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The aim of this research was to investigate distinct effects of Xanthomonas campestris pv. campestris (Xcc) and drought stress (D) and their combined effects (Xcc + D) on the activity of peroxidase (POD) and the phenolic composition in cabbage leaves (autochthonous cultivar Futoški). This pathogen causes black rot, severely affecting Brassicaceae cultivation, and in combination with drought, it leads to significant cabbage yield losses. The combined stress resulted in maximum stomatal closure, almost seven times higher compared to the control and 40% more than in drought-stressed plants. On the contrary, the photosynthesis efficiency remained unchanged. The highest accumulation of epidermal flavonoids was observed in Xcc + D plants, whereas the chlorophyll content remained stable, nitrogen balance index (NBI) decreased by 20% compared to the control and drought-stressed plants. The highest POD activity was induced by drought alone, while combined stress reduced POD activity by almost 50%. In this experiment, the optical fiber fluorescence measurements were performed directly on the surface of the investigated plant leaves (excitation and emission wavelengths of 375 nm and 400-800 nm). It was found that the intensity of the fluorescence spectra with emission maxima at 457 and 520 nm was higher in the Xcc-infected leaves than in the healthy and drought-stressed leaves. These results showed an increase in emission intensity in the spectral region corresponding to phenolics, suggesting that the accumulation of phenolic compounds may be a plant response to the pathogen infection. more...

Autochthonous cabbage cv. Futoški is known for its specific taste and quality. Its yield may be affected by plant pathogenic bacterium Xanthomonas campestris pv. campestris (Xcc). The aim of this work was to examine physiological response of cabbage cv. Futoški to infection with differently virulent Xcc strains. Pathogenicity of eighteen Xcc strains, isolated from cabbage cv. Futoški was assessed on cabbage plants under controlled greenhouse conditions. Plants were visually observed for symptoms development two weeks after inoculation and scored according to the Horsfall-Barratt scale. Based on the obtained results, Xcc strains were divided into three groups with different virulence potential, i.e. low (3.15–4.93%), medium (7.20–11.35%), and high (21.30–36.90%). These groups correspond to plants exhibiting low (L), medium (M) and high (H) disease intensity, respectively. Physiological and morphological parameters – chlorophyll, epidermal flavonoids, nitrogen balance index (NBI), leaf fresh and dry weight, as well as leaf photosynthetic parameters were measured in infected plants. The highest chlorophyll content was detected in H plants, which was accompanied by increased photosynthetic quantum yield, and NBI was also elevated by 25% in H plants compared to the L plants. Contrarily, the level of epidermal flavonoids was 25% lower in H plants compared to L plants. Necrotic-induced leaf chlorophyll reallocation, and consequently increased photosynthetic efficacy, may be linked to plants survival strategies under infection and maintaining availability of resources. Defense strategies through activation of secondary metabolism in most infected plants were not observed, as shown by similar values of epidermal flavonoids compared to control. more...

The resurrection plant Ramonda serbica Panc. survives long desiccation periods and fully recovers metabolic functions within one day upon watering. We aimed to identify key candidates and pathways involved in desiccation tolerance in R. serbica by employing a systems biology approach, combining transcriptomics and proteomics. A total of 68,694 differentially expressed genes (DEGs; p-value<0.005 and abs(log2FC)≥2) were obtained in R. serbica leaves upon desiccation. Among them, 23,935 and 26,169 genes were upregulated and downregulated in desiccated leaves (DL) and hydrated leaves (HL), respectively. By differential TMT-based proteomic analysis 1192 different protein groups were identified after filtering with at least two unique peptides per protein. In total, 229 protein groups were more abundant in HL and 179 in DL (p-value<0.05 and abs(FC)≥1.3). The majority of the DAPs and DEGs involved in photosynthesis, transport, secondary metabolism, and signaling, were less abundant in DL. On the other hand, proteins and transcripts associated with fermentation, N-metabolism, heme, protein synthesis, folding and assembly, C1- metabolism, and late embryogenesis abundant proteins, were more accumulated in DL. A poor correlation between proteomic and transcriptomic results was detected for mitochondrial electron transport and ATP production, gluconeogenesis, glycolysis, tricarboxylic acid cycle, and enzymatic H2O2 scavengers due to different mRNA half-life, protein turnover, dynamic posttranscriptional and posttranslational modifications. Finally, desiccation tolerance in R. serbica is a species-specific process orchestrated by several metabolic pathways that are temporally and compartmentally regulated at several levels. more...

Chloroplast movement rapidly ameliorates the effects of suboptimal light intensity by accumulating along the periclinal cell walls, as well as the effects of excess light by shifting to the anticlinal cell walls. These acclimation responses are triggered by phototropins located at the plasma membrane and chloroplast envelope. Here, we used a recently developed non-invasive system sensitive to very small changes in red light leaf transmittance to perform long-term continuous measurements of dark–light transitions. As a model system, we used variegated Pelargonium zonale leaves containing green sectors (GS) with fully developed chloroplasts and achlorophyllous, white sectors (WS) with undifferentiated plastids, and higher phototropin expression levels. We observed biphasic changes in the red-light transmittance and oscillations triggered by medium intensities of white light, described by a transient peak preceded by a constant decrease in transmittance level. A slight change in red-light transmittance was recorded even in WS. Furthermore, the chloroplast position at lower light intensities affected the rapid light curves, while high light intensity decreased saturated electron transport, maximum quantum efficiency of photosystem II, and increased non-photochemical quenching of chlorophyll fluorescence and epidermal flavonoids. Our results extend the knowledge of light-dependent chloroplast movements and thus contribute to a better understanding of their role in regulating photosynthesis under fluctuating light conditions. more...

Three basil plant varieties (Ocimum basilicum var. Genovese, Ocimum x citriodorum, and Ocimum basilicum var. purpurascens) were grown under moderate light (about 300 umol photons m-2 s-1) in a glasshouse or growth chamber and then either transferred to an open field (average daily dose: 29.2 kJ m-2 d-1) or additionally exposed to UV-B irradiation in a growth chamber (29.16 kJ m-2 d-1), to reveal the variety-specific and light-specific acclimation responses. Total antioxidant capacity (TAC), phenolic profile, ascorbate content, and class III peroxidase (POD) activity were used to determine the antioxidant status of leaves under all four light regimes. Exposure to high solar irradiation at the open field resulted in an increase in TAC, total hydroxycinnamic acids (HCAs, especially caffeic acid), flavonoids, and epidermal UV-absorbing substances in all three varieties, as well as a two-fold increase in the leaf dry/fresh weight ratio. The supplemental UV-B irradiation induced preferential accumulation of HCAs (rosmarinic acid) over flavonoids, increased TAC and POD activity, but decreased the ascorbate content in the leaves, and inhibited the accumulation of epidermal flavonoids in all basil varieties. Furthermore, characteristic leaf curling and UV-B-induced inhibition of plant growth were observed in all basil varieties, while a pro-oxidant effect of UV-B was indicated with H2O2 accumulation in the leaves and spotty leaf browning. The extent of these morphological changes, and oxidative damage depended on the basil cultivar, implies a genotype-specific tolerance mechanism to high doses of UV-B irradiation. more...

Chloroplast movement rapidly ameliorates the effects of suboptimal light intensity by accumulating along the periclinal cell walls, as well as the effects of excess light by shifting to the anticlinal cell walls. These acclimation responses are triggered by phototropins located at the plasma membrane and chloroplast envelope. Here, we used a recently developed non-invasive system sensitive to very small changes in red light leaf transmittance to perform long-term continuous measurements of dark–light transitions. As a model system, we used variegated Pelargonium zonale leaves containing green sectors (GS) with fully developed chloroplasts and achlorophyllous, white sectors (WS) with undifferentiated plastids, and higher phototropin expression levels. We observed biphasic changes in the red-light transmittance and oscillations triggered by medium intensities of white light, described by a transient peak preceded by a constant decrease in transmittance level. A slight change in red-light transmittance was recorded even in WS. Furthermore, the chloroplast position at lower light intensities affected the rapid light curves, while high light intensity decreased saturated electron transport, maximum quantum efficiency of photosystem II, and increased non-photochemical quenching of chlorophyll fluorescence and epidermal flavonoids. Our results extend the knowledge of light-dependent chloroplast movements and thus contribute to a better understanding of their role in regulating photosynthesis under fluctuating light conditions. more...

Due to increased urbanization and industrialization, the emission of toxic material into the atmosphere is in expansion, which has a negative impact on the environment and human health. In this research, we monitored the effect of air pollution on the peroxidase (POD) activity and total antioxidant capacity of different tree species during the growing season. The main goal was to determine which tree species developed the highest tolerance to unfavorable environmental conditions at the end of growing season, based on the response of their antioxidative metabolism. The greatest change in POD activity was observed in the Fagus sylvatica L. leaves, where enzyme activity was more than doubled in the autumn, in comparison to spring. On the other hand, decrease in POD activity was the greatest in Cedrus atlantica (Endl.) Manetti ex Carrière needles. Moreover, total antioxidative capacity was altered during growing season in almost all examined tree species. The Magnolia spp. showed the most consistent response to the given environmental pollution with both portrayed parameters induced during growing season. In general, we can conclude that the tree species investigated in this research possess distinctive tolerance potential to air pollutants. more...

Three basil plant varieties (Ocimum basilicum var. Genovese, Ocimum × citriodorum, and Ocimum basilicum var. purpurascens) were grown under moderate light (about 300 µmol photons m−2 s−1) in a glasshouse or growth chamber and then either transferred to an open field (average daily dose: 29.2 kJ m−2 d−1) or additionally exposed to UV-B irradiation in a growth chamber (29.16 kJ m−2 d−1), to reveal the variety-specific and light-specific acclimation responses. Total antioxidant capacity (TAC), phenolic profile, ascorbate content, and class III peroxidase (POD) activity were used to determine the antioxidant status of leaves under all four light regimes. Exposure to high solar irradiation at the open field resulted in an increase in TAC, total hydroxycinnamic acids (HCAs, especially caffeic acid), flavonoids, and epidermal UV-absorbing substances in all three varieties, as well as a two-fold increase in the leaf dry/fresh weight ratio. The supplemental UV-B irradiation induced preferential accumulation of HCAs (rosmarinic acid) over flavonoids, increased TAC and POD activity, but decreased the ascorbate content in the leaves, and inhibited the accumulation of epidermal flavonoids in all basil varieties. Furthermore, characteristic leaf curling and UV-B-induced inhibition of plant growth were observed in all basil varieties, while a pro-oxidant effect of UV-B was indicated with H2O2 accumulation in the leaves and spotty leaf browning. The extent of these morphological changes, and oxidative damage depended on the basil cultivar, implies a genotype-specific tolerance mechanism to high doses of UV-B irradiation. more...

Street trees are important component of urban forest presenting a first barrier between air pollution originated from vehicle traffic and pedestrians. It implies that an improvement of air quality in urban areas greatly depends on green biomass, in short, the bigger and greener tree crown, better for human health and wellbeing. Determination of Leaf Nitrogen Balance Index (LNBI) and chlorophyll concentration (ChlC) by a non-invasive methodology and a user friendly instrument (Dualex 4, Force), widely used in agronomy and horticulture, was tested here for the assessment of tree fitness in urban zones. Investment of energy and resources either in growth or defence according to the tradeoff strategy of plants may be indicated by LNBI, which approximately presents a Nitrogen/Carbon ratio. We selected few tree species from Belgrade’s streets to determine those two parameters during summer. We also presented the changes in those parameters of the introduced bamboo species within ten years at several urban locations in Belgrade differing in air pollution aiming to evaluate usefulness the LNBI parameter in access of multiyear exposure to the effect of intense vehicle traffic. Numerous limiting factors for development of healthy tree crowns in urban ecosystem, such as low capacity to cope with toxic pollutant, sensitivity to diseases, early senescence and etc., greatly depends on tree species. We propose this methodology may also contribute in the process of choice of the adequate tree species to be planted along streets. more...

Stres suše, u kombinaciji sa svetlošću visokog intenziteta zračenja, predstavlja jedan od najrasprostranjenijih abiotskih faktora koji ima negativan uticaj na rastenje i prinos biljaka. U cilju ispitivanja uticaja sniženog nivoa apscisinske kiseline (ABA) na razvijanje strategija neophodnih za toleranciju biljaka na sušu, u ovom istraživanju korišćena su dva genotipa paradajza sa konstitutivno različitim sadržajem ABA, divlji tip Ailsa Craig i flacca mutant. Biljke su gajene na svetlosti nižeg i višeg intenziteta i bile podvrgnute jednom, odnosno trima ciklusima suše, koji su bili praćeni periodima rehidratacije. Uticaj suše i rehidratacije praćen je na morfološkom (sveža i suva masa, površina listova) i fiziološkom nivou (provodljivost stoma, ukupni vodni potencijal), kao i primenom biohemijskih (određivanje ugljenih hidrata, aminokiselina, askorbata) i molekularnih metoda (praćenje ekspresije gena uključenih u metabolizam ABA i određivanje ekspresije nekodirajučih RNK molekula). Rezultati prikazani u ovoj disertaciji pokazali su da je održavanje homeostaze ABA od presudnog značaja za rastenje i razviće paradajza i u uslovima optimalnog vodnog režima, kao i da je flacca mutant pogodan model sistem za proučavanje uticaja smanjene akumulacije ABA na razvoj strategija za razvijanje tolerancije biljaka na sušu. Pokazano je da akumulacija osmotski aktivnih jedinjenja kod oba genotipa, kao i promene na morfološkom nivou značajno doprinose razvoju mehanizama tolerancije paradajza na sušu. Izlaganje biljaka ciklusima suše indukovalo je promene u akumulaciji antioksidativnih komponenti (askorbat i epidermalni flavonoidi), strukturi ćelijskog zida, ali i u ekspresiji nekodirajućih RNK molekula, što potencijalno može doprineti razvijanju memorije kod paradajza na ponovljeni stres suše., Drought stress combined with high light intensity is one of the most common abiotic factors that have a negative impact on plant growth and yield. In order to examine the effect of reduced abscisic acid (ABA) level in the development strategies necessary for drought tolerance in plants, tomato genotypes with constitutively different ABA content, wild type Ailsa Craig and flacca mutant, were used in this study. Plants grown on either lower or higher light intensity were subjected to one or three drought cycles, followed by periods of rehydration. The impact of drought and rehydration was monitored on morphological (fresh and dry weight, leaf area) and physiological level (stomatal conductivity, leaf water potential), and by measuring biochemical (carbohydrates, amino acids, ascorbate) and molecular parameters (expression of genes involved in ABA metabolism and expression of noncoding RNA molecules). The results obtained in this dissertation showed that maintaining ABA homeostasis is crucial for tomato growth and development, even in optimal water regimes, and also that flacca mutant is a suitable model system for studying the impact of reduced ABA accumulation in development of drought tolerance strategies. It has been noticed that morphological changes and osmolyte accumulation in both genotypes significantly contribute in developing drought tolerance mechanisms of tomato plants. Exposure of plants to several drought cycles has induced changes in the accumulation of antioxidant components (ascorbate and epidermal flavonoids), cell wall structure, but also in the expression of non-coding RNA molecules, which could potentially contribute to memory development in tomatoes. more...

Stres suše, u kombinaciji sa svetlošću visokog intenziteta zračenja, predstavlja jedan od najrasprostranjenijih abiotskih faktora koji ima negativan uticaj na rastenje i prinos biljaka. U cilju ispitivanja uticaja sniženog nivoa apscisinske kiseline (ABA) na razvijanje strategija neophodnih za toleranciju biljaka na sušu, u ovom istraživanju korišćena su dva genotipa paradajza sa konstitutivno različitim sadržajem ABA, divlji tip Ailsa Craig i flacca mutant. Biljke su gajene na svetlosti nižeg i višeg intenziteta i bile podvrgnute jednom, odnosno trima ciklusima suše, koji su bili praćeni periodima rehidratacije. Uticaj suše i rehidratacije praćen je na morfološkom (sveža i suva masa, površina listova) i fiziološkom nivou (provodljivost stoma, ukupni vodni potencijal), kao i primenom biohemijskih (određivanje ugljenih hidrata, aminokiselina, askorbata) i molekularnih metoda (praćenje ekspresije gena uključenih u metabolizam ABA i određivanje ekspresije nekodirajučih RNK molekula).Rezultati prikazani u ovoj disertaciji pokazali su da je održavanje homeostaze ABA od presudnog značaja za rastenje i razviće paradajza i u uslovima optimalnog vodnog režima, kao i da je flacca mutant pogodan model sistem za proučavanje uticaja smanjene akumulacije ABA na razvoj strategija za razvijanje tolerancije biljaka na sušu.Pokazano je da akumulacija osmotski aktivnih jedinjenja kod oba genotipa, kao i promene na morfološkom nivou značajno doprinose razvoju mehanizama tolerancije paradajza na sušu.Izlaganje biljaka ciklusima suše indukovalo je promene u akumulaciji antioksidativnih komponenti (askorbat i epidermalni flavonoidi), strukturi ćelijskog zida, ali i u ekspresiji nekodirajućih RNK molekula, što potencijalno može doprineti razvijanju memorije kod paradajza na ponovljeni stres suše., Drought stress combined with high light intensity is one of the most common abiotic factors that have a negative impact on plant growth and yield. In order to examine the effect of reduced abscisic acid (ABA) level in the development strategies necessary for drought tolerance in plants, tomato genotypes with constitutively different ABA content, wild type Ailsa Craig and flacca mutant, were used in this study. Plants grown on either lower or higher light intensity were subjected to one or three drought cycles, followed by periods of rehydration. The impact of drought and rehydration was monitored on morphological (fresh and dry weight, leaf area) and physiological level (stomatal conductivity, leaf water potential), and by measuring biochemical (carbohydrates, amino acids, ascorbate) and molecular parameters (expression of genes involved in ABA metabolism and expression of noncoding RNA molecules).The results obtained in this dissertation showed that maintaining ABA homeostasis is crucial for tomato growth and development, even in optimal water regimes, and also that flacca mutant is a suitable model system for studying the impact of reduced ABA accumulation in development of drought tolerance strategies.It has been noticed that morphological changes and osmolyte accumulation in both genotypes significantly contribute in developing drought tolerance mechanisms of tomato plants.Exposure of plants to several drought cycles has induced changes in the accumulation of antioxidant components (ascorbate and epidermal flavonoids), cell wall structure, but also in the expression of non-coding RNA molecules, which could potentially contribute to memory development in tomatoes. more...

Three varieties of basil (Ocimum x citriodorum, Ocimum basilicum var. Genovese and Ocimumbasilicum var. purpurascens) were used to examine the effect of different PAR intensities (100, 400and 1400 µmol photons m-2s-1), as well as different UV-B/PAR ratios, on leaf phenolics accumulation, and components of the ascorbate-glutathione cycle. Phenolic compounds represent themost abundant class of secondary metabolites, and their function in plants involves protectionagainst numerous abiotic stresses, role in growth and development, flowering, reproduction andseed dispersion. A preferential accumulation of HCAs over Flav, induction of class III POD activityand decreased ascorbate content were characteristic responses to pro-oxidative effect of the highUV-B/PAR ratio in all three basil varieties. The most remarkable result was the lack of accumulationof epidermal UV absorbing substances, which appeared to be a crucial photoprotective mechanism in sunlight. The contrasting effect of ecologically relevant UV-B radiation on basil plants,pro-oxidative vs. acclimative, was determined by the quality and intensity of the background light.Acclimation of basil to high light comprises a number of processes, among which are the accumulation of epidermal flavonoids and total leaf phenolics, antioxidant response (increase in Asc andGSH) and lack of downregulation of PSII upon increasing light intensity. Among varieties that weused as model system in this study, purple basil, with the highest constitutive amount of anthocyanidins, showed the least induction of epidermal flavonoids and lack of light effect upon transferfrom initial 50 to 250 µmol photons m-2s-1. more...

Ramonda serbica Panc. is a resurrection plant species that can survive desiccation for a longperiod and fully resume metabolic functions upon rewatering in a very short period, even within48 h. The goal of this study was to identify key candidates and pathways involved in desiccation tolerance in R. serbica. To achieve this, systems biology approach combining transcriptomics,proteomics, and analysis of specific metabolites was employed. In addition, FTIR analysis of thecell wall polymers and a detailed analysis of the photosynthetic electron transport (PET) chainwere performed. In total, 1192 different protein groups were quantified by TMT-based comparative quantitative proteomics. Among them, 408 protein groups showed a statistically significantdifference in abundance between hydrated (HL) and desiccated leaves (DL). Upon desiccation, themajority of proteins related to photosynthetic processes were less abundant, while chlorophyllfluorescence measurements implied shifting from linear photosynthetic transport (PET) to cyclicelectron transport (CET). The amounts of H2O2 scavenging enzymes, including ascorbate-glutathione cycle components, catalases, peroxiredoxins, Fe-, and Mn- superoxide dismutase (SOD) werereduced in DL. However, four Cu/ZnSOD isoforms, three polyphenol oxidases, six germin-like proteins (GLPs), and 22 late embryogenesis abundant proteins (LEAPs; mainly LEA4 and dehydrins),were desiccation-inducible. Desiccation-induced cell wall remodelling by changes in cell wallpolymer composition might be linked with pectin demethylesterification and GLP-derived H2O2/HO•. Our study demonstrated that desiccation tolerance in R. serbica is a complex, species-specific process orchestrated by several metabolic pathways and regulatory networks acting at the transcript, protein, metabolite and physiological levels. more...

Drought causes huge agricultural and economic losses worldwide. Silicon (Si) is considered a beneficial element for plants. It mitigates stress caused by salinity, drought, and high and low temperatures by promoting antioxidant production. However, the underlying mechanisms are still not elucidated. We investigated Si fertilisation effect on photosynthetic parameters, trichome number, leaf optical properties, as well as profiles of amino acids and polyphenols in barley exposed to water shortage. Silicon was applied in three growth stages: (i) before the flag leaf emergence; (ii) prior to the grain filling phase; (iii) at the grain filling phase start. Drought negatively impacts photochemical efficiency, stomatal conductance, photosynthetic pigment content, and leaf reflective and transmissive properties. Si application between flag leaf emergence and grain filling had the strongest effect on light reflectance. Among all analyzed phenolics, saponarin was the most abundant in all samples, irrespective of water regime and Si supply. Caffeoyl ester was the only hydroxycinnamic acid showing significant accumulation with the latest applied Si compared to no added Si upon drought. The major amino acids in barley leaves were glutamate, glutamine, aspartate, asparagine, and serine. Aspartate content was the highest in leaves exposed to drought without Si addition, while lysine was the most accumulated in the leaves supplemented by Si at the grain filling phase start. Proline was 2.5 times more abundant in the leaves exposed to drought regardless of Si treatment. Taken together, although Si did not mitigate drought stress effects, its effect was dependent on the barley growth phase prior to supplementation. more...

Uzimajući u obzir klimatske promjene koje podrazumijevaju smanjenje količine padavina i porast temperatura, suša je postala globalni problem za koji se smatra da će biti aktuelan još dugo vremena u budućnosti. Osim problema koje stvara u brojnim životnim sferama, suša je jedan od najozbiljnijih faktora koji negativno utiče na poljoprivredu, s obzirom da nedovoljno vodosnabdijevanje negativno utiče na rast i razvoj biljaka. U uslovima suše povećana produkcija reaktivnih vrsta kiseonika može da izazove pomjeranje ravnoteže u ćelijskim oksidoredukcionim reakcijama u smjeru oksidacije te da dovede do nastanka oksidativnog stresa. Posljedice oksidativnog stresa su strukturna i funkcionalna oštećenja ćelijskih komponenti koja dovode do poremećaja u metabolizmu i funkcionisanju ćelije.Veoma važnu ulogu u toleranciji biljaka na stres izazvan sušom ima antioksidativni sistem zaštite koji neizbježno uključuje enzime superoksid dismutazu, katalazu, peroksidaze Klase III i askorbat peroksidazu, ali takođe i niskomolekularne antioksidante poput askorbata, glutationa, fenola i karotenoida. Posljednjih godina se naglo povećao interes za korištenje ekološki opravdanih i neinvazivnih sredstava kojima se unaprijeđuje problem vodosnabdijevanja biljaka, a velika pažnja je posvećena primjeni prirodnih aluminosilikata, od kojih je najpoznatiji zeolit. Iako nisu mnogobrojni, postoje radovi koji upućuju da ovaj prirodni mineral može značajno da doprinese poboljšanju vodnog režima biljaka zbog osobine vezivanja te uravnoteženog otpuštanja vode. U ovoj doktorskoj disertaciji predmet istraživanja je uključio dvije biljne vrste različite po tipu fotosintetičkog metabolizma i adaptivnim strategijama na prilagođavanje na sušu, a to su paradajz (Solanum lycopersicum L.) i kukuruz (Zea mays L.). Fokus istraživanja bio je ispitivanje mogućnosti primjene zeolita u svrhu sprječavanja ili ublažavanja posljedica stresa izazvanog sušom kod biljaka paradajza i kukuruza, ali i ispitivanje mogućeg različit, Taking into account climate change, which implies a precipitation decreasing and temperatures rising, drought has become a global problem that is considered to be relevant for a long time to come. In addition to the problems it creates in many spheres of life, drought is one of the most serious factors that negatively affects agriculture, given that insufficient water supply disrupts the growth and development of plants. The production of reactive oxygen species in drought conditions can cause an inbalance of cellular redox homeostasis in the direction of oxidation and lead to the formation of oxidative stress. The consequences of oxidative stress are structural and functional damages of cellular compartments which leads to disturbance of metabolism and cell function. A very important role in plant tolerance to drought stress has the antioxidant protection systems that inevitably include theenzymes superoxide dismutase, catalase, Class III peroxidases and ascorbate peroxidase, but also low molecular weight antioxidants such as ascorbate, glutathione phenol and carotenoids. In recent years, there has been a sharp increase in interest in the use of environmentally sound and non- invasive means to improve the water supply of plants, and much attention has been paid to the use of natural aluminosilicates, the most famous of which is zeolite. Although not numerous, there are studies that suggest that this natural mineral can significantly contribute to the improvement of the water regime of plants due to the binding properties and balanced release of water. In this PhD thesis, the subject of research included two plant species different in type of photosynthetic metabolism and adaptive drought adaptation strategies, namely tomatoes (Solanum lycopersicum L.) and maize (Zea mays L.). The focus of research was to examine the possibility of using zeolite to prevent or mitigate the effects of drought stress in tomato and maize plants, but also to examine the possible diff more...

Two tomato genotypes with constitutively different ABA level, flacca mutant and wild type of Ailsa Craig cv. (WT), were subjected to three repeated drought cycles, with the aim to reveal the role of the abscisic acid (ABA) threshold in developing drought tolerance. Differential responses to drought of two genotypes were obtained: more pronounced stomatal closure, ABA biosynthesis and proline accumulation in WT compared to the mutant were compensated by dry weight accumulation accompanied by transient redox disbalance in flacca. Fourier-transform infrared (FTIR) spectra analysis of isolated cell wall material and morphological parameter measurements on tomato leaves indicated changes in dry weight accumulation and carbon re-allocation to cell wall constituents in flacca, but not in WT. A higher proportion of cellulose, pectin and lignin in isolated cell walls from flacca leaves further increased with repeated drought cycles. Different ABA-dependent stomatal closure between drought cycles implies that acquisition of stomatal sensitivity may be a part of stress memory mechanism developed under given conditions. The regulatory role of ABA in the cell wall restructuring and growth regulation under low leaf potential was discussed with emphasis on the beneficial effects of drought priming in developing differential defense strategies against drought. more...

The present study examined the effects of Candidatus Phytoplasma solani infection on antioxidative metabolism in leaves and roots of carrot (Daucus carota L.). Disease symptoms appeared at the end of June in the form of the chlorosis on some of the leaves, which became intensely red one week later, while the previously healthy leaves from the same branch becme chlorotic. A few days later, all leaves from the infected leaf branch were intensely red. Infected plants also had slower growth compared to the healthy ones with fewer leaf branches developed. The roots of infected plants were less developed, seared, or gummy with or without brown-colored root hair. The presence of the pathogen was detected by sequencing the 16S rRNA. National Center for Biotechnology Information (NCBI) BLAST analyses of the obtained sequence revealed 100% identity of tested strain with deposited Ca. Phytoplasma solani strains from various countries and hosts, all belonging to the "stolbur" group (16SrXII-A). Identity of 99.74% was found when the tested Serbian strain (MF503627) was compared with the reference stolbur strain STOL11 (AF248959). The oxidative damage of membranes in carrot cells was accompanied by a decrease in the content of photosynthetic pigments. Furthermore, for the determination of specific scavenging properties of the extracts, in vitro antioxidant assay was performed. In phytoplasma-infected carrot leaves, there was a greater reduction in the level of glutathione content (GSH); however; flavonoids and anthocyanidins seem to be responsible for the accompanied increased antioxidative capacity against hydroxyl radical and hydrogen peroxide. more...

Resurrection plant Ramonda serbica Panc. survives desiccation for a long period and fully recovers metabolic functions already within one day upon watering [1]. Besides osmotic stress, desiccation provokes the accelerated generation of reactive oxygen species. The aim of our study was obtaining more insight into the mechanisms of desiccation tolerance in R. serbica by TMT labelled comparative quantitative proteomics of hydrated (HL) and desiccated leaves (DL). After de novo transcriptome analysis, 189456 transcripts with 189003 unigenes were annotated with seven common databases. Proteomic analysis allowed for the relative quantification of 895 different protein groups, 321 with a statistically significant difference in abundance between FL and DL. Among them, 25% referred to chloroplast and almost the same percentage were associated with desiccation and oxidative stress. Almost all differentially abundant proteins related to photosynthetic processes were down-regulated in DL, while those required for protein translation were more abundant in HL. Within differentially abundant proteins involved in antioxidative defence, the levels of enzymes involved in ascorbate-glutathione cycle, peroxiredoxins, Fe and Mn superoxide dismutase (SOD) were all reduced in DL, while germin-like proteins, three Cu/Zn SOD isoforms and polyphenol oxidases were more abundant in DL compared with HL. The protein family with the highest number of members showing the greatest accumulation upon desiccation comprised twenty different late embryogenesis abundant proteins (LEAPs), similarly as found by differential transcriptomic analysis. Taken together, our results imply a key role of LEAPs and Cu/Zn SOD in protective mechanism against desiccation in R. serbica, that may have significant implications on drought-related studies of crops grown in arid areas. This work was supported by the Science Fund of the Republic of Serbia (PROMIS project LEAPSyn-SCI, grant number 6039663). M.V. wishes to ackn more...