper glycine content can relieve the effect of drought stress on C. bungeana., N. Yang, C.-L. Wang, W.-P. He, Y.-Z. Qu, Y.-S. Li., and Seznam literatury
Photosynthesis is amongst the plant cell functions that are highly sensitive to any type of changes. Sun and shade conditions are prevalent in fields as well as dense forests. Dense forests face extreme sun and shade conditions, and plants adapt themselves accordingly. Sun flecks cause changes in plant metabolic processes. In the field, plants have to face high light intensity and survive under such conditions. Sun and shade type of plants develops a respective type of chloroplasts which help plants to survive and perform photosynthesis under adverse conditions. PSII and Rubisco behave differently under different sun and shade conditions. In this review, morphological, physiological, and biochemical changes under conditions of sun (high light) and shade (low light) on the process of photosynthesis, as well as the tolerance and adaptive mechanisms involved for the same, were summarized., S. Mathur, L. Jain, A. Jajoo., and Obsahuje bibliografické odkazy
Limitations in photosystem function and photosynthetic electron flow were investigated during leaf senescence in two field-grown plants, i.e., Euphorbia dendroides L. and Morus alba L., a summer- and winter-deciduous, shrub and tree, respectively. Analysis of fast chlorophyll (Chl) a fluorescence transients and post-illumination fluorescence yield increase were used to assess photosynthetic properties at various stages of senescence, the latter judged from the extent of Chl loss. In both plants, the yield of primary photochemistry of PSII and the content of PSI remained quite stable up to the last stages of senescence, when leaves were almost yellow. However, the potential for linear electron flow along PSII was limited much earlier, especially in E. dendroides, by an apparent inactivation of the oxygen-evolving complex and a lower efficiency of electron transfer to intermediate carriers. On the contrary, the corresponding efficiency of electron transfer from intermediate carriers to final acceptors of PSI was increased. In addition, cyclic electron flow around PSI was accelerated with the progress of senescence in E. dendroides, while a corresponding trend in M. alba was not statistically significant. However, there was no decrease in PSI activity even at the last stages of senescence. We argue that a switch to cyclic electron flow around PSI during leaf senescence may have the dual role of replenishing the ATP and maintaining a satisfactory nonphotochemical energy quenching, since both are limited by hindered linear electron transfer., C. Kotakis, A. Kyzeridou, Y. Manetas., and Obsahuje bibliografii
Vochysia divergens Pohl is considered to be a flood-adapted, light-demanding pioneer species that has been invading grasslands of the Brazilian Pantanal. In these areas, a successful invasion requires an ability to tolerate physiologically wide fluctuations in surface hydrology and shading induced by a dense cover of grasses and other vegetation. We evaluated how flooding and shading affected the photosynthetic performance of V. divergens saplings by measuring light-saturated gas exchange (net photosynthetic rate, PN; stomatal conductance, gs), and intercellular CO2 (PN/Ci) and photosynthetic photon flux density
(PN/PPFD) response curves over a 61-d field experiment. Shading and flooding reduced significantly light-saturated PN and gs and affected multiple aspects of the leaf gas exchange response of V. divergens to variations in PPFD and CO2. Flooding influenced the physiology of this species more than shading. Given the success of V. divergens at invading and expanding in seasonally flooded areas of the Pantanal, the results were surprising and highlighted the physiological ability of this species to tolerate suboptimal conditions. However, the consistently higher light-saturated PN and gs under nonflooded conditions suggested that the invasive success of V. divergens might not be related to its physiological potential during flooding, but to situations, when flooding recedes during the dry season and soil water availability is adequate. and A. C. Dalmolin ... [et al.].
Salt stress causes extensive losses to agricultural crops, including wheat, throughout the world and has been the focus of wide research. Though, information is scarce on the potential of ancient wheat relatives in tackling this major limiting factor. Thus, six hulled tetraploid wheat genotypes (HW) were compared to a
free-threshing durum wheat genotype (FTW) under different NaCl concentrations, ranging from 0 to 150 mM, at early growth stages in a sand culture experiment. Salt stress induced significant declines in the leaf chlorophyll (Chl) a, Chl b, total Chl, and carotentoid contents; the extent of the declines was greater in FTW compared to HW. Mean leaf proline (3.6-fold) and Na+ (1.58-fold) concentrations and Na+/K+ (2.48-fold) drastically increased with 150 mM of NaCl; the magnitude of the increases was greater in HW compared to FTW. While the carotenoids concentration decreased with progressive salinity both in HW and FTW, the activities of antioxidant enzymes, i.e., catalase, ascorbate peroxidase, and peroxidase were reduced in FTW, but remained unchanged in HW. The above responses to 150 mM NaCl were associated with a significant decrease in shoot dry mass of FTW and lack of significant changes in that of HW. Findings of the present study could help pave the way for further studies on physiological and molecular mechanisms of salt tolerance in these durum wheat relatives., S. Tabatabaei, P. Ehsanzadeh., and Seznam literatury
European beech (Fagus sylvatica L.) seedlings of three different origins were used to evaluate the effect of water deficit and recovery during the most vulnerable phase of forest tree life. Gas-exchange characteristics and fluorescence rapid light curves were studied in the seedlings from a warm region (PV1, 530 m a.s.l.), seedlings from a moderately warm region (PV2, 625 m a.s.l.), optimal for beech, and in seedlings from a cool region (PV3; 1,250 m a.s.l.). Changes in photosynthetic characteristics caused by water deficit were similar, but their intensity was dependent on the origin of the seedlings. Simulation of drought conditions by the interruption of watering led to a decrease in the efficiency of primary photochemistry in PSII, with the most significant decrease in the PV2 seedlings. Conversely, water deficit affected most significantly gas exchange in PV3, where the recovery process was also the worst. The PV1 demonstrated the highest resistance to water deficit. Drought-adaptation of beech seedlings at non-native sites seems to be linked to water availability and to the origin of the beech seedlings., E. Pšidová, Ľ. Ditmarová, G. Jamnická, D. Kurjak, J. Majerová, T. Czajkowski, A. Bolte., and Obsahuje bibliografii
Small rainfall events (≤ 5 mm) have short intervals, but account for a large proportion of the annual rainfall frequency in arid lands. To explore possible strategies used by desert plants to utilize the small rainfall events, we investigated the photosynthetic responses of 28 species to 1 mm and 6 mm of simulated rainfall in the Junggar Basin, northwest China. The species were grouped into four plant functional types: short-life-cycle herbs, long-life-cycle herbs, non-phreatophyte shrubs, and phreatophyte shrubs. The results showed that the net photosynthetic rate, stomatal conductance, and transpiration rate increased in most of the herbs, but they responded differently to the rainfall treatments. However, the water-use efficiency did not significantly differ after 1 and 6 mm rainfall treatments in most of the shrubs. The maximum water absorption by leaves and the percentage increase of a leaf water content (LWC) were higher in the herbs than those in the shrubs. Plants with dense trichomes had the highest LWC. The results suggested that the desert plants benefited from the
micro-environment humidity provided by the small rainfall events., Y. Wu, X. J. Zheng , Y. Li., and Obsahuje seznam literatury