Photosynthetically Active Research Articles

Supplementary Far-Red Light for Photosynthetic Active Radiation Differentially Influences the Photochemical Efficiency and Biomass Accumulation in Greenhouse-Grown Lettuce.

Adding far-red (FR, 700-800 nm) light to photosynthetic active radiation (400-700 nm) proved to be a possible approach to increasing plant biomass accumulation for lettuce production in indoor vertical farms with artificial lighting as a sole-source lighting. However, how FR light addition influences plant growth, development, and metabolic processes and the optimal value of FR photon flux density for greenhouse-grown lettuce under sunlight are still unclear. This work aims to quantify the value of supplementary FR light with different intensities on lettuce morphological and physiological characteristics in a greenhouse. Lettuce 'Dasusheng' (Lactuca sativa L.) was grown in a greenhouse under seven light treatments, including white plus red LEDs with FR photon flux density at 0, 10, 30, 50, 70, and 90 µmol m-2 s-1 (WR, WR + FR10, WR + FR30, WR + FR50, WR + FR70, and WR + FR90, respectively), and lettuce grown with sunlight only was marked as natural light (NL). FR light addition improved the electron transport flux per cross section and performance index (PIabs, PItotal) and decreased the changes in relative variable fluorescence of lettuce leaves compared to plants under NL. Specifically, the PIabs of lettuce leaves were 41%, 41%, 38%, 33%, 26%, and 25% lower under control than in plants under treatments WR + FR90, WR + FR70, WR + FR50, WR + FR30, WR + FR10, and WR, respectively. Leaf number, leaf area, and biomass accumulation of lettuce followed a quadratic function with increasing FR light intensity and were the highest under treatment WR + FR50. The shoot fresh weight and dry weight of lettuce were increased by 111% and 275%, respectively, under treatment WR + FR50 compared to NL. The contents of vitamin C, reducing sugar, total soluble sugar, and starch in lettuce showed a similar trend with biomass accumulation. In conclusion, with commonly used photosynthetic photon flux density (PPFD, 400-700 nm) around 200 μmol m-2 s-1, supplementary FR light intensity of 30~50 μmol m-2 s-1 was suggested to enhance the photochemistry efficiency, biomass accumulation, and carbohydrates' contents in greenhouse-grown lettuce.

Биопрепараты как факторы повышения продуктивности сои

Abstract. In 2021–2023, in the forest-steppe zone of North Ossetia – Alania, research was carried out on the use of biological products (growth regulator “Giberelon” and microfertilizer “Ul’tramag Kombi”) on soybean crops of Vilana, Irbis, Vita varieties. The purpose of the work is to improve the technology of soybean cultivation, aimed at improving productivity and grain quality through the use of biological products. Scientific novelty. For the first time in the foothill zone of the republic, the influence of biologics (growth regulator and micronutrients) on photosynthetic activity, the size and quality of soybean crops of various ripeness was studied. Methods. The object of research was three high-yielding soybean varieties - Vilana, Irbis, Vita (breeding of the Federal Research Center of the V. S. Pustovoit Research Institute of Oilseeds). Among the biological products used were "Giberelon" (70 g/ha), a plant growth stimulator based on gibberellic acids; "Ultramag Combi" (2 l/ha) – a concentrated complex micronutrient for leafy top dressing of cereals. Observations and records were carried out according to generally accepted methods of field experience. Results. It has been established that the use of biological products “Giberelon” and “Ul’tramag Kombi” increases the symbiotic activity of soybeans and the amount of fixed nitrogen in the air. During the growing season, the largest number of active nodules were formed in plots where plants were treated with “Ul’tramag Kombi” microfertilizer. With the use of “Ul’tramag Kombi” microfertilizer, the mass of nodules also increased by 18.7–19.9 g compared to the control. The biological products used stimulated plant growth, where the highest plant height was noted for varieties ranging from 79.1–115.1 cm. The yield of soybean crops using the growth regulator “Giberelon” (with an application rate of 70 g/ha) increased by 0.13–0.25 t/ha, with the use of “Ul’tramag Kombi” microfertilizer (with an application rate of 2 l/ha) – by 0.28–0.47 t/ha. The average level of profitability for all studied varieties of experimental variants was 65.25 %, which is 28.75 % higher than the control variants.

CuO nanoparticles' effect on the photosynthetic performance in seed tissues of Inga laurina (Fabaceae).

Copper oxide nanoparticles (CuONPs) have been produced on a large scale because they can be applied across various fields, especially in nano-enabled healthcare and agricultural products. However, the increasing use of CuONPs leads to their release and accumulation into the environment. The CuONPs uptaken by seeds and their implications on germination behavior have been reported, but little is known or understood about their impact on photosynthesis in seed tissues. To fill knowledge gaps, this study evaluated the effects of CuONP concentrations (0-300mg L-1) on the photosynthetic activity of Inga laurina seeds. The microscopy data showed that CuONPs had an average size distribution of 57.5 ± 0.7nm. Copper ion release and production of reactive oxygen species (ROS) by CuONPs were also evaluated by dialysis and spectroscopy experiments, respectively. CuONPs were not able to intrinsically generate ROS and released a low content of Cu2⁺ ions (4.5%, w/w). Time evolution of chlorophyll fluorescence imaging and laser-induced fluorescence spectroscopy were used to monitor the seeds subjected to nanoparticles during 168h. The data demonstrate that CuONPs affected the steady-state maximum chlorophyll fluorescence ( ), the photochemical efficiency of photosystem II ( ), and non-photochemical quenching ( ) of Inga laurina seeds over time. Besides, the significantly increased at the seed development stage, near the root protrusion stage, probably due to energy dissipation at this germination step. Additionally, the results indicated that CuONPs can change the oscillatory rhythms of energy dissipation of the seeds, disturbing the circadian clock. In conclusion, the results indicate that CuONPs can affect the photosynthetic behavior of I. laurina seeds. These findings open opportunities for using chlorophyll fluorescence as a non-destructive tool to evaluate nanoparticle impact on photosynthetic activity in seed tissues.

Multistoried woodlot based agroforestry system for improved resource utilization and incomes for farmer

Diversification of cropping pattern coupled with the development of suitable technology packages is crucial to meet the ever-increasing demand for diversified products and sustained farmers’ incomes. We evaluated different woodlot-based multistoried agroforestry systems for their effectiveness to mitigate the devastating effects of climate change by offering multifaceted benefits. Specifically, the present study aimed to assess the yield and probability of woodlot based multistoried agroforestry system with two vegetables, i.e., potato and brinjal during the period of 2019–2020. The vegetables were planted on the floor of the orchard where pineapple were planted in the same row with the trees. The experiment was laid out in a Randomized Complete Block Design (RCBD) with three replications. The results revealed that the upper-storied woody plants and sole vegetables received 100 % Photosynthetically Active Radiation (PAR) but incident light gradually decreased for brinjal and potato, which were grown at the floor of woody trees. The vegetables experienced 55.85(T3), 60.70(T2), 66.38(T1), and 100 (T4) % PAR under different tree crop combinations respectively. In both cases the highest BCR (3.75) and (3.09) was obtained in the ghoraneem + pineapple based multistoried agroforestry system for potato and brinjal production, respectively, which may considered as the best technique for higher production, crop diversification, and maximization of land use efficiency.

Photosynthetic activity and growth of poblano pepper biofertilized with plant growth promoting rhizobacteria and arbuscular mycorrhizal fungi

The rhizosphere of plants are natural hosts for beneficial microorganisms such as plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF). The objective of this work was to determine the effect of a consortium of AMF and three strains of PGPR on growth, gas exchange and phosphorus content in poblano pepper plants. An experiment was established in a completely randomized design with factorial arrangement, with two factors: AMF [Funneliformis geosporum and Claroideoglomus sp. (AM) and without AM (WM)] and PGPR [Rhizobium nepotum (B1), Serratia plymuthica (B2), Pseudomonas tolaasii (B3) and without PGPR (WB)]; generating eight treatments: T1) AM+B1, T2) AM+B2, T3) AM+B3, T4) AM+WB, T5) WM+B1, T6) WM+B2, T7) WM+B3 and T8) WM+WB. Plant height, number of leaves, leaf area, number of flowers, dry biomass, phosphorus content and AMF colonization were measured; internal CO2 concentration (Ci), transpiration rate (E), stomatal conductance (gS) and photosynthesis rate (Pn) were determined in leaves. Co-inoculation with AM+B3 promoted greater height (35%), number of leaves (66%), leaf area (62%), dry biomass (140%), phosphorus content (195%) and mycorrhizal colonization (26%); AM+B2 improved Ci (5%), E (8%), gS (5%) and Pn (9%) in poblano pepper leaves, compared to the control treatment (WM+WB). Biofertilization with AMF and PGPR improved gas exchange and growth of poblano pepper.

Variation in the role of the flag‐leaf in reproductive effort of semiarid rangeland bunchgrasses

AbstractUnderstanding the mechanisms underlying viable seed production of perennial bunchgrasses is critical to improving restoration and conservation success in Great Basin sagebrush steppe rangelands. We studied the effects of pre‐ and post‐anthesis flag‐leaf removal and post‐anthesis seed‐head shading on reproductive effort in two important rangeland restoration species, the exotic crested wheatgrass (Agropyron cristatum) and native squirreltail (Elymus elymoides). Flag‐leaf removal had distinct, species‐specific effects on seed filling. Pre‐anthesis flag‐leaf removal in crested wheatgrass reduced the proportion of filled seeds, while post‐anthesis removal did not. In contrast, squirreltail increased filled seed proportions regardless of flag‐leaf removal timing. Neither flag‐leaf removal treatment affected seed quality, as quantified by seed‐specific mass (in grams per square meter), which significantly reduced with seed‐head shading in both species. Seed‐head shading reduced total propagule production (unfilled + filled seeds) in crested wheatgrass but increased it in squirreltail, possibly due to our shading method protecting from seed‐head herbivory or high‐light stress. Flag‐leaf removal in the squirreltail also induced a negative shading effect on filled seed area, mass, and specific mass. These findings suggest flag leaves can modulate reproductive effort outside of seed provisioning, either by maintaining pre‐fertilized seed viability, as in crested wheatgrass, or acting as a competitive sink to the fully emerged seed‐head, as in squirreltail. Moreover, this study demonstrates photosynthetic activity by the seed‐head itself is critical to the expression of seed quality traits important to seedling establishment success of semiarid perennial bunchgrasses.

Tetraselmis species for environmental sustainability: biology, water bioremediation, and biofuel production.

With increasing demand of fossil fuels and water pollution and their environmental impacts, marine green microalgae have gained special attention in both scientific and industrial fields.This is due to their fast growth in non-arable lands with high photosynthetic activity, theirmetabolic plasticity, as well as theirhigh CO2 capture capacity. Tetraselmis species, green and eukaryotic microalgae, are not onlyconsidered as a valuable source of biomolecules including pigments, lipids, and starch but also widely used in biotechnological applications. Tetraselmis cultivation for high-value biomolecules and industrial use was demonstrated to be a non-cost-effective strategy because of its low demand in nutrients, such as phosphorus and nitrogen. Recently, phycoremediation of wastewater rich in nutrients, chemicals, and heavy metals has become an efficient and economic-alternative that allows the detoxification of waters and inducesmechanisms in algal cells for biomolecules rich-energy synthesis to regulate their metabolic pathways. This review aims to shed light on Tetraselmis species for their different culture conditions and metabolites bioaccumulation, as well as their human health and environmental applications. Additionally, phycoremediation of contaminants associated to biofuel production in Tetraselmis cells and their different intracellular and extracellular mechanismshave also been investigated.

Biochemical changes due to photothermal acclimation of Oedogonium and associated implications for photosynthetic growth and biomass utilisation

Freshwater filamentous algae have potential for wastewater bioremediation and bioproduct generation. This study investigated the separate and combined effects of growth irradiance regime (300 ± 25 μmol.m−2.s−1 with 13:11 dark:light cycle or 775 ± 25 μmol.m−2.s−1 with 8:16 dark:light cycle) and temperature (15 ± 1 or 25 ± 1 °C) during acclimation on the adaptive biochemistry and photosynthetic activity of Oedogonium with the higher and lower levels representing average outdoor conditions in summer and winter in Melbourne, Australia, respectively. Photoprotective pigments were upregulated in response to either high irradiance regime or temperature, while the chlorophyll content was also reduced when both stressors were combined. The upregulation of protective adaptations slightly lowered photosynthetic efficiency, which was more dramatically impaired by the reduced chlorophyll at high temperature and irradiance. The polar lipid content increased from ~10% to ~30% of total lipid content, the protein content decreased by ~10% and the starch content increased by 30% in response to higher irradiance and temperature, with implications for biomass utilisation. These changes in biochemical composition due to long-term acclimation suggests the potential for compositional stratification in stable floating filamentous algae mats due to the presence of self-shading. Further, the shading created by the upper layers in the mat can be expected to provide further protection to the biomass at the lower levels against photooxidative stress. The results reveal the impact of variations on seasonal growth conditions and filamentous mat depth on the composition and productivity of the algae.

Above- and Below-Ground Interactions and Interspecific Relationships in Wheat/Maize Systems

Above- and below-ground interactions play a crucial role in achieving higher yields in intercropping systems. Nonetheless, it remains unclear how these interactions impact intercropping crop growth and regulate interspecific relationships. This study aimed to quantify the impact of above- and below-ground interactions on crop yield by determining the dynamics of dry matter accumulation, photosynthetically active radiation (PAR) transmittance, and leaf area index (LAI) in intercropped wheat and maize. Three below-ground intensities were set for an intercropping system: no root separation (CI: complete interaction below ground), 48 μm nylon mesh separation (PI: partial interaction below ground), and 0.12 mm plastic sheet separation (NI: no interaction below ground). Two densities were set for maize: low (45,000 plants hm−2) and high (52,500 plants hm−2). At the same time, corresponding monoculture treatments were established. The grain yields in the CI and PI treatments were, on average, 23.7% and 13.7% higher than those in the NI treatment at high and low maize densities, respectively. Additionally, the grain yield for high density was 12.3% higher than that of low density in the CI treatment. The dry matter accumulation of intercropped wheat under the CI and PI treatments was, on average, 9.1%, 14.5%, and 9.0% higher than that in the NI treatment at the flowering, filling, and maturity stages, respectively. The dry matter accumulation of intercropped maize at the blister, milk, and physiological maturity stages increased by 41.4%, 32.1%, and 27.8%, respectively, under the CI treatment compared to the NI treatment. The PAR transmittance and LAI of maize at the V6 stage were significantly increased by increasing the intensity of below-ground interactions. This study showed that complete below-ground interaction contributed to a significant increase in the competitiveness of intercropped wheat with respect to maize (Awm) under the high-density maize treatment, especially at the filling stage of wheat. Moreover, the CI treatment enhanced the recovery effects of maize (Rm) after wheat harvesting. Increasing the intensity of below-ground interactions can significantly enhance the Awm and Rm in intercropping systems, favoring the accumulation of crop dry matter mass and light energy utilization to increase system yields.

Controlling algal growth using ultrasonic technology and conceptual implementation in the real-life system

ABSTRACT The present work reports a study on the interactive response of algae and other microorganisms coexisting in a natural water body to ultrasonic treatment for effective algal growth inhibition using ultrasonic treatments. The cellular damage caused by treatment was also visualised through SEM imaging. For an ultrasonic exposure of 10–30 min at 30 kHz frequency with ultrasonic power dissipated in the range of 4.2–12.5 W, the reduction in the algal cell density was changed from 37.82 to –52.73% after 7 days of observation period. The gradual decrease in the chlorophyll concentration signified the reduced photosynthetic activity after treatment. The damage created on the cell membrane by ultrasound was evaluated through the increased permeability of electrolytes from the cells and the rise in the conductivity of water. Following the lab-scale experimental studies and interpretation of the results obtained, field trials were carried out at a local natural pond (40*35 sq. metre) for 6 months and secondary clarifier in a local industry (20 m diameter) for 2 months, with some system working based on low power ultrasonic transmitters (power ∼ 25 W/h and frequency 20–40 kHz) and promising improvement in water quality could be observed with 85% and more than 95% algae removal efficiency, respectively.

Response mechanism of ecosystem gross primary productivity to cloud and aerosol changes in a Chinese winter-wheat cropland.

Changes in clouds and aerosols may alter the quantity of solar radiance and its diffuse components, as well as air temperature (Ta) and vapor pressure deficit (VPD), thereby affecting canopy photosynthesis. Our aim was to determine how ecosystem gross primary productivity (GPP) responds to the cloudiness and aerosol depth changes, as indicated by diffuse light fraction (fDIF). The environmental factors that caused these responses were examined using 2 years of eddy covariance data from a winter-wheat cropland in northern China. The GPP decreased significantly along with the fDIF in a nonlinear pattern, with a determination coefficient of 0.91. Changes in fDIF altered total photosynthetic active radiation (PAR), diffuse PAR, Ta and VPD. The variations in GPP with fDIF in both fDIF change Phase I (fDIF < 0.65) and Phase II (fDIF > 0.65) resulted from the combined effects of multiple environmental factors. Because the driving factors were closely correlated, a path analysis was used to distinguish their respective contribution to the GPP response to fDIF by integrating path coefficients. In Phases I and II, the decreased responses of GPP to fDIF were mainly caused by total PAR and diffuse PAR, respectively, which contributed approximately 49% and 37% to GPP variations, respectively. Our research has certain implications for the necessity to consider fDIF and to incorporate diffuse light into photosynthetic models.

Synergistic effects of heterotrophic and phototrophic metabolism for Haematococcus lacustris grown under mixotrophic conditions

AbstractMixotrophic cultivation of Haematococcus lacustris is one of the most promising strategies to produce natural astaxanthin. During mixotrophic growth, microalgae assimilate and metabolize organic carbon in addition to photosynthetic growth, resulting in increased biomass productivity. Several studies have evaluated the effect of different organic carbon sources on mixotrophic growth in various microalgae species. However, knowledge of detailed growth kinetics as a function of substrate concentration and light intensity is lacking. In this study, the growth kinetics of H. lacustris using four different carbon sources and the effect of light under mixotrophic and photoautotrophic conditions are described. Mixotrophic cultivation showed significant differences in respect to applied substrate and achieved maximum specific growth rates of 0.91 ± 0.13, 0.19 ± 0.05, 0.36 ± 0.05, and 0.23 ± 0.05 day−1, for acetate, methanol, glucose, and glycerol, respectively. Optimal growth at mixotrophic conditions using acetate was 1.8 times higher than the sum of hetero- and photoautotrophic growth. Furthermore, the optimum light intensity was 1.3 times higher for mixotrophic than for autotrophic growth. Thus, mixotrophy increases light intensity tolerance. These results indicate a strong interconnection between carbon metabolism and photosynthetic activity and lay the foundation for more detailed mathematical models describing the mixotrophic growth of H. lacustris. Graphical Abstract

Evaluation of the coupling of EMACv2.55 to the land surface and vegetation model JSBACHv4

Abstract. We present the coupling of the Jena Scheme for Biosphere–Atmosphere Coupling in Hamburg version 4 (JSBACHv4) to the ECHAM/MESSy Atmospheric Chemistry (EMAC) model. With JSBACH, the soil water bucket model in EMAC is replaced by a diffusive hydrological transport model for soil water that includes water storage and infiltration in five soil layers, preventing soil from drying too rapidly and reducing biases in soil temperature and moisture. A three-layer soil scheme is implemented, and phase changes in water in the soil are considered. The leaf area index (LAI) climatology in EMAC has been substituted with a phenology module calculating the LAI. Multiple land cover types are included to provide a state-dependent surface albedo, which accounts for the absorption of solar radiation by vegetation. Plant net primary productivity, leaf area index and surface roughness are calculated according to the plant functional types. This paper provides a detailed evaluation of the new coupled model based on observations and reanalysis data, including ERA5/ERA5-Land datasets, Global Precipitation Climatology Project (GPCP) data and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data. Land surface temperature (LST), terrestrial water storage (TWS), surface albedo (α), net top-of-atmosphere radiation flux (RadTOA), precipitation (precip), leaf area index (LAI), fraction of absorbed photosynthetic active radiation (FAPAR) and gross primary productivity (GPP) are evaluated in particular. The strongest correlation (r) between reanalysis data and the newly coupled model is found for LST (r=0.985, with an average global bias of −1.546 K), α (r=0.947, with an average global bias of −0.015) and RadTOA (r=0.907, with an average global bias of 3.56 W m−2). Precipitation exhibits a correlation with the GPCP dataset of 0.523 and an average global bias of 0.042 mm d−1. The LAI optimisation yields a correlation of 0.637 with observations and a global mean deviation of −0.212. FAPAR and GPP exemplify two of the many additional variables made available through JSBACH in EMAC. FAPAR and observations show a correlation of 0.663, with an average global difference of −0.223, while the correlation for GPP and observations is 0.564 and the average global difference is −0.001 kg carbon km−1. Benefiting from the numerous added features within the simulated land system, the representation of soil moisture is improved, which is critical for vegetation modelling. This improvement can be attributed to a general increase in soil moisture and water storage in deeper soil layers and a closer alignment of simulated TWS with observations, mitigating the previously widespread problem of soil drought. We show that the numerous newly added components strongly improve the land surface, e.g. soil moisture, TWS and LAI, while surface parameters, such as LST, surface albedo or RadTOA, which were mostly prescribed according to climatologies, remain similar. The coupling of JSBACH brings EMAC a step closer towards a holistic comprehensive Earth system model and extends its versatility.

Biogeochemical plumbing of pioneer mangrove intertidal flats in French Guiana

Migrating mudbanks are characteristic features of the vast Amazon-Guianas coastline along Northeastern South America. As illustrated by sites in French Guiana, consolidating mudflats that periodically transition to mangrove forest are permeated by extensive crustacean burrow systems, sometimes in isolation but more often in close association with morpho-sedimentary structures such as tidal pools and channels. Burrow structures are critical to mangrove growth. In this study, we evaluated the ways in which burrows act as complex conduits that plumb deposits for solute exchange with overlying water. We sampled burrows during low tide when irrigation is inhibited and burrow water rapidly becomes anoxic. The products of diagenetic reactions, for example: NH4+, N2, and Si(OH)4, build up with time, revealing sedimentary reaction rates and fluxes. When oxygenated, burrow walls are zones of intense coupled redox reactions such as nitrification-denitrification. Build-up often is lower in burrows connected directly to tidal pools where photosynthetic activity consumes remineralized nutrients, and burrows can remain periodically irrigated at low tide. During flood, burrows, particularly those that connect tidal pools laterally to channels, can be rapidly flushed and oxygenated as channel water rises and then spreads across flats. Burrow flushing produces enhanced concentrations of nutrients within the leading edge of the flood as seawater moves progressively towards and into adjacent mangroves. Estimates of burrow volumes obtained from drone surveys together with burrow solute production rates allow upscaling of burrow-sourced metabolite fluxes; however, these are extremely variable due to variable burrow geometries, connections between burrows, pools, and channels, and burrow water residence times (oxygenation). The flushing of burrows during flood results in a rectification of sediment-water fluxes shoreward and enhances the delivery of nutrients from the flats into adjacent mangroves and pools, presumably stimulating colonization and forest growth.

Chromophoric dissolved organic matter traces seasonally changing coastal processes in a river-influenced region of the western Bay of Bengal.

The optical characteristics of colored dissolved organic matter (CDOM) serve as a convenient tool for evaluating coastal processes, e.g., river runoff, anthropogenic inputs, primary production, and bacterial/photochemical processes. We conducted a study on the seasonal and spatial variability of absorbance and fluorescence characteristics of CDOM and nutrients in the coastal waters near the Gauthami estuary of River Godavari, the largest peninsular river of India, for a year. The surface aCDOM(350) showed a significant inverse relation with salinity in the coastal region, indicating a conservative mixing of marine and terrestrial end members. The aCDOM(350) was not conservative in the offshore (100m isobath) waters due to enrichment by secondary sources. Seasonal variability in optical properties indicated diverse sources for CDOM, as revealed by principal component analysis. The excitation-emission matrix (EEM) spectra followed by parallel factor analysis (EEM-PARAFAC) revealed four distinct fluorophores. The tyrosine (B) fluorophore showed a predominant increase in the post-monsoon season (October to January), while tryptophan (T) was relatively more enriched, coincident with nutrient enrichment and transparency increase during the early monsoon phase (July). The biological index (BIX), which reflects recent photosynthetic activity, also displayed relatively higher values during the early monsoon. The humic fluorophores A and M, and humification index (HIX) were relatively enriched during the later phase of monsoon (July-October). HIX was > 4 in a few samples of the offshore region (100-m isobath) and indicated a probable contamination from drill-mud (bentonite) used in hydrocarbon exploration. During the monsoon, the relationship between T and B with CDOM was not evident due to the masking of B fluorescence in intact protein. However, during the post-monsoon (POM) and pre-monsoon (PRM) periods, this masking effect was not observed, likely due to protein degradation via bacterial and photochemical processes, respectively. Temporal variability in nutrients indicated that high ammonium levels were produced during POM (OM bacterial degradation), and high nitrite levels were observed during PRM (due to primary production). This study provides foundational insights into the use of CDOM for understanding the impact of diverse environmental, river discharge, and anthropogenic factors on coastal ecosystems.

Compositions, sources, and bioavailability of colloidal organic matter in Lake Taihu

Colloidal organic matter (COM) exists ubiquitously in natural waters, and plays a pivotal role in biogeochemical cycles. Lake Taihu is confronted with severe eutrophication and algal blooms. Field investigations were carried out in Lake Taihu and two inflow rivers for two years to identify the source of COM and explore the bioavailability of COM to algae. Compositions and sources of COM were analyzed through UV absorption coefficients and parallel factor analysis of three-dimensional excitation emission matrix spectra (3D EEMs-PARAFAC). Absorption coefficient a(350) of COM in rivers surpassed that in the lake, SUVA254 exhibited noteworthy seasonal variations, and SR indicated a stable autochthonous characteristic. Three components were identified by PARAFAC analysis: tryptophan-like (C1), humic-like (C2), and tyrosine-like (C3). Fluorescence indexes showed that C1 and C3 were mainly autochthonously produced and C2 was derived from allochthonous inputs. The bioassays were conducted to assess the bioavailability of COM to the dominant species, Microcystis aeruginosa. The results showed that colloids supplied rich carbon sources and trace metals, supporting the growth of Microcystis aeruginosa. The specific growth rate, Chl a content, and biological increment of Microcystis aeruginosa in 50 % colloid-added treatment exceeded those in 20 % and 75 % treatments. Simultaneously, the effective quantum yield (Fv/Fm) and the apparent photosynthetic electron transport rate (ETRmax) demonstrated that the photosynthetic activity of Microcystis aeruginosa was higher in 20 % treatment. These findings help in understanding the intricate mechanisms of COM in lake ecosystems, and provide the robust scientific foundation for water management and protection in Lake Taihu.

Investigating the temporal lag and accumulation effect of climatic factors on vegetation photosynthetic activity over subtropical China

Monitoring vegetation photosynthesis in China’s subtropical regions using remote sensing is challenging because of the complex ecosystems and climate variability. Previous studies often pay less attention on the influence of multiple climatic factors on the temporal effects (lag and accumulation) of vegetation photosynthesis, thereby underestimating their impact. This study utilizes a dataset comprising Solar-induced chlorophyll fluorescence (SIF) data (GOSIF product), MODIS Land Cover product (MCD12C1), and various climatic variables. Analytical methods including Theil-Sen Median trend analysis, the Mann-Kendall test, partial correlation analysis, and the optimal parameter-based geographical detector (OPGD) model were employed to explore the temporal dynamics of subtropical vegetation SIF responses to climatic factors and to identify their climate drivers in subtropical China. The study findings indicate that (1) vegetation photosynthesis, as indicated by SIF, exhibited an increasing trend in the majority of Chinese subtropical regions, which constitute over 80 % of the study area, with particularly pronounced enhancements in the southern and central western parts of the Chinese subtropics. (2) Soil moisture primarily exhibits lag effects on SIF, particularly in evergreen needleleaf forests, deciduous broadleaf forests, and mixed forests, whereas temperature does not exhibit significant temporal effects. Solar radiation and vapor pressure deficits impact SIF through both lag and accumulation effects. Under the lag and accumulation effects, the proportion of significant correlations between climatic factors and vegetation SIF increases by 36.71 % ∼ 43.8 %, excluding temperature. (3) Temperature is the dominant factor affecting vegetation SIF, particularly in the evergreen needleleaf forest. Interactions between climatic factors have a significantly stronger influence on SIF than individual factors. Notably, the explanatory power of the vapor pressure deficit increases substantially when it interacts with other factors. Studying the lag and accumulation effects of climatic factors on photosynthesis aids in accurately predicting vegetation responses to climate change, thereby improving the accuracy of global carbon cycle models and guiding the development of carbon sequestration management strategies.

ОЦЕНКА АГРОБИОЛОГИЧЕСКИХ РЕСУРСОВ ЛАНДШАФТОВ СЕЛЬСКОХОЗЯЙСТВЕННОГО ИСПОЛЬЗОВАНИЯ ТУРКЕСТАНСКОЙ ОБЛАСТИ РЕСПУБЛИКИ КАЗАХСТАН В УСЛОВИЯХ ИЗМЕНЯЮЩЕГОСЯ КЛИМАТА

The article presents the results of assessment of agrobiological resources of landscapes of agricultural use of Turkestan region under conditions of changing climate, which were based on the developed concept of reference yields of H. Tooming. To develop an algorithm for assessing the agrobiological resources of the region, a climatic research base for 1941...2020 was created for 18 meteorological stations located in different natural zones, which made it possible to determine the peculiarities of the formation of different categories of agricultural yields due to climate change. The obtained results of the research on the state of agrobiological resources of landscapes of the region on potential productivity of agricultural lands, on photosynthetically active radiation (PAR) input using the concept of reference yields in spatial and temporal scales have shown that there is a stable trend to increase the potential productivity of agricultural lands on photosynthetically active radiation input, climatic potential-possible productivity and decrease the potential productivity of agricultural lands on - photosynthetically active radiation input, climatic potential-possible productivity and decrease the potential productivity of agricultural lands on - photosynthetically active radiation input.

Photosynthetic activity of crops and sequestration of atmospheric carbon by meadow clover and spring wheat in crop rotation

The purpose of the research is to estimate the intensity of absorption of light energy by crop rotation crops during the growing season and determine the amount of atmospheric carbon absorbed during photosynthesis. In a long-term stationary experiment, the absorption of photosynthetically active radiation (FAR) by crops of meadow clover for 2 years of use and spring wheat in variants without fertilizers and when applying N60P60K60 was studied. Chlorophyll A, chlorophyll B and carotene, which serve as photoreceptors-pigments of photosynthesis in higher plants, were used to assess the intensity of absorption of light energy. The most active period of absorption of HEADLIGHTS by meadow clover leaves was noted from the stalking phase to flowering, the amount of chlorophyll A and B in the leaves was 11.08…14.32 mg/g dry weight, carotene – 2.2…3.3 mg/g dry weight. During photosynthesis, the carbon content in clover leaves varied in the range of 40.4…45.5 %. The content of the main products of photosynthesis, sugars, decreased from 9.8 % in the stalking phase to 3.4 % during seed formation. The most intensive process of photosynthesis of spring wheat took place during the period from the tillering phase to the beginning of maturation, the chlorophyll content was 9.14…11.90 mg/g dry weight, carotene was 2.5…4.3 times lower. Most sugars were noted at the beginning of entering the tube: without fertilizers – 15.3 %, when applying NPK of 60 kg d. v./ ha – 17.2 %. The amount of carbon absorbed by meadow clover crops during photosynthesis during the growing season, depending on the experimental options, was 2.26…2.42 t/ha (8.09…8.66 t/ha CO2), spring wheat – 1.49…1.93 t/ha (5.33…6.90 t/ha CO2).

Enhancing Abiotic Stress Tolerance in Fruit Trees Using Microbial Biostimulants

Global climate change has significantly reduced the yield of many crops due to various abiotic stressors. These stressors include water-related issues such as drought and flooding, thermal changes like extremely low and high temperatures, salinity, and adverse soil pH conditions including alkalinity and acidity. Biostimulants have emerged as promising and effective tools for mitigating the damage caused by these abiotic stressors in plants, ultimately enhancing both the quantity and quality of crops. Biostimulants are naturally derived substances that include humic acid, protein hydrolysates, nitrogenous compounds, seaweed extracts, beneficial bacteria, and molds. Even at low concentrations, biostimulants play a critical role in activating important plant enzymes, inducing antioxidant defenses, improving water relations and photosynthetic activity, stimulating hormone-like activities (particularly auxins, gibberellins, and cytokinins), and modulating root system development. This review discusses the physiological effects of microbial biostimulants on the quality and productivity of fruit crops, as well as their experimental applications.