Efficiency of a photosynthetic apparatus in plants growing in cadmium-spiked soil as well as plant biomass and cadmium accumulation were assessed in two cabbage cultivars (early and late) in a long-term pot experiment. Cadmium concentrations were 10 and 40 mg(Cd) per kg of dry mass of soil. The early cultivar showed a dose-dependent and stable decrease in SPAD index, while in plants of the late cultivar the response was reversible and less pronounced. A huge drop in the effective quantum yield of PSII photochemistry, photochemical quenching, nonphotochemical quenching, and electron transport rate in the third week of vegetation indicated susceptibility of the early cultivar to cadmium, contrary to the late one. Fresh mass of plants of the early cultivar was diminished by both doses of Cd. For the late cultivar, there was no change in these parameters, indicating its possible usability for phytoremediation, provided the reclaimed area is fenced and protected. Particular attention should also be paid towards late cultivars cabbage farming in areas with a high Cd content. On the other hand, the early cultivar may serve as a bioindicator of Cd-contamination.

We investigated the physiological responses of two epiphytic orchids under three light regimes of 20, 50, and 70% of total daily radiation under drought and rewatering conditions. Stanhopea tigrina was the one more affected because it exhibited strong photoinhibition and reduction of both electron transport rate and nocturnal acidity under drought and high radiation. However, this species maintained relatively high relative water content (RWC) values and underwent osmotic adjustment during the drought period and recovered photosynthetic variables during watered period. Prosthechea cochleata maintained similar water and photosynthetic responses to light conditions during the drought period and was more tolerant than S. tigrina. Principal component analysis provided evidence that water variables, such as RWC and succulence of both leaf and pseudobulb, were the most important variables for both species. Our results suggest that S. tigrina is more sensitive to drought than P. cochleata, and could be more affected by global warming.

Photoprotective pigments, like those involved in the xanthophyll cycle, help plants avoid oxidative damage caused by excess radiation. This study aims to characterize a spectrum of strategies used to cope with light stress by a diverse group of prairie plants at Cedar Creek Ecosystem Science Reserve (East Bethel, MN). We find that concentrations of photosynthetic and photoprotective pigments are highly correlated with one another and with other physiological traits across species and over time, and tend to be phylogenetically conserved. During a period of water limitation, plots dominated by species with constitutively low pigment concentrations showed a greater decline in mean reflectance and photochemical reflectance index, a reflectance-based indicator of photoprotective physiology, possibly due to alterations in canopy structure. Our findings suggest two contrasting strategies for withstanding light stress: (1) Using photoprotective pigments to dissipate excess energy, and (2) altering canopy structure to minimize absorbance of excess radiation.

Our present work showed that the expression of genes encoding PTOX (terminal oxidase of chlororespiration) and PGR5 (one essential component of cyclic electron transfer) were stimulated by red and blue light, but the stimulation under red light was soon reversed by subsequent far-red light. The expression levels of PTOX and PGR5 under simulated light quality conditions in line with maize-soybean relay strip intercropping (SRI) were obviously lower than those under simulated soybean monocropping (SM), since the lower red:far-red ratio under SRI. Measurements on photosynthetic and chlorophyll fluorescence parameters suggested a decline of assimilatory power supply and a lower nonphotochemical quenching under SRI as compared to SM. In this case, weaker PGR-dependent cyclic electron transfer and chlororespiration under SRI, suggested by lower expression levels of PGR5 and PTOX, could be considered as means of reducing excitation energy dissipation to allocate more power toward CO₂ assimilation.

On the occasion of the 50th anniversary of the international journal Photosynthetica in 2017 we briefly report on the establishment of this journal and on Dr. Zdeněk Šesták, the renowned researcher of photosynthesis processes who, in cooperation with the Czechoslovak Academy of Sciences, founded this essential science journal in Prague in 1967.

Many RNA recognition motif (RRM)-containing proteins are known to exist in chloroplasts. Major members of the RRM protein family, which are chloroplast ribonucleoproteins (cpRNPs), have been investigated in seed plants, including tobacco and Arabidopsis thaliana, but never in early land plants, such as bryophytes. In this study, we surveyed RRM proteins encoded in the moss Physcomitrella patens genome and predicted 25 putative chloroplast RRM proteins. Among them, two RRM-containing proteins, PpRBP2a and PpRBP2b, resembled cpRNPs and were thus referred to as cpRNP-like proteins. However, knockout mutants of either one or two PpRBP2 genes exhibited a wild type-like phenotype. Unlike Arabidopsis cpRNPs, the levels of mRNA accumulation in chloroplasts were not affected in the PpRBP2 knockout mutants. In addition, the efficiency of RNA editing was also not altered in the mutants. This suggests that PpRBP2a and 2b may be functionally distinct from Arabidopsis cpRNPs.

Atmospheric CO₂ concentration continues to rise and is predicted to reach approximately 700 ppm by 2100. Some predictions suggest that the dry season in West Africa could be extended with climate change. This study examined the effects of elevated CO₂ concentration and water deficit on growth and photosynthesis of juvenile cacao. Light-saturated photosynthesis (P_max), quantum efficiency, and intrinsic water-use efficiency increased significantly in response to elevated CO₂, as did a range of growth and development responses (e.g. leaf area and leaf number), but the magnitude of the increase was dependent on the water treatment. Stomatal index was significantly greater in the elevated CO₂ treatment; an atypical response which may be a reflection of the environment in which cacao evolved. This study shows a positive effect of elevated CO₂ on juvenile cacao which may help to alleviate some of the negative impacts of water deficit stress.

Carbonic anhydrase (CA) is a metalloenzyme that performs interconversion between CO₂ and the bicarbonate ion (HCO₃ ^-). CAs appear among all taxonomic groups of three domains of life. Wide spreading of CAs in nature is explained by the fact that carbon, which is the major constituent of the enzyme's substrates, is a key element of life on the Earth. Despite the diversity of CAs, they all carry out the same reaction of CO₂/HCO₃ ^- interconversion. Thus, CA obviously represents a universal enzyme of the carbon-based life. Within the classification of CAs, here we proposed the existence of an extensive family of CA-related proteins (γCA-RPs)-the inactive forms of γ-CAs, which are widespread among the Archaea, Bacteria, and, to a lesser extent, in Eukarya. This review focuses on the history of CAs discovery and integrates the most recent data on their classification, catalytic mechanisms, and physiological roles at various organisms.

Vegetation in grasslands is changing at an unprecedented rate. In the Nebraska Sandhills, this shift is attributed in part to encroachment of the woody species Juniperus virginiana. We investigated changes in resource availability and their feedback on seasonal trends in photosynthetic characteristics of J. virginiana trees scattered in open grasslands vs. a dense 57-year-old stand. Dense stand exhibited lower volumetric soil water content, NH₄ ⁺, NO₃ ^-, and δ¹³C, as well as foliage δ¹³C, δ¹⁵N, and N content, compared to grasslands. Water potential was higher in trees in grasslands compared to dense stand. J. virginiana in dense stand exhibited similar trends to trees in grasslands for net photosynthetic rate (P _N), stomatal conductance, transpiration, maximum photochemical efficiency of PSII, maximum carboxylation velocity, and maximum rate of electron transport. P _N peaked early summer and declined in the fall, with trees in open grasslands lagging behind those in dense stand. Plasticity of this species may place it at a competitive advantage in the Sandhills, further altering grasslands vegetation and ecosystem processes.

'Hass' and 'Fuerte' avocado plants were grown under well-watered or waterlogged conditions. Results indicated significant effects on the majority of the allometric parameters in waterlogged plants, with 'Fuerte' displaying a more pronounced growth inhibition. Waterlogged conditions caused a progressive and simultaneous decline in net photosynthetic rate and stomatal conductance, earlier in 'Fuerte' than in 'Hass'. Maximal potential quantum yield of PSII was unaffected by the soil water regime and/or variety and leaf water potential values in waterlogged plants were not more negative compared with control plants. 'Fuerte' waterlogged plants exhibited increased contents of thiobarbituric acid reactive substances, whereas oxidative injury was not detected in 'Hass'. Finally, none of the two cultivars displayed valuable antioxidant potential, as evidenced by the decreased activities of the antioxidant enzymes superoxide dismutase, guaiacol peroxidase, glutathione peroxidase, and ascorbate peroxidase.

Water availability is an important factor for plant growth in arid environments. In recent decades, vermicompost (VC) fertilizer has been used in agriculture as a safe and effective fertilizer with high water-holding capacity. The aim of the present study was to characterize effects of VC fertilizer on photosynthetic activity of chickpea (Cicer arietinum L. cv. Karaj) under drought conditions at three different growth stages. Tests were carried out with four volumetric ratios of VC to soil, i.e., 0:100, 10:90, 20:80, and 30:70, and three levels of drought stress, i.e., no stress (NS), moderate drought (MS), and severe drought (SS) (100, 75, and 25% of field capacity, respectively). Evaluations were performed at the seedling, flowering, and podding stage. We found that the VC treatment under NS conditions significantly increased total chlorophyll content [Chl (a+b)], intercellular CO₂ concentration (C _i), net photosynthetic rate (P _N), transpiration rate (E), and maximal quantum yield of PSII photochemistry (F_v/F_m) at all three stages. The VC addition of 10 and 20% significantly enhanced the Chl content and F_v/F_m under MS and F_v/F_m, C _i, and P _N under SS at the flowering stage. In conclusion, our results proved a positive effect of the VC fertilizer on photosynthesis of chickpea under NS conditions, but it was not found under MS and SS.

Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39) is one of the key enzymes involved in assimilation of CO₂ in chloroplasts. Phylloplane microfungi and their metabolites have been reported to affect the physiology of host plants, particularly, their photosynthesis. However, information is lacking on the effect of these microflora on the physiology of chloroplasts. The current study emphasized the impact of two dominant phylloplane fungi, Aspergillus niger and Fusarium oxysporum, on activity of Rubisco in tomato chloroplasts. Ergosterol, which is a component of only fungal cell membranes and is not synthesized by plants, have been demonstrated to elicit activity of Rubisco. In the present study, it was demonstrated through in silico, in vitro, and in vivo approaches. Results demonstrated that the fungal metabolites, which contained ergosterol, could double Rubisco activity. Maximum carboxylation rate of Rubisco increased also in ergosterol-treated plants. Michaelis-Menten constant of Rubisco was also slightly affected. Ergosterol was found also to influence and enhance the binding of CO₂ and ribulose-1,5-bisphosphate to Rubisco. Therefore we can postulate that the physiology of the chloroplast is probably influenced by phylloplane microfungi.

Two greenhouse experiments were conducted in order to investigate the effects of different levels of water stress on gas exchange, chlorophyll fluorescence, chlorophyll content, antioxidant enzyme activities, lipid peroxidation, and yield of tomato plants (Solanum lycopersicum cv. Jinfen 2). Four levels of soil water content were used: control (75 to 80% of field water capacity), mild water stress (55 to 60%), moderate water stress (45 to 50%), and severe water stress (35 to 40%). The controlled irrigation was initiated from the third leaf stage until maturity. The results of two-year trials indicated that the stomatal conductance, net photosynthetic rate, light-saturated photosynthetic rate, and saturation radiation decreased generally under all levels of water stress during all developmental stages, while compensation radiation and dark respiration rate increased generally. Water stress also declined maximum quantum yield of PSII photochemistry, electron transfer rate, and effective quantum yield of PSII photochemistry, while nonphotochemical quenching increased in all developmental stages. All levels of water stress also caused a marked reduction of chlorophyll a, chlorophyll b, and total chlorophyll content in all developmental stages, while activities of antioxidant enzymes, such as superoxide dismutase, peroxidase, and catalase, and lipid peroxidation increased.

Extreme conditions, such as drought, high temperature, and solar irradiance intensity, are major factors limiting growth and productivity of grapevines. In a field experiment, kaolin particle film application on grapevine leaves was examined during two different summer conditions (in 2012 and 2013) with the aim to evaluate benefits of this practice against stressful conditions hindering photochemical processes. We used chlorophyll a fluorescence to investigate attached leaves. Two months after the application, during the hottest midday, the kaolin-treated plants showed by the JIP test significantly higher quantum yield of PSII photochemistry, flux ratios, maximum trapped excitation flux of PSI, absorption flux, electron transport flux, maximum trapped energy flux per cross section, and performance index than plants under control conditions in the warmer year. On the contrary, the treated plants showed a lower initial slope of relative variable fluorescence and a decrease in the absorption and electron transport per cross section. The JIP test showed higher efficiency of PSII in the plants treated with kaolin mainly in 2013 (higher temperature and drought). Our results supported the hypothesis that the accumulation of active PSII reaction centres was associated with decreased susceptibility to photoinhibition in the kaolin-treated plants and with more efficient photochemical quenching. Grapevines in the Douro Region seems to profit from the kaolin application.

The recomposition of deforested environments demands the acclimation of seedlings in nurseries. This process induces changes in physiological, anatomical, and morphological traits of plants, favouring their establishment after transplantation to the field. The present study aimed to verify the influence of full-sun acclimation on seedling hardiness. For the purpose, leaf gas-exchange, plant anatomical and morphological parameters of three tree species [Ceiba speciosa (A. St.-Hil.) Ravenna (Malvaceae), Croton floribundus Spreng. (Euphorbiaceae), and Cecropia pachystachya Trecul (Urticaceae)], which are used for reforestation in the Brazilian Atlantic biome, were evaluated. Seedlings were grown under 40% of total PPFD (shaded control) and under full sun (acclimated) for 168 days. The acclimation process induced a higher leaf production rate in C. speciosa and C. floribundus, whereas C. pachystachya seedlings replaced their leaves quickly, irrespective of the light conditions. The newly developed leaves of all three species presented a lower area and thicker palisade parenchyma, resulting in a reduced specific leaf area. The seedlings of C. speciosa and C. pachystachya showed increases in light-saturated net photosynthesis and transpiration rates, whereas water-use efficiency generally remained unchanged in all three species. The full-sun acclimated seedlings of C. pachystachya showed a reduced relative growth rate, lower height/stem diameter (H/D) and shoot to root dry mass ratios, characteristics that may result in greater physical resistance and ability for water and nutrient uptake to support the higher transpiratory demand under full sun. The reduction of the H/D ratio also occurred in the acclimated seedlings of C. speciosa. The seedlings of C. floribundus showed few changes during acclimation, but they did not seem to be affected by excessive light. In spite of the observed differences among the three species, all of them developed hardiness characteristics, mainly related to leaf anatomy, which should favour their establishment after transplantation to the field.

Excitation kinetics based on feedback regulation of chlorophyll (Chl) fluorescence of leaves measured with the chlorophyll fluorometer, FluoroMeter Modul (FMM), are presented. These kinetics showed the variation of excitation light (laser power, LP) regulated by the feedback mechanism of the FMM, an intelligent Chl fluorometer with embedded computer, which maintains the fluorescence response constant during the 300-s transient between the dark- and lightadapted state of photosynthesis. The excitation kinetics exhibited a rise of LP with different time constants and fluctuations leading to a type of steady state. The variation of excitation kinetics were demonstrated using the example of primary leaves of etiolated barley seedlings (Hordeum vulgare L. cv. Barke) during 48 h of greening in the light with gradual accumulation of Chl and development of photosynthetic activity. The excitation kinetics showed a fast rise followed by a short plateau at ca. 30 s and finally a slow constant increase up to 300 s. Only in the case of 2 h of greening in the light, the curve reached a stable steady state after 75 s followed by a slight decline. The final LP value (at 300 s of illumination) increased up to 12 h of greening and decreased with longer greening times. The active feedback mechanism of the FMM adjusted the excitation light during the measurement to the actual photosynthetic capacity of the individual leaf sample. In this way, the illumination with excessive light was avoided. The novel excitation kinetics can be used to characterize health, stress, disease, and/or product quality of plant material.

At present, research activities on the role of orchard systems in sequestering atmospheric CO₂ remain scarce. This paper aimed to contribute to assessing the carbon balance of a Mediterranean olive (Olea europea) orchard. The net ecosystem exchange, the ecosystem respiration and the gross primary production were computed for two consecutive years through eddy covariance, and the different biomass accumulation terms were also inferred in the same period through an inventorial method. The net carbon exchange ranged from 13.45 t(C) ha^-1 year^-1 to 11.60 t(C) ha^-1 year^-1. Very similar values [12.2 and 11.5 t(C) ha^-1 year^-1] were found with the direct carbon accumulation inventory. The intensive farming management (irrigation included) and the young age of the plants (12-16 years old), still in an active growing phase, led the olive plantation to be a higher carbon sink with respect to other evergreen orchards reported in the literature.

We investigated the effects of long-term acclimation of Eucalyptus nitens seedlings to ultraviolet-A (UV-A) irradiation (320-400 nm) on phenolic compounds (gallotannins, stilbenes, and flavonols), photochemical efficiency, and chlorophyll and carotenoid contents. Seedlings were raised under four nutrient regimes, ranging from low to high application rates, in an environment that included or excluded UV-A irradiance. Our aims were: to classify phenolic compounds that absorb in the UV-A and their relative contribution to total UV-A absorption; to identify how phenolic compounds respond to UV-A exposure and exclusion, and to determine how plant nutrient status affects acclimation of photo-and pigment-chemistry to UV-A exposure and exclusion. Gallotannins contributed to only a minor fraction of total absorption within the lower range (320-360 nm) of the UV-A spectrum. Stilbene and flavonol compounds dominated absorption within the 320-360 and 360-400 nm ranges, respectively. Contents of gallotannin were generally high in UV-A-exposed seedlings. Although there was a significant effect of UV-A on contents of stilbenes, a general response (across nutrient treatment comparisons) was not evident. Contents of flavonols were not affected by UV-A exposure. Contents of gallotannin, stilbene, and flavonols decreased from low to high nutrient-application treatments. There were no effects of UV-A on photochemical efficiency or pigment-chemistry.

The γ-subunits of chloroplast ATP synthases are about 30 amino acids longer than the bacterial or mitochondrial homologous proteins. This additional sequence is located in the mean part of the polypeptide chain and includes in green algae and higher plants two cysteines (Cys198 and Cys204 in Chlamydomonas reinhardtii) responsible for thiol regulation. In order to investigate its functional significance, a segment ranging from Asp-D210 to Arg-226 in the γ-subunit of chloroplast ATP synthase from C. reinhardtii was deleted. This deletion mutant called T2 grows photoautotrophically, but slowly than the parental strain. The chloroplast ATP synthase complex with the mutated γ is assembled, membrane bound, and as CF₀CF₁ displays normal ATPase activity, but photophosphorylation is inhibited by about 20 %. This inhibition is referred to lower light-induced transmembrane proton gradient. Reduction of the proton gradient is apparently caused by a disturbed functional connection between CF₁ and CF₀ effecting a partially leaky ATP synthase complex.

The review sums up research conducted at CIAT within a multidiscipline effort revolving around a strategy for developing improved technologies to increase and sustain cassava productivity, as well as conserving natural resources in the various eco-edaphic zones where the crop is grown, with emphasis on stressful environments. Field research has elucidated several physiological plant mechanisms underlying potentially high productivity under favourable hot-humid environments in the tropics. Most notable is cassava inherent high capacity to assimilate carbon in near optimum environments that correlates with both biological productivity and root yield across a wide range of germplasm grown in diverse environments. Cassava leaves possess elevated activities of the C₄ phosphoenolpyruvate carboxylase (PEPC) that also correlate with leaf net photosynthetic rate (P _N) in field-grown plants, indicating the importance of selection for high P _N. Under certain conditions such leaves exhibit an interesting photosynthetic C₃-C₄ intermediate behaviour which may have important implications in future selection efforts. In addition to leaf P _N, yield is correlated with seasonal mean leaf area index (i.e. leaf area duration, LAD). Under prolonged water shortages in seasonally dry and semiarid zones, the crop, once established, tolerates stress and produces reasonably well compared to other food crops (e.g. in semiarid environments with less than 700 mm of annual rain, improved cultivars can yield over 3 t ha^-1 oven-dried storage roots). The underlying mechanisms for such tolerance include stomatal sensitivity to atmospheric and edaphic water deficits, coupled with deep rooting capacities that prevent severe leaf dehydration, i.e. stress avoidance mechanisms, and reduced leaf canopy with reasonable photosynthesis over the leaf life span. Another stress-mitigating plant trait is the capacity to recover from stress, once water is available, by forming new leaves with even higher P _N, compared to those in nonstressed crops. Under extended stress, reductions are larger in shoot biomass than in storage root, resulting in higher harvest indices. Cassava conserves water by slowly depleting available water from deep soil layers, leading to higher seasonal crop water-use and nutrient-use efficiencies. In dry environments LAD and resistance to pests and diseases are critical for sustainable yields. In semiarid zones the crop survives but requires a second wet cycle to achieve high yields and high dry matter contents in storage roots. Selection and breeding for early bulking and for medium/short-stemmed cultivars is advantageous under semiarid conditions. When grown in cooler zones such as in tropical high altitudes and in low-land sub-tropics, leaf P _N is greatly reduced and growth is slower. Thus, the crop requires longer period for a reasonable productivity. There is a need to select and breed for more cold-tolerant genotypes. Selection of parental materials for tolerance to water stress and infertile soils has resulted in breeding improved germplasm adapted to both favourable and stressful environments.

The effects of drought on thylakoid acyl lipid composition, photosynthetic capacity (P _max), and electrolyte lekage were evaluated in two-months-old peanut cultivars (57-422, 73-30, GC 8-35) growing in a glasshouse. For lipid studies, plants were submitted to three treatments by withholding irrigation: control (C), mild water stress (S1), and severe water stress (S2). Concerning membrane and photosynthetic capacity stability, drought was imposed by polyethylene glycol (PEG 600). In the cv. 73-30 a sharp decrease in the content of thylakoid acyl lipids was observed, already under S1 conditions, whereas cv. 57-422 was strongly affected only under S2. Cv. GC 8-35 had the lowest content of acyl lipids under control conditions, a significant increase under S1 conditions, and only under S2 a decrease occurred. Thus concerning lipid stability, cv. 73-30 was the most sensitive. Among lipid classes, phospholipids and galactolipids were similarly affected, as was MGDG relatively to DGDG. Water deficit imposed by PEG induced a higher increase in electrolyte leakage in cv. 73-30 than in the other cvs. A positive relationship between acyl lipid concentration and membrane integrity was found in all studied cvs. A positive association between acyl lipid concentration, membrane integrity, and P _max was found in the cvs. 57-422 and 73-30.

Photosynthetic capacity (PC) of three peanut cultivars (Arachis hypogaea L. cvs. 57-422, 73-30, and GC 8-35) decreased during drought stress (decline in relative water content from ca. 95 to 70 %) and recovered two days after rewatering. Mild water stress was not limiting for the total ribulose-1,5-bisphosphate carboxylase/oxygenase activity, since this enzyme activity increased under drought. Photosystem (PS) 2 and PS1 (the latter only in cv. GC 8-35) electron transport activities decreased under drought. The ratio of the variable to maximal chlorophyll fluorescence (Fv/Fm) decreased mainly in the cv. GC 8-35. All cultivars showed decreases in photochemical quenching (qP) and quantum yield of PS2 electron transport (Φe). Increase of basal fluorescence (F0) was observed in the cvs. 73-30 and GC 8-35, while the cv 57-422 showed a decrease. After rewatering a sharp increase was observed in the majority of the parameters. Thus under the present stress conditions, the cv GC 8-35 was the most affected for all the parameters under study. The cv. 57-422 showed a higher degree of tolerance being gradually affected in photosynthetic capacity (PC) in contrast to the two other cvs. which showed a sharp decrease in PC at the beginning of the drought cycle.