In the natural environment plants are well adapted to minimize damages which only occurs under ex... more In the natural environment plants are well adapted to minimize damages which only occurs under extreme conditions. In the frame of "physiological window" mild drought induces in plants regulation of water loss and uptake allowing maintenance of their leaf relative water content within the limits where the photosynthetic capacity shows no or little changes. But severe drought induces in plants unfavourable changes leading to inhibition of photosynthesis and growth. The most severe drought stress is desiccation. On the basis of presence or absence of bulk water, the mechanisms of protection are different. While the mechanisms conferring drought tolerance are mainly based on structural stabilization by preferential hydration, desiccation tolerance mechanisms are based on the replacement of water by molecules that form hydrogen bonds. The roles of stomatal and non-stomatal limitation, the behaviour of PS2, specific proteins and Rubisco, lipids and sugars, as well as mechanisms of acclimation and stress tolerance in droughted plants are discussed.
The effects of simulated acid rain on some chlorophyll fluorescence characteristics and photosynt... more The effects of simulated acid rain on some chlorophyll fluorescence characteristics and photosynthetic gas exchange at different light intensities and CO2 concentrations of bean plants were investigated. Measurements were carried out 3, 5 and 24 h after spraying. The results showed that a single acid rain (pH 1.8) treatment of bean plants reduced gas exchange, the maximal carboxylating efficiency and photochemical quenching. This treatment led also to increased CO2 compensation point and non‐photochemical quenching and changed the shape of CO2 and light curves of photosynthesis. Both stomatal and non‐stomatal factors contributed to the decreased photosynthetic rate, but their proportion changed with time of recovery of the photosynthetic ampparatus. Three hours after the treatment, the stomatal factors predominated in photosynthesis reduction, while during the next experimental period (5–24 h), mainly non‐stomatal factors determined the decreased photosynthetic rate. It is suggested that the effects observed in consequence of acid rain treatment could be due to an increased intracellular accumulation of H+ and harmful ions contained in the cocktail. This probably led to impaired membrane permeability, enhancement of stroma acidity, uncoupled electron transport and insufficient accumulation of ATP and NADPH, which affected carbon metabolism.
The effect of short-term exposure to elevated CO 2 concentration and high irradiance on the activ... more The effect of short-term exposure to elevated CO 2 concentration and high irradiance on the activity of superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol peroxidases (GPX) and catalase (CAT), and on the extent of the lipid peroxidation was studied in bean (Phaseolus vulgaris L.) plants. Plants were exposed for 4 d (8 h a day) to irradiance of 100 (LI) or 1000 (HI) µmol m-2 s-1 at ambient (CA, 350 µmol mol-1) or elevated (CE, 1300 µmol mol-1) CO 2 concentration. Four-day exposure to CE increased the leaf dry mass in HI plants and RuBPC activity and chlorophyll content in LI plants. Total soluble protein content, leaf dry matter and RuBPC activity were higher in HI than in LI plants, although the HI and CE increased the contents of malonyldialdehyde and H 2 O 2. Under CA, exposure to HI increased the activity of APX and decreased the total SOD activity. Under CE, HI treatment also activated APX and led to reduction of both, SOD and GPX, enzymes activities. CE considerably reduced the CAT activity at both irradiances, possibly due to suppressed rate of photorespiration under CE conditions.
Jasna Paradiž, Determining the genetic vulnerability of plants due to ionizing radiation: a compr... more Jasna Paradiž, Determining the genetic vulnerability of plants due to ionizing radiation: a comprehensive analysis of the cytogenetic balance and responses of the Allium root meristem to various radiation doses .
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
AL-actinic light; CEF-cyclic electron flow around PSI; Chl-chlorophyll; F0-minimal fluorescence y... more AL-actinic light; CEF-cyclic electron flow around PSI; Chl-chlorophyll; F0-minimal fluorescence yield of the dark-adapted state; F0'-minimal fluorescence yield of the light-adapted state; Fm-maximal fluorescence yield of the dark-adapted state; Fm'-maximal fluorescence yield of the light-adapted state; Fv-variable chlorophyll fluorescence; Fv/Fm-maximal quantum yield of PSII photochemistry; LCP-light-compensation point; MT-multiple-turnover flash; NPQ-nonphotochemical quenching; P700-reaction center chlorophyll of PSI; P700 +-oxidized form of PSI reaction center; PNmax-saturating level of oxygen evolution; PQ-plastoquinone; qE-energy-dependent component of NPQ; R-recovery; ST-single-turnover flash; WUE-water-use efficiency; Φf,D-quantum yield of nonregulated energy dissipation of PSII; ΦNPQ-quantum yield of the regulated energy dissipation of PSII; ΦPSII-actual photochemical efficiency of PSII. Acknowledgments: This work was financially supported by Bulgarian Science Fund under project KП-06-H26/11. The seeds of the wt and mutant lut2 of Arabidopsis thaliana were a generous gift from Prof. R. Bassi.
As medicinal plants are generally collected from the wild flora, it is of fundamental importance ... more As medicinal plants are generally collected from the wild flora, it is of fundamental importance to identify the optimum growth conditions for increasing the yield and quality potential of ex-situ cultivated plants. Effects of different soil water content [20, 40, 60 and 80 % of water holding capacity (WHC)] on growth, physiology and biochemical profile of Achillea millefolium group-related cv. Proa were investigated in the present study. Alterations in drug herbage, chlorophyll content, quantum efficiency of photosystem II, essential oil rate and composition, proline content and lipid peroxidation, antioxidant activity and flavonoid content of the plants under different plant and soil water status were determined. Decrease in soil water status under 40 % of WHC resulted in degradation of chlorophyll pigments, reduction in photochemical efficiency and lower dry matter production. The essential oil (EO) rate of cv. Proa was higher under limited and excessive water content of soil whereas the main component of EO, chamazulene, was negatively correlated with WHC of soil. Our results suggest a general trend of inverse correlation of antioxidant capacity and flavonoid content with essential oil rate in contrast to the positive correlation of these parameters with chamazulene content. The data obtained may serve as a basis of programming the optimum soil moisture conditions for successful cultivation of cv.Proa.
Targeting sonic hedgehog pathway in combination with proton radiation or gamma irradiation decrea... more Targeting sonic hedgehog pathway in combination with proton radiation or gamma irradiation decreases viability of glioma cell lines .
The effect of light quality on growth, photosynthesis, leaf anatomy and volatile isoprenoids of a... more The effect of light quality on growth, photosynthesis, leaf anatomy and volatile isoprenoids of a monoterpene-emitting herbaceous species (Solanum lycopersicum L.) and an isoprene-emitting tree (Platanus orientalis L.).
Blueberries are an increasingly important h~ticultural crop in New Zealand and other coun~es. Fru... more Blueberries are an increasingly important h~ticultural crop in New Zealand and other coun~es. Fruit ripen over an extended period, with considerable differences in storage and other qualities. Tissue concentrations of abscisic acid (ABA), 1-aminocyciopmpane-l-carboxylic acid (ACC), malonyl-ACC and also ACC oxidase activity and ethylene evolution were determined at 5 stages of colour development on 2 harvest dates. These were related to &y matter, sucrose and reducing sugar content. ACC concentrations, and the proportion conjugated varied between harvest dates, while ethylene evolution and ABA concentrations were similar. ABA concentrations were high relative to other fruit, exceeding 10 nmole/g fw prior to full ripeness. ABA was present in higher concentration in mesocarp than in seeds or pericarp/cuticle. It is proposed that ABA is implicated in dry matter acquisition, but is not a primary determinant of colour development or ethylene regulation.
Beta vulgaris L. is a crop selected for cultivation in Space for its nutritional properties. Howe... more Beta vulgaris L. is a crop selected for cultivation in Space for its nutritional properties. However, exposure to ionizing radiation (IR) can alter plant photosynthetic performance and phytochemical production in the extraterrestrial environment. This study investigated if plant growth under different light quality regimes (FL—white fluorescent; RGB—red–green–blue; RB—red–blue) modifies the photosynthetic behavior and bioactive compound synthesis of plants sprouted by dry seeds irradiated with carbon or titanium high-energy ions. The study evidenced that: (i) the plant response depends on the type of heavyion; (ii) control and C-ion-irradiated plants were similar for photosynthetic pigment content and PSII photochemical efficiency, regardless of the LQ regime; (iii) under FL, net photosynthesis (AN) and water use efficiency (iWUE) declined in C- and Ti-ion plants compared to control, while the growth of irradiated plants under RGB and RB regimes offset these differences; (iv) the in...
Light quality plays an essential role in setting plant structural and functional traits, includin... more Light quality plays an essential role in setting plant structural and functional traits, including antioxidant compounds. This paper aimed to assess how manipulating the light spectrum during growth may regulate the photosynthetic activity and fruit bioactive compound synthesis in Solanum lycopersicum L. cv. ‘Microtom’ to improve plant physiological performance and fruit nutritional value. Plants were cultivated under three light quality regimes: red-green-blue LEDs (RGB), red-blue LEDs (RB) and white fluorescent lamps (FL), from sowing to fruit ripening. Leaf functional traits, photosynthetic efficiency, Rubisco and D1 protein expression, and antioxidant production in fruits were analyzed. Compared to FL, RGB and RB regimes reduced height and increased leaf number and specific leaf area, enhancing plant dwarf growth. The RGB regime improved photosynthesis and stomatal conductance despite lower biomass, favoring Rubisco synthesis and carboxylation rate than RB and FL regimes. The RB...
This study evaluated if specific light quality (LQ) regimes (white fluorescent, FL; full-spectrum... more This study evaluated if specific light quality (LQ) regimes (white fluorescent, FL; full-spectrum, FS; red-blue, RB) during plant growth modified morphological and photosynthetic traits of Solanum lycopersicum L. ‘Microtom’ plants irradiated at the dry seed stage with 25 Gy 48Ca ions (IR). The irradiation reduced plant size while it increased leaf dry matter content (LDMC) and relative water content (RWC) compared to the control. FS and RB light regimes determined a decrease of plant height and a rise of RWC compared to FL plants. The irradiation under FS and RB regimes favoured the development of dwarf plants and improved the leaf water status. Under the FL regime, irradiated plants showed reduced photosynthesis and stomatal conductance. The opposite behavior was observed in RB irradiated plants in which gas exchanges were significantly stimulated. RB regime enhanced Rubisco expression in irradiated plants also inducing anatomical and functional adjustments (i.e., increase of leaf ...
Platanus orientalis is considered endangered species that is almost extinct in the natural ecosys... more Platanus orientalis is considered endangered species that is almost extinct in the natural ecosystems of Western Europe and, because of its hydrophilic habitat, may also be strongly affected by increasing water limitations in Eastern Europe. The effects of drought stress were studied and compared in young plane trees of two ecotypes from Bulgarian and Italian regions. The dynamics of drying and following re-watering was monitored in vivo by changes in activity of photosynthetic light phase reactions in leaves of 4-5 month old seedlings subject to controlled moderate water limiting regime for 12 days and subsequent recovery by controlled gradual irrigation for 10 days. The physiological state of photosynthetic machinery was estimated by analysis of signals of prompt and delayed chlorophyll a fluorescence measured in attached plane leaves by the Multifunctional Plant Efficiency Analyzer (Hansatech Instruments Ltd., UK). Prompt chlorophyll a fluorescence directly correlates to the redo...
Platanus orientalis is considered endangered species that is almost extinct in the natural ecosys... more Platanus orientalis is considered endangered species that is almost extinct in the natural ecosystems of Western Europe and, because of its hydrophilic habitat, may also be strongly affected by increasing water limitations in Eastern Europe. The effects of drought stress were studied and compared in young plane trees of two ecotypes from Bulgarian and Italian regions. The dynamics of drying and following re-watering was monitored in vivo by changes in activity of photosynthetic light phase reactions in leaves of 4-5 month old seedlings subject to controlled moderate water limiting regime for 12 days and subsequent recovery by controlled gradual irrigation for 10 days. The physiological state of photosynthetic machinery was estimated by analysis of signals of prompt and delayed chlorophyll a fluorescence measured in attached plane leaves by the Multifunctional Plant Efficiency Analyzer (Hansatech Instruments Ltd., UK). Prompt chlorophyll a fluorescence directly correlates to the redo...
In the natural environment plants are well adapted to minimize damages which only occurs under ex... more In the natural environment plants are well adapted to minimize damages which only occurs under extreme conditions. In the frame of "physiological window" mild drought induces in plants regulation of water loss and uptake allowing maintenance of their leaf relative water content within the limits where the photosynthetic capacity shows no or little changes. But severe drought induces in plants unfavourable changes leading to inhibition of photosynthesis and growth. The most severe drought stress is desiccation. On the basis of presence or absence of bulk water, the mechanisms of protection are different. While the mechanisms conferring drought tolerance are mainly based on structural stabilization by preferential hydration, desiccation tolerance mechanisms are based on the replacement of water by molecules that form hydrogen bonds. The roles of stomatal and non-stomatal limitation, the behaviour of PS2, specific proteins and Rubisco, lipids and sugars, as well as mechanisms of acclimation and stress tolerance in droughted plants are discussed.
The effects of simulated acid rain on some chlorophyll fluorescence characteristics and photosynt... more The effects of simulated acid rain on some chlorophyll fluorescence characteristics and photosynthetic gas exchange at different light intensities and CO2 concentrations of bean plants were investigated. Measurements were carried out 3, 5 and 24 h after spraying. The results showed that a single acid rain (pH 1.8) treatment of bean plants reduced gas exchange, the maximal carboxylating efficiency and photochemical quenching. This treatment led also to increased CO2 compensation point and non‐photochemical quenching and changed the shape of CO2 and light curves of photosynthesis. Both stomatal and non‐stomatal factors contributed to the decreased photosynthetic rate, but their proportion changed with time of recovery of the photosynthetic ampparatus. Three hours after the treatment, the stomatal factors predominated in photosynthesis reduction, while during the next experimental period (5–24 h), mainly non‐stomatal factors determined the decreased photosynthetic rate. It is suggested that the effects observed in consequence of acid rain treatment could be due to an increased intracellular accumulation of H+ and harmful ions contained in the cocktail. This probably led to impaired membrane permeability, enhancement of stroma acidity, uncoupled electron transport and insufficient accumulation of ATP and NADPH, which affected carbon metabolism.
The effect of short-term exposure to elevated CO 2 concentration and high irradiance on the activ... more The effect of short-term exposure to elevated CO 2 concentration and high irradiance on the activity of superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol peroxidases (GPX) and catalase (CAT), and on the extent of the lipid peroxidation was studied in bean (Phaseolus vulgaris L.) plants. Plants were exposed for 4 d (8 h a day) to irradiance of 100 (LI) or 1000 (HI) µmol m-2 s-1 at ambient (CA, 350 µmol mol-1) or elevated (CE, 1300 µmol mol-1) CO 2 concentration. Four-day exposure to CE increased the leaf dry mass in HI plants and RuBPC activity and chlorophyll content in LI plants. Total soluble protein content, leaf dry matter and RuBPC activity were higher in HI than in LI plants, although the HI and CE increased the contents of malonyldialdehyde and H 2 O 2. Under CA, exposure to HI increased the activity of APX and decreased the total SOD activity. Under CE, HI treatment also activated APX and led to reduction of both, SOD and GPX, enzymes activities. CE considerably reduced the CAT activity at both irradiances, possibly due to suppressed rate of photorespiration under CE conditions.
Jasna Paradiž, Determining the genetic vulnerability of plants due to ionizing radiation: a compr... more Jasna Paradiž, Determining the genetic vulnerability of plants due to ionizing radiation: a comprehensive analysis of the cytogenetic balance and responses of the Allium root meristem to various radiation doses .
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
AL-actinic light; CEF-cyclic electron flow around PSI; Chl-chlorophyll; F0-minimal fluorescence y... more AL-actinic light; CEF-cyclic electron flow around PSI; Chl-chlorophyll; F0-minimal fluorescence yield of the dark-adapted state; F0'-minimal fluorescence yield of the light-adapted state; Fm-maximal fluorescence yield of the dark-adapted state; Fm'-maximal fluorescence yield of the light-adapted state; Fv-variable chlorophyll fluorescence; Fv/Fm-maximal quantum yield of PSII photochemistry; LCP-light-compensation point; MT-multiple-turnover flash; NPQ-nonphotochemical quenching; P700-reaction center chlorophyll of PSI; P700 +-oxidized form of PSI reaction center; PNmax-saturating level of oxygen evolution; PQ-plastoquinone; qE-energy-dependent component of NPQ; R-recovery; ST-single-turnover flash; WUE-water-use efficiency; Φf,D-quantum yield of nonregulated energy dissipation of PSII; ΦNPQ-quantum yield of the regulated energy dissipation of PSII; ΦPSII-actual photochemical efficiency of PSII. Acknowledgments: This work was financially supported by Bulgarian Science Fund under project KП-06-H26/11. The seeds of the wt and mutant lut2 of Arabidopsis thaliana were a generous gift from Prof. R. Bassi.
As medicinal plants are generally collected from the wild flora, it is of fundamental importance ... more As medicinal plants are generally collected from the wild flora, it is of fundamental importance to identify the optimum growth conditions for increasing the yield and quality potential of ex-situ cultivated plants. Effects of different soil water content [20, 40, 60 and 80 % of water holding capacity (WHC)] on growth, physiology and biochemical profile of Achillea millefolium group-related cv. Proa were investigated in the present study. Alterations in drug herbage, chlorophyll content, quantum efficiency of photosystem II, essential oil rate and composition, proline content and lipid peroxidation, antioxidant activity and flavonoid content of the plants under different plant and soil water status were determined. Decrease in soil water status under 40 % of WHC resulted in degradation of chlorophyll pigments, reduction in photochemical efficiency and lower dry matter production. The essential oil (EO) rate of cv. Proa was higher under limited and excessive water content of soil whereas the main component of EO, chamazulene, was negatively correlated with WHC of soil. Our results suggest a general trend of inverse correlation of antioxidant capacity and flavonoid content with essential oil rate in contrast to the positive correlation of these parameters with chamazulene content. The data obtained may serve as a basis of programming the optimum soil moisture conditions for successful cultivation of cv.Proa.
Targeting sonic hedgehog pathway in combination with proton radiation or gamma irradiation decrea... more Targeting sonic hedgehog pathway in combination with proton radiation or gamma irradiation decreases viability of glioma cell lines .
The effect of light quality on growth, photosynthesis, leaf anatomy and volatile isoprenoids of a... more The effect of light quality on growth, photosynthesis, leaf anatomy and volatile isoprenoids of a monoterpene-emitting herbaceous species (Solanum lycopersicum L.) and an isoprene-emitting tree (Platanus orientalis L.).
Blueberries are an increasingly important h~ticultural crop in New Zealand and other coun~es. Fru... more Blueberries are an increasingly important h~ticultural crop in New Zealand and other coun~es. Fruit ripen over an extended period, with considerable differences in storage and other qualities. Tissue concentrations of abscisic acid (ABA), 1-aminocyciopmpane-l-carboxylic acid (ACC), malonyl-ACC and also ACC oxidase activity and ethylene evolution were determined at 5 stages of colour development on 2 harvest dates. These were related to &y matter, sucrose and reducing sugar content. ACC concentrations, and the proportion conjugated varied between harvest dates, while ethylene evolution and ABA concentrations were similar. ABA concentrations were high relative to other fruit, exceeding 10 nmole/g fw prior to full ripeness. ABA was present in higher concentration in mesocarp than in seeds or pericarp/cuticle. It is proposed that ABA is implicated in dry matter acquisition, but is not a primary determinant of colour development or ethylene regulation.
Beta vulgaris L. is a crop selected for cultivation in Space for its nutritional properties. Howe... more Beta vulgaris L. is a crop selected for cultivation in Space for its nutritional properties. However, exposure to ionizing radiation (IR) can alter plant photosynthetic performance and phytochemical production in the extraterrestrial environment. This study investigated if plant growth under different light quality regimes (FL—white fluorescent; RGB—red–green–blue; RB—red–blue) modifies the photosynthetic behavior and bioactive compound synthesis of plants sprouted by dry seeds irradiated with carbon or titanium high-energy ions. The study evidenced that: (i) the plant response depends on the type of heavyion; (ii) control and C-ion-irradiated plants were similar for photosynthetic pigment content and PSII photochemical efficiency, regardless of the LQ regime; (iii) under FL, net photosynthesis (AN) and water use efficiency (iWUE) declined in C- and Ti-ion plants compared to control, while the growth of irradiated plants under RGB and RB regimes offset these differences; (iv) the in...
Light quality plays an essential role in setting plant structural and functional traits, includin... more Light quality plays an essential role in setting plant structural and functional traits, including antioxidant compounds. This paper aimed to assess how manipulating the light spectrum during growth may regulate the photosynthetic activity and fruit bioactive compound synthesis in Solanum lycopersicum L. cv. ‘Microtom’ to improve plant physiological performance and fruit nutritional value. Plants were cultivated under three light quality regimes: red-green-blue LEDs (RGB), red-blue LEDs (RB) and white fluorescent lamps (FL), from sowing to fruit ripening. Leaf functional traits, photosynthetic efficiency, Rubisco and D1 protein expression, and antioxidant production in fruits were analyzed. Compared to FL, RGB and RB regimes reduced height and increased leaf number and specific leaf area, enhancing plant dwarf growth. The RGB regime improved photosynthesis and stomatal conductance despite lower biomass, favoring Rubisco synthesis and carboxylation rate than RB and FL regimes. The RB...
This study evaluated if specific light quality (LQ) regimes (white fluorescent, FL; full-spectrum... more This study evaluated if specific light quality (LQ) regimes (white fluorescent, FL; full-spectrum, FS; red-blue, RB) during plant growth modified morphological and photosynthetic traits of Solanum lycopersicum L. ‘Microtom’ plants irradiated at the dry seed stage with 25 Gy 48Ca ions (IR). The irradiation reduced plant size while it increased leaf dry matter content (LDMC) and relative water content (RWC) compared to the control. FS and RB light regimes determined a decrease of plant height and a rise of RWC compared to FL plants. The irradiation under FS and RB regimes favoured the development of dwarf plants and improved the leaf water status. Under the FL regime, irradiated plants showed reduced photosynthesis and stomatal conductance. The opposite behavior was observed in RB irradiated plants in which gas exchanges were significantly stimulated. RB regime enhanced Rubisco expression in irradiated plants also inducing anatomical and functional adjustments (i.e., increase of leaf ...
Platanus orientalis is considered endangered species that is almost extinct in the natural ecosys... more Platanus orientalis is considered endangered species that is almost extinct in the natural ecosystems of Western Europe and, because of its hydrophilic habitat, may also be strongly affected by increasing water limitations in Eastern Europe. The effects of drought stress were studied and compared in young plane trees of two ecotypes from Bulgarian and Italian regions. The dynamics of drying and following re-watering was monitored in vivo by changes in activity of photosynthetic light phase reactions in leaves of 4-5 month old seedlings subject to controlled moderate water limiting regime for 12 days and subsequent recovery by controlled gradual irrigation for 10 days. The physiological state of photosynthetic machinery was estimated by analysis of signals of prompt and delayed chlorophyll a fluorescence measured in attached plane leaves by the Multifunctional Plant Efficiency Analyzer (Hansatech Instruments Ltd., UK). Prompt chlorophyll a fluorescence directly correlates to the redo...
Platanus orientalis is considered endangered species that is almost extinct in the natural ecosys... more Platanus orientalis is considered endangered species that is almost extinct in the natural ecosystems of Western Europe and, because of its hydrophilic habitat, may also be strongly affected by increasing water limitations in Eastern Europe. The effects of drought stress were studied and compared in young plane trees of two ecotypes from Bulgarian and Italian regions. The dynamics of drying and following re-watering was monitored in vivo by changes in activity of photosynthetic light phase reactions in leaves of 4-5 month old seedlings subject to controlled moderate water limiting regime for 12 days and subsequent recovery by controlled gradual irrigation for 10 days. The physiological state of photosynthetic machinery was estimated by analysis of signals of prompt and delayed chlorophyll a fluorescence measured in attached plane leaves by the Multifunctional Plant Efficiency Analyzer (Hansatech Instruments Ltd., UK). Prompt chlorophyll a fluorescence directly correlates to the redo...
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