Search Results (74)

Pinus radiata D. Don is planted in South Central Chile on a wide range of sites using genetically improved genotypes for timber production. As drought events are expected to increase with ongoing climatic change, the variability in gas exchange, which could impact growth and water use, needs to be evaluated. In this study, we assessed the genotypic variability of leaf-level light-saturated photosynthesis (A_sat), stomatal conductance (g_s), transpiration (E), intrinsic water use efficiency (iWUE), and Chlorophyll a fluorescence (OJIP-test parameters) among 30 P. radiata genotypes (i.e., full-sib families) from third-cycle parents at age 6 years on three sites in Central Chile. We also evaluated tree height (HT), diameter at breast height (DBH), and stem index volume (VOL). Families were ranked for HT as top-15 and bottom-15. In the OJIP-test parameters we observed differences at the family level for the maximum quantum yield of primary PSII photochemistry (Fv/Fm), the probability that a photon trapped by the PSII reaction center enters the electron transport chain (ψ_Eo), and the potential for energy conservation from photons captured by PSII to the reduction in intersystem electron acceptors (PI_ABS). Fv/Fm, PI_ABS, and ψ_Eo ranged from 0.82 to 0.87, 45 to 95, and 0.57 to 0.64, respectively. Differences among families for growth and not for leaf-level physiology were detected. DBT, H, and VOL were higher in the top-15 families (12.6 cm, 8.4 m, and 0.10 m³, respectively) whereas A_sat, g_s, E, and iWUE were similar in both the top-15 and bottom-15 families (4.0 μmol m⁻² s⁻¹, 0.023 mol m⁻² s⁻¹, 0.36 mmol m⁻² s⁻¹, and 185 μmol mol m⁻² s⁻¹, respectively). However, no family by site interaction was detected for growth and leaf-level physiology. The results of this study suggest that highly improved genotypes of P. radiata have uniformity in leaf-level physiological rates, which could imply uniform water use at the stand-level. The family variation found in PI_ABS suggests that this parameter could be incorporated to select genotypes tolerant to environmentally stressful conditions. Full article

Light is a source of energy for photosynthesis and hence promotes the regulation of multiple physiological and metabolic processes in photoautotrophic organisms. Understanding how brown macrophytes adjust the physical and biochemical properties of photosynthetic membranes in response to high-irradiance environments has received little attention so far. Particularly, it concerns the lipid flexibility of thylakoid membranes. We examined the lipid classes, fatty acid (FA) profiles, chloroplast ultrastructure, and photosynthetic performance of the brown macroalga Undaria pinnatifida after long-term exposure to high light (HL) and moderate light (ML) intensities, at 400 and 270 µmol photons m⁻² s⁻¹, respectively. U. pinnatifida responded to HL with a reduction in the level of thylakoid membrane lipids, monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfoquinovosyldiacylglycerol (SQDG), and phosphatidylglycerol (PG), while the character of lipid modulations was specific. The content of storage lipids, triacylglycerols enriched in n-3 polyunsaturated fatty acids (PUFAs), increased under HL. The general response to long-term HL for the studied thylakoid membrane lipids, but not for SQDG, was the remodeling of FA composition towards increasing the percentages of saturated and monounsaturated acyl groups over PUFAs, suggesting a photoprotective strategy against the intensification of lipid peroxidation. In all, we showed that remodeling in photosynthetic membrane lipids accompanied by structural changes in chloroplasts and modulations in photosynthetic performance augmented the ability of U. pinnatifida to counteract high-intensity light, thereby contributing to its survival potential under suboptimal irradiance conditions. Full article

The invasive aquatic macrophyte Pontederia crassipes (water hyacinth) exhibits exceptional adaptability across a wide range of light environments, yet the mechanistic basis of its photosynthetic plasticity under both high- and low-light stress remains poorly resolved. This study integrated chlorophyll fluorescence and gas-exchange analyses to evaluate three photosynthetic models—rectangular hyperbola (RH), non-rectangular hyperbola (NRH), and the Ye mechanistic model—in capturing light-response dynamics in P. crassipes. The Ye model provided superior accuracy (R² > 0.996) in simulating the net photosynthetic rate (P_n) and electron transport rate (J), outperforming empirical models that overestimated P_nmax by 36–46% and J_max by 1.5–24.7% and failed to predict saturation light intensity. Mechanistic analysis revealed that P. crassipes maintains high photosynthetic efficiency in low light (LUE_max = 0.030 mol mol⁻¹ at 200 µmol photons m⁻² s⁻¹) and robust photoprotection under strong light (NPQ_max = 1.375, PSII efficiency decline), supported by a large photosynthetic pigment pool (9.46 × 10¹⁶ molecules m⁻²) and high eigen-absorption cross-section (1.91 × 10⁻²¹ m²). Unlike terrestrial plants, its floating leaves experience enhanced irradiance due to water-surface reflection and are decoupled from water limitation via submerged root uptake, enabling flexible stomatal and energy regulation. Distinct thresholds for carboxylation efficiency (CE_max = 0.085 mol m⁻² s⁻¹) and water-use efficiency (WUE_i-max = 45.91 μmol mol⁻¹ and WUE_inst = 1.96 μmol mmol⁻¹) highlighted its flexible energy management strategies. These results establish the Ye model as a reliable tool for characterizing aquatic photosynthesis and reveal how P. crassipes balances light harvesting and dissipation to thrive in fluctuating environments. These resulting insights have implications for both understanding invasiveness and managing eutrophic aquatic systems. Full article

Basil is best known as an aromatic and medicinal herb due to its rich profile of bioactive compounds. While secondary metabolite production, coupled with growth, has been well studied, photosynthesis has often been overlooked in this regard. In this study, we investigate the effect of light intensities of blue, green, red, and white light of semiconductor LEDs up to 10000 µmol m⁻² s⁻¹ on photosynthetic efficiency and primary and secondary metabolism. Chlorophyll fluorescence data indicate that the conversion of light into chemical energy is the same under green, red, and white light, and 35% increased under blue light. Primary metabolism, represented by assimilation rate, shows that blue light has the lowest assimilation, whereas red and (surprisingly) green light have the highest. Light saturation is reached at 1500 µmol m⁻² s⁻¹, while assimilation under green light is maintained up to 5000 µmol m⁻² s⁻¹. The earliest photoinhibition occurred under blue light in comparison to the other light wavelength under investigation. Blue light also enhances the production of phenolic and flavonoid concentrations up to 40% or 100%, respectively. These results show that photosynthesis, photoinhibition, and secondary metabolite production are wavelength-dependent and indicate how energy fluxes between these processes are related. Full article

The leaf economic spectrum framework explains how plants optimize leaf traits for productivity, distribution, and stress tolerance. Orchids in Southwestern China’s karst forests, especially lithophytic species, are challenged by prolonged drought and limited light availability. This study investigated different leaf strategies between lithophytic and terrestrial orchids under the harsh karst environment. We measured key leaf traits, including photosynthesis, structure, biomechanics, nitrogen allocation, and water relations, in twenty-two lithophytic and six terrestrial orchids in a subtropical karst forest. After accounting for phylogenetic influences, we found that lithophytic orchids had a higher leaf mass per area, cuticle thickness, and biomechanical resistance (F_p) but a lower maximum photosynthetic rate (A_max-mass), nitrogen allocation to photosynthesis (N_T), and saturated water content (SWC) than terrestrial orchids. These results suggest that lithophytic orchids prioritize structural investment and stress tolerance over photosynthetic efficiency. Across species, N_T correlated positively with A_max-mass and negatively with F_p, highlighting nitrogen allocation as a key mechanism in leaf cost–benefit strategies. Additionally, SWC emerged as a critical driver of variation in multiple traits, supporting its integration into the leaf economic spectrum for orchids in karst ecosystems. This study offers new insights into orchid adaptation in subtropical karst environments, with implications for plant resilience under changing climates. Full article

Non-photosynthetic photoreceptors detecting different wavelength ranges in the UV and visible region of spectra may trigger algal acclimation and homeostasis. We studied Plocamium cartilagineum responses based on the saturation of photosynthesis by Amber light and supplementation by different light qualities, applying an experimental design able to simulate a daily cycle in a fully automated system. Thalli were exposed to Amber, Amber + UV-A, Amber + Blue and Amber + Green radiation treatments under two nitrate levels (60 and 240 μM) for enrichment lasting two weeks. P. cartilagineum photosynthesis and biochemistry were measured during different experimental periods. Photosynthesis showed only slight variations, emphasizing that other response variations could be activated by photomorphogenic pathways. Nitrate assimilation was higher in the treatments containing blue and green lights, potentially caused by increasing nitrate reductase activity. Photosynthetic pigments and mycosporine-like amino acids were affected over the two weeks, being mostly influenced by UV-A and blue radiations with the highest nitrate concentration. The shinorine content of thalli under blue radiation with 240 μM of nitrate increased at day 7, possibly modulated by a blue light photoreceptor. The increase in the bioactive compounds in the short-term by specific light qualities under optimal photosynthetic performance was found to be a relevant biotechnological strategy. Full article

Urban forests play important roles in carbon sequestration and climate change mitigation. However, their adaptive mechanisms and limitations on photosynthesis throughout the canopy are poorly understood. This study takes the most widely distributed 50-year-old camphor plantations (Cinnamomum camphora) in Shanghai as the research objects. We investigated the variations in leaf morphology and photosynthetic physiology and biochemistry at six different canopy positions during a summer and an autumn period. We discovered that on account of leaf nitrogen loss and water deficit, light-saturated photosynthesis (A_max) declined in upper sunlit leaves despite being exposed to high sunlight in the same fashion as stomatal and mesophyll conductance (g_sw, g_m), photochemical quenching coefficient and actual photochemical efficiency of PSII (Φ_PSII, q_P), and maximum rate of electron transport and carboxylation (J_max, V_cmax) during the growing season. Although seasonal change had little effect on A_max, the relative importance of limitations varied temporally. Mesophyll and biochemical limitation were the major contributors to the decline in the A_max in upper sunlit leaves between summer and autumn, respectively. Our study highlights the constraints of carbon fixation capacity in dense stands of mature camphor trees and offers technical support for the accurate prediction of canopy photosynthesis and the enhancement of carbon sequestration management in urban forests. Full article

Dynamic changes in diurnal light and temperature are a natural phenomenon, particularly pronounced in arid environments. However, it remains unclear whether the coupling of diurnal light and temperature fluctuations contributes to the capability and evolution of lipid accumulation in arid terrestrial microalgae. Here, we characterized the effects of diurnal light and temperature fluctuations on the growth, photosynthesis, lipids, carbohydrates, proteins and fatty acids in Vischeria sp. WL1, an oil-producing Eustigmatophyceae microalga sourced from an arid steppe. The photosynthetic activity parameters (F_v/F_m, PI_abs, ψ₀ and φ_E0) were the highest, while parameters of damage and energy dissipation (W_k and DI_O/RC) were the lowest, under the diurnal light cycle (DLC) among all conditions and then followed by the diurnal light–temperature cycle (DLTC). DLTC led to reduced growth and biomass but enhanced lipid accumulation, with lipid content reaching a maximum of 54.7% on day 4. This observation may suggest a carbon reallocation from carbohydrates toward lipid synthesis. DLTC resulted in an increase in the saturated fatty acids (SFA) content on day 12 and only in C18:2 among polyunsaturated fatty acids (PUFA) on day 4 while lowering eicosapentaenoic acid (EPA) concentration and content on day 12. Together, our findings will contribute to the understanding of the adaptive strategies of terrestrial microalgae to the arid environment, as well as the beneficial clues for exploring terrestrial microalgae for oil production. Full article

Light serves as the unique driving force of photosynthesis in plants, yet its intensity varies over time and space, leading to corresponding changes in the photosynthetic rate. Here, the photosynthetic induction response under constant and fluctuating light was examined in naturally occurring saplings of four sun-demanding woody species, Eucalyptus. Ficus macrocarpa L., Hibiscus syriacus L. and Ficus carica L. We aimed to find out the relations among gas exchange parameter adaptions among different species during photosynthetic induction. The net photosynthetic rates (A) versus time course curves were sigmoidal or hyperbolic after the dark-adapted leaves were irradiated by continuous saturated light. Compared with other species, Ficus carica L. have the largest net photosynthesis rate, stomatal conductance to CO₂ (g_sc), and the maximum carboxylation rate (V_cmax) at both the initial and steady photosynthetic state. The initial g_sc (g_sci) was as much as sixfold higher compared to the other shrub, Hibiscus syriacus L. The time required to reach 90% of A (t_A90) was 7–30 min; t_A90 of Ficus carica L. and Ficus macrocarpa L. were lower than that of the other two species. The time required to reach 90% of g_sc (t_gsc90) significantly lagged behind t_A90 among species. Biochemical induction was fast in leaves of Ficus carica L., as about 4 min were needed to reach 90% of V_cmax, while the other species needed 7–18 min. Correlation analysis showed that the t_gsc90 was the main factor in limiting t_A90, especially for Eucalyptus spp. and Hibiscus syriacus L.; g_sci was negatively correlated with t_gsc90 among species. Moreover, time-integrated limitation analysis revealed that g_sc still accounted for the largest limitation in constraining A of Eucalyptus spp. and Hibiscus syriacus L. and Ficus macrocarpa L. Overall, the findings suggest that to enhance the carbon gain by woody species under naturally dynamic light environments, attention should be focused on improving the rate of stomatal opening or initial stomatal conductance. Full article

Accurate photosynthetic parameters obtained from photosynthetic light-response curves (LRCs) are crucial for enhancing our comprehension of plant photosynthesis. However, the task of fitting LRCs is still demanding due to diverse variations in LRCs under different environmental conditions, as previous models were evaluated based on a limited number of leaf traits and a small number of LRCs. This study aimed to compare the performance of nine LRC models in fitting a set of 108 LRCs measured from paddy rice (Oryza sativa L.) grown in field across 3 years under different leaf positions, leaf ages, nitrogen levels, irrigation levels, and varieties. The shape of 108 LRCs varies significantly under a range of leaf traits, which can be typed into three leaf light-acclimation types—high-light leaves (HL-1 and HL-2), and low-light leaves (LL). The accuracy of these models was evaluated by (1) LRCs from three acclimation types: HL-1 and HL-2, and LL; and (2) LRCs across three irradiance stages: light-limited, light-saturated, and photoinhibition. Results indicate that the Ye model emerged as the top performance among the nine models, particularly in the photoinhibition stage of LL leaves, with median values of R², SSE, and AIC of 0.99, 2.39, and −14.03, respectively. Furthermore, the Ye model produced the most accurate predictions of key photosynthetic parameters, including dark respiration (R_D), light-compensation point (I_comp), maximum net photosynthetic rate (P_Nmax), and light-saturation point (I_sat). Results also suggest that P_NImax and I_max were the most appropriate parameters to describe photosynthetic activity at the light-saturation point. These findings have significant implications for improving the accuracy of fitting LRCs, and thus robust predictions of photosynthetic parameters in rice under different environmental conditions. Full article

This study conducted a comparative analysis on the effects of smart automatic and semi-automatic irrigation methods on the physiological characteristics and growth of Prunus × yedoensis Matsum. seedlings. The smart automatic irrigation system, which activates irrigation when the soil moisture drops below 15%, demonstrated superior characteristics in sap-wood area and bark ratio, as well as excellent water management efficiency, compared to the semi-automatic irrigation method, which involves watering (2.0 L) for 10 min at 60 min intervals starting at 8 AM every day. The analysis of soil moisture content changes under varying weather conditions and irrigation methods showed that smart automatic irrigation effectively maintained optimal moisture levels. Moreover, sap flow in the smart automatic irrigation treatment was more efficiently regulated in response to seasonal variations, showing a strong correlation with climatic factors such as temperature and solar radiation. In contrast, the semi-automatic irrigation treatment led to excessive sap flow during the summer due to a fixed watering schedule, resulting in unnecessary water supply. Analysis of photosynthesis parameters and chlorophyll fluorescence also revealed that smart automatic irrigation achieved higher values in light compensation and saturation points, maximizing photosynthetic efficiency. These findings suggest that the smart automatic irrigation system can enhance plant growth and water use efficiency, contributing to sustainable water management strategies. This research provides critical foundational data for developing efficient agricultural and horticultural irrigation management strategies in response to future climate change. Full article

The rapid, effective restoration of degraded peatlands is urgently needed to reduce their current high levels of carbon loss. The re-introduction of Sphagnum moss, along with re-wetting, is key to returning carbon sequestration and retention capabilities to northern degraded bogs. Micropropagated Sphagnum has already been applied in large quantities, and more is planned, for restoration projects in Britain and parts of Europe. A comparison with wild-sourced Sphagnum material is therefore pertinent to demonstrate its safety and suitability for wide-scale application. Six Sphagnum species of both micropropagated and wild-sourced origin were assessed for photosynthetic capacity, nutrient content, form parity, chlorocyst size, and chloroplast numbers. Micropropagated Sphagnum had significantly higher light-saturated photosynthesis (P_max) rates, little color expression, an open growth habit, greater chloroplast numbers, and more numerous, smaller shoot apices than wild-sourced Sphagnum. Higher P_max rates were associated with a lower bulk density and higher tissue nutrient concentrations. Potentially, greater chloroplast numbers in micropropagated Sphagnum facilitate higher photosynthesis rates, driving rapid growth in early-stage plants, particularly in optimum moisture conditions. Micropropagated Sphagnum can be used confidently, propagated in large quantities, and will likely establish well on application to sites where re-wetting has already occurred, therefore making it highly beneficial for the restoration of degraded bogs. Full article

L-cysteine, a precursor of essential components for plant growth, is synthesized by the cysteine synthase complex, which includes O-acetylserine(thiol) lyase (OAS-TL) and serine acetyltransferase. In this work, we investigated how S-benzyl-L-cysteine (SBC), an OAS-TL inhibitor, affects the growth, photosynthesis, and oxidative stress of Ipomoea grandifolia plants. SBC impaired gas exchange and chlorophyll a fluorescence, indicating damage that compromised photosynthesis and reduced plant growth. Critical parameters such as the electron transport rate (J), triose phosphate utilization (TPU), light-saturation point (LSP), maximum carboxylation rate of Rubisco (V_cmax), and light-saturated net photosynthetic rate (P_Nmax) decreased by 19%, 20%, 22%, 23%, and 24%, respectively. The photochemical quenching coefficient (q_P), quantum yield of photosystem II photochemistry (ϕ_PSII), electron transport rate through PSII (ETR), and stomatal conductance (g_s) decreased by 12%, 19%, 19%, and 34%, respectively. Additionally, SBC decreased the maximum fluorescence yield (F_m), variable fluorescence (F_v), and chlorophyll (SPAD index) by 14%, 15%, and 15%, respectively, indicating possible damage to the photosynthetic apparatus. SBC triggered root oxidative stress by increasing malondialdehyde, reactive oxygen species, and conjugated dienes by 30%, 55%, and 61%, respectively. We hypothesize that dysfunctions in sulfur-containing components of the photosynthetic electron transport chain, such as the cytochrome b₆f complex, ferredoxin, and the iron–sulfur (Fe-S) centers are the cause of these effects, which ultimately reduce the efficiency of electron transport and hinder photosynthesis in I. grandifolia plants. In short, our findings suggest that targeting OAS-TL with inhibitors like SBC could be a promising strategy for the development of novel herbicides. Full article

This study analyzed the leaf spectral properties and photosynthesis rates of greenhouse-grown bell pepper leaves according to the growth period and leaf position to investigate the changes in carbon assimilation function according to leaf aging. Photosynthesis, growth, transpiration, stomatal conductance, light transmittance, and light reflectance were measured. As the plants’ growth progressed, the number of leaves, fresh weight, and dry weight increased, but the specific leaf area decreased, likely due to the increased distribution of assimilates to reproductive organs. The average photosynthesis rate, according to the measured dates, exhibited a high value despite a large standard error, which was likely influenced by measurement errors caused by external environmental factors. The reflectance and transmittance increased from the upper to the middle and bottom leaves, and the absorption ratio decreased in the same order. The green light spectrum (500–580 nm) had a lower absorption ratio than other spectra because the green coloration of the leaves increased the light reflectance of this spectrum. As the PPFD increased where the leaf was positioned higher, the photosynthesis rate, transpiration amount, and stomatal conductance also increased. The higher the leaf position, the higher the photosynthesis rate, the amount of transpiration, and the stomatal conductance. As the CO₂ concentration increased, the photosynthesis rate increased, but the transpiration and stomatal conductance changed little, indicating that the gas exchange within leaves was hardly affected by CO₂, but the light levels promoted photosynthesis. From the results of this study, the optical properties of the leaves indicate that they are consistent with Lambert–Beer’s law, which implies that the length of the optical path is linearly proportional to the number of molecules in the absorption layer. We obtained the light saturation point and CO₂ saturation point of bell peppers grown in a greenhouse and were able to determine the physiological changes in the leaves with increasing leaf age. Therefore, based on this information, it appears that a leaf removal model based on the productivity of bell pepper leaves could be developed. Full article

Conventional water and nitrogen (N) management practice in north China, comprising flood irrigation and N fertilizer broadcast (FB), limits sustainable wheat production. Drip fertigation (DF) has been widely adopted in wheat production in recent years and has effectively improved yields. However, the responses of the yield and quality to the N topdressing rate (NTR) under DF are still unclear. This study determined the responses of the wheat yield and quality to NTR under DF, as well as assessing whether DF could synergistically increase the yield and quality. A field experiment was conducted in north China for two seasons (2021–2023) using a split-plot design with three replicates. The main plot used the management practice (FB and DF) and the sub-plot had N treatment (no N applied, and NTRs of 0, 40, 80, 120, and 160 kg ha⁻¹ with 150 kg N ha⁻¹ as basal fertilizer, denoted as N0, T0, T40, T80, T120, and T160, respectively). Our results showed that high and saturated wheat yields (12.08 and 11.46 t ha⁻¹) were obtained under DF at T80, and the highest yields were produced at T160 (11.71 and 11.30 t ha⁻¹) under FB. Compared with FB, the greatest yield increase of 10.4–12.6% was achieved at T80 under DF. A higher spike number due to the increased effective stem percentage and a greater grain weight because of enhanced post-anthesis biomass production (BP_post) explained the improved yield under DF. The enhanced post-anthesis radiation use efficiency (RUE) led to the greater BP_post under DF. The enhanced specific leaf N, antioxidant capacity, and stomatal conductance under DF explained the higher light-saturated photosynthesis rate of flag leaves, which partly led to the increased post-anthesis RUE. NTR higher than 80 kg ha⁻¹ did not enhance the yield, but it significantly improved the gliadin and glutelin contents, thereby leading to a higher total protein content, better gluten characteristics, and superior processing quality. Therefore, drip fertigation is a practical strategy for increasing both yield and quality with reduced water input and appropriate N input in irrigated winter wheat in north China. Applying 80 kg ha⁻¹ of NTR under drip irrigation produces a high yield, but further gain in grain quality needs a higher NTR. Full article