Photosynthetic Potential Research Articles

Photosynthetic activity and productivity of durum wheat (Triticum durum Desf.) affected by certain preparations and various terms of sowing

Abstract: In 2019-2020, in the experimental field of the Field Crops Institute, Chirpan a field experiment with durum wheat cultivar Predel (Triticum durum Desf.) was conducted. Three sowing dates were tested: Early sowing (05 – 10 October), Normal sowing (20-25 October – standard) and Late sowing (05-10 November). In early sowing, 2 retardants were studied: Cearon 480 SL – 1 l/ha and Medax top – 1 l/ha and 2 insecticides: Proteus 110 OD – 625 ml/ha and Mageos – 100 g/ha, as well as the mixtures between them. During late sowing, 2 stimulants were studied: Naturamin plus – 1.5 l/ha and Raiza mix – 750 ml/ha and 2 foliar liquid fertilizers: Mix for cereal SC – 1.5 l/ha and Trimax SC – 1.5 l/ha, as well as the mixtures between them. These preparations and fertilizers are applied after stage 3-4 leaves of durum wheat, in the so-called “Closure of crops”. In the case of early sowing variants, this stage occurs in autumn, and in the case of late sowing variants, the stage occurs in spring. In the early sowing of durum wheat, the leaf area, photosynthetic potential, biological and economic yield are the greatest in the combinations of retardants Cearon and Medax top with the insecticides Proteus and Mageos. In the late sowing of durum wheat, the leaf area, photosynthetic potential, biological and economic yield are the highest in the combinations of the stimulants Naturamin plus and Raiza mix with the leaf fertilizers Mix for cereals and Trimax. In these variants, the leaf area dies faster during the milk development stage. The net photosynthesis productivity in the combinations is lower than in the independent use of the respective preparations and fertilizers. The harvest index in the late and normal sowing variants is higher than in the early durum wheat sowing variants.

Estimation of genotypic features of effects of plant treatment with growth regulators on canopy parameters and yield of winter wheat

Aim. A study of the effects of growth regulators derived from natural raw materials on the photosynthetic apparatus surface and the yield of winter wheat. Methods. Morphometric, spectrophotometric, statistical. Results. An increase in the value of canopy chlorophyll index (ChlI) of Smuhlianka and Astarta varieties under the treatment of plants with Stimpo growth stimulator was established at anthesis, a positive effect of the regulator Regoplant – only for Smuhlianka variety at milk-wax ripeness. Chlorophyll photosynthetic potential (ChlP) during the period anthesis – milk-wax ripeness increased significantly under the use of growth regulators in both varieties, while the efficiency of treatments had varietal differences: growth was greater (11–18% compared to control) in the variety Smuhlianka than in the variety Astarta (6–7%). A positive correlation was established between the yield and ChlP during the period anthesis – milk-wax ripeness. Under the action of treatment of plants with growth regulators, the increase in grain yield was significant (0.29–0.45 t/ha) only in the variety Smuhlianka. Conclusions. The positive effect of treatments of plants with growth regulators, obtained from natural raw materials, on the value of canopy ChlI at anthesis and ChlP during period anthesis – milk-wax ripeness was established. A positive correlation between the winter wheat yield and ChlP during the period anthesis – milk-wax ripeness was found. Varietal differences in the effect of growth regulators treatment of plants on ChlP and yield were found.
 Keywords: Triticum aestivum L., grain productivity, chlorophyll index, chlorophyll photosynthetic potential, growth regulator.

The Crosstalk of Melatonin and Hydrogen Sulfide Determines Photosynthetic Performance by Regulation of Carbohydrate Metabolism in Wheat under Heat Stress.

Photosynthesis is a pivotal process that determines the synthesis of carbohydrates required for sustaining growth under normal or stress situation. Stress exposure reduces the photosynthetic potential owing to the excess synthesis of reactive oxygen species that disturb the proper functioning of photosynthetic apparatus. This decreased photosynthesis is associated with disturbances in carbohydrate metabolism resulting in reduced growth under stress. We evaluated the importance of melatonin in reducing heat stress-induced severity in wheat (Triticum aestivum L.) plants. The plants were subjected to 25 °C (optimum temperature) or 40 °C (heat stress) for 15 days at 6 h time duration and then developed the plants for 30 days. Heat stress led to oxidative stress with increased production of thiobarbituric acid reactive substances (TBARS) and hydrogen peroxide (H2O2) content and reduced accrual of total soluble sugars, starch and carbohydrate metabolism enzymes which were reflected in reduced photosynthesis. Application of melatonin not only reduced oxidative stress through lowering TBARS and H2O2 content, augmenting the activity of antioxidative enzymes but also increased the photosynthesis in plant and carbohydrate metabolism that was needed to provide energy and carbon skeleton to the developing plant under stress. However, the increase in these parameters with melatonin was mediated via hydrogen sulfide (H2S), as the inhibition of H2S by hypotaurine (HT; H2S scavenger) reversed the ameliorative effect of melatonin. This suggests a crosstalk of melatonin and H2S in protecting heat stress-induced photosynthetic inhibition via regulation of carbohydrate metabolism.

Global variation in the fraction of leaf nitrogen allocated to photosynthesis

Plants invest a considerable amount of leaf nitrogen in the photosynthetic enzyme ribulose-1,5-bisphosphate carboxylase-oxygenase (RuBisCO), forming a strong coupling of nitrogen and photosynthetic capacity. Variability in the nitrogen-photosynthesis relationship indicates different nitrogen use strategies of plants (i.e., the fraction nitrogen allocated to RuBisCO; fLNR), however, the reason for this remains unclear as widely different nitrogen use strategies are adopted in photosynthesis models. Here, we use a comprehensive database of in situ observations, a remote sensing product of leaf chlorophyll and ancillary climate and soil data, to examine the global distribution in fLNR using a random forest model. We find global fLNR is 18.2 ± 6.2%, with its variation largely driven by negative dependence on leaf mass per area and positive dependence on leaf phosphorus. Some climate and soil factors (i.e., light, atmospheric dryness, soil pH, and sand) have considerable positive influences on fLNR regionally. This study provides insight into the nitrogen-photosynthesis relationship of plants globally and an improved understanding of the global distribution of photosynthetic potential.

Identification of the photosynthetic potential of spring oat varieties in the Lower Volga Re-gion

In 2017-2019, in the agro-climatic conditions of the Lower Volga region, the experience of studying spring oat varieties of different ecological and geographical origin from the world collection of VIR was laid, in order to determine their photosynthetic potential, and to identify varieties with high photosynthetic productivity. Over the years of research, the most adapted varieties of this crop were selected, their photosynthetic potential was determined, and the intensity of photosynthesis during the reproductive period of development (during the main growth phases) of spring oats in the conditions of the Lower Volga region was analyzed. On average, for 3 years of studying the collection varieties of spring oats in terms of the net productivity of photosynthesis, samples were noted: Myrtle, Athlete, Urs guara, Urs penca, p. 1. 3326 It was determined that with the growth of (FP) and (BPF), the yield of oats also increased. Since this indicator directly depends on the physiological and bioclimatic processes occurring in plants during ontogenesis. In the highest yield in 2017, it varied from 0.66 to 2.01 / ha. In 2018, the minimum yield values for all varieties were obtained from 0.51 t / ha of the Dookie 10 variety to 1.78 t / ha of the Mir variety. In the conditions of 2019, the yield variability by variety was from 0.60 t / ha to 1.94 t / ha. Thus, out of the 8 studied varieties, 5 were identified - p.1. 3326, Guara Urs, Urs foam, Athlete, Myrtle, as highly productive, and therefore the most resistant to abiotic stresses of the conditions of the Lower Volga region.

The influence of abiotic factors on the growth and development of parsnip plants

The main drivers influencing plant growth, yield increase and its quality characteristics are biotic and abiotic factors. Combinations of abiotic stresses, such as drought and heat, have a much greater impact on yields and product quality. Plants' response to these stresses can vary depending on the species and different stages of development. Understanding the mechanisms and how they protect plants from stress has become vital for improving the yield and quality of parsnip products in changing climates. The purpose of the study was to determine the influence of abiotic factors (temperature and precipitation) on the yield, duration of phenological phases of growth and development of plants, the dynamics of leaf and root mass growth of parsnip in the conditions of the Right-Bank Forest-Steppe of Ukraine. The research was carried out in the field experiment of the Department of Vegetable Growing and Closed Ground in the National Research Institute “Fruit and Vegetable Garden” of NUBiP of Ukraine within the conditions of the Right-Bank Forest-Steppe of Ukraine during 2015-2017. The area of the registered plot was 11.3 m2, and the repetition rate of the experiment is four times. The placement of variants is systematic. The research found that the shortest sowing-emergence period lasted 16 days in the variants sown in the 3rd ten-day period of May and the 1st ten-day period of June. A significant delay of 21 days in this period was noted for sowings from 1st to 3rd ten-day periods of April. The duration of the period from the beginning of root crop formation to bunch ripeness was the shortest when sown in the 1st ten-day period of April – 28 days, and the longest when sown in the 1st ten-day period of June – 51 days. The growing season ranged from 110 to 165 days and was characterised by GDD (> 10 °C) of 1102.4-1439.0 °C and precipitation of 128.1-225.2 mm. After sowing in April, intensive growth of root crops from 2.9 to 3.5 g / day was observed in the second half of August. After sowing in May, the greatest increase in root crops from 2.1 to 2.7 g/day was noted in the first half of September. Thus, for sowings in the 1st ten-day period of June, this figure was the highest in the second half of September (1.9 g/day). The variant sown in the 1st ten-day period of April provided a high yield of root crops of 50.3 t/ha, which is 5.3 t/ha or 11.8% significantly more than the control variant. When sowing in the following terms, a significant decrease in yields was observed compared to the control, namely: for 3rd ten-day period of April – by 3.5 t/ha, or 7.7%, for 1st ten-day period of May – by 8.8 t/ha, or 19.6%, for 2nd ten-day periods of May – by 17.4 t/ha, or 38.6%, for 3rd ten-day periods of May – by 23.0 t/ha, or 51.1%, for 1st ten-day period of June – by 31.7 t/ha, 70.6% compared to the control. A strong direct correlation (r = 0.74-0.99) was found between the growing season and yield, root mass, marketability, and biochemical parameters, namely: dry matter, dry soluble matter, sugars, vitamin C. An inverse correlation (r = -0.98) was observed between the duration of the growing season and nitrates. Increasing the growing season by 10 days increases the yield up to 6.9 t/ha, marketability up to 2.7%, root weight up to 31 g, dry matter content up to 0.7%, dry soluble matter up to 0.3%, sugars up to 0.5%, vitamin C up to 0.8 mg/100 g and reduces the nitrate content to 8.4 mg/kg. Leaf area, photosynthetic potential, and net photosynthetic productivity are strongly directly related (r = 0.92-0.98) to yield. For increasing the leaf surface area to 1.0 thousand m2 the yield is also growing up to 0.7 t/ha. Increasing the photosynthetic potential to 0.05 million m2 days/ha increases the yield to 0.2-1.2 t/ha. Also, the yield increases to 0.3-0.7 t/ha with an increase in net photosynthetic productivity to 0.05 g/m2 per day. The molecular knowledge on plant responses to abiotic stress is promising for further study and is likely to advance crop resilience to climate change and increase the economic efficiency of production

Application of remote sensing technologies for studying urban forests in conditions of technogenic impact

In this work, an attempt was made to assess the possible change in the photosynthetic potential of the forests of New Moscow, depending on the degree of their remoteness from the territories with technogenic impact, based on the data of remote sensing of the earth. Because of constructing the time series of the spectral index NDVI, the value of the photosynthetic potential of homogeneous forest areas at different distances from the old borders of Moscow was estimated. Studies have shown that the average NDVI values of forests increase with distance from the borders with Old Moscow. The lowest NDVI values (0.70) are typical for forests located at a short distance from Moscow. In the central part of New Moscow, the index is 0.72, and the highest NDVI values (0.75) are observed within the settlements located in the south near the border with the Kaluga region.

Improving the yield potential in maize by constructing the ideal plant type and optimizing the maize canopy structure

AbstractUnderstanding the impact of changes in the crop canopy on yield is important in order to meet future food demands. We designed a field experiment to investigate the relationships between crop‐related factors and yield gaps in maize to enhance crop yields from 2010 to 2018 in Qitai, China. Maize grain yields (n = 247) were divided into four yield ranges: <15 Mg ha−1 (n = 30), 15–18 Mg ha−1 (n = 79), 18–21 Mg ha−1 (n = 114), and >21 Mg ha−1 (n = 24). The characteristics of the maize canopy structure as well as the light interception, photosynthetic potential, and radiation utilization efficiency in these four yield ranges were analyzed. The canopy structure of treated fields with yields >21 Mg ha−1 had a higher leaf area index (7.2), lower ear ratio (0.39), longer internodes above the ear (20.1 cm), larger leaf orientation value (LOV) above the ear (48.6), smaller leaf angle above the ear (18°), and smaller LOV below the ear (36.0) when compared to the other treatments. These findings suggested that the yield gap is dependent on canopy structure, and the evolutionary trend also accounted for significant increases in post‐LAD (p < 0.01), changes in crop growth rate (CGR; p < 0.01), net assimilation rate (NAR; p < 0.05), and radiation utilization efficiency. The radiation utilization efficiencies in the 15–18, 18–21, and >21 Mg ha−1 treatments (1.23, 1.28, and 1.38 g MJ−1, respectively) were higher than for the <15 Mg ha−1 treatment (1.10 g MJ−1). Furthermore, there are opportunities to narrow the yield gaps by optimizing the canopy structure to make full use of the solar radiation resources. Our results will help breeders choose an ideal canopy structure to improve yield. In addition, our results may serve as a general guide for other maize growing regions.

Characteristics of protective forest strips and their reclamation effect on sunflower in the zone of southern carbonate chernozems

The article deals with the issues related to the characteristics of protective forest strips and their impact on the yield of agricultural crops in the Troitsky farm of the Mikhailovsky district of the Volgograd region. Methodology. The characteristics of forest strips are typical. The spatial orientation of protective forest strips, species composition, height, undergrowth, number of rows, distance between rows and seats in a row, density and safety of plantings, width, openwork, design of forest strips are considered. Forest strips with sunflower biocenosis represent the ecosystem. The inter-lane space was taken into account from the forest strip at a distance of: 5; 10; 15; 25 and 35 heights (H). The control was the middle of the inter-lane cell. The bio-productivity of sunflower was determined by the phases of development: leaf area, assimilating surface, photosynthetic potential. For the analytical expression of the spatial dynamics of the photosynthetic potential an exponential dependence was used. Oil content at the end of the growing season was measured on the basis of interstate standards GOST 10857-64, GOST 13586.3 and GOST 10853-88 using a digital laboratory moisture-oil meter VMTSL-12M. The aim of the research was to identify the reclamation effect of the influence of protective forest strips on the bioproductivity of sunflower with minimal tillage (or no-till technology). Conclusion. Features of the bio-productivity of sunflower hybrid in the inter-lane space are expressed in the patterns of development of assimilating the surface on logistics and photosynthetic potential is exponential. The yield of the hybrid varies depending on the weather conditions, the presence of nutrients in the soil and does not differ fundamentally by year. Consequently, the cultivation of the LG-5456 hybrid in humid years in the zone of influence of forest strips using the no-till technology showed good results. The obtained data prove that forest-reclamation plantings in agricultural landscapes are one of the most durable and environmentally friendly factors for increasing the productivity of agricultural land.

Probing the structural basis of Citrus phytochrome B using computational modelling and molecular dynamics simulation approaches

Phytochromes (Phys) are known as red/far-red light photoreceptors and are responsible for directing the photosensory responses across the species, majorly from fungal, bacterial and plant kingdoms. Such responses majorly include photosynthetic potential and pigmentation in bacteria, whereas in a plant, they are involved in chloroplast development and photomorphogenesis. Many prokaryotic Phys have been modelled for their structural and functional analysis, but their plant counterparts have not been explored yet. To date, only the crystal structures of the photo-sensing module (PSM) of PhyB isoform from Arabidopsis thaliana and Glycine max have been resolved experimentally. Thus, in this study, we elucidated the complete 3D structure of Citrus PhyB. Initially, the structure and organization of the Citrus PhyB have been predicted computationally, which were found to have the same domain organization as A. thaliana and G. max PhyBs, yet their considerable distinct structural difference indicated potential divergence in signaling and functioning. Therefore, to evaluate the structural implications of Citrus PhyB, we compared its structure with A. thaliana and G. max PhyBs using molecular dynamics (MD) simulation approaches. The modeling studies revealed that the region of Citrus PhyB-GAF domain possibly contributes to the variations between Citrus, A. thaliana and G. max PhyBs structures. Hence, structural and molecular insights into Citrus PhyB can help to understand better the Phys and thus, an essential framework can be designed for optogenetic reagents and various agricultural/horticulture benefits.

Effects of Water Stress and Auxin Application on Growth and Yield of Two Sugarcane Cultivars under Greenhouse Conditions

Water stress (drought and flood) is one of the major factors that limits sugarcane growth and yield. The two greenhouse experiments were conducted at Khon Kaen University, Thailand. The first experiment investigated the individual and combined effects of droughts and floods on two sugarcane cultivars. The results showed that photosynthetic potential, based on chlorophyll a fluorescence (PSII) and chlorophyll content, exhibited a response to the water regime treatments. However, stomatal conductance in the K93-219 cultivar was higher than the KK3 cultivar. Similarly, plant height, number of tillers, number of stems, fresh stem weight, and sugar quality were not affected by the varying water regime conditions imposed on both of the sugarcane cultivars. However, drought or flood conditions, whether alone or in combination, reduced the fresh stem weight, with regards to the water regimes and cultivars. In general, a combination of drought and flood reduced the fresh stem weight as opposed to drought or flood alone. The KK3 cultivar gave a higher fresh stem weight than the K93-219 cultivar under dual stress conditions. The second experiment investigated the auxin application rates at different growth stages on two sugarcane cultivars under flood conditions. The results revealed that the application of auxin at 10 mg L−1 increased the number, and fresh weight, of adventitious roots over the control (0 mg L−1). The cultivar K93-219 produced a higher number, and fresh weight, of adventitious roots. However, the amount of aerenchyma in the adventitious roots was not affected by auxin application rates, growth stages, or cultivars. Similarly, plant height, leaf width, number of stems, fresh stem weight, and sugar quality were not affected by auxin rates. Auxin application at five months of age increased leaf width and fresh stem weight over the control. The cultivar K93-219 tended to produce a higher fresh stem weight than the KK3 cultivar.

ВЛИЯНИЕ ЖИДКИХ КОМПЛЕКСНЫХ УДОБРЕНИЙ И РЕГУЛЯТОРА РОСТА НА ФОТОСИНТЕТИЧЕСКУЮ ДЕЯТЕЛЬНОСТЬ И ПРОДУКТИВНОСТЬ КОСТРЕЦА БЕЗОСТОГО

The article presents experimental material obtained in the conditions of Mordovia on leached black soil on the effect of MEGAMIX liquid complex fertilizers and Albit growth regulator on photosynthesis production process and productivity of awnless brome. Two-factor field experiments were carried out on the crops of awnless brome on an experimental field at OAO “Mordoviyagosplem” in Ozerny village, urban district of Saransk in 2018 - 2020, according to the following scheme: Factor A - Time of application of liquid complex fertilizers and growth regulator. 1 - At the phase of spring growth, 2 - At the phase of stem elongation, 3 - At the phase of spring growth + in the phase of stem elongation. Factor B - Liquid complex fertilizers and growth regulator. 1. - Without application of liquid complex fertilizers and growth regulator (control). 2. - Megamix-pro. 3. - Megamix nitrogen. 4 - Albit. The results of our research indicate that leafiness of awnless brome prevailed (26.0 and 24.4%) when Megamix-pro and Megamix-nitrogen were used at the time of spring growth; predominant leaf area (47.8 thousand m2 / ha), photosynthetic potential (2.31 million m2 • days / ha), dry matter yield (8.75 t / ha) were formed with application of Megamix nitrogen at the time of spring growth; and net productivity of photosynthesis was the highest without application of these preparations (5.8 g / m2 per day) and with spraying the plants with Megamix-profi and Megamix-nitrogen (5.3 g / m2 per day) at the phase of stem elongation. Photosynthesis productivity was the lowest in case application of Megamix-profi and Megamix-nitrogen at the spring growth phase (224 and 228 g of seeds per 1,000 PhP units).

The self-adaption capability of microalgal biofilm under different light intensities: Photosynthetic parameters and biofilm microstructures

Microalgae biofilm-based culture systems have received considerable attention because their water requirements and harvesting costs are lower, and biomass productivity is higher, than in suspended culture systems. The photosynthetic properties and microstructure of microalgae biofilms have fundamental effects on biofilm growth. We investigated the photosynthetic parameters, microstructures, biomass accumulation, and CO2 fixation rate of Chlorella sp. biofilms cultured under a series of light intensities (20, 50, 100, 200, and 400 μmol·m−2·s−1). The results indicated that microalgae biofilms had higher photosynthetic potentials and more porous microstructures under low light intensities, and that both of these promoted the efficiency of photon use. In contrast, biofilms under high light intensities exhibited higher photo-protection capabilities and more compact microstructures, which protected microalgae against photo damage. The study revealed that microalgae biofilms have excellent self-adaption capabilities to cope with varying light intensities, and these have significant implications for selection of the optimal light intensity when designing more efficient biofilm-based microalgae culture systems.

Photosynthetic Potential Of Spring Barley Plants In The Steppe Zone

Today, an increase in the real potential of grain crops, including spring barley, is a necessary condition for elements of crop cultivation technologies. Therefore, given the limited resource potential of spring barley crops, their fastidiousness to the soil, considerable attention should be paid to the photosynthetic potential of plants and the standardised application of mineral fertilisers. The aim of the study was to improve the elements of the technology of growing promising varieties of spring barley by establishing the mineral nutrition effect on the photosynthetic activity of plants in the conditions of the Luhanska Oblast. This study provides examples of improving some technologies for growing promising varieties of spring barley and determines the optimal norms for applying mineral nutrition to ensure the high photosynthetic potential of these plants in the climatic conditions of the steppe zone of Ukraine. It was found that the use of ammonium nitrate had a positive effect on the leaf area, increasing it by 1-2.2 thousand m2 /ha compared to the control for all varieties studied. The combined use of diammonium phosphate and ammonium nitrate contributed to an increase in the leaf area by 2-4. 4 thousand m2 /ha compared to the control variant. Simultaneous application of ActiBION increased the total leaf area for all samples studied by 3.8-6.4 thousand m2 /ha. The best indicators among the studied varieties were observed on the six-row variety Helios and the double-row variety Stalker. The six-row variety Vakula and the two-row variety Adapt showed slightly lower results. Further research implies the study of the influence of photosynthetic activity of promising varieties of spring barley on crop productivity in the steppe zone of Ukraine. The findings can be recommended for production as one of the elements in the technology of growing spring barley in the climatic conditions of the Luhanska Oblast

Metabolic Reliance on Photosynthesis Depends on Both Irradiance and Prey Availability in the Mixotrophic Ciliate, Strombidium cf. basimorphum.

Many species of the ciliate genus Strombidium can acquire functional chloroplasts from a wide range of algal prey and are thus classified as generalist non-constitutive mixotrophs. Little, however, is known about the influence of irradiance and prey availability on their ability to exploit the photosynthetic potential of the chloroplasts, and how this may explain their spatial and temporal distribution in nature. In this study, inorganic carbon uptake, growth, and ingestion rates were measured for S. cf. basimorphum under three different irradiances (10, 40, and 120 μmol photons m–2 s–1) when acclimated to three different prey densities (5 × 103, 1 × 104, and 4 × 104 cells mL–1), as well as when allowed to deplete the prey. After prey depletion, cultures survived without prey longest (∼6 days) at the medium irradiance treatment (40 μmol photons m–2 s–1), while ciliate density, inorganic carbon uptake rates, and cellular chl-a content declined fastest at the highest irradiance treatment. This indicates that the ciliates may be unable to maintain the chloroplasts functionally without replacement at high irradiances. Ingestion rates were not shown to be significantly influenced by irradiance. The maximum gross growth efficiency (GGE) in this study (1.1) was measured in cultures exposed to the medium test irradiance and lowest prey density treatment (5 × 103 cells mL–1). The relative contribution of inorganic carbon uptake to the ciliate carbon budget was also highest in this treatment (42%). A secondary GGE peak (0.99) occurred when cultures were exposed to the highest test irradiance and the medium prey density. These and other results suggest that S. cf. basimorphum, and other generalist non-constitutive mixotrophs, can flexibly exploit many different environmental conditions across the globe.

Ethylene reduces glucose sensitivity and reverses photosynthetic repression through optimization of glutathione production in salt-stressed wheat (Triticum aestivum L.)

Ethylene plays a crucial role throughout the life cycle of plants under optimal and stressful environments. The present study reports the involvement of exogenously sourced ethylene (as ethephon; 2-chloroethyl phosphonic acid) in the protection of the photosynthetic activity from glucose (Glu) sensitivity through its influence on the antioxidant system for adaptation of wheat (Triticum aestivum L.) plants under salt stress. Ten-day-old plants were subjected to control and 100 mM NaCl and treated with 200 µl L−1 ethephon on foliage at 20 days after seed sowing individually or in combination with 6% Glu. Plants receiving ethylene exhibited higher growth and photosynthesis through reduced Glu sensitivity in the presence of salt stress. Moreover, ethylene-induced reduced glutathione (GSH) production resulted in increased psbA and psbB expression to protect PSII activity and photosynthesis under salt stress. The use of buthionine sulfoximine (BSO), GSH biosynthesis inhibitor, substantiated the involvement of ethylene-induced GSH in the reversal of Glu-mediated photosynthetic repression in salt-stressed plants. It was suggested that ethylene increased the utilization of Glu under salt stress through its influence on photosynthetic potential and sink strength and reduced the Glu-mediated repression of photosynthesis.

Mechanisms of silicon-induced fungal disease resistance in plants

Silicon (Si) acts as a beneficial element for plant growth and provides protection against abiotic and biotic stresses. Despite numerous reports on the beneficial role of Si in enhancing plant resistance to fungal pathogens, the underlying mechanisms remain largely unclear. Silicon shows antifungal activity; however, Si-induced improved disease resistance is partly manifested by the formation of Si polymerized mechanical obstruction under the cuticle and in cell walls, which prevents fungal ingress. Moreover, rapid production of defense compounds through secondary metabolic pathways is thought to be a key mechanism of Si-induced chemical defense against fungal pathogens beyond the physical barrier. Besides, improved mineral nutrition assures the healthy status of Si-supplied plants and a healthy plant exhibits better photosynthetic potential, antioxidant capacity and disease resistance. Multiple plant hormones and their crosstalk mediate the Si-induced basal as well as induced resistance; nonetheless, how root uptake of Si systemically modulates resistance to foliar diseases in low Si accumulating plants, needs in-depth investigation. Recent studies also indicate that Si influences effector-triggered immunity by affecting host recognition and/or limiting receptor-effector interactions. Here we review the role of Si in plant response to fungal pathogens. We also discuss and propose potential mechanisms of Si-induced enhanced disease resistance in plants. Finally, we identify some limitations of research approaches in addressing the beneficial roles of Si in biotic stress management.

Complex effect of fertilizers and drip irrigation eggplant yield

Relevance and methods. In the dry steppe zone of flat Dagestan, the beneficial effect of drip irrigation in combination with organic fertilizers on the yield and quality of Almaz eggplant fruits has been proven. Results. It was established that out of the three studied soil moisture thresholds (70, 80 and 90% HB), the best conditions for plant growth and development, optimization of their photosynthetic activity are created at a moisture threshold of 80% HB in combination with the introduction of 40 t / ha manure + N320P120K210. The combination of factors under study makes it possible to increase the leaf surface index by an average of 24.3%, which contributes to an increase in the photosynthetic potential by 15.7% and an increase in the efficiency of the use of photosynthetically active radiation by crops by 2.5 times in comparison with the unfertilized background by 90% НВ. In conditions of a shortage of irrigation water, drip irrigation in combination with fertigation in the form of three root fertilizing with nitrogen fertilizers increases the efficiency of its use by reducing the water consumption for the formation of a unit of production from on average with 164.8 to 66.4 m3 /t. It has been proven that the best combination of yield-forming factors ensuring the highest eggplant yield - 62.3…63,6 t / ha, is the use of drip irrigation with the maintenance of soil moisture in the active 0.5 m layer during the growing season within 80...100% HB in the complex with the introduction of 40 t / ha of manure and N320P120K210.

Low-level pharmaceuticals alter stream biofilm structure and function

ABSTRACT Pharmaceuticals and personal care products (PPCPs) are a contaminant class of worldwide concern and a potential source of global change. To better understand the impact of low levels of PPCPs on stream biofilm structure and function, we conducted laboratory mesocosm experiments in which biofilms cultivated in streams draining areas of different land use (natural, agricultural, and urban) were exposed to low levels (5 µg L−1) of several common pharmaceuticals. We performed several functional assays and assessed differences in biofilm bacterial community composition among pharmaceutical treatments and streams. Pharmaceutical treatments altered the functional capacity and diversity of biofilms, but had no significant effect on carbon uptake or photosynthetic potential. Biofilm bacterial communities differed with land use, and pharmaceutical treatments decreased the relative abundances of Alcanivorax and Halioglobus and increased the relative abundance of Pseudomonas, indicating a shift to more drug-tolerant groups. Overall, our results provide evidence that PPCPs may act as ecological disruptors even at low levels, altering biofilm structure and some aspects of ecosystem function, and potentially influencing important biogeochemical processes in streams.

Influence of growth stimulants and microfertilizers on the productivity of Carthamus tinctorius in the steppe zone of the Saratov Right Bank

In the course of the research, it was found out that the highest rates of photosynthetic activity of Carthamus tinctorius were noted in the variant where pre-sowing treatment of seeds with a growth stimulator zircon + treatment of crops in the budding phase with siliplant microfertilizer was carried out. In this variant, the leaf area of the best variety Ershovsky 4 was 35.3 thousand m2 / ha, dry aboveground biomass - 7.49 t / ha, photosynthetic potential - 1941 thousand m2 / ha·day; net productivity of photosynthesis - 3.86 g / m2·day. On average for 2018–2020, the highest yield of safflower oilseeds of the Ershovsky 4 variety reached 1.89 t / ha. The highest (1.74 t / ha) average annual yield of safflower oilseeds of Astrakhanskiy 747 variety was also obtained using a similar option. To ensure a consistently high productivity of Carthamus tinctorius agrocenoses in the arid conditions of the steppe zone of the Saratov Right Bank, it is recommended to expand the cultivation areas of the most adapted variety Ershovsky 4, using pre-sowing seed treatment with a zircon growth stimulator (30 ml / t) and processing crops in the budding phase with siliplant micronutrient fertilization (1 , 0 l / ha).