Salicylic acid (SA) and nitric oxide (NO) form a new group of plant growth substances that cooperatively interact to promote plant growth and productivity. Water deficit (WD) stress is a major limiting factor for photosynthesis, which in turn limits crop yield. However, the mechanism of SA and NO in stimulating photosynthesis has not yet been elucidated. Therefore, in this study, we investigated the SA- and NO-mediated photosynthetic adaptability of maize seedlings to WD in terms of photosynthetic parameters, activities and mRNA levels of CO₂ assimilation enzymes. Our results showed that SA alleviated the WD-induced reduction of photosynthetic performance. The activities of Rubisco and Rubisco activase enzymes increased significantly due to SA pretreatment. Moreover, higher transcription rates of Rbc L, ZmRCAα and ZmRCAβ mRNA further confirmed the effects of SA on CO₂ assimilation. WD or SA-induced decreases or increases of CO₂ assimilation ability were further decreased after c-PTIO addition.

Specific leaf area (SLA) is a key trait to screen plants for ecological performance and productivity; however, the relationship between SLA and photosynthesis is not always up-scalable to growth when comparing multiple species with different life cycles. We explored leaf anatomy in annual and perennial species of Physaria, and related it to photosynthesis and water loss. The annual Physaria gracilis had higher SLA, thinner leaves, and lower investment in protective tissues, than perennial P. mendocina. Physaria angustifolia (annual), and P. pinetorum (perennial) showed intermediate values. Both perennials had a thicker palisade and high photosynthesis, relative to annuals. The larger leaf veins of perennials should allow high water availability to the mesophyll. The thicker palisade should determine high resistance to water flow and help explain their high water-use efficiency. These leaf functions reflect the construction of long-lived leaves that efficiently use resources under environmental limitations of arid environments.

Drought stress causes changes in vein and stomatal density. The objectives of this study were to determine (1) if the changes in vein and stomatal density are coordinated in cotton (Gossypium hirsutum L.) and (2) how these changes affect water-use efficiency (WUE). The results showed significant positive correlations between vein density and stomatal density when cotton was grown under different degrees of drought stress. WUE was significantly positively correlated with the densities of both veins and stomata. Stomatal pore area and stomatal density on the abaxial leaf side, but not the adaxial side, were significantly correlated with WUE, stomatal conductance, leaf net photosynthetic rate, and transpiration rate. In conclusion, coordinated changes in vein and stomatal density improve the WUE of cotton under drought stress. The abaxial leaf side plays a more important role than the adaxial side in WUE and gas exchange.

Populus × euramericana cv. 'Neva' is an important tree species in northern China. In the study, we used its potted oneyear- old seedlings as experimental material and established three treatments (CK, 0.5X, and 1.0X) according to the concentrations of phenolic acids in order to examine the effects of different concentrations on the photosynthetic characteristics and growth of poplar. With increasing concentrations of phenolic acids, the net photosynthetic rate, stomatal limitation, transpiration rate, apparent quantum yield, photochemical quenching coefficient, electron transport rate, chlorophyll content, and total biomass decreased significantly. The intercellular CO₂ concentration, light-compensation point, nonphotochemical quenching, malondialdehyde content, and root/shoot ratio increased significantly. Peroxidase and superoxide dismutase activities initially decreased and then increased. We concluded that phenolic acids significantly inhibited poplar's photosynthesis and the higher phenolic acid concentration, the greater inhibition of photosynthesis occurred. This inhibition effect was mainly caused by nonstomatal factors. Phenolic acids induced noticeable photoinhibition, resulted in the irreversible damage of membrane structure, and then changed intracellular metabolic processes. To cope with phenolic acid stress, poplar seedlings increased dissipation of excess light energy and distributed relatively more biomass to underground parts within carbon allocation.

Caffeine, a purine alkaloid, is reported to act both as an inducer or inhibitor to plant growth in various species. The aim of this study was to examine the effect of exogenous caffeine on tobacco (Nicotiana tabacum) plants, a plant that does not naturally synthesise caffeine. A hydroponic experiment was carried out in a growth chamber for 14 d using Hoagland's solution supplemented with 0 (control), 25, 50, 100, 1,000; and 5,000 μM caffeine. None of the investigated caffeine concentrations significantly decreased the net photosynthetic rate except the highest concentrations of 1,000 and 5,000 μM. Light microscopy of thick-sectioned roots showed that 1,000 μM and 5,000 μM caffeine-treated plants possessed deformed epidermal cells, reduced number of cortical cells, and deformed vascular tissues with cells exhibiting thickened xylem walls as compared with control plants. Moreover, transmission electron micrographs of roots revealed that mitochondria and the plasma membrane were affected.

LED lamps with various combinations of red (R) and blue (B) wavelengths were used to supplement sunlight for the growth of a heat-resistant (HR) and heat-sensitive (HS) recombinant inbred lines (RIL) of lettuce. The RB-LED ratios were 100R:0B (0B), 92R:8B (8B), 84R:16B (16B), and 76R:24B (24B) with an equal PPFD of 100 μmol m^-2 s^-1. The greatest leaf expansion rates were observed at 8B for both genotypes. All HR-RILs had similar values of growth parameters and specific leaf area (SLA). However, higher values of growth parameters were observed in HS-RIL with 0B, 8B, and 16B than that under 24B and sunlight. Furthermore, HS-RIL had higher SLA under 0B compared to other conditions. Photosynthetic light-use efficiency and maximal oxygen evolution rate were the lowest under 8B for both genotypes. The quality of LED lighting, if provided, seemed to implicate genotype dependence, probably as a result of their different sensitivities to heat stress.

In this study, we investigated maximal quantum yield of PSII photochemistry(F_v/F_m),effective quantum yield of PSII photochemistry (Φ_PSII), and nonphotochemical quenching (NPQ) of walnut (Juglans regia 'Xinxin2') leaves with different leaf-to-fruit ratios (LFRs). The results indicated that the increasing LFR increased the values of F_v/F_m, Φ_PSII, and NPQ in leaves on the girdled shoot with one and two leaves, and decreased the values of F_v/F_m and Φ_PSII in leaves on the girdled shoot with five leaves, whereas had no effect on the chlorophyll (Chl) fluorescence in leaves on the girdled shoot with three and four leaves. These results indicate that the effects of LFR on Chl fluorescence depend on a LFR range and show a transitional trend transition, and that excessive fruit load accelerates leaf senescence resulting in the destruction of the reaction center in PSII.

Macroalgae must be able to survive in conditions of different light intensities with no damage to their physiological performance or vital processes. Irradiance can stimulate the biosynthesis of certain photoprotective compounds of biotechnological interest, such as pigments and proteins. Pterocladiella capillacea is a shade-grown alga, which play a role key in the balance of marine ecosystems. In addition, it is considered one of the best sources of bacteriological agar and agarose with a wide pharmacological potential. In order to evaluate the photosensitivity in P. capillacea under 60 (control) and moderate light intensity of 300 μmol(photon) m^-2 s^-1, photosynthetic performance and chemical composition were assessed. P. capillacea showed photosensitivity without evidence of photodamage. The results indicate the possibility to increase a growth rate and probably infer productivity in long-term cultivation by stimulation at moderate light intensity. Increasing photosynthetic pigment and protein contents were also observed under medium light, an interesting result for functional ingredient approaches.

In the past decade, utilization of nanostructured materials has increased intensively in a wide range of applications. Titanium dioxide nanoparticles (TiO₂ NPs), for instance, can be applied for the inactivation of various pathogens through photo-induced generation of reactive oxygen species. Although TiO₂ NPs with high antimicrobial activity are of great importance, in practice, their phytotoxic effects have not yet been fully clarified. In this study, we investigated the potential phytotoxicity of TiO₂ NPs on grapevine (Vitis vinifera L.) under field conditions. After foliar exposure, two particularly stress-sensitive parameters, photosynthetic function and the flavonol profile, were examined. Micro- and macroelement composition of the leaves was also studied by ICP-AES measurements. We found that TiO₂ NPs significantly decreased the net CO₂ assimilation and increased stomatal conductance, indicating metabolic (nonstomatal) inhibition of the photosynthesis. The lower electron transport rate and lower nonphotochemical quenching in treated leaves are indicative of diminished photoprotective processes.

We conducted a hydroponic experiment in order to study effects of the ammonium/nitrate ratio (0:15, 5:10, 7.5:7.5, and 10:5) on photosynthetic characteristics and biomass accumulation in Brassica chinensis under low light intensity and water stress. Results showed that net photosynthetic rate, transpiration rate, intrinsic water-use efficiency, stomatal conductance, intercellular CO₂ concentration, effective quantum yield of PSII photochemistry, electron transport rate, and nonphotochemical quenching were lower in the treatment (low light intensity and water deficit) than those in the control, whereas stomatal limitation increased. Minimum fluorescence, maximal quantum yield of PSII photochemistry, and photochemical quenching were largely unchanged. Pigment contents first increased and then decreased as the ammonium/nitrate ratios were altered, with significant differences between treatment and control observed at all ratios except for 10:5. Biomass first increased slightly and then decreased both in treated and control plants. Results suggest that economic losses caused by extreme conditions can be minimized by a proper adjustment of the ammonium/nitrate ratio.

This study aimed to determine the effects of plant growth-promoting rhizobacteria Bacillus subtilis JS on the growth and physiological changes of Populus euramericana and Populus deltoides × P. nigra. Poplar seedlings were treated with B. subtilis JS and their growth was monitored for up to 120 d. Three different types of treatments [control, B1 (B. subtilis:double-distilled water, 1:100, v/v), and B2 (1:50)] were established. B. subtilis JS enhanced seedling height by 62% and total biomass by 37% after 120 d. Physiologically, the photosynthetic rate increased by 54%, and the total chlorophyll (Chl) content, foliage nitrogen and phosphate content were significantly higher after treatment with B2 than that of the control. These results suggest that the total Chl content is directly related to not only the photosynthetic capacity of the foliage but also to the nitrogen content, indicating that the strain JS may promote the growth of poplar.

Soil metal contamination leads to a decrease in a yield of crops and is a threat to human health. In the present study, the properties (i.e., photosynthetic pigments, gas-exchange parameters, chlorophyll fluorescence, biomass, leaf area, leaf mass per area) of three green vegetables (i.e., Brassica chinensis, Chrysanthemum coronarium, Brassica alboglabra) grown under various Cu treatments [0, 200, 400, and 600 mg(Cu) kg^-1] were measured and analysed. The results showed that soil Cu contamination resulted in the damage of photosynthetic pigments, negative effects on gas exchange, and hampered growth of all three vegetables. However, it did not significantly influence PSII functions of the three vegetables. It indicates that soil Cu contamination negatively affected photosynthesis particularly due to stomatal factors, but not due to the damage of photosynthetic apparatus.

Changes of chlorophyll (Chl) a fluorescence and photosynthetic pigment contents were analysed in galled leaves (visibly damaged and undamaged parts) and intact leaves. The values of minimal fluorescence of the dark-adapted state, maximal quantum yield of PSII photochemistry, effective quantum yield of PSII photochemical conversion, and photochemical quenching coefficient decreased in Ulmus pumila L. leaves galled by Tetraneura ulmi (L.) and in U. glabra Huds. galled by Eriosoma ulmi (L.). Colopha compressa (Koch.) feeding affected these parameters only in damaged parts of U. laevis Pall. galled leaves. The increasing number of T. ulmi galls progressively decreased photosynthetic performance. In gall tissues of all analysed aphid species, the lowest photosynthetic pigment content was found, indicating that the photosynthetic capacity must have been low in galls. Significant reduction of Chl and carotenoid contents were observed in damaged and undamaged portions of galled leaves only in the case of T. ulmi feeding.

The photosynthesis was investigated 30 d after Pb treatment in Myrica rubra seedlings. The Pb treatment resulted in significantly increased Pb concentrations in shoots. Low Pb concentration exposure (≤2 mM) reduced the net photosynthetic rate (P_N), transpiration rate (E), and stomatal conductance (gs) without affecting the intercellular CO₂ concentration (C_i), chlorophyll (Chl) content, and Chl fluorescence parameters. At 10 d after severe Pb treatment (≥4 mM), P_N was inhibited and accompanied by Chl damage, while at 30 d, the inhibition of P_N was followed by an increase of C_i and a decrease of gs, E, Chl content, and Chl fluorescence parameters. M. rubra showed a promising prospect for use in the soil phytoremediation, when Pb concentration is low, but the remediation efficiency of M. rubra is limited if Pb exceeds 2 mM.

We examined effects of late-season heat stress (L-SHS) on chlorophyll (Chl) fluorescence parameters and yield of bread wheat as well as roles of phosphate bio-fertilizer (PB-F) and Zn and B to compensate for the likely effects of heat stress. Factors were planting date (21 November and 5 January to coincide with grain filling to L-SHS) as the main factor, no inoculation (control) and inoculation of the seeds with PB-F as the sub-factor, and foliar application of water (control), Zn, B, and Zn + B as 3 L ha^-1 as sub-sub factor. Results revealed that L-SHS reduced maximal quantum yield of PSII photochemistry, effective quantum yield of PSII photochemistry, efficiency of PSII in the light-adapted state, and the grain yield. Moreover, L-SHS increased the nonphotochemical quenching. The PB-F mitigated the effects of L-SHS on Chl fluorescence, yield, and yield components. Among nutrients, the combined Zn + B was more effective in reducing the effects of L-SHS than that of Zn and B alone. Nevertheless, there was an interaction between foliar nutrients application and PB-F, suggesting that Zn application alone had a profound influence on improving Chl fluorescence parameters and increased yield in combination with PB-F.

In order to test the effects of irrigation depth on winter wheat photosynthesis, four treatments were applied in a field experiment using PVC growth tubes (identical amounts of water were applied on the land surface, and at 60, 75, and 90% of the depth for the winter wheat root distribution, denoted as D0, D60, D75, and D90, respectively). Compared to the surface irrigation treatment D0, the leaf area index, chlorophyll content, net photosynthetic rate, transpiration rate, stomatal conductance, and intercellular CO₂ concentration increased with irrigation depths. The values of these indicators obtained by the underground irrigation treatment D75 were higher than those of D60 and D90, and thus D75 was found to be the optimum irrigation depth. Furthermore, a positive but not significant correlation (r = 0.62) between carbon isotope discrimination (Δ¹³C) and grain yield was found. This study improves our understanding of the mechanism of underground water distribution control with depth, and the efficiency of water-saving irrigation for winter wheat.

Twentieth-century photosynthesis research had strong roots in Germany, with the cell physiologist Otto H. Warburg being among its most influential figures. He was also one of the few scientists of Jewish ancestry who kept his post as a director of a research institution throughout the Nazi period. Based on archival sources, the paper investigates Warburg's fate during these years at selected episodes. He neither collaborated with the regime nor actively resisted; he was harrassed by bureaucracy and denunciated to the secret police, but saved by powerful figures in economy, politics, and science. Warburg reciprocated this favour with problematic testimonies of political integrity after 1945. Warburg's case, thus, defies wellestablished notions of how scientists in Germany lived and worked during the Nazi regime, and, therefore, helps provide a more nuanced perspective on this theme.

While reading the paper by Vredenberg (2018) published in Photosynthetica (10 January, 2018), I was inspired to write this letter.

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.

Light-response curves of seedlings of five light-demanding (LD) and four shade-tolerant (ST) neotropical tree species, native to the Brazilian Atlantic biome, were analyzed, aiming to verify differences between these functional groups regarding the light use. We hypothesized that variations in the light requirement of seedlings would occur not only between LD and ST species, but also within these functional groups. The apparent quantum yield of CO₂ assimilation, dark respiration rate (R_D), photorespiration rate (R_P), light-compensation point (I_comp), light-saturation point (I_max), and light-saturated photosynthetic rate (P_Nmax) were estimated from fitted light-responses curves and using equations available in the literature. The results revealed great differences between the functional groups. R_D, R_P, I_comp, I_max, and P_Nmax were effectively higher in the LD than those in the ST species. Furthermore, a continuum of strategies regarding the light use was observed, matching with some ecological characteristics of the species studied here.

Stagnant flooding (SF) is a serious threat for rice production in rainfed lowland areas of Southeast Asian countries. To overview the SF effect, photosynthetic performances and productivity were studied with three landraces (Ravana, Kamini, and Rashpanjor) and four high-yielding cultivars (Savitri, Savitri-Sub1, Gayatri, and Varshadhan) of rice under medium depth (40-50 cm) of water level. Stagnant flooding significantly increased the stem elongation and decreased yield and yield attributing parameters. The chlorophyll a fluorescence rises from O- to P-step with distinct J- and I-step were noticed in all the cultivars up to 75 d of SF. Prolonged flooding (> 2 months) perturbed both donor and acceptor side of PSII. Vitality indices (PI_ABS and PI_TOT) decreased greatly under prolonged SF. Analysis of O-J-I-P transients suggests that the information is useful for agricultural planning with the purpose to enhance rice yield under lowland medium depth SF.

Ferredoxin (Fd) is a small soluble iron-sulfur protein essential in almost all oxygenic photosynthetic organisms. It contains a single [2Fe-2S] cluster coordinated by four cysteine ligands. It accepts electrons from the stromal surface of PSI and facilitates transfer to a myriad of acceptors involved in diverse metabolic processes, including generation of NADPH via Fd-NADP-reductase, cyclic electron transport for ATP synthesis, nitrate reduction, nitrite reductase, sulfite reduction, hydrogenase and other reductive reactions. Fd serves as the central hub for these diverse cellular reactions and is integral to complex cellular metabolic networks. We describe advances on the central role of Fd and its evolutionary role from cyanobacteria to algae/plants. We compare structural diversity of Fd partners to understand this orchestrating role and shed light on how Fd dynamically partitions between competing partner proteins to enable the optimum transfer of PSI-derived electrons to support cell growth and metabolism.

Although deciduous and evergreen conifers are expected to utilize needle nitrogen differently, their interspecific differences in the ozone sensitivity remain unclear. We compared the growth and physiological responses to elevated O₃ concentrations in deciduous Japanese larch (Larix kaempferi) and evergreen Sakhalin fir (Abies sachalinensis) seedlings. Seedlings of both species were exposed to 62.5 ± 1.95 nmol(O₃) mol^-1 during the day time in open-top chambers. Elevated O₃ had no effect on height or diameter growth in either of the species but suppressed photosynthetic parameters. A decline in photosynthetic nitrogen-use efficiency was observed in both species. However, needle N content in larch was decreased by O₃, whereas it was not decreased in fir. Needle N responses to O₃ were different between larch and fir seedlings, indicating that the O₃ sensitivity of photosynthesis could vary depending on needle N dynamics. We also observed a higher correlation between photosynthesis and needle N even under O₃ exposure, particularly in the mass-based relationship with higher accuracy. The result indicated that mass-based needle N could explain difference in O₃ sensitivity of photosynthesis between the different leaf habits in larch and fir seedlings.

The aim of the study was to assess the physiological status of Brassica seedlings grown in two types of soils following a single application of smoke water (SW). One soil was contaminated with heavy metals from a local smelter, and another was sandy and poor in nutrients. Three-week monitoring indicated that soil composition was the primary factor affecting chlorophyll fluorescence (CF) parameters, growth, and development of seedlings, and the contaminants affected the plants more than the lack of nutrients. SW aggravated the negative impact of heavy metals, which became visible when the plants transiently suffered from the heavy metal exposure. Most of CF parameters changed suddenly but then the trend reversed indicating that plants gradually adapted to the specific conditions. However, this was not reflected in the final biomass of the seedlings. This might be due to redirection of photosynthates towards protective mechanisms against toxic effects of metals.

The objective of this experiment was to study the effects of night chilling on the photosynthetic characteristics of cotton (Gossypium hirsutum L.) at a boll-forming stage. The results suggest that overreduction of PSII after night chilling (≤ 10°C) led to excess excitation energy in cotton leaves. The night chilling (compared to 22°C) reduced PSI acceptor side limitation under moderate and high light intensity and increased maximum photooxidizable P700. This suggests that in contrast to PSII, PSI was protected from photoinhibition due to night chilling. However, PSII activity and linear electron transport were not significantly affected by the 30/16°C treatment. In addition, the night chilling (≤ 10°C) increased the quantum yield of cyclic electron transport. This suggests that cyclic electron transport around PSI might be important to prevent photoinhibition of PSI and PSII in cotton under night chilling stress.

Drought has become an essential environmental factor limiting plant productivity. In order to detect differences in chlorophyll (Chl) a fluorescence, Chl concentration (in SPAD units), and yield parameters of yellow lupin ('Morocco 4' and 'Taper') and pea ('Wenus' and 'SZD165'), drought stress was initiated by withholding water for 14 d (25% of field water capacity). A significant decrease of leaf relative water content was found in tested cultivars. SPAD values did not show significant changes in all cultivars. The maximum photochemical efficiency and area over the Chl a fluorescence induction curve decreased in both species under drought. Performance index in lupin did not change significantly under drought while it declined in pea. Among the tested cultivars, lupin cv. 'Morocco 4' maintained the highest efficiency of the photosynthetic apparatus as well as the highest number of pods, seeds per plant, height, and dry mass of shoots under drought conditions.

Efficient degradation of damaged D1 during the repair of PSII is carried out by a set of dedicated FtsH proteases in the thylakoid membrane. Here we investigated whether the evolution of FtsH could hold clues to the origin of oxygenic photosynthesis. A phylogenetic analysis of over 6000 FtsH protease sequences revealed that there are three major groups of FtsH proteases originating from gene duplication events in the last common ancestor of bacteria, and that the FtsH proteases involved in PSII repair form a distinct clade branching out before the divergence of FtsH proteases found in all groups of anoxygenic phototrophic bacteria. Furthermore, we showed that the phylogenetic tree of FtsH proteases in phototrophic bacteria is similar to that for Type I and Type II reaction centre proteins. We conclude that the phylogeny of FtsH proteases is consistent with an early origin of photosynthetic water oxidation chemistry.

In this review, using the network analysis, based on the bibliometric data, collected from Web of Science Core Collection database, we followed the development of chlorophyll fluorescence research (CFR) during 1947-2018. We confirmed dramatic increase in diversity of CFR from late 90-ties and vigorous development of this discipline in the last ten years. They are parallel to an increase in number of research areas and institutions involved and were triggered by the accumulation of knowledge and methodological, technological, and communication advances, especially modern fluorimeters and fluorescence techniques. The network analysis of keywords and research areas confirmed CFR changed into modern, multidisciplinary, highly collaborative discipline, in which in spite of many 'core' disciplines as plant science, environmental sciences, agronomy/food science and technology, the promising, modern areas developed: biochemistry and molecular biology, remote sensing, and big data artificial intelligence method.