We determined for Vicia faba L the influence of nitrogen uptake and accumulation on the values of photon saturated net photosynthetic rate (PNmax), quantum yield efficiency (α), intercellular CO2 concentration (Ci), and carboxylation efficiency (Ce). As leaf nitrogen content (NL) increased, the α converged onto a maximum asymptotic value of 0.0664±0.0049 μmol(CO2) μmol(quantum)-1. Also, as NL increased the Ci value fell to an asymptotic minimum of 115.80±1.59 μmol mol-1, and Ce converged onto a maximum asymptotic value of 1.645±0.054 μmol(CO2) m-2 s-1 Pa-1 and declined to zero at a NL-intercept equal to 0.596±0.096 g(N) m-2. α fell to zero for an NL-intercept of 0.660±0.052 g(N) m-2. As NL increased, the value of PNmax converged onto a maximum asymptotic value of 33.400±2.563 μmol(CO2) m-2 s-1. PN fell to zero for an NL-intercept of 0.710±0.035 g(N) m-2. Under variable daily meteorological conditions the values for NL, specific leaf area (δL), root mass fraction (Rf), PNmax, and α remained constant for a given N supply. A monotonic decline in the steady-state value of Rf occurred with increasing N supply. δL increased with increasing N supply or with increasing NL. and Yinsuo Jia, V. M. Gray.
Climate change impacts environmental conditions that affect photosynthesis. This review examines the effect of combinations of elevated atmospheric CO2, long photoperiods, and/or unfavorable nitrogen supply. Under moderate stress, perturbed plant source-sink ratio and redox state can be rebalanced but may result in reduced foliar protein content in C3 plants and a higher carbon-to-nitrogen ratio of plant biomass. More severe environmental conditions can trigger pronounced photosynthetic downregulation and impair growth. We comprehensively evaluate available evidence that microbial partners may be able to support plant productivity under challenging environmental conditions by providing (1) nutrients, (2) an additional carbohydrate sink, and (3) regulators of plant metabolism, especially plant redox state. In evaluating the latter mechanism, we note parallels to metabolic control in photosymbioses and microbial regulation of human redox biology.
Leaf gas exchange and plant water relations of three co-occurring evergreen Mediterranean shrubs species, Quercus ilex L. and Phillyrea latifolia L. (typical evergreen sclerophyllous shrubs) and Cistus incanus L. (a drought semi-deciduous shrub), were investigated in order to evaluate possible differences in their adaptive strategies, in particular with respect to drought stress. C. incanus showed the highest annual rate of net photosynthetic rate (PN) and stomatal conductance (gs) decreasing by 67 and 69 %, respectively, in summer. P. latifolia and Q. ilex showed lower annual maximum PN and gs, although PN was less lowered in summer (40 and 37 %, respectively). P. latifolia reached the lowest midday leaf water potential (Ψ1) during the drought period (-3.54±0.36 MPa), 11 % lower than in C. incanus and 19 % lower than in Q. ilex. Leaf relative water content (RWC) showed the same trend as Ψ1. C. incanus showed the lowest RWC values during the drought period (60 %) while they were never below 76 % in P. latifolia and Q. ilex; moreover C. incanus showed the lowest recovery of Ψ1 at sunset. Hence the studied species are well adapted to the prevailing environment in Mediterranean climate areas, but they show different adaptive strategies that may be useful for their co-occurrence in the same habitat. However, Q. ilex and P. latifolia by their water use strategy seem to be less sensitive to drought stress than C. incanus. and A. Bombelli, L. Gratani.
A controlled growth chamber experiment was conducted to investigate the short-term water use and photosynthetic responses of 30-d-old carrot seedlings to the combined effects of CO2 concentration (50-1 050 µmol mol-1) and moisture deficits (-5, -30, -55, and -70 kPa). The photosynthetic response data was fitted to a non-rectangular hyperbola model. The estimated parameters were compared for effects of moisture deficit and elevated CO2 concentration (EC). The carboxylation efficiency (α) increased in response to mild moisture stress (-30 kPa) under EC when compared to the unstressed control. However, moderate (-55 kPa) and extreme (-70 kPa) moisture deficits reduced α under EC. Maximum net photosynthetic rate (PNmax) did not differ between mild water deficit and unstressed controls under EC. Moderate and extreme moisture deficits reduced PNmax by nearly 85 % compared to controls. Dark respiration rate (RD) showed no consistent response to moisture deficit. The CO2 compensation concentration (Γ) was 324 µmol mol-1 for -75 kPa and ranged 63-93 µmol mol-1 for other moisture regimes. Interaction between moisture deficit and EC was noticed for PN, ratio of intercellular and ambient CO2 concentration (Ci/Ca), stomatal conductance (gs), and transpiration rate (E). PN was maximum and Ci/Ca was minimum at -30 kPa moisture deficit and at C a of 350 µmol mol-1. The gs and E showed an inverse relationship at all moisture deficit regimes and EC. Water use efficiency (WUE) increased with moisture deficit up to -55 kPa and declined thereafter. EC showed a positive influence towards sustaining PN and increasing WUE only under mild moisture stress, and no beneficial effects of EC were noticed at moderate or extreme moisture deficits. and A. Thiagarajan, R. R. Lada.
This study focused on the deleterious effect of anthracene (ANT) and role of a surfactant, Triton (TX-100), in recovery from inhibitory effect of ANT. Fast chlorophyll (Chl) fluorescence measurements were performed in wheat plants. Results revealed that maximum quantum yield of PSII, area over the fluorescence curve, performance index (PI), and reaction centre density was negatively affected by ANT treatment. The effects on PSII quantum efficiency, reaction centre density, absorption, and trapping were partially recovered by TX-100. PSII heterogeneity in terms of PSII antenna heterogeneity, corresponding to PSII α, β, and γ centres, and reducing side, corresponding to QB-reducing and QB-nonreducing centres, were also investigated. The damage caused by ANT to PSII antenna heterogeneity was recovered almost by 100% owing to TX-100., C. Sharma, S. Mathur, R. S. Tomar, A. Jajoo., and Obsahuje bibliografii
Terbium (Tb^'*") was ušed as a fluorescence probe in the study of calcium-binding sites on 33 kDa protein of photosystem 2. The fluorescence of Tb^^ was enhanced markedly when bound to the 33 kDa protein, and the non-radiative energy transfer between tryptophan (Trp) residue and Tb^+, bound to the calcium-binding sites on the 33 kDa protein, took plače. According to the Forster non-radiative energy transfer mechanism, the average distance between the bound Tb3+ and Trp residue was found to be 1.05 nm. The pH titration indicated that major groups in the 33 kDa protein, involved in Ca2+ ions binding, were the carboxylic side groups of the glutamic acid and/or aspartic acid.
Increasing human and industrial activities lead to heavy metal pollution. Heavy metal chromium (Cr) is considered to be a serious environmental contaminant for the biota. Phytotoxic effects of Cr were studied in wheat plants. Growth parameters were largely inhibited as a result of disturbances in the plant cell metabolism in response to Cr toxicity. Chromium toxicity led to decline in a number of active reaction centres of PSII, rate of electron transport, and change in PSII heterogeneity. Chromium did not cause any change in heterogeneity of the reducing side. A significant change in antenna size heterogeneity of PSII occurred in response to Cr toxicity. Chromium seems to have extensive effects on the light harvesting complex of PSII., S. Mathur, H. M. Kalaji, A. Jajoo., and Obsahuje seznam literatury
Among the most important quality parameters of irrigation water used for greenhouse crops, alkalinity of water is considered critical due to its impact on soil or growing medium solution pH. In this study, plant growth, Fe content, photosynthetic pigment content, maximal quantum yield of PSII photochemistry (Fv/Fm), performance index (PI), leaf relative water content (LRWC), and soluble sugars concentration were investigated in nongrafted and grafted tomato (Lycopersicon esculentum Mill. cv. Red stone) plants onto five rootstocks of eggplant (Solanum melongena cv. Long purple), datura (Datura patula), orange nightshade (Solanum luteum Mill.), local Iranian tobacco (Nicotiana tabacum), and field tomato (Lycopersicon esculentum Mill. cv. Cal.jn3), exposed to 0, 5, and 10 mM NaHCO3 concentrations, to determine whether grafting could improve alkalinity tolerance of tomato. Significant depression of leaf area, leaf and stem dry mass, shoot and root Fe content and LRWC under high NaHCO3 level was observed in both grafted and ungrafted plants. The highest reduction in the shoot Fe content was observed at 10 mM sodium bicarbonate in control plants (greenhouse tomato). Moreover, at high HCO3- level, the highest percentage of LRWC reduction was also recorded in ungrafted plants. Values of Fv/Fm and PI decreased significantly at 5 and 10 mM NaHCO3 irrespective of rootstock type. The present study revealed that soluble sugars content, photosynthetic pigments content, Fv/Fm and PI values in plants grafted onto datura rootstock were higher than those in nongrafted and rest of the grafted plants. Thus, the use of datura rootstock could provide a useful tool to improve alkalinity tolerance of tomato plants under NaHCO3 stress., Y. Mohsenian ... [et al.]., and Obsahuje bibliografii
Seeds of Suaeda salsa were cultured in dark for 3 d and betacyanin accumulation in seedlings was promoted significantly. Then the seedlings with accumulated betacyanin (C+B) were transferred to 14/10 h light/dark and used for chilling treatment 15 d later. Photosystem 2 (PS2) photochemistry, D1 protein content, and xanthophyll cycle during the chilling-induced photoinhibition (exposed to 5 °C at a moderate photon flux density of 500 µmol m-2 s-1 for 3 h) and the subsequent restoration were compared between the C+B seedlings and the control (C) ones. The maximal efficiency of PS2 photochemistry (Fv/Fm), the efficiency of excitation energy capture by open PS2 centres (Fv'/Fm'), and the yield of PS2 electron transport (ΦPS2) of the C+B and C leaves both decreased during photoinhibition. However, smaller decreases in Fv/Fm, Fv'/Fm', and ΦPS2 were observed in the C+B leaves than in C ones. At the same time, the deepoxidation state of xanthophyll cycle, indicated by (A+Z)/(V+A+Z) ratio, increased rapidly but the D1 protein content decreased considerably during the photoinhibition. The increase in rate of (A+Z)/(V+A+Z) was higher but the D1 protein turnover was slower in C+B than C leaves. After photoinhibition treatment, the plants were transferred to a dim irradiation (10 µmol m-2 s-1) at 25 °C for restoration. During restoration, the chlorophyll (Chl) fluorescence parameters, D1 protein content, and xanthophyll cycle components relaxed gradually, but the rate and level of restoration in the C+B leaves was greater than those in the C leaves. The addition of betacyanins to the thylakoid solution in vitro resulted in similar changes of Fv/Fm, D1 protein content, and (A+Z)/(V+A+Z) ratio during the chilling process. Therefore, betacyanin accumulation in S. salsa seedlings may result in higher resistance to photoinhibition, larger slowing down of D1 protein turnover, and enhancement of non-radiative energy dissipation associated with xanthophyll cycle, as well as in greater restoration after photoinhibition than in the control when subjected to chilling at moderate irradiance. and C.-Q. Wang, T. Liu
The effects of iso-osmotic salinity and drought stresses on leaf net photosynthetic rate (PN) in two wheat (Triticum aestivum L.) cultivars BR 8 and Norin 61, differing in drought tolerance, were compared. In drought-sensitive Norin 61, the decline of PN was larger than that in drought-tolerant BR 8. Under NaCl treatment, PN decreased in two phases similarly in both cultivars. In the first phase, photosynthetic depression was gradual without any photochemical changes. In the second phase, photosynthetic depression was rapid and accompanied with a decline of the energy conversion efficiency in photosystem 2 (ΦPS2). Our observations suggest that the osmotic factor may induce a gradual depression of photosynthesis due to stomatal closure under both stress treatments. However, under NaCl treatment, a ionic factor (uptake and accumulation of excess Na+) may have direct effects on electron transport and cause more severe photosynthetic depression. The drought tolerance mechanism of BR 8 was insufficient to maintain single-leaf photosynthesis under salinity. and S. Muranaka, K. Shimizu, M. Kato.