Intensity Of Photosynthesis Research Articles

Effect of different doses of apple pomace to the substrate on photosynthetic efficiency and yield in common buckwheat in a model experiment

Abstract By-products of apple juice pressing should be used for the benefit of the environment. One way to manage them is to add them to the soil in raw or composted form as a natural fertiliser and source of organic matter. A study was therefore undertaken to test several doses of apple pomace to the substrat on photosynthetic parameters and yield of buckwheat. The experiment was conducted in a vegetation hall under controlled, automatic irrigation to 60% of the field water capacity. The model study used the cultivar Red corolla and three doses of apple pomace applied to pots in the following amounts: 0 control, 70, 140 and 210 g per pot, which corresponded to field volume: 1, 2 and 3 t·ha−1. Four photosynthetic parameters (Pn, E, Gs and Ci) were measured and the water use efficiency was determined. Chlorophyll fluorescence (Fv/Fm and PI) was also investigated. The most suitable variant for buckwheat was the using 210 g which resulted in increased photosynthesis intensity, chlorophyll fluorescence and buckwheat yield.

Improving global gross primary productivity estimation using two-leaf light use efficiency model by considering various environmental factors via machine learning

Distinguishing gross primary productivity (GPP) into sunlit (GPPsu) and shaded (GPPsh) components is critical for understanding the carbon exchange between the atmosphere and terrestrial ecosystems under climate change. Recently, the two-leaf light use efficiency (TL-LUE) model has proven effective for simulating global GPPsu and GPPsh. However, no known physical method has focused on integrating the overall constraint of intricate environmental factors on photosynthetic capability, and seasonal differences in the foliage clumping index (CI), which most likely influences GPP estimation in LUE models. Here, we propose the TL-CRF model, which uses the random forest technique to integrate various environmental variables, particularly for terrestrial water storage (TWS), into the TL-LUE model. Moreover, we consider seasonal differences in CI at a global scale. Based on 267 global eddy covariance flux sites, we explored the functional response of vegetation photosynthesis to key environmental factors, and trained and evaluated the TL-CRF model. The TL-CRF model was then used to simulate global eight-day GPP, GPPsu, and GPPsh from 2002 to 2020. The results show that the relative prediction error of environmental stress factors on the maximum LUE is reduced by approximately 52 % when these factors are integrated via the RF model. Thus the accuracy of global GPP estimation (R2 = 0.87, RMSE = 0.94 g C m−2 d−1, MAE = 0.61 g C m−2 d−1) in the TL-CRF model is greater than that (R2 = 0.76, RMSE = 2.18 g C m−2 d−1, MAE = 1.50 g C m−2 d−1) in the TL-LUE model, although this accuracy awaits further investigation among the released GPP products. TWS exerts the greatest control over ecosystem photosynthesis intensity, making it a suitable water indicator. Furthermore, the results confirm an optimal minimum air temperature for photosynthesis. Overall, these findings indicate a promising method for producing a new global GPP dataset, advancing our understanding of the dynamics and interactions between photosynthesis and environmental factors.

Assessment of Genetic Diversity in Garden Pea (Pisum sativum L.) and Identification of Promising Lines for Hybridization

The current study is being conducted to understand the degree of genetic divergence in order to discover more diversified parents for pea genetic advancement. The creation of high yielding varieties with stable productivity, resistance to diseases and unfavorable environmental conditions, various maturing types, a high rate of organic matter accumulation during the early stages of growth, a sufficiently high intensity of photosynthesis, increases in protein content, essential amino acids, and favorable ratios among them are the most important tasks for pea breeding. The present investigation was carried out at vegetable research farm and laboratory works in the department of Horticulture (Vegetable and Floriculture), BAU, Sabour, Bhagalpur, Bihar during the Rabi season 2020-21. The genotype Kashi Mukti, Kashi Uday, Kashi Nandini and VM-11 of cluster II exhibited superiority for earliness in first flower, days to 50% flowering and days to first picking and significantly better performance as measured by the lowest cluster mean and a substantial improvement in performance while the genotype Haze-02 of cluster IV exhibited superiority for inter-nodal length , plant height , seeds per pod and total sugars (%) based on maximum cluster mean with significantly better performance. It is anticipated that progenies from such diversified crossings will exhibit a broad range of genetic diversity and more potential for transgressive segregant isolation in the later generations. Therefore, a multiple crossing program using these genotypes may be used to retrieve transgressive segregants.

Water Affecting Photosynthesis of Seedlings Growing in the Oopen

An assessment of the decrease in the photosynthesis intensity due to the lack of moisture were carried out on 6-year-old oak, pine and spruce seedlings grown in containers in the open air within the Serebryanoborsky forestry district by the Institute of Forest Science of the RAS (Moscow region). We determined at which values of pre-dawn water potential (PWP) seedlings growing in the open are resistant to the lack of moisture. Almost all seedlings of these species with insufficient water supply have a depression of photosynthesis, which occurs more rapidly as the moisture deficit increases and at lower solar radiation. In case of an oak, when the PWP reaches –1.1 MPa, the intensity of photosynthesis decreases by half, and in case of pine and spruce — at a PVP equal to –0.8 MPa. For the oak, the intensity of photosynthesis drops to zero at –3.0 MPa, in pine — at –1.6 ÷ –1.8 MPa, in spruce — at –1.5 MPa. Thus, the most resistant to the lack of moisture is oak, then pine, and the most demanding in terms of water supply is spruce.

Оценка влияния старовозрастных ельников на углеродный баланс таежных лесов Валдая

Monitoring the photosynthesis- and respiration-related characteristics of the old-aged forests of the Valday Region is of paramount importance since it is imperative that the role of all factors contributing to their carbon balance should be evaluated. This work presents data on seasonal dynamics of midday carbon-dioxide exchange and photosynthetic productivity of the Norway spruce (Picea abies L.) in May - October 2018-2020. It was established that the main factors determining the CO2 assimilation rate of the spruce are the air temperature and illumination. The average annual photosynthesis intensity level was more than two times higher than the light-dependent respiration level. Significant interseasonal changes in spruce photosynthetic productivity were revealed: the maximum and minimum photosynthetic productivity was detected in June-July and October, respectively. The interannual changes were related to the weather conditions and to the state of the forest stand in the tested area. The total carbon dioxide uptake by spruce needles in 2018, 2019, and 2020 was 3.3, 2.13, and 1.15 ton of CO2∙ha-1∙year-1. The average value of net primary production (0.37 ton of C∙ha-1∙year-1) and the positive carbon dioxide balance of the Norway spruce testify to a considerable influence of old-aged spruce forests on the carbon balance of the forest cenoses of the Valday Region.

Methods of increasing the seed productivity of the new variety of sage medicinal Fioletovy Aromat

Relevance. Salvia officinalis L. is an important essential oilseed crop with anti-inflammatory, antimicrobial and antioxidant properties. Providing the pharmaceutical industry with raw materials of Salvia in full is possible due to the expansion of production areas and the availability of the maximum amount of highquality seed material of new promising varieties.Methods. In 2019-2022 in the conditions of the North Caucasus branch of VILAR on a new variety of Salvia Fioletovy aromat II year of vegetation by staging small-scale experiments were conducted to study the systematic application of organomineral fertilizer – EcoFus and growth regulators of different mechanism of action – Zircon, Epin-extra, retardant Hardy to increase seed productivity and seed quality. The area of the experimental plots was 12 m2. Treatment with EcoFus was carried out at the beginning of regrowth, and with bioregulators – during the budding phase. The consumption of the working solution is 300 l/ha. Control variants of medicinal crops were treated with water.Results. Application of EcoFus in the phase of regrowth contributed to the activation of the intensity of photosynthesis and increase in the accumulation of plastic substances, which allowed plants to enter the generative phase earlier, the budding phase came 2-3 days earlier than in the control. Subsequent treatment of budding plants with growth regulators led to earlier and more friendly flowering, the time of seed ripening was reduced by 3-4 days. The highest efficiency was observed in the variants of joint application of EcoFus with Zircon or Hardy, where the number of inflorescences on plants increased, seed setting and seed productivity increased by 37-42%, seed quality also improved – weight of 1000 seeds increased by 9-10% and germination by 6-7%.

Salinity Mitigates the Negative Effect of Elevated Temperatures on Photosynthesis in the C3-C4 Intermediate Species Sedobassia sedoides.

The adaptation of plants to combined stresses requires unique responses capable of overcoming both the negative effects of each individual stress and their combination. Here, we studied the C3-C4 (C2) halophyte Sedobassia sedoides in response to elevated temperature (35 °C) and salinity (300 mM NaCl) as well as their combined effect. The responses we studied included changes in water-salt balance, light and dark photosynthetic reactions, the expression of photosynthetic genes, the activity of malate dehydrogenase complex enzymes, and the antioxidant system. Salt treatment led to altered water-salt balance, improved water use efficiency, and an increase in the abundance of key enzymes involved in intermediate C3-C4 photosynthesis (i.e., Rubisco and glycine decarboxylase). We also observed a possible increase in the activity of the C2 carbon-concentrating mechanism (CCM), which allowed plants to maintain high photosynthesis intensity and biomass accumulation. Elevated temperatures caused an imbalance in the dark and light reactions of photosynthesis, leading to stromal overreduction and the excessive generation of reactive oxygen species (ROS). In response, S. sedoides significantly activated a metabolic pathway for removing excess NADPH, the malate valve, which is catalyzed by NADP-MDH, without observable activation of the antioxidant system. The combined action of these two factors caused the activation of antioxidant defenses (i.e., increased activity of SOD and POX and upregulation of FDI), which led to a decrease in oxidative stress and helped restore the photosynthetic energy balance. Overall, improved PSII functioning and increased activity of PSI cyclic electron transport (CET) and C2 CCM led to an increase in the photosynthesis intensity of S. sedoides under the combined effect of salinity and elevated temperature relative to high temperature alone.

Photosynthetic potential of Malus domestica columnar group

Productivity is one of the primary economic and biological characteristics of an apple tree variety; it is this characteristic that determines the value and economic feasibility of the variety. The photosynthetic activity of the leaf surface of plants plays a leading role in forming the potential productivity of the apple tree. By "potential productivity," we mean the productivity of plants under conditions of ideal agroenvironment, optimal nutrition, and absence of diseases. To diagnose the potential productivity of cultivars we used an indicator of chlorophyll fluorescence induction–induction coefficient (Кі). According to our data, the Кі of leaves of columnar cultivars ranged from 0.720 to 0.740, indicating a high level of efficiency of photophysical processes near the photosystem II (PS II) reaction centers. For plants of columnar cultivars, the viability index ranged from 1.78 to 2.19. It has been established that individual age sections of tree trunks form different productivity potentials. Thus, based on the chlorophyll a (Chl a) fluorescence induction index, a higher intensity of photosynthesis was observed in the leaves of the cultivars ‘Valuta’, ‘Favoryt’, and ‘Bilosnizhka’ on seven to nine-year-old trunks. In contrast, for ‘Tantsivnytsia’, the highest intensity was observed on the oldest spur formation (14–19 years old). In traditional apple cultivars, the intensity of photosynthesis, as indicated by Кі, decreased with the age of spur formation; however, such a decline was not observed in columnar cultivars. The leaves of plants from the traditional cultivar ‘Idared’, situated on a homogeneous shoot, exhibited the highest photosynthetic intensity based on the F680γt / F680βt light intensity. Conversely, in the leaves of three-year-old spur formations, a 25.3% decrease in photosynthetic intensity was observed, falling to a 45.7% decrease in six-year-olds. With the optimal combination of agroecological factors for columnar cultivars, stability in the photosynthetic potential across various complex spur formations is observed. In typical apple cultivars, the age of spur formation leads to a suppression of photosynthetic intensity. The cultivar ‘Bilosnizhka’ is characterized by the highest Chl a/ Chl b content, indicating lower adaptability. In the leaves of this cultivar, the amount of Chl a exceeded Chl b by three times; in contrast, in the cultivars ‘Sparta’ and ‘Tantsivnytsia’, the difference was 2.5 times higher. This value (2.5x) correlates with increased adaptability to the conditions in which they were studied. The highest level of leaf net productivity of photosynthesis (NPP) is observed in plants of the ‘Valuta’ cultivar (13.9 g/m² for day); in the cultivars ‘Bilosnizhka’, ‘Favoryt’, ‘Bolero’, ‘Sparta’, ‘Tantsivnytsia’, and ‘Papirovka’, the accumulation of dry matter is lowered by 32.6–40.6%.

PHYSIOLOGICAL PARTICULARITIES OF MAIZE PLANTS AND THE EFFECT OF SOME ANTIOXIDANTS UNDER CONDITIONS OF MODERATE DROUGHT

Complex investigation on the effect of Thiourea, Galmet and Thiogalmet compositions on water status, intensity of photosynthesis, water use efficiency, growth and yield of ‘P458’ maize plants under conditions of natural humidity in field trials was performed. The beneficial effect of seed and foliage pre-treatment with Thiourea, Galmet and, in particular, the new chemical composition Thiogalmet on plants’ biological processes conditioning a better realisation of the physiological processes associated with plant growth and productivity was established. A significantly greater positive impact of Thiogalmet on the optimisation of hydration degree, water retention capacity, stomatal conductance for CO2/H2O, assimilation, water use efficiency, plant growth and productivity was recorded. There was an additive action of Thiourea and Galmet in the composition of the Tiogalmet preparation. Thiogalmet increased the yield per unit area and improved the commercial quality of the grain. Treating plants with Thiourea, Galmet and Thiogalmet ensured a 27.20, 52.08 and 68.20% yield increase, respectively, compared to the plants in the control variant. Therefore, a major effect was registered in the plants treated with the new composition. The obtained information demonstrates the possibility of mitigating the adverse effects of drought on the physiological response and production by applying antioxidants.

The influence of the hydrometeorological factors on the CO2 fluxes from the oligotrophic bog surface.

The influence of the hydrometeorological factors on the CO2 fluxes from the oligotrophic bog surface.

THE INFLUENCE OF THE TREATMENT WITH FUNGICIDES ON THE PHYSIOLOGICAL PROCESSES IN PRUNUS PERSICA (L.) BATSCH ATTACKED BY MONILINIA FRUCTIGENA (ADERH. & RUHL.) HONEY

Researches regarding the influence of the treatment with fungicides on the physiological processes were carried out on Prunus persica (L.) Batsch, Redhaven variety, cultivated in the climatic conditions in Oltenia region. The physiological researches were performed on July 20th 2022, both for peach trees treated with Dithane M-45 (0,2%) fungicide and also for the peach trees attacked by Monilinia fructigena (Aderh. & Ruhl.) Honey, in which treatments have not been performed. In the leaves of the plants attacked by the pathogen it was observed that the physiological processes’ intensity (photosynthesis and transpiration intensity) is lower as a result of the effects produced by the pathogen manifested by drying young shoots with the convexity of their top, the presence of brown spots on the fruits and the appearance of the fructifications of the pathogen. In the attacked leaves there were recorded lower values of chlorophyll content, in comparison with the leaves of plants treated with fungicide, thus existing a positive correlation between this content and the photosynthesis intensity.

THE EFFECTS OF THE TREATMENT WITH FUNGICIDES ON THE PHYSIOLOGICAL PROCESSES IN PRUNUS AVIUM L. ATTACKED BY STIGMINA CARPOPHILA (LÉV.) M.B. ELLIS

Researches regarding the effects of the treatment with fungicides on the physiological processes were carried out on Prunus avium L.,Carmen variety, cultivated in the climatic conditions in Oltenia region. Physiological research was carried out on June 26 th 2022, on cherry trees treated with the fungicide Dithane M45 (0.2%), in comparison with cherry trees attacked by Stigmina carpophila (Lév.) M.B. Ellis in which no treatments were performed. In the leaves attacked by the pathogen it was noticed that the photosynthesis intensity and transpiration intensity record lower values as a result of the effects produced by the pathogen manifested by the emergence of small pink-purple spots, bounded by a reddish-brown border, that gradually enlarges and become necrotic at the centre. The linear regressions performed between the physiological processes intensity and the photosynthetic active radiation, the leaf temperature and the stomatal conductance show a positive correlation between these. In the attacked leaves there were recorded lower values of chlorophyll content, in comparison with the leaves of plants in which fungicide treatments have been performed.

The effect of soil liming, nitrogen and potassium application on the growth, development and physiological parameters of Calendula officinalis L.

The effect of soil liming and the addition of different doses of nitrogen and potassium on the growth, development and operation of FAS pot marigold plants (Calendula officinalis L. abrikosovy jam variety was studied. Experimental options: option 1 (control); option 2 (lime 4.6 t/ha); option 3 (lime 4.6 t/ha, N70K140); option 4 (lime 4.6 t/ha, N100K200). The plants were grown at an illumination intensity of PAR 200 mmol/m2, with a photoperiod of 12 hours before the flowering stage. The results of the study showed that the application of lime and mineral fertilizers significantly increased the biomass, height, leaf area of plants and the intensity of photosynthesis, accelerated the development of plants compared with the control. At the same time, the greatest influence on plant productivity was exerted by the introduction of lime into the soil, which caused a maximum increase in the intensity of photosynthesis and the water use efficiency (WUE), an increase in the number of inflorescences and their mass. The addition of urea and potassium sulfate caused an additional increase in plant weight and leaf area. There was no significant effect of nitrogen and potassium addition on the chlorophyll content, stomatal conductance, transpiration intensity and WUE.

Compacted crops of medicinal and essential oil crops

The characteristics of the growth and development of medicinal and essential oil plants in mono and compacted crops in open ground were studied. Compacted cropping involves the joint cultivation of two (binary) or more crops in one field. Compared to monospecies crops, this method effectively solves the problems of increasing productivity and plant resistance to stress. Purpose of the work: to establish the allelopathic effect of medicinal and essential oil plants in dense sowing. The experimental methodology included the joint cultivation in open ground of medicinal main crops - spearmint (Menthaspicata L.), lemon balm (Melissaofficinalis L.), garden strawberry (Fragariachiloensis L.), and calendula officinalis (Calendulaofficinalis L.) were chosen as complementary crops.), dill (Anethumgraveolens L.). Compacted crops significantly reduce the intensity of transpiration and stomatal conductivity of the main crops. The intensity of photosynthesis largely depends on the species characteristics of the plants, so strawberry plants in binary crops increased photosynthetic activity, while mint and lemon balm on the contrary, they increased the intensity of photosynthesis during monospecies cultivation. According to the results of the studies, the inhibitory effect of calendula officinalis plants in binary crops with lemon balm, spearmint, and garden strawberries was established. At the same time, the use of dill in binary crops increases the yield of spearmint and lemon balm.

ФОТОСИНТЕТИЧЕСКАЯ ПРОДУКТИВНОСТЬ ИСКУССТВЕННО СОЗДАННЫХ ФИТОЦЕНОЗОВ С ПРИМЕНЕНИЕМ ОСАДКА СТОЧНЫХ ВОД

The results of studies on the use of sewage sludge (SS) as an unconventional chemical meliorant for the formation of antierosion vegetation cover on sand pits of technogenic origin are presented. Two variants of applying SS on the surface of the technogrunt were studied: 1 - fragmentally with a layer of 2-3 cm, 2 - with a continuous layer of 5-10 cm. In experimental variants with SS, the indicators of biological productivity for the 4th year of life were greater than in the control: plant height - by 3,5-4,5 times; reserves of aboveground phytomass - by 29 and 56 times. It is shown that long-term SS, which has undergone the processes of humification and leaching, is a promising and inexpensive meliorant suitable for increasing the fertility of sandy industrial soil and creating highly productive stable phytocenoses on them. Festuca rubra L. (the dominant species of perennial grasses) was chosen to assess the degree of SS influence on the state of artificially created phytocenoses. The efficiency of the photosynthetic apparatus (FA) of this species was estimated by the following informative indicators: the content of plastid pigments, the intensity of photosynthesis, and the chlorophyll index. It was revealed that the highest absolute indicators of aboveground phytomass and chlorophyll content are typical for plants in the experimental variant with continuous application of SS. However, the calculated indicators of the efficiency of the FA showed that the productivity of the chlorophyll unit is higher in the experimental variant with fragmentary application of SS. The maximum values of the FA performance indicators of Festuca rubra in the experimental variants were noted in the first half of the growing season. At the end of the season, due to the strong thickening of the cover and changes in the light regime, a sharp decrease in the photosynthetic activity of assimilating organs was noted. Thus, the state of artificially created stable phytocenoses, based on the estimate of photosynthetic productivity, confirms the most promising use of fragmentary application of SS during restoration activities.

Impact of anionic synthetic surfactants of lead ions and their combinations on the pigment profile of freshwater plant organisms Ceratophyllum demersum and Egeria densa

The development of human civilization inevitably leads to the development of production with increasing emissions of many chemicals into the environment. This is especially noticeable in relation to surface waters of fresh water bodies. A very alarming point is that the amount of toxic anthropogenic substances, including heavy metals, is growing every year and is increasingly disturbing the existing ecological balance. Plant organisms of water bodies are among the first to experience the effects of any anthropogenic pollutants and especially heavy metals and surfactants, the amount of which increases in the water of rivers and lakes. Very important in this is the complex of morpho-physiological adaptations associated with restructuring in the structure of chloroplasts. Changes in the content of photosynthetic pigments in plants of two species (Ceratophyllum demersum and Egeria densa) were assessed when they were exposed to very common technogenic substances (lead ions and a solution of anionic synthetic surfactants). In plants, there is a decrease in the activity of molecular transport, inhibition of H+-ATPase, leading to a decrease in the pH of the cytoplasm and activation of hydrolases, which enhance the breakdown of biopolymers. This leads to changes in the expression of individual genes and increased synthesis of a number of stress proteins. Under these conditions, the assembly of cytoskeletal elements is activated, the structures of membrane proteins and lipids change, the level of ATP decreases, free radical processes are activated and the intensity of photosynthesis is inhibited.

Активность супероксиддисмутазы и каталазы в лишайниках с разным составом фотобионтов

Data on the activity of catalase and superoxide dismutase in the thalli of the cyanolichen Peltigera praetextata and the green algal lichen Hypogymnia physodes (See Fig. 1) at different ontogenetic conditions are not available in the literature. At the same time, the study of antioxidant system of lichen thalli with different photobionts during ontogenesis is relevant and can contribute to understanding the mechanisms of adaptation of symbionts to changing environmental conditions, and also serve as indicators of the functional state of the organism. The aim of the study was to investigate the activity of catalase and superoxide dismutase enzymes in lichen thalli P. praetextata and H. physodes at different stages of ontogenesis. P. praetextata and H. physodes thalli samples were collected from aspen and pine trunks under similar ecological conditions of mixed aspen-spruce communities in the middle taiga (62°15'15.9'' N, 33°58'746.1'' E, 61°50'17'' N, 34°23'13'' E, the Republic of Karelia) and northern taiga (64°34'13.9' 'N, 43°15'48'' E, Arkhangelsk Oblast, 64° 33'19'' N, 30°20'46'' E, the Republic of Karelia). Based on morphological features, thalli samples were divided into groups of different age. P. praetextata thalli were divided into 3 groups: virginal (pregenerative, young thalli without reproduction structures), generative (thalli with apothecia and phyllidia – structures of vegetative reproduction), and senile thalli (thalli with signs of degradation over a larger area). H. physodes thalli were divided into 2 groups: virginil and senile thalli; generative thalli with apothecia are extremely rare in the study areas. Catalase activity measured based on enzymatic degradation of hydrogen peroxide, superoxide dismutase activity was determined spectrophotometrically by inhibition of photoreduction of nitroblue tetrazolium, protein content was determined by the method Bradford. Statistical analysis of the data was carried out using one-way analysis of variance. The protein content (mg/g dry mass) in P. praetextata thalli within the studied sample averaged 1.12 ± 0.09, in H. physodes thalli – 2.45 ± 0.32. The activity of superoxide dismutase (units/mg of protein) in thalli of P. praetextata reached an average of 0.34 ± 0.12, in thalli of H. physodes – 0.09 ± 0.01. The values of catalase activity (µmol H2O2/µg protein) in P. praetextata thalli averaged 2.06 ± 0.48, H. physodes – 0.49 ± 0.07. For the thalli of the cyanolichen P. praetextata, a lower (2 times) protein content (See Fig. 2) and a higher (4-5 times) activity of superoxide dismutase (See Fig. 3) and catalase (See Fig. 4) were found in compared with the chlorobiont lichen H. physodes. The species P. praetextata belongs to the group of cyanolichens, and its photobiont is cyanobacteria of the genus Nostoc located in the algal layer of the thallus. In both lichen species, the maximum values of catalase activity were established for virginal thalli, and the minimum values for senile thalli. Perhaps this is due to the high intensity of "growth respiration" of young lichen thalli, which leads to the formation of reactive oxygen species. Differences in the activity of superoxide dismutase in thalli of different ontogenetic stages in the studied species were not shown. In the thalli of P. praetextata and H. physodes, the activity of catalase in thalli from the northern taiga communities is higher than in the thalli of the middle taiga, while the activity of superoxide dismutase, on the contrary, was on average higher in the lichen thalli of the middle taiga. This might be due to variability in the intensity of photosynthesis and respiration along the latitudinal gradient. In lichens, catalase activity can be a marker of mycobiont respiration, and superoxide dismutase activity is a marker of photobiont photosynthesis. The question of contribution of the fungal or algal components of the lichen thallus to the activity of antioxidant enzymes remains open.

PHYSIOLOGICAL CHARACTERISTICS OF THE SPECIES RUSCUS ACULEATUS L. ADAPTED TO THE CLIMATIC CONDITIONS OF THE SOUTH-WESTAREA OF THE OLTENIA REGION-ROMANIA

Ruscus aculeatus L. is a protected species represented by significant populations in the the southwest area of the Oltenia region.The studies carried out in Mehedinti County, within the forests of Corcova locality, were conducted between July and September 2023, during a period characterised by minimal precipitation. In these conditions, Ruscus aculeatus plants were notably unaffected, with chlorophyll levels remaining relatively stable.The values of photosynthesis intensity remained constant during the determinations and were not influenced by the water regime. While these values may be considered low compared to other species, they are correlated with stomatal conductance and transpiration intensity.Despite the general intolerance of most shade plants to dry soil, Ruscus aculeatus demonstrates an exceptional ability to adapt to both shade conditions and severe drought.

Promising photosynthetic parameters Y(II) and NPQ for predicting barley drought tolerance

The purpose of the current work was to identify photosynthetic parameters that are predictors of barley drought tolerance, determined at early stages of development, and to verify the results obtained in field conditions. The study was carried out with the barley varieties ‘Leon’, ‘Ratnik’ and ‘Foks 1’, used in mutation breeding to develop drought-resistant genotypes. Drought was modeled by stopping irrigation. Plant resistance was estimated by changes in chlorophyll fluorescence (Fv /Fm, Y(II), NPQ) and morphometric parameters (leaf length, wet and dry weight) compared to the control group with normal water supply. Under stress-free conditions, the variety ‘Leon’ demonstrated a statistically significantly lower efficiency of photosynthesis in terms of Y(II) and Fv /Fm (0.535 ± 0.005 and 0.776 ± 0.004, respectively) in comparison with other varieties (0.577 ± 0.005 and 0.788 ± 0.001 for the variety ‘Foks 1’; 0.574 ± 0.004 and 0.787 ± 0.001 for the variety ‘Ratnik’). When modeling drought, there has been established a decrease in all morphometric indicators for all varieties relative to the control, with the highest degree of inhibition for the variety ‘Ratnik’ (70.16 ± 3.88 %; 8.09 ± 0.73 %; 68.50 ± 4.42 % for leaf length, wet and dry weight, respectively) and with the lowest degree for the variety ‘Leon’ (88.06 ± 7.83 %; 26.51 ± 7.11 %; 79.32 ± 11.17 %, respectively). A decrease in the photosynthesis intensity was manifested in the suppression of Fv /Fm and Y(II) and an increase in NPQ, with the earliest changes in the parameters Y(II) and NPQ in the varieties ‘Foks 1’ and ‘Ratnik’ (on the 4th and 5th day, respectively), compared to the variety ‘Leon’ (on the 7th day). In the field conditions, there has been estimated productivity of the varieties and its dependence on precipitation. A positive correlation between the difference in yield of two varieties ‘Leon’ and ‘Ratnik’, contrasting in their response to drought, and the amount of precipitation during the active vegetation period in 2014–2017 and 2022 (Pearson’s R2 = 0.77, p < 0.05) has been identified. The most sensitive parameters of photosynthesis, which can be used to predict resistance to moisture deficiency, were Y(II) and NPQ.

Exploring the fluorescence action spectrum of photosynthesis

The mathematical study of the fluorescence action spectrum of photosynthesis was performed. The calculation of typical spectra for photosynthesis was done for the red and blue frequencies. The transition of the action spectrum of photosynthesis from wavelengths to the frequency scale was completed. A numerical method based on the use of the inverse Fourier transform approach was used to obtain a relaxation curve for the impulse (time) characteristic of fluorescence. It turned out that the radius vector of the module of impulse response in polar coordinates makes one half-turn or half of the period of light oscillations in time. It was established that the optical medium of a plant during the relaxation time has a negative space charge of electrons, inverse properties and properties of the coherent radiation. The condition of neutrality of the material environment is not met. It was found that the ratio of the variable chlorophyll fluorescence for red and blue light has almost the same value. An analysis of the dependence of the quality factor of the chlorophyll spectrum on frequency shows that the fluorescence energy loss in blue light significantly exceeds the energy loss in red light. The proposed method can be used for express analysis of the intensity of photosynthesis. It was also concluded that plants can emit ultra-wideband signals. The relaxation time of chlorophyll fluorescence is shorter than the relaxation time of electronic polarization in atoms (molecules). As a result, a population inversion is created in the optical medium of chlorophyll - there are more atoms in the upper energy level than in the lower level. Due to this, stimulated emission and amplification of light of the radiative recombination occur. In this case, the emission of fluorescence light becomes coherent. All these properties of plants are considered for the first time and have not been described either in domestic or in foreign articles.