Fluorine, one of the most abundant elements found on earth, acts as an environmental xenobiotics even at sparingly low concentrations. Uncontrolled anthropogenic activities have steeply increased the F content in the air, water, and soil. Irrigation of crops and vegetables with F contaminated groundwater or agricultural practices in contaminated soils adversely affect their physiological and biochemical parameters, leading to inhibited growth and productivity. Some plants can translocate the toxic ions from roots to shoots and accumulate them in the edible parts. Bioaccumulations of F have hazardous outcomes, as their concentrations in edible parts can be higher than the safe value. Screening of F hyperaccumulators and F-tolerant plants has been performed to facilitate phytoremediation. Some plant bioindicators have been identified which can be used to analyse the extent of atmospheric F pollution. Cumulative use of these organisms through proper scientific planning programs can potentially improve the agricultural soil quality in terms of their toxic F content. Future research should focus on proper execution of these phytoremediative strategies via robust field trials. High throughput genetic analyses should also be performed to identify quantitative trait loci which can be exploited to generate F-tolerant characters in susceptible crop cultivars.

Gibberellic acid (GA) is a natural plant growth regulator (PGR) which stimulates germination, vegetative growth, flowering, and fruit formation. However, when high concentrations of GA are used, it inhibits plant growth and development and causes abnormalities in the plant tissue. In our study, we determined the effects of different concentrations of GA on Allium cepa L. var. cepa roots. Increasing concentrations of GA (50 - 5 000 mg dm^-3) were used in A. cepa root growth inhibition tests. Further, random amplified polymorphic DNA technique was used for determination of possible genotoxic effects of 600 - 1200 mg dm^-3 GA on A. cepa root tips. Our findings show cytotoxic and genotoxic effects of these concentrations of GA and indicate that the difference among control and treatment groups were statistically significant.

The effects of a short (30 min) heat shock (HS) on plants subsequently grown under a salinity stress (SS, 200 mM NaCl) for 10 d were investigated in barley (Hordeum vulgare L.) cv. Tokak 157/37. The maximum temperature for HS allowing plant survival was 45 °C. The root length was significantly decreased by SS, whereas HS alone did not affect root growth. Interestingly, HS stimulated root elongation under SS. An osmotic adjustment was promoted in leaves by SS. On the contrary, HS increased the osmotic potential in leaves in the absence of SS, and partly counteracted the effect of SS in the HS+SS treatment. Cu/Zn-SOD, HvAPX, HvCAT2, HSP17, HSP18, and HSP90 were transcribed in leaves of HS-treated plants, but not in control plants. The HSP70 was constitutively transcribed in both the SS and control plants, but after HS, a shorter amplicon was also observed. The genes coding antioxidants, Cu/Zn-SOD, HvCAT2 and HvAPX, were differentially influenced by SS or HS+SS in the roots and leaves. In the roots, the mRNA content of BAS1, HvDRF1, HvMT2, and HvNHX1 increased after the HS treatment. In a recovery experiment in which plants were grown to maturity after HS and HS+SS stress exposure, the plant height increased and the time to maturity was reduced in comparison with SS. Our results show that HS could stimulate plant growth and reduce some of the negative effects of SS, and that it affected the transcription of several stress-related genes.

Tea plant (Camellia sinensis) is a typical plant that accumulates abundant aluminum (Al) and fluoride (F). Al and F play vital roles in the growth and development in tea plant. MYB (myeloblastosis) is one of the largest transcription factor families in plant, which plays an important role in the stress responses. As the largest and multifunctional subfamily of MYB, R2R3-MYB subfamily participates in multiple abiotic stresses in plant. However, there are few studies about R2R3-MYB in tea plant, especially in the accumulation of Al and F during its growth. Here, we identified 43 CsMYB genes from the transcriptome database of tea plant and analyzed the relative expression in Al and F treatments. According to the Arabidopsis thaliana classification, 43 CsMYB genes are divided into 18 subgroups via phylogenetic tree analysis. All 43 CsMYB proteins have the typical R2R3-MYB domain by MEME prediction. Moreover, 9 CsMYB genes (CsMYB11, CsMYB17, CsMYB29, CsMYB38 to CsMYB43) that related to abiotic stress were selected from 43 CsMYB genes for a further study, and the relative expressions showed that they are tissue-specifically expressed. In addition, the results of different concentrations of Al treatments showed that CsMYB11, -17, -29, -38 and -41 are stimulated by Al treatment. The results of different concentrations of F treatments showed that the CsMYB11, -17, -38, -39, -40, -41, -42 and -43 participate in F accumulation of C. sinensis roots. Our research establishes a solid foundation for further investigation into the molecular functions of R2R3-MYB transcription factors in C. sinensis.

Five in vitro culture systems with different ventilation rates were used to investigate the influence of vessel environment on photosynthesis, dark respiration, ethylene evolution, and rosmarinic acid (RA) production in sweet basil (Ocimum basilicum L.) micropropagated shoots. The systems under comparison were two bioreactors with either temporary (RITA™) or stationary (Growtek™) immersion, and three types of vessels (Magenta™, Microbox ECO ₂ ™, and PCCV25™) that are largely used for plant micropropagation. Shoots of green-leaved cv. Genovese and purple-leaved cv. Dark Opal were cultured on a modified Murashige and Skoog medium containing 0.25 mg dm^-3 6-benzylaminopurine. The instantaneous rates of photosynthesis, dark respiration, and ethylene production were determined by gas chromatography measuring CO₂ and ethylene concentrations in vessel headspaces. The tissue RA content was determined by HPLC in HCl-methanol extracts. The explant growth and morphology were significantly affected by culture conditions and cultivars. The largest biomass production was observed under the photomixotrophic culture conditions provided by Growtek™, whereas the highest RA content in shoot tissues was found in the RITA™ photomixotrophic system, where ethylene accumulated to the greatest extent.

The reverse transcription quantitative real-time PCR (RT-qPCR) is becoming increasingly important for gene expression studies. However, the accuracy and reliability of RT-qPCR depend on normalizing expression to reference genes. In this study, ten candidate reference genes, including cyclophilin (CYP), elongation factor 1b (EF1b), α-tubulin (TUA5), β-tubulin (TUB4), ubiquitin10R (UBQ10R), 60S ribosomal RNA (60S), alcohol dehydrogenase (ADH3), metalloprotease (MTP), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and actin (ACT2) were evaluated for the stability of expression in three tissues of two peanut cultivars [Zhonghua 2(ZH₂) and 99-1507] under Al stress by four statistical algorithms (geNorm, NormFinder, BestKeeper, and RefFinder). The results suggested that the top-ranked reference genes under Al-induced programmed cell death (PCD) in peanut were UBQ10R, EF1b and CYP, with the most suitable combination of reference genes being [UBQ10R+ACT2]. The UBQ10R exhibited the most stable expression in all samples, while TUB4 was the least stable gene. The relative expression of AhMC1 (the caspase-like protease family gene, which played a significant role in Al-induced PCD) showed that there was no significant difference with the best reference gene and the best gene combination in RT-qPCR normalization, but there was significant difference with the least stable gene TUB4 as reference gene. This is the first study to evaluate the stability of reference genes in peanut under Al-induced PCD, and the results will provide guidance to identify appropriate reference genes for further RT-qPCR analyses under Al stress in peanut.

In our previous study on geranium, we showed that increases in growth irradiance from sub-optimal to near-optimal could delay boron deficiency effects on photosynthesis. In this study, we further investigated the effects of growth irradiance on tolerance to B stress by growing geranium (Pelargonium × hortorum cv. Maverick White) under sub- to supra-optimal B concentrations (4.5, 45, and 450 μM) and under three irradiances of 100, 300, or 500 μmol m^-2 s^-1 PAR for 30 d. In general, at low and medium irradiances, sub- and supra-optimal B availability decreased root and shoot dry masses, but at high irradiance, the B stress was prevented. Net photosynthetic rate decreased by the supra-optimal B concentration at the high irradiance only suggesting B-related photoinhibition. Tissue B content and root specific B uptake only modestly decreased by the low B treatment, but increased greatly by the high B availability, and the higher irradiance decreased the tissue B content and the root B uptake only at the low and medium B supplies. Interestingly, the increases in irradiance decreased the content and uptake of all other nutrients, except Fe uptake. Effects of the B stress on the content of other nutrients were variable, but the B stress often exacerbated decreases in nutrient content with the increasing irradiance which would be especially important under nutrient-limiting conditions. Hence, in this study, the B stress effects on growth were mitigated by the increases in growth irradiance, which offset negative effects on physiology, and the protective effects of irradiance were likely caused by its positive effects on plant carbon/energy status rather than on tissue B content or B uptake.

Flood in rice fields at the time of seed sowing and early seedling establishment causes extensive crop loss due to the inability of the seeds to tolerate and overcome submergence. In the present study, rice genotypes from Assam, India tolerant to hypoxia during germination were identified through systematic screening of deep-water rice genotype collection from flood-prone ecosystem of Brahmaputra river valley. The difference in tolerance to hypoxia during germination within the species provides scope for identification of novel hypoxia-responsive factors involved in tolerance as mechanism of tolerance may not be conserved across tolerant germplasms. Tolerant genotypes were further subjected to physiological and molecular characterization. Growth rate kinetics in tolerant genotypes new Rangdhakekua bao (RKB) and cultivar Khao Hlan On (KHO) from International Rice Research Institute (IRRI) used as positive control exhibited stronger escape strategy under hypoxic condition compared to sensitive genotype IR-64 (negative control). Activities of α-amylase and pyruvate decarboxylase were significantly higher in RKB and KHO than in IR-64, while no significant difference was observed in the alcohol dehydrogenase activity. Reverse transcription quantitative PCR confirmed increased amounts of transcripts of sucrose nonfermenting 1 related protein kinase, myeloblastosis-related protein S1, rice amylase 3D, and trehalose phosphate phosphatase 7 genes, which are known to be involved in hypoxia signaling cascade. Besides, transcription factors (TFs) like ethylene responce factors 71 and 63, ethylene insensitive 3-like 1a and proteins like expansins A7 and A2, which are involved in cell elongation had also significantly higher amounts in RKB compared to IR-64. Additional factors that include TFs like ERF71 and ERF63 that shows perturbation at transcription even within tolerant genotypes might constitute the genotype-specific regulation, evolved as a part of its adaptive mechanism to survive under submerged conditions.

Aluminum stress usually reduces plant root growth due to the accumulation of Al in specific zones of the root apex. The objectives of this study were to determine the localization of Al in the root apex of Sorghum bicolor (L.) Moech. and its effects on membrane integrity, callose accumulation, and root growth in selected cultivars. Seedlings were grown in a nutrient solution containing 0, 27, or 39 μM Al³⁺ for 24, 48, and 120 h. The Al stress significantly reduced root growth, especially after 48 and 120 h of exposure. A higher Al accumulation, determined by fluorescence microscopy after staining with a Morin dye, occurred in the root extension zone of the sensitive cultivar than in the tolerant cultivar. The membrane damage and callose accumulation were also higher in the sensitive than resistant cultivar. It was concluded that the Al stress significantly reduced root growth through the accumulation of Al in the root extension zone, callose accumulation, and impairment of plasma membrane integrity.

Roles for nitric oxide (NO) and reactive oxygen species (ROS) during pollen-tube growth have been well established in angiosperms, but there remains lack of information regarding their potential signalling roles in pollen tubes in gymnosperms. Here, the pollen-tube elongation of Arizona cypress (Cupressus arizonica Greene) was investigated. Nitric oxide, ROS, and actin were detected using their respective fluorescent probes. Both NO and ROS were observed in the nuclei of generative cells and pollen-tube cells, and in the cytoplasm in the tip region. An intracellular NO content in the pollen cells was lowered using an NO scavenger or an NO-synthase inhibitor. Similarly, an endogenous ROS content in the pollen cells was lowered using an NAD(P)H oxidase inhibitor. These treatments reduced pollen germination and pollen-tube growth, and induced severe morphological abnormalities. Inhibition of NO and ROS accumulation also severely disrupted the actin cytoskeleton in the pollen tubes. These data indicate that NO and ROS had signalling roles in pollen germination and pollen-tube formation in cypress.

Phenylalanine ammonia lyase (PAL) is a key enzyme in the phenylpropanoid pathway responsible for biosynthesis of many secondary metabolites, such as anthocyanins, flavanols, and lignins. The objective of this work was to determine the effect of different rootstock/scion combinations on Prunus tree growth, PAL gene expression, and PAL activity in order to identify compatibility of different graft combinations. The study was performed with peach (P. persica cv. Chimarrita) grafted on two peach rootstocks (Capdeboscq and Tsukuba1) and one Japanese apricot (P. mume cv. Umezeiro). Two or three years after grafting, the growth of peach scion on Umezeiro was weak and finally the death of some trees occurred. The peach rootstocks induced vigorous growth without any tree loss through the three years of evaluation. However, PAL activity and expression of PAL encoding genes were higher in Umezeiro as compared to the other rootstocks. These results show that the differential gene expression together with the PAL activity is a promising strategy to predict graft incompatibility.

Eukaryotic elongation factor Tu has been implicated in responses to heat stress and viral infection. In this study, the turnip mosaic virus (TuMV)-response gene BcLRK01, which encodes a leucine-rich repeat receptor-like kinase, was probed using the cDNA library of TuMV-infected leaves of non-heading Chinese cabbage (Brassica campestris ssp. chinensis). The BcEF-Tu gene, which encodes chloroplast elongation factor Tu, was obtained and verified by a yeast two-hybrid system to interact with the BcLRK01 gene. TuMV infection depressed the expression of this gene, whereas a heat stress induced its expression. Overexpression of BcEF-Tu enhanced the viability of Escherichia coli transformants under the heat stress. These results demonstrate that elongation factor BcEF-Tu responded to the TuMV infection and heat stress. This is the first report on chloroplast EF-Tu in non-heading Chinese cabbage which provides a theoretical basis for the functional research of EF-Tu.

In plants, calcineurin B-like proteins (CBLs) and CBL-interacting protein kinases (CIPKs) regulate Ca2+ signalling and so responses to biotic and abiotic stresses. However, the details of specific CIPKs functions in various stress responses are poorly understood. Here, we report roles of dicot and monocot CIPK2 genes in response to salinity and heavy metals. Arabidopsis thaliana AtCIPK2 was found to be universally expressed in different tissues and organs and furthermore induced by salinity. Overexpression of AtCIPK2 or Tibetan Plateau wild barley (Hordeum spontaneum) HsCIPK2 in Arabidopsis alleviated toxic effects of NaCl and mercury on seed germination and root growth. Similarly, reduced toxic effects of copper and cadmium on seed germination, but not on root growth, were observed in these transgenic lines. Live-cell fluorescence imaging analysis revealed that HsCIPK2 was predominantly distributed in the cytoplasm and nucleus and weakly localized at the plasma membrane (PM), but its PM association was rapidly enhanced upon exposure to high salinity and mercury. These results suggest an involvement of CIPK2 in plant tolerance to salinity and mercury and provide a new insight into physiological functions of CIPKs in plant response to heavy metals.

With the dramatic increase in nanotechnologies, it has become probable that biological systems will be exposed to excess of nanoparticles (NPs). However, the impact of NPs on plants, remains to be explored. The aim of this research was to determine the effects of ZnO NPs on tomato (Solanum lycopersicum L.) plants. Plant growth, photosynthetic characteristics, chlorophyll fluorescence parameters, and activities of antioxidative enzymes were measured in 35-d-old plants. The ZnO NP treatments significantly inhibited tomato root and shoot growth, decreased the content of chlorophylls a and b, and reduced photosynthetic efficiency and some other chlorophyll fluorescence parameters in a concentration-dependent manner. However, the supernatant of ZnO NP suspensions did not affect growth of tomato, despite the presence of small amounts of Zn²⁺. Taken together, these results suggest that toxic effects on tomato plants were from ZnO NPs, not from Zn²⁺ released into the solution; toxicity was likely caused by reduced chlorophyll content and damaged photochemical system, which in turn limited photosynthesis and led to the reduction in biomass accumulation. Also, ZnO NPs enhanced the transcription of genes related to antioxidant capacity, suggesting that ZnO NPs could enhance the defence response by increasing activities of antioxidant enzymes.

Low temperature is one of the most severe abiotic stress factors that limit chrysanthemum growth and development. Natural temperature changes are more complex, and cold stress from a laboratory incubator cannot accurately represent the natural temperature stress. Here, nine separate high-throughput mRNA sequencing technology (RNA-Seq) libraries were generated from the RNA sample of roots from different temperatures, including chilling (Ch), freezing (Fr), and control (CK). The 7 069 and 3 952 differentially transcribed genes were identified as CK vs. Ch and CK vs. Fr, respectively. The Kyoto encyclopedia of genes and genomes pathway (KEGG) enrichment analysis showed that significantly different flavonoid biosynthesis and linolenic acid pathways commonly appeared in CK vs. Ch and CK vs. Fr. Arginine and proline metabolism, lipid metabolism, fatty acid degradation, and fructose and mannose metabolism pathways were found in CK vs. Ch, and only in the CK vs. Fr enrichment metabolic pathway included steroid biosynthesis and monoterpenoid biosynthesis. The transcription of genes on differential metabolic pathways and MYBs were successfully validated using quantitative real-time PCR. At the same time, the antioxidant activity, malondialdehyde, and proline content were analyzed under low temperature. These datasets may aid in understanding and carrying out future studies on the molecular basis of cold stress and contribute to chrysanthemum breeding.

Plants exhibit morphological plasticity in response to changes in the proportion of far-red radiation (FR). However, little is known about the response to a sudden increase of FR component. Cucumber seedlings were acclimatized to radiation without FR (FR-) for 1 - 5 d after germination, and then transferred to radiation containing FR (FR+) at levels similar to those in natural sunlight. Other seedlings were acclimatized to FR- or FR+, which was maintained continuously. The sudden increase in FR damaged the cotyledons and the first true leaf, especially when radiation was changed from FR- to FR+ at days 3 or 4 after germination. Necrosis of the damaged leaves may have resulted from inhibition of water flow in leaf xylem, because wilting and decreased stomatal conductance were observed simultaneously with leaf necrosis. Plants in the treatment groups that showed the most frequent damage showed two peaks in cotyledon elongation. This suggests that the leaves that had been acclimatized to FR- were easily damaged by the sudden promotion of leaf expansion caused by FR+.

Osmotic stress causes a series of morphological, physiological, biochemical, and molecular changes that alters plant growth, development, and productivity around the globe. Phytohormones, nutrients, and transcription factors may induce adaptive responses to osmotic stress in plants. We evaluated the effect of osmotic stress induced by 18.5 % polyethylene glycol (PEG) or 100 mM NaCl on growth, content of abscisic acid (ABA), chlorophyll (Chl), sodium, and potassium, and the expression of multifunctional NAC transcription factors in rice cultivars (the salt-tolerant Cotaxtla and salt-sensitive Tres Ríos). The PEG and NaCl decreased shoot height and increased ABA content in both cultivars, and reduced root length in cv. Tres Ríos. The PEG increased Chl content in cv. Cotaxtla leaves. NaCl reduced shoot K⁺ content in cv. Tres Ríos and increased shoot and root Na⁺ content in both cultivars, thus resulting in a decreased K⁺/Na⁺ ratio. Of the 57 NAC genes evaluated, two of them were repressed (Os10g42130 and Os07g04560) and two other induced (Os02g34970 and OsNAC10) in cv. Cotaxtla in response to PEG, whereas three of them were repressed (Os10g42130, Os07g04560 and Os08g10080), and six induced (Os02g56600, Os02g34970, Os11g08210, Os05g34830, OsNAC6, and OsNAC10) in response to NaCl. In the cv. Tres Ríos, we found two genes repressed (Os10g42130 and Os07g04560), and five induced (Os08g33910, Os03g60080, Os06g51070, OsNAC6, and OsNAC10) in response to PEG, while only two genes were repressed (Os10g42130 and Os07g04560) but 13 induced (Os03g21060, Os08g39110, Os03g60080, Os01g15640, Os06g51070, Os09g33490, Os04g40130, Os12g29330, Os02g36880, Os11g08210, Os05g34830, OsNAC6, and OsNAC10) by NaCl. Osmotic stress affected more severely cv. Tres Ríos than cv. Cotaxtla plants. These different responses might be regulated by ABA and NAC transcription factors.

Interactions between three genotypes of a silver fir (Abies alba Mill.) embryogenic callus and Heterobasidion abietinum, H. parviporum, and H. annosum were examined in dual cultures. The aim of this study was to determine whether dual cultures can be used to evaluate the degree of fungal virulence at an embryogenic level, and whether different genotypes of a callus show different susceptibility. The dual cultures were performed on Schenk and Hildebrandt medium. Mycelial growth of H. parviporum and H. annosum was significantly stimulated in the presence of the callus but was not directional in nature. The embryogenic callus died between six and nine days after being colonized by H. parviporum suggesting that this was the most virulent species. By contrast, the callus remained healthy for up to 50 d after colonization with H. abietinum suggesting that this was the least virulent species. The callus of the A. alba genotype which originated in the mountain region of Poland remained healthy and alive for a significantly longer period than the other two genotypes in the dual cultures with all three Heterobasidion species even though overgrown by mycelium suggesting that the mountain genotype had the strongest defence response to Heterobasidion infection.

Soil salinity leads to a reduction in plant growth, germination, relative water content, and production of wheat plants worldwide. Chitosan showed a positive effect on plant growth and development and improved plant stress tolerance. The current study aimed to examine the effect of different chitosan concentrations on the gamma-aminobutyric acid (GABA) shunt pathway in germinating seeds of wheat (Triticum durum L.) under salt stress (25 - 200 mM NaCl). We determined the seed germination pattern, seed moisture content, GABA shunt metabolites (GABA, glutamate, and alanine), oxidative damage in terms of malondialdehyde (MDA) accumulation, and the glutamate decarboxylase (GAD) mRNA transcription. Pre-treatment of wheat seeds with chitosan improved germination by enhancing germination percentage, seedling length, and seedling fresh and dry masses under salt stress. Data showed an increase in GABA shunt and their metabolites (alanine and glutamate), MDA content, and GAD mRNA transcription, and a decrease in germination percentage, seedling length, seedling fresh and dry masses for both untreated and chitosan-treated seeds under salt stress. Our results suggest that the elevation of GABA in chitosan-treated seeds was able to maintain metabolic stability under salt stress. The MDA content increased in chitosan-treated seeds as NaCl concentration increased, however, the increase was slightly lower than the MDA content in untreated seeds which confirmed that chitosan activates GAD mRNA expression that leads to activate GABA shunt to involve in the reduction of membrane damage and activation of reactive oxygen species scavenging systems under salt stress. Consequently, this study demonstrated that chitosan significantly enhanced the accumulation of GABA and amino acids metabolism to maintain the C:N balance and improved salt tolerance in wheat seeds during seed germination.

Tetracentron sinense Oliv, the only tall deciduous tree in the family Tetracentraceae, is listed as a national second-grade key protected plant in China. To reveal the effect of associated species, irradiance, and altitudes on photosynthetic capacity of T. sinense, photosynthetic physiological characteristics of T. sinense and its associated species Acer pictum and Pterocarya stenoptera were measured by a Li-6400 portable photosynthetic meter. The light saturation point (LSP), the maximum net photosynthetic rate of the P_N-PAR (P_Nmax), carboxylation efficiency (CE), the maximum net photosynthetic rate of the P_N-CO₂ (P^*_Nmax), carbon dioxide compensation point (CCP) and light respiration rate (R_p) of T. sinense in forest gap (FG) were higher than those in forest edge (FE) and understory (US). In FE, the net photosynthetic rate (P_N), light compensation point (LCP), LSP, P^*_Nmax of T. sinense were lower than those of Pterocarya stenoptera, while the LSP, P_Nmax, and saturation point of carbon dioxide (C_iast) of T. sinense in US were lower than those of Acer pictum and Pterocarya stenoptera. The specific leaf area (SLA) of T. sinense decreased with reduction in the irradiance. With increasing altitude, the P_Nmax, LSP, and SLA of young individuals of T. sinense (YT) increased; the LCP of YT or the LSP of mature individuals of T. sinense (MT) increased first and then decreased. The results showed that 1) the photosynthetic capacity and adaptability of T. sinense were better in FG than that in FE and US; 2) the photosynthetic capacity of T. sinense in FE and US was weaker than that of its associated species, and its ecological range of light adaptation was also narrower than that of its associated species, placing T. sinense at a competitive disadvantage, which may be one of the important reasons for its poor regeneration; and 3) the environmental conditions at higher altitude can contribute to the growth and survival of T. sinense. Therefore, active artificial intervention should be undertaken to expand area of forest gap for T. sinense and transplant its seedlings to higher altitude to promote growth and population regeneration of T. sinense.

Heavy metal toxicity in soils has been considered as major constraints for oilseed rape (Brassica napus L.) production. In the present study, toxic effects of chromium (Cr) were studied in 6-d-old seedlings of four different cultivars of B. napus (ZS 758, Zheda 619, ZY 50, and Zheda 622). The elevated content of Cr inhibited seedling growth, decreased the content of photosynthetic pigments, and activities of antioxidant enzymes, as well as increased the content of malondialdehyde and reactive oxygen species in all the cultivars. The Cr content in different parts of plants was higher in Zheda 622 than in other cultivars. The electron microscopic study showed changes in ultrastructure of leaf mesophyll and root tip cells at 400 μmol Cr, and these changes were more prominent in Zheda 622. An increased size and number of starch grains and number of plastoglobuli, damaged thylakoid membranes, and immature nucleoli and mitochondria were observed in leaves. In roots, enlarged vacuoles, disrupted cell walls and cell membranes, an increased number of mitochondria and a size of nucleolus, as well as plasmolysis (in Zheda 622) were observed. On the basis of these findings, it can be concluded that cv. Zheda 622 was more sensitive to Cr as compared to other three cultivars.

Tobacco (Nicotiana tabacum L.) plants were cultured in vitro photoautotrophically at three levels of irradiance (PAR 400-700 nm): low (LI, 60 µmol m^-2 s^-1), middle (MI, 180 µmol m^-2 s^-1) and high (HI, 270 µmol m^-2 s^-1). Anatomy of the fourth leaf from bottom was followed during leaf development. In HI and MI plants, leaf area expansion started earlier as compared to LI plants, and both HI and MI plants developed some adaptations of sun species: leaves were thicker with higher proportion of palisade parenchyma to spongy parenchyma tissue. Furthermore, in HI and MI plants palisade and spongy parenchyma cells were larger and relative abundance of chloroplasts in parenchyma cells measured as chloroplasts cross-sectional area in the cell was lower than in LI plants. During leaf growth, chloroplasts crosssectional area in both palisade and spongy parenchyma cells in all treatments considerably decreased and finally it occupied only about 5 to 8 % of the cell cross-sectional area. Thus, leaf anatomy of photoautotrophically in vitro cultured plants showed a similar response to growth irradiance as in vivo grown plants, however, the formation of chloroplasts and therefore of photosynthetic apparatus was strongly impaired.

Bacterial leaf blight (BLB) is a common disease that affects rice development and yield. The effects of major nutrients, especially nitrogen, on rice BLB susceptibility have been considered when devising rational fertilization strategies. However, the defense mechanism of rice against BLB under phosphate (Pi)-deficient conditions remains uncertain. Jasmonic acid (JA) is a phytohormone produced by rice plants to respond to abiotic and biotic stresses. Here, the involvement of the JA pathway in rice response to Xanthomonas oryzae pv. oryzae (Xoo) under low Pi was investigated in two contrasting rice cultivars G299 and G22. Expressions of JA-related genes under low Pi and Pi-related genes under JA treatment were assessed. The resistant capacity of G299 and G22 against Xoo infection was also investigated. In the JA-sensitive and Pi-sensitive cv. G299, JA-related genes were highly expressed under low Pi, and low Pi-responsive genes were strongly upregulated under JA treatment. Neither JA nor Pi pathways were activated in the JA-tolerant and low Pi-tolerant cv. G22. Low Pi strongly enhanced rice resistance to Xoo in cv. G299. Our study demonstrated that Pi deficiency confers rice resistance to Xoo. The JA pathway modulates the response to low Pi, depending on the cultivar. Pi-response genes are involved in Pi stress and may participate in the regulation of overall plant growth under various abiotic stresses. These findings provide new insights into the interaction between phosphate deficiency and the JA pathway and the subsequent effect on plant disease resistance.

The “Centre for Experimental Plant Biology”, a joint project of the Institute of Experimental Botany of the Czech Academy of Sciences and CEITEC (represented by Mendel and Masaryk Universities), focused on elucidating  the mechanisms of plant responses to abiotic and biotic stresses and their combinations at the cellular level, in intact plants during vegetative and reproductive stages, and fruit development. The consortium demonstrated the importance of shared research facilities, complementary approaches, and knowledge exchange, addressing demanding questions  in plant biology. The consortium made breakthrough in plant-pathogen interactions, including identification of  exocyst-syntaxin cooperation in non-host resistance. The results confirmed the fundamental role of phytohormones in stress responses, including negative correlation of leaf bioactive gibberellins with drought stress, and the role of cytokinins in ROS homeostasis, sulphur metabolism, and heat stress responses, including volatile emission. Molecular analyses revealed expansin-mediated cell wall remodelling, brassinosteroid-mediated regulation of root growth through PIN2, the role of ALBA and LARP6C proteins in pollen development under abiotic stress, and heat stress impact on fertilization rate, embryo and seed development. Gene Set Enrichment and RNA-Seq analyses allowed to identify crucial genes involved in the apple scab resistance network. The main results obtained during the five-year project are summarised here.

Solanum nigrum L. is an annual undomesticated berry plant of Solanaceae. The fruits of S. nigrum are tiny, but there are about 25 seeds in a single fruit. The total number of seeds produced in one plant can reach more than 3 000. The height is about 30 - 40 cm, and the whole growth cycle is two months when S. nigrum was cultivated in the light incubator of the laboratory. The Agrobacterium tumefaciens-mediated transformation has been established in S. nigrum. So S. nigrum has the characteristics of model plants. AcMYB110, an R2R3-MYB transcription factor from kiwi (Actinidia spp.), was transformed into S. nigrum mediated by A. tumefaciens. The results indicated that the petals of 35S:AcMYB110 S. nigrum plants are pink compared with white petals in wild-type plants, and content of anthocyanins was significantly increased in the pericarp from young fruit to its maturity, especially in the central part of the fruit flesh. The results showed that the ectopic expression of AcMYB110 in S. nigrum is consistent with the expression of AcMYB110 in kiwi. This suggests that AcMYB110 plays a conserved role in regulating anthocyanins synthesis in fruits and can be potentially applied for improvement of the anthocyanins content in horticulture fruits breeding.

Brassinosteroids (Brs) have drawn wide attention due to their protective role against toxicity of heavy metals in plants. To better understand the role of Br in arsenic (As) and cadmium (Cd) uptake by rice plants, a hydroponic experiment was conducted to investigate the combined effect of 24-epibrassinolide (Br24) or 28-homobrassinolide (Br28) and iron plaque (IP) on As and Cd uptake and accumulation in rice seedlings. Six-week-old seedlings were sprayed with 0.2 or 0.02 μM Br24 or Br28 and grown in nutrient solution for 3 d, and then 20 or 60 mg Fe²⁺ dm^-3 (Fe20 and Fe60) was used to induce root IP formation for 3 d. These seedlings with or without Br and with or without IP were exposed to solution containing 0.5 mg dm^-3 As^III or Cd for 9 d. The results showed that rice growth decreased when Br24 were applied, but it increased when combination of Br24 and IP was applied. Fe concentrations in dithionite-citratebicarbonate (DCB) extracts were increased after 0.2 or 0.02 μM Br24 application in the absence of IP, but decreased by Br24 in the presence of IP. In the absence of IP, As and Cd content in leaves was significantly reduced by 0.02 μM Br24 and 0.2 μM Br28, respectively. The As content in leaves was also reduced by the combination of 0.02 and 0.2 μM Br28 and IP, and the Cd content in leaves was reduced by the combined effect of 0.2 μM Br24 and IP. These results indicate that Br24 and Br28 could impede As and Cd accumulation, and the interactions between Br and IP may have a potential in restricting the transport of As and Cd into rice shoots.

The pollen tube grows rapidly, exclusively at its tip, to deliver its sperm for fertilization. The polarized tip growth of pollen tubes is dependent on the highly dynamic actin cytoskeleton. Plant LIM proteins (named after initials of containing proteins Lin11, Isl-1, and Mec-3) have been shown to regulate actin bundling in different cells, however, their roles in pollen tube growth have remained obscure. Here, we report the function of Arabidopsis LIM proteins PLIM2a and PLIM2b in pollen tube growth. The PLIM2a mutation resulted in short and swollen Arabidopsis pollen tube with defective actin bundles. The expression of the construct green fluorescent protein (GFP)-PLIM2b led to fluorescence of the actin bundles in germinating pollen and also the long actin bundles along the growing pollen tubes in Arabidopsis, but not of the short and sparse actin bundles that characterize the tip regions of the pollen tubes. There is a partially redundant function between PLIM2a and PLIM2b in the shank actin bundle organization during Arabidopsis pollen tube growth, as PLIM2b could rescue for the defective shank actin bundles in PLIM2a mutation pollen tubes. This report suggests critical roles of PLIM2a/PLIM2b in actin configuration during Arabidopsis pollen germination and tube growth.

Cadmium is a widely spread pollutant and the objective of this study was to study the effects of different concentrations of Cd (0, 50, and 100 μM) on the soybean seedlings treated for 10 d. The growth was inhibited and chlorophyll content, net photosynthetic rate, stomatal conductance, intercellular CO₂ concentration, probability that a trapped exciton moves an electron into the electron transport chain beyond QA - (ET_O/TR_O), performance indexes (PI_ABS), and amount of active reaction centres per excited cross section (RC/CS_O) were decreased with the increasing Cd concentration. The leaf reflectance increased in visual range (500-670 nm) and decreased in near-infrared range (750-1 000 nm). The accumulation of Cd in the roots was much higher than that in the stems and leaves.

Abiotic stresses strongly impair plant development and might impose detrimental effects particularly on seedlings. Irradiance and water deficit are relevant factors, which affect performance of young plants under controlled conditions. In our study, we investigated the influence of water shortage combined with different radiation sources - light emitting diodes (LED) and compact fluorescence lamps (CFL) - on physiological and biochemical parameters of young apple plants. Stress responses were assessed by fluorescence-based indices, while relative water, chlorophyll (Chl), and proline content served as reference parameters. The watering regime had a higher impact on biochemical indicators than the radiation sources. Lower Chl content was determined in plants grown under LED both in control and in water deficit plants. Nitrogen balance index and nitrogen balance index with red radiation excitation showed similar patterns regarding leaf Chl results in relation to the radiation source, being higher under CFL. In contrast, the flavonol index was higher in plants cultivated under LED. Stomatal conductance and maximal photochemical efficiency emphasised a radiation quality effect with higher values for CFL. In conclusion, fluorescence indices related to nitrogen status and flavonol content are promising parameters to sense physiological impairments under the given conditions. However, discrepancies compared to previous studies might be related to the different plant species, the nature of dehydration, and the measuring conditions.

Gibberellins (GAs) are a large family of tetracyclic diterpenoids, controlling important aspects of growth and development throughout the plant life cycle. To explore the possibility that gibberellin A₃ (GA₃) signalling induces epigenetic alteration(s), we carried out a field experiment study using Nicotiana tabacum as a model system. The GA₃ application on leaves resulted in increased plant-height, foliage density, leaf cell area, and trichome density. The plants exposed to GA₃ also exhibited: 1) increased chromatin de-condensation, 2) reduced global DNA methylation, 3) reduced DNA methyltransferases (NtDNMTs) activities accompanied by decreased amounts of NtMET1 and NtCMT3 transcripts, and 4) partial restoration of phenotype and expression of epigenetically silenced reporter transgene. Based on these observations, we propose that GA₃ application induces complex epigenetic re-programming, which may lead to distinct developmental phenotypes. These results could provide an important insight for future studies on epigenetic mechanism(s) in other important crops.