Efficiency Of Photosynthetic Apparatus Research Articles

Plant growth regulators improve the yield of white lupin (Lupinus albus) by enhancing the plant morpho-physiological functions and photosynthesis under salt stress

BackgroundWhite lupin (Lupinus albus L.) is a multi-purpose, climate resilient, pulse crop with exceptionally high protein content that makes it a suitable alternative of soybean in livestock feed. Although white lupin grows well on marginal sandy soils, previous studies have reported its sensitivity towards salinity stress. This experiment aims to assess the influence of salinity stress and mitigating role of plant growth regulators (PGRs) on performance of white lupin.MethodologyThe white lupin plants were sown in pots maintained at three salinity levels (1, 3 and 4.5 dS m− 1) throughout the growing season and foliar sprayed with different PGRs, including ascorbic acid, potassium chloride, boric acid, ammonium molybdate and methionine at sowing, four weeks after emergence and at the initiation of flowering. Foliar spray of distilled water and salinity level of 1 dS m− 1 were maintained as control treatments. Data were recorded for seed germination indices, plant growth, antioxidant enzymes and photosynthetic efficiency variables.ResultsThe severe salinity stress (4.5 dS m− 1) reduced the germination indices by 9–50%, plant growth traits by 26–54%, root nodulation by 12–26%, grain development by 44–53%, antioxidant enzymes activity by 13–153% and photosynthetic attributes by 1–8% compared to control (1 dS m− 1). Different PGRs improved several morpho-physiological attributes in a varied manner. The application of potassium chloride improved seed vigour index by 53%, while ascorbic acid improved root nodulation by 12% and number of pods per cluster by 75% at the severe salinity level. The foliar application of PGRs also displayed a recovery of 140% in the activity of superoxide dismutase and 70% in catalase. The application of multi zinc displayed an improvement of 37% in plant relative chlorophyll, while ascorbic acid brought an increase of 25% in non-photochemical quenching and 21% in photochemical quenching coefficient at the severe salinity level. On contrary, the application of PGRs brought a relatively modest improvement (8–13%) in quantum yield of photosystem II at slight to moderate (3 dS m− 1) salinity stress. The correlation analysis confirmed a partial contribution of leaf area and seed vigour index to overall photosynthetic efficiency of white lupin.ConclusionsClearly, salinity exerted a negative impact on white lupin through a decline in chlorophyll content, activity of antioxidant enzymes and efficiency of photosynthetic apparatus. However, PGRs, especially ascorbic acid and potassium chloride considerably improved white lupin growth and development by mitigating the negative effects of salinity stress.

Fluorescence parameters of chlorophyll a halophytes as a response to salinity of post mining subsidence reservoirs

The increasing salinity of water in reservoirs is caused by climate change. On the other hand, an increase in salinity promotes the group species, halophytes that tolerate or need NaCl for growth. The aim of this study was to identify the response of facultative halophytes’ photosynthetic apparatus efficiency ( PE) to water salinity. The study covered the spiny water nymph ( Najas marina L.) population in four mining subsidence reservoirs. Najas marina is a facultative halophyte which means that it can occur in both fresh and salt water. This plant has the characteristics of the species invasive, such as rapid biomass growth, and wide ecological tolerance. Water salinity, described by conductivity, in the reservoirs ranged from 646 to 3061 μS∙cm –1. PE was expressed in terms of chlorophyll a fluorescence parameters, which were collected in situ using a Pocket PEA device. Water parameters using a YSI ProDSS probe were identified. Data analysis was performed using OJIP test and s the non-parametric Spearman’s rank test (p ≤ 0.05). The relationship between chlorophyll a fluorescence parameters and water parameters showed that conductivity, salinity, water clarity, and nitrate content statistically significantly affected PE (p <0.05). Generally, the higher salinity e.g. more than 3000 μS∙m –1, supports PE of facultative halophyte at the stage of optimum development in the vegetation season.

Photosynthetic apparatus efficiency, phenolic acid profiling and pattern of chosen phytohormones in pseudometallophyte Alyssum montanum

The present study investigated the response of non-metallicolous (NM) and metallicolous (M) Alyssum montanum shoots cultured in vitro on a medium supplemented simultaneously with heavy metals (HMs) to identify mechanisms involved in alleviating metal-induced damage. Plant status in respect to photosynthetic apparatus efficiency was determined and linked with changes in biochemical composition of shoots, namely phenolic acids’ and stress-related phytohormones. Results showed the considerable inter-ecotype differences in (1) the photosynthetic pigments’ amount, (2) the functioning of membrane electron transporters as well as (3) the linear and alternative electron transport pathways, whose lower values were reported in NM than in M HM-treated culture. Photosynthetic apparatus protection in M specimens was assured by the activation of cinnamic acid synthesis (by phenylalanine ammonia lyase) and its further transformations to benzoic acid derivatives with high ability to counteract oxidative stress, that was accompanied by the overexpression of jasmonic acid stimulating antioxidant machinery. In turn, detrimental HM effects on NM shoots could result from the diminution of most phenolics’ accumulation, and only the content of coumarate (produced by bifunctional phenylalanine/tyrosine ammonia lyase) and rosmarinic acid increased. All these together with an enhanced concentration of abscisic acid might suggest that NM strategy to cope with HMs is based mostly on a restriction of metal movement with transpiration flow and their limited distribution in leaves. Summarizing, our findings for the first time point out the physiological and metabolic adaptation of pseudometallophyte A. montanum to adverse conditions.

Potassium deficiency impact on the photosynthetic apparatus efficiency of radish

Potassium is an essential nutrient for plants and its limited resources impose the improvement of the fertilizer-use efficiency. To address this issue, it is important to understand its roles in the photosynthesis and to provide a quick, noninvasive method for diagnosing its deficiency in plants. The impact of potassium deficiency on the photochemical phase of photosynthesis has not been well understood. In this work, we present the K+-deficiency effect on gas exchange, chlorophyll content, and electron transport chain in two hybrid cultivars of radish. Our results showed that one of the cultivars proved to be tolerant and maintained the net photosynthetic rate at the level of the control plants. In both cultivars, the effect on the photochemical phase of photosynthesis was observed. We suspect that low K+ availability impaired the balance of the H+ influx to thylakoid lumen which increased its acidification and triggered the downregulation mechanism leading to the rearrangement of PSII complexes and an increase in energy dissipation.

The role of monochromatic red and blue light in tomato early photomorphogenesis and photosynthetic traits

Plant development and physiology are strongly influenced by the environmental light spectrum that triggers and controls several functional and structural response in plants. However, few studies investigated the effect of monochromatic light during plant photomorphogenesis from seed imbibition up to seedling development. The present research aimed to assess the mechanisms engaged by plants to optimize light harvesting and utilization of different wavelengths during the early photomorphogenesis in tomato, a high-value crop cultivated worldwide. Seeds were germinated in a growth chamber under four light treatments (100 % red light, R; 100 % blue light, B; 60 % red 40 % blue light, RB; white light, W) and seedlings were grown up to sixteen days. Hypocotyl and cotyledon development were measured during the early stages of growth. Chlorophyll fluorescence measurements, D1 and Rubisco protein expression, as well as chlorophyll and carotenoids content, were determined on the first true leaves to assess in the early growth stage the efficiency of photosynthetic apparatus. Tomato early photomorphogenesis was strongly influenced by light quality. The seedling growth under red-blue and white light determined comparable responses, enhancing both photosynthesis and biomass production compared to monochromatic treatments. The pure R light stimulated hypocotyl elongation, cotyledon expansion, plant height, and leaf area, but produced seedlings with reduced photosynthetic capacity as indicated by the lowest Rubisco content and photochemical efficiency, and the highest thermal dissipation. Monochromatic blue light induced in seedlings the highest Rubisco amount, more compact size and reduced biomass, but similar level of pigments and photochemical efficiency compared to other light treatments. Our data indicate that the lack of blue or red light negatively affects early tomato development, in term of morphology and physiology. However, blue wavelengths resulted more critical than red ones for the functionality of the photosynthetic apparatus.

Response of Potato (Solanum Tuberosum L.) Plants to Spraying by Hydrogen Peroxide

The biocidal properties of hydrogen peroxide (H2O2) could be used in plant protection. However, the effects of H2O2 foliar spraying on the performance of the potato photosynthetic apparatus are still unclear. A pot experiment was conducted to investigate the effect of foliar spraying, which was done twice, with various H2O2 concentrations (1, 3, 6, 12, and 18%) on the potato photosynthetic apparatus efficiency and antioxidant capacity. The measurements were taken four times: on the first and seventh day after each application. Foliar spraying with 1% H2O2 concentration was the most stimulating for the course of physiological processes in leaves. Further increased doses of H2O2 enhanced stress in plants which is manifested by a decrease in pigment levels, photosynthetic attributes, antioxidant capacity in leaves, and fresh mass above-ground parts of potato plants. The intensive effect of spraying was particularly observed on the first day after application, while later, the activity of the photosynthetic apparatus and antioxidant capacity increased. The study provides information that foliar spraying with 1% H2O2 can be taken into account in further research on the development of a potato plant protection methods.

Manganese Repairs the Oxygen-Evolving Complex (OEC) in Maize (Zea mays L.) Damage During Seawater Vulnerability

This study was aimed to investigate how exogenous manganese (Mn) would limit damage in the oxygen-evolving complex (OEC) and photosynthetic apparatus of maize seedlings caused during seawater vulnerability. In this study, seawater was applied in 2-week-old maize (Zea mays L.) seedling, and the degree of damage of photosynthetic pigment pool, the OEC, and net electron transport rate were observed. Mn supplement was also added in maize seedlings to limit the damage of the OEC and photosynthetic apparatus caused during salinity. Leaf relative water content (RWC), fresh weight (FW), and photosynthetic pigment pool (chlorophyll a, chlorophyll b, and carotenoids) sharply declined after 7 days of treatment; however, Mn supplement increased these values. Chlorophyll fluorescence induction (OJIP) transients showed low Fv/Fo, an additional K step, enhanced variable fluorescence (VK) and degree of damage to the OEC (WK) during salinity, and indicates damage of OEC at electron donor side of photosystem II (PSII). The OEC intact within PSII was a primary damage center during salinity which inhibited electron transport process that resulted in a huge loss of maximum quantum yield of PSII (Fv/Fm), but a significant recovery in photosynthetic apparatus was observed after exogenous application of manganese. Structural and functional integrity of the photosynthetic apparatus was recovered up to a certain extent after exogenous application of Mn. Findings from this study should help to understand the basic knowledge of photosynthetic apparatus efficiency in response to damage caused by exposure to seawater. Outcomes of this study will be used to mitigate salinity problem with Mn supplement for growth and development of crops.

Can Ceylon Leadwort (Plumbago zeylanica L.) Acclimate to Lead Toxicity?-Studies of Photosynthetic Apparatus Efficiency.

Ceylon leadwort (Plumbago zeylanica) is ornamental plant known for its pharmacological properties arising from the abundant production of various secondary metabolites. It often grows in lead polluted areas. The aim of presented study was to evaluate the survival strategy of P. zeylanica to lead toxicity via photosynthetic apparatus acclimatization. Shoots of P. zeylanica were cultivated on media with different Pb concentrations (0.0, 0.05, and 0.1 g Pb∙l−1). After a four-week culture, the efficiency of the photosynthetic apparatus of plants was evaluated by Chl a fluorescence measurement, photosynthetic pigment, and Lhcb1, PsbA, PsbO, and RuBisCo protein accumulation, antioxidant enzymes activity, and chloroplast ultrastructure observation. Plants from lower Pb concentration revealed no changes in photosynthetic pigments content and light-harvesting complex (LHCII) size, as well as no limitation on the donor side of Photosystem II Reaction Centre (PSII RC). However, the activity and content of antioxidant enzymes indicated a high risk of limitation on the acceptor side of Photosystem I. In turn, plants from 0.1 g Pb∙l−1 showed a significant decrease in pigments content, LHCII size, the amount of active PSII RC, oxygen-evolving complex activity, and significant remodeling of chloroplast ultrastructure indicated limitation of PSII RC donor side. Obtained results indicate that P. zeylanica plants acclimate to lead toxicity by Pb accumulation in roots and, depending on Pb concentration, by adjusting their photosynthetic apparatus via the activation of alternative (cyclic and pseudocyclic) electron transport pathways.

The Ageing Process Affects the Antioxidant Defences and the Poly (ADPribosyl)ation Activity in Cistus Incanus L. Leaves.

The ageing process in living organisms is characterised by the accumulation of several deleterious changes occurring in cells and tissues. The increase of reactive oxygen species with the advancement of age is responsible for the oxidative damage to proteins, lipids and DNA, enhancing the risk of diseases. The antioxidant response and the activation of the poly(ADP-ribosyl)ation process represent the first defences activated by organisms at all life stages to counteract damage to cell structures and genomic material. The regulation of poly(ADP ribosyl)ation with age is little known in plants, especially in combination with antioxidant defences modulation. In this study, the relationships between poly (ADP-ribose) polymerase (PARP) activity and enzymatic and non-enzymatic antioxidant pool have been studied together with the photosynthetic apparatus efficiency in the Mediterranean species Cistus incanus L., examining leaves at different developmental stages: young, mature and senescent. The photosynthetic performance was evaluated by chlorophyll a fluorescence measurement, the total soluble and fat-soluble antioxidant capacity, as well as the activities of enzymes superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and glutathione-S-transferase (GST), were determined by spectrophotometer, PARP activity was assessed by radioactive labelling. The highest photochemical activity was observed in young leaves, together with the highest GST activity. With the progress of the ageing process, the non-enzymatic antioxidant pool (namely ascorbic acid, α-tocopherol) declined, reaching the lowest value in senescent leaves, whereas PARP activity rose significantly. The overall results indicate that the decline of photosynthetic apparatus efficiency during senescence is due to the reduction of specific defences against oxidative damages, which increase the damages to DNA, as demonstrated by PARP activity rise.

Efficiency of the photosynthetic apparatus of Myriophyllum spicatum L. under anthropopression – a case study from Upper Silesian

The current type of global economy and environmental management requires a change in its approach to the use of natural resources in order to meet human needs. A system approach and an analysis of the importance of anthropogenic ecosystems appears to be an effective tool for sustainable development of urban and post-industrial areas. One example of anthropogenic ecosystems are mining water reservoirs, formed in the basins of subsidence, affecting the increase of biodiversity in the area poor in the surface water reservoirs. This study presents analysis of the impact of water quality in anthropogenic reservoirs on the Myriophyllum spicatum L. photosynthetic apparatus efficiency. Five reservoirs with different water quality were analysed. The photosynthetic apparatus performance of macrophytes was measured using the chlorophyll fluorescence signal through a Pocket PEA fluorimeter. The results showed that electron transport decreased with deteriorating water quality of reservoirs. This leads to a weakening of the population of Myriophyllum spicatum, which, as a further consequence, may lead to an acceleration of eutrophication of reservoirs.

Studies of chlorophyll fluorescence intensity in apricot leaves during wilting processes

This work characterises the chlorophyll fluorescence intensity of apricot leaves in the process of dehydration and identification of cultivars and forms with high potential drought resistance. The experiment was performed using selected leaves of two cultivars of apricot breeding (‘Kryumskij Amur’ - control), the introduction ‘Bukuriya’, Nikita Botanical Gardens, and promising hybrid ‘84-929’. We found that leaves of studied genotypes in 24 h of wilting lose 42.7 (‘84-929’) to 48.4% (‘Bukuriya’) of water. Recovery of leaves’ turgor was also significantly varied. In ‘Kryumskij Amur’ full water content in leaves led to decrease of the photosynthetic apparatus efficiency During this period of wilting efficiency of primary photosynthesis reactions (Fv/Fo) decreased in 15% and the rate of photosynthesis systems photosynthetic ((Fm- Fst)/Fm) and photochemical (Fm/Fst) activity was 1.3-1.5-fold inhibited. The hybrid form ‘84-929’ noted the most stable rate of photosynthetic processes during the long period of wilting (up to 12 h). The lowest curve points were recorded in ‘Bukuriya’, indicating a weak drought resistance of this cultivar. Higher drought tolerance is a characteristic of ‘Kryumskij Amur’ due to its water-holding capacity of leaves.

Evaluation of heavy metal-induced responses in Silene vulgaris ecotypes

Silene vulgaris is a pseudometallophyte that spontaneously occurs in various ecological niches. Therefore, three ecotypes of this species representing calamine (CAL), serpentine (SER), and non-metallicolous (NM) populations were investigated in this study. Owing to the presence of Pb or Ni ions in natural habitats from metallicolous populations originated, we used these metals as model stressors to determine the survival strategy of tested ecotypes and analyze metal distribution at various levels of organism organization. We focused on growth tolerance, non-enzymatic antioxidants, and photosynthetic apparatus efficiency as well as anatomical and ultrastructural changes occurred in contrasting ecotypes exposed in vitro to excess amounts of Pb2+ and Ni2+. Although Ni application contributed to shoot culture death, the study revealed that the mechanisms of Pb detoxification differed between ecotypes. The unspecific reaction of both metallicolous specimens relied on the formation of effective mechanical barrier against toxic ion penetration, while the Pb appearance in the protoplasts led to the activation of ecotype-specific intracellular defense mechanisms. Hence, the response of CAL and SER ecotypes was almost unchanged under Pb treatment, whereas the reaction of NM one resulted in growth disturbances and physiological alternations. Moreover, both metallicolous ecotypes exhibited increase generation of reactive oxygen species (ROS) in leaves, even before the harmful ions got into these parts of plants. It may implicate the potential role of ROS in CAL and SER adaptation to heavy metals and, for the first time, indicate on integral function of ROS as signaling molecules in metal-tolerant species.

Dust accumulation due to anthropogenic impact induces anatomical and photochemical changes in leaves of Centranthus ruber growing on the slope of the Vesuvius volcano.

In Mediterranean ecosystems, some natural areas are exposed to severe anthropogenic impact. Especially in summer, the considerable number of tourists visiting such areas, often with vehicles, causes deposition of dust over the vegetation due to formation of powder clouds, also favoured by wind erosion, high temperature, low precipitation and incoherent soil structure. The main aim of this study was to analyse whether the deposition of dust can induce changes in leaf anatomical functional traits and in the efficiency of photosynthetic apparatus in Centranthus ruber, a species widespread in Mediterranean ecosystems. Leaf morpho-functional traits were quantified in plants growing at sites characterised by high (HD) and low (LD) dust deposition, in periods with high anthropogenic impact. Analyses included quantification of chlorophyll fluorescence emission parameters, photosynthetic pigment concentration as well as stomatal size and frequency, leaf lamina thickness, quantification of intercellular spaces and phenolics in the mesophyll through microscopy. The overall analysis suggested that the different conditions of dust deposition induced different adjustment of morpho-functional traits in leaves of C.ruber. High dust deposition shielded the leaf lamina, protecting the photosynthetic apparatus from excess light and favoured plant photochemical efficiency. Leaves exposed to low dust deposition showed higher accumulation of phenolic compounds, protecting chloroplast membranes and characterised by high thermal dissipation of excess light. Such adaptive phenomena can affect vegetation dynamics due to possible different species-specific plant responses, resulting in different plant competitiveness under the limiting conditions of Mediterranean environments.

Nitrogen assimilation pathways and ionic homeostasis are crucial for photosynthetic apparatus efficiency in salt-tolerant sunflower genotypes

Sunflower (Helianthus annuus L.) is an important oilseed crop that is sensitive to salt stress. We performed an investigation to elucidate the mechanisms of salinity tolerance in two commercial sunflower genotypes of contrasting salt tolerance. The BRS 321 genotype exhibited greater plant growth than the Catissol genotype upon exposure to 100 mM NaCl-stress, indicating that BRS 321 is more tolerant to salt stress than Catissol. The superior performance of BRS 321 plants was attributed to the decreased accumulation of toxic ions (Na+) in roots and improved photosynthetic machinery efficacy. In NaCl-stress conditions, BRS 321 plants displayed greater CO2 assimilation which was associated with an increase in the effective quantum yield of PSII, electron transport rate, and photochemical quenching (qP), as well as improved chlorophyll and carotenoid contents. Significantly, nitrogen metabolism in the salt-tolerant genotype was altered to act as an alternative electron sink, dissipating excess energy and increasing the plant’s capacity to withstand the deleterious salt effects. In conclusion, salt tolerance in BRS 321 compared to the Catissol genotype could be attributed to improved photosynthetic performance and decreased Na+ uptake.

Seasonal Dynamics of the Phytoplankton Photosynthetic Apparatus Efficiency in Black Sea Coastal Regions

A study of the fluorescence characteristics of phytoplankton in the coastal regions off the Crimean coasts of the Black Sea showed that the seasonal dynamics of the activity of the phytoplankton photosynthetic apparatus is identical both in Sevastopol Bay and inshore waters. The mean monthly values of the photochemical efficiency of photosystem II over 1 year vary within narrow limits and are close to the values of Diatoms and Dynophycea grown under optimal conditions. Phytoplankton in Black Sea coastal regions is provided with nutrients, and its developmental conditions are close to optimal. The light intensity that saturates the electron transport rate increases sevenfold from winter to summer. In summer, it coincides with the results of the phytoplankton photosynthesis rate measurements, and in winter it varies up to fivefold.

Variability examination of photosynthetic pigment content and specific leaf area in individual maize (Zea mays L.) plants

Currently, maize is one of the most important crops (Zea mays L.) both globally and in Hungary. We compared physiological parameters of a maize genotype – p9903 – at two different experimental sites in a field experiment. Furthermore, we examined these parameters’ variability in individual plants on the leaves with different ages. Absolute chlorophyll content of the leaves were analysed, separately that of chlorophyll a and chlorophyll b. We also measured the absolute carotenoid contents of leaves. Furthermore, we calculated these photosynthetic pigments’ content ratio. Specific leaf area (SLA) and dry matter weight were also measured in order to characterise plant production. The results obviously reflect the decreasing in the efficiency of photosynthetic apparatus on the low yield site. Otherwise, we identify significant differences only in certain cases of leaves.

Soil application of P can mitigate the copper toxicity in grapevine: physiological implications

Abstract The continuous use of copper-based fungicides in viticulture to contrast fungal diseases may result into an accumulation of Cu in the topsoil, reaching toxicity levels for plants and soil biota. A possible strategy to mitigate the negative effects of excess of Cu could involve the formation of insoluble molecules by the application of P to the soil. The aim of this study was to evaluate the effectiveness P soil application as a strategy to alleviate the toxic effect of excess of Cu on potted grapevines plants, with particular emphasis on the physiological response of plants. Micropropagated plants of 1103 Paulsen rootstock were grown according to a factorial experimental design with two factors: Cu (4 levels: 0, 100, 200, 300 mg kg−1 dw) and P (2 levels: 0 and 100 mg kg−1 dw) and three replicates. Net photosynthesis, efficiency of PSII photochemistry and linear electron transport rate decreased as soil Cu concentration increased. The addition of P increased net photosynthesis, improved the efficiency of PSII photochemistry and linear electron transport rate, but decreased stomatal conductance. As a consequence, shoot and root biomass declined with the increase of Cu concentration in soil, while the increment of P tackled this decline and improved nutritional status. CuEDTA extractable fraction in soil was increased by both the supply of Cu and P; this because the addition of P in combination with the highest Cu soil concentration determined a decrease of soil pH. In conclusion, the addition of P to the soil mitigated Cu excess toxicity symptoms in grape through a preservation of photosynthetic apparatus efficiency and an improvement of nutrient uptake.

The acclimatization strategies of kidney vetch (Anthyllis vulneraria L.) to Pb toxicity

Kidney vetch (Anthyllis vulneraria L.) is a well-known Zn hyperaccumulator. Zn often occurs with Pb in one ore; thus, plants inhabiting waste dumps are exposed not only to Zn but also to Pb toxicity. While the response of kidney vetch to Zn toxicity is relatively well known, the Pb survival strategy of Anthyllis vulneraria has not been the subject of investigations. The aim of presented research was to determine the survival strategy of kidney vetch exposed to high lead concentrations. Shoot explants of a calamine kidney vetch ecotype were placed on agar media containing 0.0, 0.5, 1.0, and 1.5 mM Pb. Morphological, physiological, and biochemical responses, in particular photosynthetic apparatus of plantlets, were examined. The most pronounced changes were observed in plants grown on media supplemented with 1.5 mM Pb after 8 weeks of culture. Increased dry weight and high lead accumulation were observed in roots. Similarly, in shoots, increased dry weight and a decreased number of newly formed shoots were recorded. The accumulation of lead was many times lower in shoots than in roots. In leaf cells’ ultra-structure, looser arrangement of chloroplast thylakoid grana was observed. Despite the decrease in chlorophyll a and carotenoid content, the photosynthetic apparatus remained efficient due to the lack of photoinhibition and increased electron transport rate beyond photosystem II (PSII). For the first time, an acclimatization mechanism based on maintaining the high efficiency of photosynthetic apparatus resulting from increasing of electron transport rate was described.

Emergence and morphophysiology of Sunki mandarin and other citrus genotypes seedlings under saline stress

The scarcity of good quality water is a limiting factor for irrigated agriculture, especially in arid and semiarid regions, where water sources generally contain high concentrations of ions. In such conditions, it is essential to cultivate genotypes with economic potential and tolerance to salinity. Considering the importance of citrus and the need to identify genetic materials that adapt to saline stress, this study evaluates the salinity tolerance of 10 genotypes with rootstock potential. For the irrigation water, five levels of electrical conductivity (ECw: 0.8, 1.6, 2.4, 3.2 and 4.0 dS/m at 25 °C) were used in a randomized block design with three replications, and seed germination and growth variables, as well as physiological plant parameters, were evaluated. The germination rate of the hybrid TSKC × CTARG – 019 was the best under salt conditions, as it was the genotype with the highest tolerance to salinity in the germination stage. Salinity reduced the growth of the citrus genotypes, with the possibility of using water with EC of up to 1.6 dS/m in the rootstock formation stage. Salt stress affected the photosynthetic rate of the genotypes ‘San Diego’ citrandarin and TSKC × CTSW – 018 by reducing the stomatal conductance, restricting the diffusion of CO2 into the substomatal camera. The genotypes TSKC × CTARG – 019, TSKC × CTTR – 012 and TSKC × TRBK – 007 have the greatest potential for growth and photosynthetic apparatus efficiency when subjected to salinity.

Pigments, efficiency of photosynthesis and winter wheat productivity

Purpose. To analyze characteristics of pigment apparatus and photosynthetic efficiency of wheat in connection with the perspectives to increase yielding capacity. Methods. Field, small-plot, morphometric, spectrophotometric, high-performance liquid chromatography, statistical ones. Results. The results of comparative studies of the photosynthetic apparatus characteristics of two winter wheat varieties at different levels of its organization (chloroplast, leaf, and crop), with more than 40 years difference of breeding time, are presented. It was shown that under different growing conditions the modern variety ‘Favorytka’ differed both by higher content of chlorophyll as the main photosynthetic pigment and its gross amount in the leaves, as well as specific leaves weight and longer functioning of crop photosynthetic apparatus at the late stages of vegetation than old variety ‘Myronivska 808’. Based on the changes of the de-epoxidation state of xanthophyll cycle pigments, caused by variation of light conditions, the better photosynthetic apparatus efficiency of variety ‘Favorytka’ was established. All these changes ultimately contributed to more efficient use of absorbed light energy for biomass formation of this variety. Found on the analysis of the own data and literature, it is shown that increasing the efficiency of photosynthesis is a promising strategy for rai­sing plant productivity. Conclutions. It was found that the increase of yield of modern winter wheat variety ‘Favorytka’, as compared with variety ‘Myronivska 808’ to be bred in the 60s, was accompanied with a rise of content and gross amount of chlorophyll and a prolongation of functioning of crop photosynthetic apparatus during the reproductive period. In addition, the modern variety was characterized by an increase in photosynthetic productivity due to more efficient use of absorbed light energy.