Fluorescence Induction Parameters Research Articles

The influence of powdery mildew (Sawadaea bicornis (Wallr.) Miyabe) on chlorophyll fluorescence in Norway maple (Acer platanoides L.) seedlings

The article presents the results of research on impact of Sawadaea bicornis (Wallr.) Miyabe on the state of photosynthetic apparatus in Acer platanoides L. seedlings using a technique of chlorophyll fluorescence induction (ChlF) measurement, which at the present time can be implemented through the use of biosensors. The research was conducted in September 2022 in the territory of the Botanical Garden of Oles Honchar Dnipro National University. To diagnose a violation of the native chlorophyll photosynthesis in fresh leaves of A. platanoides, a portable fluorometer “Floratest” was used (selected spectral range for fluorescence intensity measurement was 670–800 nm). The research was carried out on fresh leaves of Norway maple seedlings both not unaffected and affected with powdery mildew. Analysis of the data obtained indicates a high sensitivity of the parameters of chlorophyll fluorescence induction to damage by the disease regardless of environmental conditions of local growth of A. platanoides seedlings. The high informativeness of induction changes in chlorophyll fluorescence in the structural organization of chloroplasts in Norway maple leaves determined by the parameters Fo, Fm, Fv, Fv/Fо, Fv/Fm, (Fm–Fst)/Fst, (Fp–Fо)/Fv was revealed. This study demonstrated the effectiveness of using the studied chlorophyll fluorescence parameters to detect severe stress in Norway maple seedlings caused by powdery mildew exposure when the fungus affects more than 50% of the leaf blade area. It is further necessary to conduct dynamic studies throughout the growing season to determine the effectiveness of using these parameters to detect mild stress in the early stages of infection. Therefore, our research showed that the method of induction of chlorophyll fluorescence using the “Floratest” device allows you to quickly determine the general condition of the plant by evaluating photosynthesis, which is the main life process. Analysis of chlorophyll fluorescence parameters is a powerful and effective tool for determining the effect of a parasitic fungus on a plant.

Effect of antigibberellins on morphogenesis, photosynthetic apparatus, productivity and their residual content in tomato fruits

The application of growth and development regulators on crops in order to optimize their production process is one of the leading tasks of modern plant physiology. Retardants – gibberellin inhibitors are widely used for this purpose. We investigated the effect of foliar treatment with EW-250, ССС-750 and 2-СEPA on morphogenesis, leaf apparatus, content of photosynthetic pigments, indices of chlorophyll fluorescence induction, CO2 gas exchange, and residual amounts of drugs in the fruits of tomato (Lycopersicon esculentum Mill.) Bobcat hybrid. The field experiment was laid on plots with an area of 33 m2. The treatment of the plants was carried out at the budding stage. Morphometric indices were determined at the stages of flowering and fruit formation. The chlorophylls content was determined in the raw material by the spectrophotometric method. Indices of photosystem II (PSII) photochemical activity were determined according to the parameters of chlorophyll fluorescence induction after a half-hour exposure of plants in the dark using a portable single-beam fluorimeter "Floratest". The determination of the residual content of retardants in the fruits was carried out on a Shimadzu GC gas chromatograph with a mass spectrometric detector – GCMS- QP2020 EI. All gibberellin inhibitors reduced linear plant size. The number of leaves on the plants decreased under 2-CEPA treatment, and increased after the application of EW-250. Treatment with 2-CEPA decreased, EW-250 significantly increased, and CCC-750 practically did not change the leaves’ fresh and dry weight. Leaf area and leaf index decreased under 2-CEPA treatment, but practically did not change when EW-250 and ССС-750 were applied. All antigibberellin drugs increased the leaf specific leaf weight and thickened the leaf lamina due to the growth of chlorenchyma cells. At the same time, growth inhibitors increased the volume of columnar parenchyma cells and practically did not change the size of spongy parenchyma cells. Retardants increased the chlorophylls content in leaves, while the ethylene producer 2-CEPA did not change this index. The plants’ chlorophyll index after treatment with drugs increased significantly. The whole plant dry weight increased under EW-250 treatment, decreased after 2-CEPA application, and did not change under CCC-750. It was established that the photosynthetic rate increased under the EW-250 treatment, both in the flowering stage and in the stage of fruit formation, while when using 2-CEPA and CCC-750, it occurred only at the stage of fruit formation. The most significant positive changes of PSII photochemical activity indices were observed under the use of EW-250. Under the action of the drug, the maximum and actual quantum efficiency of PSII increased, the linear electron transport accelerated, and the fraction of reaction centers that did not transfer electrons from the primary acceptor QA to QB decreased, at the same time the chlorophyll fluorescence decay coefficient significantly increased, which indicates an increase in the CO2 assimilation intensity. Retardants increased the proportion of the fruit in the whole plant dry weight. All growth regulators increased net photosynthetic efficiency. A significant increase in fruit yield occurred under EW-250 treatment. When using CCC-750, the index tended to increase, while under the influence of 2-CEPA the yield decreased. The residual amounts of EW-250 and CCC-750 in the fruits did not exceed the maximum permissible concentrations.

Phytochrome-Dependent Regulation of Melon Resistance to Fusarium Wilt

The effect of pre-sowing seed treatment with light in the red spectral region on the resistance of melon plants (Cucumis melo) of the cultivar Kichkintoy to Fusarium wilt damage caused by Fusarium oxysporum f. sp. melonis was investigated. The directly-opposite effects of red and far red light on the degree of plant damage by the pathogen, which was determined by the special symptoms of the disease on the leaves and stems of plants, were revealed. When alternating seed treatment with red and far red light, the final effect was determined by the type of irradiation that acted last. The results of photobiological testing made it possible to establish the participation of the phytochrome system in the control of the resistance of melon plants of the cv. Kichkintoy to Fusarium wilt. It is shown that there is a high positive correlation between the parameters of chlorophyll fluorescence induction of leaves reflecting the functional activity of the photosynthetic apparatus and the degree of damage to plants grown from non-irradiated seeds and seeds irradiated with red light. The results of the conducted studies establish the possibility of effective regulation of the resistance of the melon cv. Kichkintoy to the defeat of F. oxysporum f. sp. melonis through photoactivation of the phytochrome system of seeds before sowing.

ASSESSMENT OF THE COMPLEX INFLUENCE OF BIOPREPARATIONS ON THE PROCESS OF CHLOROPHYLL FLUORESCENCE INDUCTION IN POTATO LEAVES BY ORGANIC CULTIVATION TECHNOLOGY

Organic farming is gaining increasing popularity due to growing demand for environmentally friendly organic produce. However, to cultivate high and sustainable yields of organic products, it is important to use biological preparations. Biological preparations have different mechanisms of action aimed at improving nutrient availability and absorption, enhancing physiological processes, stimulating plant growth and development, as well as protecting crops from diseases and pests. To optimize the cultivation technology and select the right combination of biological preparations, research is necessary to demonstrate the impact of these preparations on plants at different stages of development. The aim of this study was to determine the comprehensive effect of biological preparations with different functionalities depending on the methods of application on the induction of chlorophyll fluorescence in potato leaves under organic cultivation technology. The research was conducted at the Volyn State Agricultural Research Station of the National Academy of Agrarian Sciences of Ukraine. In a two-factor study, the effects of the EcoStern destructor at a dose of 1.2 liters/hectare and the biological preparations Mikohelp, Agat, Regoplant, Fitohelp, and Stimp were investigated. Measurements of chlorophyll fluorescence induction parameters were carried out using the portable fluorometer "Flora-test," which provides express diagnostics of the plant's condition at early stages of its development. The comprehensive application of the biodestructor with biological preparations resulted in the improvement of photosynthetic processes. An increase in the parameters Fmax, Fv, Fv/Fmax, (Fmax - Fst)/Fst relative to the control was established. The best results in terms of photosynthesis productivity (Fv/Fmax) were observed with the application of the biodestructor EcoStern (1.2 liters/hectare) in combination with the application of Mikohelp in the soil at 2.0 liters/hectare and foliar application of Fitohelp at 1.0 liter/hectare.

Physiological and biochemical parameters of drought tolerance of some genotypes of garden roses

To identify drought resistance of the studied genotypes of garden roses during the period of maximum probability of drought on the Southern Coast of the Crimea, the water regime, proline concentration, enzyme activity and chlorophyll fluorescence induction parameters under controlled dehydration were studied. Analysis of water regime parameters showed that under conditions of water stress, the best water-holding and recovery capabilities were shown by leaves of cv. ‘Borisfen’ and R. hugonis species. Species R. indica, R. bracteata, R. rouletti, R. foetida showed instability of water regime under conditions imitating dry weather. Studies of changes in biochemical parameters revealed that under relatively mild wilting conditions after removal of stress, metabolic processes are restored in R. hugonis, R. bracteata, R. indica and cv. ‘Borisfen’. Wilting under conditions imitating dry weather does not cause irreversible metabolic disturbances in R. hugonis, R. bracteata, and cv. ‘Borisfen’. Under different wilting conditions, cv. ‘Borisfen’and R. foetida species had relatively stable functioning of FS II. Simulation of dry weather led to irreversible disturbances in the oxygen-releasing complex and thylakoid destruction in R. gallica during the stressor, and in R. indica and R. bracteata species - after recovery of water availability. The highest drought tolerance is in in cv. ‘Borisfen’and R. hugonis sprcies.

Effects of chilling on the photosynthetic performance of the CAM orchid Phalaenopsis.

Crassulacean acid metabolism (CAM) is one of the three main metabolic adaptations for CO2 fixation found in plants. A striking feature for these plants is nocturnal carbon fixation and diurnal decarboxylation of malic acid to feed Rubisco with CO2 behind closed stomata, thereby saving considerable amounts of water. Compared to the effects of high temperatures, drought, and light, much less information is available about the effects of chilling temperatures on CAM plants. In addition a lot of CAM ornamentals are grown in heated greenhouses, urging for a deeper understanding about the physiological responses to chilling in order to increase sustainability in the horticultural sector. The present study focuses on the impact of chilling temperatures (10°C) for 3 weeks on the photosynthetic performance of the obligate CAM orchid Phalaenopsis 'Edessa'. Detailed assessments of the light reactions were performed by analyzing chlorophyll a fluorescence induction (OJIP) parameters and the carbon fixation reactions by measuring diel leaf gas exchange and diel metabolite patterns. Results showed that chilling already affected the light reactions after 24h. Whilst the potential efficiency of photosystem II (PSII) (Fv/Fm) was not yet influenced, a massive decrease in the performance index (PIabs) was noticed. This decrease did not depict an overall downregulation of PSII related energy fluxes since energy absorption and dissipation remained uninfluenced whilst the trapped energy and reduction flux were upregulated. This might point to the presence of short-term adaptation mechanisms to chilling stress. However, in the longer term the electron transport chain from PSII to PSI was affected, impacting both ATP and NADPH provision. To avoid over-excitation and photodamage plants showed a massive increase in thermal dissipation. These considerations are also in line with carbon fixation data showing initial signs of cold adaptation by achieving comparable Rubisco activity compared to unstressed plants but increasing daytime stomatal opening in order to capture a higher proportion of CO2 during daytime. However, in accordance with the light reactions data, Rubisco activity declined and stomatal conductance and CO2 uptake diminished to near zero levels after 3 weeks, indicating that plants were not successful in cold acclimation on the longer term.

Field Study of the Effects of Two Different Environmental Conditions on Wheat Productivity and Chlorophyll Fluorescence Induction (OJIP) Parameters

Wheat is one of the main cereal crops for ensuring food supply. Thus, increasing grain yield is a major target for plant breeders, where insights into wheat productivity can be gained by studying the activity of the components of photosynthetic apparatus. The objectives of this study were to evaluate the agronomical performance of three winter wheat varieties and test photosynthetic efficiency over two different locations. Chlorophyll fluorescence was used to evaluate the maximum quantum yield of photosystem II (PSII) (TR0/ABS) and performance index on absorption basis (PIabs) of flag leaves and glumes of heads at the flowering stage until the mid-senescence stage. The grain yield of all varieties on average was significantly higher at Osijek compared to Tovarnik. Variety Tika Taka exhibited the highest yield reduction (27.1%) at Tovarnik compared to Osijek, followed by El Nino (20.5%) and Vulkan (18.7%), respectively. A higher amount of precipitation in June at Tovarnik provoked higher Fusarium head blight disease intensity, which could be seen as the bleaching of plant heads at the plots and resulted in an earlier decrease in photosynthetic activity. Therefore, earlier senescence and contracted grain fill duration could occur.

The effect of moisture deficiency on the photosynthesis of evergreen shrubs of the genus Cotoneaster L

The paper presents data on the features of the water regime (water deficit, water-retaining forces, and total hydration of leaf tissues) in four evergreen species of the genus Cotoneaster , as well as the effect of the growing water stress on the course of primary photosynthesis processes. It was found that during the periods of maximum impact of dry factors of the summer season on the Southern Coast of the Crimea, the species Cotoneaster salicifolius and Cotoneaster graucophyllus var. serotinus show signs of increased drought resistance, which is manifested in the ability to economically consume moisture by leaf tissues during wilting, and subsequently restore the normal turgescence of leaf tissues. These species maintained minimal levels of water deficit in the leaves, and the sublethal level was 12% water loss. The genotypes Cotoneaster × watereri 'Cornubia' and Cotoneaster franchetii showed relatively weak water retention capacity combined with low leaf repair capability. Water loss of more than 8-10% was already critical, after which the number of intact leaf blade tissues was unsatisfactory (less than 60%). It was found that the parameters of chlorophyll fluorescence induction (CPI) are most sensitive to lack of moisture and they are features of fast phase. Water deficiency within 10% leads to irreversible disturbances in the photosynthetic apparatus in Cotoneaster franchetii , which was expressed in a decrease in the ratio of variable and base fluorescence below the norm of vitality and the absence of pronounced peaks on the CPI curve. In the species Cotoneaster salicifolius and Cotoneaster graucophyllus var. serotinus , an increase in the level of water deficiency was accompanied by a decrease in the efficiency of the light phase of photosynthesis and an increase in the number of unrecoverable Q a in the reaction centers of PS2. However, these changes were reversible. It is concluded that the species Cotoneaster salicifolius and Cotoneaster graucophyllus var. serotinus are relatively resistant to lack of moisture and are characterized by a high level of water-retaining forces and stable operation of the photosynthetic apparatus. Controlled wilting in combination with the CPI method can be used for quick diagnostics of the drought resistance of Cotoneaster species.

Effect of Cameraria ohridella feeding on Aesculus hippocastanum photosynthesis

The complex of invasive species of phytophagous insects that can adapt to novel living conditions is constantly increasing. The ecological effect of their vital activity in the new environment is almost impossible to predict. As a result, invasions undesirable in the economic sense are often observed. The horse -chestnut leaf miner (Cameraria ohridella Deschka & Dimič, 1986, Gracillariidae) is one of these problematic invader species in the introduced range of the horse chestnut (Aesculus hippocastanum (Linnaeus, 1753), Sapindaceae). We studied the effect of C. ohridella on the state of the photosynthetic apparatus in Ae. hippocastanum leaves. Photosynthesis is the one of the processes most vulnerable to stress factors, so information about the state of photosynthetic apparatus in a plant under the influence of phytophage feeding obtained with fluorescence analysis can be significant. The feeding effect of C. ohridella caterpillars on the functional state and activity of Ae. hippocastanum photosynthetic apparatus was studied. We studied critical parameters of chlorophyll fluorescence induction reflecting the effect of a single C. ohridella generation (feeding the caterpillar for the five stages of this species’ development) on the functional links of the photosystem II in Ae. hippocastanum leaves. The data obtained show a decrease in PS II quantum efficiency (inhibition of photosynthetic activity) in the leaves from different parts of the crown; it suggests the destructive effect of C. ohridella caterpillar feeding on Ae. hippocastanum photosynthetic apparatus. Values of all key parameters of chlorophyll fluorescence indication evidence inhibition of photophysical and photochemical processes of photosynthesis and impaired coherence of Calvin cycle reactions. Study of the feeding effect of C. ohridella caterpillars on the efficiency of the main enzyme in the Calvin cycle (which closely correlates with the coefficient of fluorescence induction that characterizes the efficiency of dark photosynthetic processes) showed a significant decrease in its activity in the leaves of both the illuminated and shaded parts of the crown. Our study has shown that the method of chlorophyll fluorescence induction allows one to determine the general state of a plant in an express regime by evaluating the main process of plant life as photosynthesis. Analysis of chlorophyll fluorescence parameters is a powerful and effective tool for determining the effect of phytophages on the plant body. The obtained data allow us to apply the method of analyzing chlorophyll fluorescence induction in practice to establish the physiological state of tree flora in forests and garden farms.

Comparative Study of Drought Stress Effects on Traditional and Modern Apple Cultivars.

Genotype-dependent responses of apples to drought stress were evaluated between commercial and traditional apple cultivars. The results indicate different mechanisms of tolerance to investigated drought stress conditions. Chlorophyll fluorescence induction (OJIP) parameters, chlorophyll and carotenoid content, malondialdehyde (MDA), hydrogen peroxide (H2O2), proline, phenols and leaf water content (WC) were measured. The traditional cultivar “Crvenka” confirmed the best tolerance to a drought stress condition, presenting higher photosynthetic efficiency, higher leaf water content, higher levels of chlorophyll content and lower lipid peroxidation with greater membrane stability. The commercial cultivar “Golden Delicious Reinders” showed decreased water content in leaves, increased lipid peroxidation levels and photoinhibition. Considering all results, the commercial cultivar “Golden Delicious Reinders” was adversely affected by drought, while traditional cultivars exhibited better tolerance to drought stress.

Some special features of the water regime and the photosynthetic apparatus activity in Feijoa sellowiana (O. Berg) O. Berg plants under the water stress

When assessing the drought tolerance of Feijoa sellowiana cultivars and forms, the total water content in leaf tissues and their waterretaining and regenerative capacity were determined, and the parameters of chlorophyll fluorescence induction were measured at different water content in leaves. Current-year leaves were characterized by a higher sensitivity to drought. According to the complex of water regime parameters and characteristics of the chlorophyll fluorescence induction (CFI), it was found that the cultivar Aromatnaya Fantazia and the form 3/1 are characterized by a relatively high drought tolerance. It has been demonstrated that the common method for assessing plant tolerance by the index of their water-retaining forces, in relation to Feijoa sellowiana genotypes, does not allow determining the critical level of water deficit. It has been found that in the cultivars and forms with low water stress tolerance, with the water loss of 20-25% from the leaf tissues complete hydration, irreversible irregularities in the PS II structures occurred. The most sensitive to the lack of water in the leaves were such parameters as variable fluorescence, rate constants of the photochemical and non-photochemical deactivation of the excitation, as well as the processes of Qa reduction in the reaction centers of PS II.

Impact of negative temperatures on the state of the photosynthetic apparatus of evergreen species of <i>Osmanthus</i> Lour. genus

The results of studies of photosynthetic processes in annual leaves of two species of the genus Osmanthus - Osmanthus x fortunei and O. fragrans in the cold period on the Southern coast of the Crimea and under the controlled action of negative temperatures are presented. It is shown that the main parameters of chlorophyll fluorescence induction (CFI) in annual leaves of O. x fortunei was relatively more stable during the winter months compared to O. fragrans . The effect of temperature -8,0°C for 8 hours on the leaves of the species in O. fragrans caused a decrease in the fluorescence decay coefficient to the lower limit of the norm of vitality and a significant increase in the processes of thermal dissociation of light energy. It is established that the temperature is -10°C is critical for the leaves of O. fragrans , which indicates its lower frost resistance. Changes in the state of PSII depend on both the duration and intensity of low-temperature exposure. It was found that for the more resistant species of O. x fortunei a relatively long-term effect of -10,0°C and a short one of -8,0°C temperature have a similar effect on the state of the photosynthetic apparatus, which is probably due to the activation of protective mechanisms.

Physiological and biochemical parameters of apricot cultivars under drought conditions on the Southern Coast of the Crimea

In order to determine special features of the photosynthetic apparatus activity and the content of thread compounds in various apricot cultivars during the period of maximum drought probability on the Southern Coast of the Crimea, we studied the concentration of proline, phenolic compounds and chlorophylls, as well as the parameters of chlorophyll fluorescence induction (CFI) in some apricot cultivars ( Prunus armeniaca Lam.), characterized by various degree of drought tolerance (‘Alupkinsky’, ‘Krymskiy Amur’) are weakly resistant; Khurmai cultivar is characterized by labile resistance, and the cultivars Kazachok, Professor Smykov, Nagycorosi Orias are drought tolerant cultivars). It has been found out that drought-resistant cultivars are characterized by a relatively low content of proline in their leaves. It is supposed that this amino acid is involved in the protective reactions of apricot plants under water stress. The results of the photosynthetic apparatus studies in the presented cultivars demonstrated that in leaves, water loss less than 20% caused reversible changes in the parameters of CFI. An increase in the water deficit up to 25-30% caused the destruction of PS2 in weakly drought-resistant cultivars. The most stable photosynthetic apparatus activity was noticed in the cultivar Nagycorosi Orias. Deviations in photosynthesis processes were most pronounced during the period of water restoration in leaves.

Acclimation of photosynthetic processes and metabolic responses to elevated temperatures in cereals.

The aim of the present work was to better understand the molecular mechanisms of heat acclimation processes in cereals. A large number of winter and spring wheat, barley and oat varieties were grown under either control conditions (22/20°C) or under a mild heat stress (30°C) that induce the acclimation processes. The temperature dependence of chlorophyll a fluorescence induction and gas exchange parameters showed that heat acclimation increased the thermotolerance of the photosynthetic apparatus, but these changes did not differ sharply in the winter-spring type cereals. Similarly, to wheat, elevated temperature also led to increasing transpiration rate and reduced water use efficiency in barley and oat plants. A non-targeted metabolomic analysis focusing on polar metabolites in two selected barley (winter type Mv Initium and spring type Conchita) and in two oat varieties (winter type Mv Hópehely and spring type Mv Pehely) revealed substantial differences between both the two species and between the acclimated and non-acclimated plants. Several compounds, including sugars, organic acids, amino acids and alcohols could be separated and detected. The expression level of the CYP707, HSP90, galactinol synthase, raffinose synthase and α-galactosidase genes showed genotype-dependent changes after 1 day; however, the CYP707 was the only one, which was still upregulated in at least some of the genotypes. Results suggest that heat acclimation itself does not require general induction of primary metabolites. However, induction of specific routes, e.g. the induction of the raffinose family oligosaccharides, especially the synthesis of galactinol, may also contribute the improved heat tolerance in cereals.

Studying the Slow Induction of Chlorophyll Fluorescence for Separation Tomato Fruits by their Maturity

The maturity of tomatoes serves as a basic parameter that determines their quality. Available maturity monitoring tools allow to measure the reflection coefficients of light from the surfaces of tomato fruits at certain wavelengths. These devices have the disadvantage of insufficient reliability in assessing the stages of maturity of tomatoes, they do not take into account their internal quality and structure. (Research purpose) The research purpose is in studying the dependence of the maturity of tomatoes on the level of slow induction of chlorophyll fluorescence. (Materials and methods) The article proposes a new method for separating tomato fruits according to their maturity, eliminating the inaccuracies of existing methods, based on the physical phenomenon of slow induction of chlorophyll fluorescence. During the experiment, three botanical varieties of tomatoes with different colors of mature fruits were used: “Alcazar” (red); “Wild rose” (pink); “Orange” (yellow). Five levels of maturity of single-sized tomato fruits were selected for each variety. Authors performed a variance analysis and comparison of the average values for the Duncan criterion with the significance level at α ≤ 0.05 using statistical analysis of the SPSS V. 20 software. (Results and discussion) The article presents general pattern for these tomato varieties: as the fruit matures, the value of their maximum fluorescence induction Fm and the coefficient of specific photosynthetic activity of tomatoes Kf decreases. The differences between the maturation stages with Fm and Kf are statistically significant at α ≤ 0.05. Regardless of the botanical variety, there are high negative correlations obtained for parameters of slow chlorophyll fluorescence induction, such as Fm and Kf with maturity. (Conclusions) The dependence of the decrease in the maximum fluorescence levels of chlorophyll with an increase in the maturity of tomato fruits was found. The proposed method allows to reliably separate tomato fruits with any color of mature fruits.

Physiological and biochemical parameters of Ficus species and cultivars under dehydration conditions on the Southern coast of the Crimea

The results of the studies of proline content, peroxidase, catalase, polyphenol oxidase activity and chlorophyll fluorescence induction (ChFI) parameters in leaves of Ficus species and cultivars under controlled dehydration conditions are presented. It was shown that the ChFI parameters, the most sensitive to the lack of water availability, are the characteristics of the chlorophyll fluorescence fast phase. Proline content, peroxidase and polyphenol oxidase activity can be used to addition diagnose of drought resistance of the plants of the genus Ficus. The cultivars Sabrutsiya Rozovaya, Sary Stambulskij and the species F. palmata are relatively drought tolerant.

Physiological and Biochemical Aspects of Frost Resistance in Оlea europaea L.

The results of studies on the frost resistance of Olea europaea L. varieties and its subspecies O. europaea subsp. cuspidata (Wall. and G. Don) Cif. under the conditions of the Southern Coast of Crimea (SCC), as well as the influence of temperature close to the absolute minimum value (–15°С) on the state of the photosynthetic apparatus, catalase activity, polyphenol oxidase, and the content of proline and phenolic compounds, are shown. It was established that a relatively high frost resistance is characteristic of the Nikitskaya variety under the conditions of the SCC. Varieties Ascoliano, Coregiolo, and Razzo turned out to be slightly frost-resistant. Minimum resistance was detected in the subspecies O. europaea subsp. cuspidata. The temperature of –15°C led to irreversible disruptions in the photosynthetic apparatus of weak varieties Razzo, Coregiolo and O. europaea subsp. cuspidata, which manifested in a significant decrease in photosynthetic activity immediately after the end of low-temperature exposure (by 80.19, 50.0, and 89.78%, respectively) as well as a fluorescence decay coefficient below the vital norm. After 24 h, a slowdown in the decrease in the parameters of chlorophyll fluorescence induction (CFI) was noted in the Ascoliano and Nikitskaya varieties. It was revealed that negative temperatures contribute to a decrease in the activity of catalase in weakly resistant O. europaea genotypes (by 40–60% on average) in contrast to the frost-resistant variety Nikitskaya, in which the activity of this enzyme remained almost unchanged. The change in polyphenol oxidase activity was multidirectional. In the Razzo and Coregiolo varieties, an increase in polyphenol oxidase activity was noted (19 and 24%, respectively). A decrease (by 8 and 37%, respectively) was noted in the subspecies O. europaea subsp. cuspidata and Nikitskaya variety. It was shown that, under the influence of negative temperatures, representatives of O. europaea decrease proline concentration in leaf tissues (by 17–55%). The most significant changes were detected in the variety Coregiolo (by 45.09%). The total content of phenolic compounds decreased in all weakly frost-resistant varieties and O. europaea subsp. cuspidata by 7–42% and remained unchanged in the frost-resistant variety Nikitskaya. It has been established that negative temperatures cause irreversible changes in the photosynthetic apparatus in weakly resistant representatives of O. europaea. The correlation of the degree of frost resistance of the studied genotypes with the activity of catalase and with the content of proline and phenolic compounds in leaf tissues was revealed.

Physiological and biochemical parameters of apricot varieties characterized by various drought resistance

The aim of the presented work was to identify the peculiarities of the photosynthetic apparatus, the activity of redox enzymes and proline content in apricot varieties with different drought tolerance. Four apricot varieties such as Kazachok, Nagycorosi Orias, Khurmai and Krymsky Amur were used as objects of the studies. To determine the effect of drought on the state of the photosynthetic apparatus, a series of experiments was carried out to analyze chlorophyll fluorescence induction (ChFI) parameters, peroxidase and polyphenol oxidase activity and proline content in apricot leaves. It was found out that in summer 2018, when the amount of precipitation exceeded the climatic norm, during the period of the maximum drought probability, catalase activity decreased, polyphenol oxidase activity increased or was unchanged and the proline content did not change significantly. Extremely arid conditions in summer 2019 resulted in peroxidase and polyphenol oxidase activation and a decrease in the proline concentration in all the studied apricot varieties. However, the drought tolerant variety Nagycorosi Orias was characterized by the most stable indexes of peroxidase activity during the entire experiment. A decrease in the leaf tissue hydration was the reason for the increase in the base fluorescence and the decrease in the correlation index of the rate constants of photochemical and nonphotochemical deactivation of excitation in PS 2. In the drought tolerant varieties Nagycorosi Orias and Kazachok changes in the ChFI parameters were reversible. It has been demonstrated that disturbances during primary photosynthetic processes were most pronounced during the restoration of turgidity. It was revealed that the most sensitive parameters of ChFI in apricot are the characteristics of the fast phase. A decrease in reparative abilities in the midsummer was probably associated with age-related changes in leaves and fruit load.

Interaction between elevated temperature and different types of Na-salicylate treatment in Brachypodium dystachion

Salicylic acid (SA) plays a role in several physiological processes in plants. Exogenously applied SA is a promising tool to reduce stress sensitivity. However, the mode of action may depend on how the treatment was performed and environmental conditions may alter the effects of SA. In the present study the physiological and biochemical effects of different modes of application (soaking seeds prior sowing; spraying leaves with 0.5 mM NaSA) were compared at normal and moderately elevated temperatures (4 h; 35°C) in Brachypodium distachyon (L.) P. Beauv. plants. While soaking the seeds stimulated plant growth, spraying caused mild stress, as indicated by the chlorophyll-a fluorescence induction parameters and changes in certain protective compounds, such as glutathione, flavonoids or antioxidant enzymes. Elevated temperature also caused an increase in the glutathione-S-transferase activity, and this increase was more pronounced in plants pre-treated with NaSA. Both seed soaking or spraying with NaSA and exposure to heat treatment at 35°C reduced the abscisic acid levels in the leaves. In contrast to abscisic acid, the jasmonic acid level in the leaves were increased by both spraying and heat treatment. The present results suggest that different modes of application may induce different physiological processes, after which plants respond differently to heat treatment. Since these results were obtained with a model plants, further experiments are required to clarify how these changes occur in crop plants, especially in cereals.

Chlorophyll fluorescence for classification of tomato fruits by their maturity stage

Classification of tomato fruit and control of post-harvest maturation based on the stage of maturity at harvesting, are necessary to ensure the highest possible quality and marketability of the final ripe product. A method of sorting tomatoes to assess the degree of their maturation based on the control of their chlorophyll fluorescence induction is proposed. Tomatoes (Black baron) at five different stages of maturity were used. Variance analysis (ANOVA) was performed and the Duncan’s mean values were compared at a significance level of p ≤0.05. In addition, the correlation between the chlorophyll fluorescence induction parameters and the maturity of the same fruit was carried out using the statistical software SPSS 20.0. The general pattern of fluorescence induction analysis was revealed; as the fruit matures, the value of both maximum fluorescence induction (Fm) and the coefficient of specific photosynthetic activity of tomatoes (Kf) decreases. Both Fm and Kf exhibited a statistically significant difference (p ≤0.05) between stages of maturity. A very strong negative correlation between slow chlorophyll fluorescence induction parameters (Fm and Kf) and maturity were observed. Moreover, there is a strong positive correlation between Fm and Kf. In conclusion, the slow induction of chlorophyll fluorescence is a good indicator of the degree of maturity of tomato fruits and the proposed method had better reflected the actual ripening process of fruit per maturity stage.