Cotton (Gossypium hirsutum L.) net photosynthetic rate (P_N) decreased with leaf age and low irradiance, and the interaction of these factors might lead to decreased yields mainly in crops with a high plant density. Shade decreased leaf gas exchange, mainly in young leaves, which did not recover after exposure to an increasing irradiance. Old leaves reached P_N saturation at a lower irradiance than young leaves. Also stomatal conductance decreased with leaf age and shading. Intercellular CO₂ concentration and irradiance were inversely related. The responses of P_N to irradiance decreased as leaf aged, and it did not interact with shade suggesting that self-shading is not primarily responsible for the decreased photosynthetic rate in older cotton leaves.

Nutritional stress is one of the main limits to sugar beet yield. This study evaluated morphological and molecular responses of sugar beet to changes in sulfate availability. Morphological characteristics of the root system and the accumulation of microRNA395 (miR395) were examined in sulfate(S)-supplemented and S-deprived seedlings under hydroponic conditions. We also investigated the functional role of miR395 in regulating the expression of APS1 gene coding for ATP-sulfurylase in roots and leaves. The S-deprived seedlings showed a significant increase in the number of root tips, in the miR395 expression in leaves but not in roots, and in the expression of APS1 gene. Our results indicate that miR395 may be a useful biomarker for sulfate status in sugar beet.

Due to possible climate changes, heat stress has obtained a serious concern all over the world. Tolerance to this stress via knowledge of metabolic pathways will help us in engineering heat tolerant plants. A group of proteins called heat shock proteins are synthesized following stress and their synthesis is regulated by transcription factors. Under high temperature (HT), reactive oxygen species (ROS) are often induced and can cause damage to lipids, proteins, and nucleic acids. To scavenge the ROS and maintain cell membrane stability, synthesis of antioxidants, osmolytes, and heat shock proteins is of a vital importance. In view of above mentioned, this review highlights the detailed mechanism of pathways involving crucial steps that change during HT stress.

The effect of benzothiadiazole (BTH) and arbutin (ARB) on sugar metabolism and plant fitness in cucumber growing hydroponically in media with different doses of NO₃ ^- and urea as nitrogen sources (100 % NO₃ ^-, 75 % NO₃ ^- + 25 % urea, and 50 % NO₃ ^- + 50 % urea) was studied on the 7^th and 14^th day after the treatment. The glucose, sucrose, and chlorophyll (Chl) content, acid and alkaline invertases and lactate dehydrogenase activities, as well as leaf area of the 3^rd and 5^th leaves were determined. Urea changed the plant sugar metabolism in a dose-, time- and leaf-age-dependent manners and influenced a cucumber response to the BTH and ARB treatments. The BTH caused a significant cessation of growth, a decrease in Chl content, a reduction of leaf area, and an enhancement of lactate dehydrogenase and alkaline invertase activities. In the older leaves of the BTH-treated plants, a high accumulation of glucose and sucrose was found. At the lower dose of urea, the metabolic changes were limited. In the ARB-treated plants, the Chl content remained unchanged in all the nitrogen variants. In these plants, decrease in glucose and sucrose content and in both invertase activities was observed mainly in younger leaves of the plants grown on the high dose of urea. The ARB improved the fitness of the cucumber plants grown in the presence of urea.

Plant microRNAs (miRNAs) play important roles in regulating plant growth, development, and responses to abiotic stresses. In this study, 38 miRNAs (TaMIRs) from wheat (Triticum aestivum L.), 36 from the miRBase database, and two from our previous work were characterized and subjected to an expression pattern analysis under normal conditions and a drought stress. A semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR), real-time quantitative PCR (qPCR), and small RNA blot analyses revealed that two TaMIRs (TaMIR1120 and TaMIR1123) were root-predominant and two TaMIRs (TaMIR1121 and TaMIR1134) were leaf-predominant. Seven TaMIR precursors showed altered expressions after the drought; of these, TaMIR1136 was upregulated, whereas TaMIR156, TaMIR408, TaMIR1119, TaMIR1129, TaMIR1133, and TaMIR1139 were downregulated. These seven drought-responsive TaMIRs showed dose-dependent and typical temporal expression patterns during drought induction, and they gradually returned back under the normal growth conditions. The drought-responsive and the tissue-predominant TaMIRs had varying numbers of target genes. Randomly selected target genes exhibited opposite expression patterns to their corresponding TaMIRs suggesting that they were regulated by distinct TaMIRs through a post-transcriptional cleavage. The target genes regulated by drought-responsive and tissue-predominant TaMIRs are involved in various cellular processes, such as signal transduction, transcriptional regulation, primary and secondary metabolisms, development, and defense responses. These results provide a novel insight into the miRNA-mediated responses of wheat to drought stress.

The effects of short-term osmotic stress [a polyethylene glycol (PEG) treatment] on photosystem II (PS II) of upland and lowland rice seedlings were investigated using chlorophyll (Chl) fluorescence imaging. Spatial heterogeneity in the top fully expanded leaf for all Chl fluorescence parameters was found under stress conditions. After exposure to PEG, a decrease in the effective quantum yield of PS II photochemistry (φPS II) and photochemical quenching (qP), and an increase in non-photochemical quenching (NPQ) proceeded from the upper section to the base of the leaf. The most sensitive position in the leaf was different between the two ecotypes. Chl fluorescence parameters, net photosynthetic rates (P_N), and stomatal conductance (g_s) were more sensitive to the PEG stress in upland rice than in lowland rice. These results also indicate different leaf anatomy and development in the two rice ecotypes. Additionally, the findings suggest a more rapid stress response in upland rice.

In this study, the anthocyanin content and real-time quantitative expression of the anthocyanin biosynthesis-related genes were investigated in leaves, stems, and tubers of purple yam (Dioscorea alata L.). The anthocyanin content, its accumulation, and the expression of genes encoding phenylalanine ammonia lyase (PAL), flavanone-3-hydroxylase (F3H), anthocyanidin synthase (ANS), and UDP-glycose flavonoid glycosyl transferase (UFGT) were studied. The anthocyanin content in the leaves and stems was high at early stages of growth, but it decreased and remained at a similar level from the 35^th day onward. The anthocyanin content in the tubers firstly increased, reached a high peak at the 110^th day of growth, after which decreased. Anthocyanin accumulation rates and the expressions of the anthocyanin biosynthesis genes were high at the early stages of growth in the leaves and stems, but in tubers, two peaks were observed: at days 80 and 140 for the gene expression and at days 125 and 170 for the anthocyanin accumulation rate. Thus, there was coordination between the gene expressions and the anthocyanin accumulation rates in the various organs as well as in the entire plants.

Germin and germin-like proteins (GLPs) are a broad and diverse family of developmentally regulated proteins widely distributed in plants. Oryza sativa L. harbours a large family of GLPs and serves as a good model for their study. In the present study, a germin-like protein gene (OsRGLP1) of rice origin was characterized by its heterologous expression in tobacco. The real-time PCR established almost a uniform expression of OsRGLP1 in leaves, stem, and roots of T₁ Nicotiana tabacum cv. Samsun. Although no morphological difference was apparent between T₀ transgenic and wild-type plants, leaves of mature transgenic plants showed necrotic lesions associated with an elevated content of H₂O₂, which was evidenced by in situ 3,3'-diaminobenzidine staining. A significantly higher activity of heat resistant superoxide dismutase (SOD) was observed in the transgenic plants as compared to the wild-type. The SOD activity in the transgenic plants was insensitive to potassium cyanide and sensitive to H₂O₂.

Phospholipase D (PLD) and its product phosphatidic acid are now considered to be one of the key elements of numerous physiological processes in plants including the salicylic acid signalling pathway. The presented study investigates the transcriptional regulation of Brassica napus PLDs following treatments with defense-related stimuli. We cloned eight B. napus genes encoding members of PLDβ, γ, and δ isoforms and performed phylogenetic analysis with its ancestor species Brassica rapa and Brassica oleracea, and with the model plant Arabidopsis thaliana. Transcription of the identified genes was monitored after treatment with benzothiadiazole (BTH), methyl jasmonate (MeJA), bacterial elicitor flg22, wounding, and after infection with fungal pathogens Sclerotinia sclerotiorum and Leptosphaeria maculans. Most of the genes responded specifically to a particular treatment. Remarkably the genes encoding the PLDγ and PLDβ isoforms were up-regulated by stimuli associated with the salicylic acid signalling pathway. The generality of this finding was confirmed by the analysis of public transcriptional data from Arabidopsis thaliana.

Analysis of structural changes of octoploid triticale genomes was conducted in F₂ and F₃ generations. The plants were derived from crosses of five cultivars and breeding lines of hexaploid wheat (Triticum aestivum L.) with one cultivar of rye (Secale cereale L). The study used four marker systems: inter-simple sequence repeat (ISSR), inter-retrotransposon amplified polymorphism (IRAP), retrotransposon-microsatellite amplified polymorphism (REMAP), and a technique named inter-transposon amplified polymorphism (ITAP) developed by the authors. Most frequently, elimination of specific bands was observed, especially of rye bands. Depending on the cross combination, the percentage of eliminated rye bands ranged from 73.6 to 80.6 %. A lower percentage of wheat bands was eliminated, i.e., from 57.6 to 76.48 %, depending on the combination of crosses. The emergence of new types of bands in hybrids absent in the parental forms was the rarest phenomenon (14.5-17.9 %). The results indicate the ongoing process of genome rearrangements at the molecular level in the early generations of plant crosses that also involve repeated nucleotide sequences of DNA.

Brassinosteroids (BRs) are polyhydroxylated steroidal plant hormones that play pivotal role in the regulation of various plant growth and development processes. BR biosynthetic or signaling mutants clearly indicate that these plant steroids are essential for regulating a variety of physiological processes including cellular expansion and proliferation, vascular differentiation, male fertility, timing senescence, and leaf development. Moreover, BRs regulate the expression of hundreds of genes, affect the activity of numerous metabolic pathways, and help to control overall developmental programs leading to morphogenesis. On the other hand, the potential application of BRs in agriculture to improve growth and yield under various stress conditions including drought, salinity, extreme temperatures, and heavy metal (Cd, Cu, Al, and Ni) toxicity, is of immense significance as these stresses severely hamper the normal metabolism of plants. Keeping in mind the multifaceted role of BRs, an attempt has been made to cover the various aspects mediated by BRs particularly under stress conditions and a possible mechanism of action of BRs has also been suggested.

Triploid plants of ornamental Phlox drummondii Hook. were raised from cultures of endosperm excised from immature fruits having zygotic embryo at early dicotyledonous stage. Endosperm tissue was firstly cultured with the embryo on the Murashige and Skoog's (MS) medium supplemented with 5 μM 6-benzylaminopurine (BAP) + 10 μM α-napthaleneacetic acid (NAA) for 7 d and recultured after the embryo was removed. A friable callus appeared two weeks after removal of the embryo and it became compact callus mass in another three weeks. Upon transfer of this 5-week-old callus to the MS medium with 10 μM BAP + 2.5 μM indole-3-acetic acid (IAA), maximum percentage of green nodular shoot buds appeared from which regenerated dwarf shoots. Elongation of the dwarf shoots, however, required transfer of the individual dwarf shoots excised from the callus on the fresh medium and best results achieved on medium with low concentration of IAA (0.5 μM) in presence of 10 μM BAP. The shoots were then rooted in vitro and plants subsequently established in pots containing soil. Over 70 % of plants were triploid with a chromosome number of 2n=3x=21. Size of stem, leaves, flowers, pollen, and stomata of these triploid plants were higher and the plants were more vigorous as compared to naturally occurring diploid plants. In particular, flowers showed bright colour with enlarged central eye adding to their ornamental value.

Drought is one of the main environmental stresses and many investigators identified beneficial effects of both silicon and selenium on plant growth and development. To examine the effects of Si and Se on rice (Oryza sativa L.) responses to drought, two cultivars Giza 177 and IET 1444 pretreated with 1.5 mM Si or 0.03 mM Se were then exposed to a water stress until leaf rolling was observed. The enhanced growth of Se or Si pre-treated plants was associated with a significant increase in the content of proline and glycine betaine in both shoots and roots. Furthermore, the transcription factors (TFs), dehydration responsive element-binding protein DREB2A, and NAC5 [no apical meristem (NAM), Arabidopsis thaliana activating factor (ATAF), and cup-shaped cotyledon (CUC)] were over-expressed in the drought stressed rice shoots. Notably, a pretreatment with either Se or Si significantly enhanced the expression of both TFs, DREB2A, NAC5, as well as the expression of the ring domain containing OsRDCP1 gene and some drought specific genes, such as OsCMO coding rice choline monooxygenase and dehydrin OsRAB16b. Expression of TFs and the studied genes was markedly enhanced in the Si-stressed shoots of cv. IET 1444 which favors its drought tolerance.

C2H2-type zinc finger proteins belong to a major family of transcription factors that play a crucial role in plant stress responses. In this study, seven C2H2-type zinc finger genes (EgrZFP1-7) in Eucalyptus grandis were cloned using the RACE PCR method. EgrZFP1-7 proteins included a QALGGH motif, two zinc finger domains, and an EAR motif. They belong to a Q-type C2H2 zinc finger protein family and are classified into the subset C1. EgrZFP4 and EgrZFP6 had a higher transcription in roots than in leaves and stems, whereas the expression of the other genes did not differ in various plant tissues. The expression of EgrZFP genes in seedlings was induced by low temperatures. Time course experiments at temperatures lower than 4 °C revealed oscillating expression of EgrZFP1-6 during the cold treatment. However, EgrZFP7 showed a phasic expression pattern at the same conditions. The expression of EgrZFP1-6 was found to be enhanced by 200 mM NaCl, whereas the expression of EgrZFP7 was inhibited.

Nickel (Ni) is an irreplaceable component of urease which reduces urea toxicity, but excess of Ni has detrimental effects on plant growth. The responses of cucumber (Cucumis sativus L. cvs. Negin and Dominus) plants supplied with urea as sole N source to four Ni concentrations (0, 50, 100 and 200 μM) were investigated. Nickel at a 50 μM concentration stimulated growth and reduced urea accumulation and lipid peroxidation in the leaves. However, the application of 100 and 200 μM Ni reduced a shoot dry mass and increased a malondialdehyde (MDA) content. An activity of catalase (CAT) was not affected by 50 μM Ni, whereas it was significantly increased by 200 μM Ni. The application of Ni resulted in an enhancement of a guaiacol peroxidase (GPX) activity in the leaves. An ascorbate peroxidase (APX) activity was reduced by 200 μM Ni in cv. Negin and by 100 μM Ni in cv. Dominus.

Cold-responsive (COR) genes participate in the response of plants to low-temperature stress. In this study, we isolated and characterized a cold-responsive and light-inducible gene COR15B from Arabidopsis thaliana. Chloroplast damage caused by mutations (albino mutants seca1, secy1, and tic20) or by a norflurazon (NF) treatment resulted in a reduction of COR15B transcription. A semi-quantitative RT-PCR analysis shows that COR15B was induced by the salt stress in an abscisic acid-dependent manner. An over-expression of COR15B in Arabidopsis resulted in transgenic lines more sensitive to the NaCl treatment than the wild type. However, COR15B knockdown did not significantly affect the sensitivity of the cor15b mutant to the salt stress. Furthermore, we found that the expression of COR15A, a homologous gene of COR15B, was significantly elevated in cor15b mutant plants. All these results suggest that plants acquire the ability to fully express COR15B only after development of functional chloroplasts. The expressional reprogramming and functional backup may exist between COR15 homologues in Arabidopsis.

Agave tequilana Weber is a monocot plant species member of the Asparagaceae family. One of the characteristics of monocot species is that their embryos show only one cotyledon. In this work, the occurrence of embryos with two cotyledons and fused cotyledons in A. tequilana is reported for the first time. The occurrence of dicotyledonar embryos in a species that by definition should have only one cotyledon could bring an opportunity to elucidate the mechanisms that have given the origin to the only one cotyledon present in monocots. Syncotyly is considered in this work as the possible mechanism that gave rise to the only cotyledon mostly present in this species.

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.

Cullin, a major component of the SKP1-cullin-F box protein (SCF) complex, is a scaffold protein that binds to both SKP1 and RBX1 for selective protein degradation through the ubiquitin proteasome system. In order to study the role of cullin in common wheat, we isolated TaCullin (Cullin gene from Triticum aestivum) from wheat spike cDNA. TaCullin was expressed during all spike/grain developmental stages and in high amounts during early spike/grain development. The TaCullin gene is located on the chromosome arm 2DL. Our results suggest that unneddylated TaCullin is located in the nucleus. Based on previous proposals of Cullin-SKP1 interactions, we examined the interaction between TaCullin and SKP1-like protein (TaSKP) families by using a yeast two-hybrid approach. Yeast cotransformation demonstrated that the N-terminus of TaCullin physically interacts with TaSKP proteins. Using the yeast two-hybrid screen, we identified potential TaCullin-interacting proteins in a wheat spike library. Among the 9 clones that were identified as potential interacting partners of TaCullin, we identified E3-like ubiquitin ligase, targeting fructose-1,6-bisphosphatase (RMD5) homolog A-like protein. The interaction between TaCullin and the TaRMD5 homolog A-like protein was specifically mediated through the C-terminus of TaCullin. The results of bimolecular fluorescence complementation assay indicated that TaCullin-TaRMD5 is localized in the plasma membrane and cytoplasm. In this study, we present that TaRMD5, such as RING box protein 1 (RBX1), has the potential to interact with TaCullin, depending on the developmental stage and particular organ tissues analyzed.

Electric signaling pathways are important for rapid and long-distance communication within a plant. Changes in the electric potential (EP) inside plants have been observed during the propagation of electric signals. Increasing radiofrequency electromagnetic radiation (EMR) in the environment raise the question about possible effects of EMR on the EP of plants. In the present experiment, we investigated the effect of 2, 2.5, 3.5, and 5.5 GHz EMR with a maximum field intensity of 23-25 V m^-1 on the EP in emergent Myriophyllum aquaticum plants. The 2 and 5.5 GHz exposures caused significant (16 and 13 %) decreases in the standard deviation of rapid fluctuations observed in the EP. The greatest change was caused by 2.5 GHz EMR (23 % increment), although it was not statistically significant. A recovery of the EP was only after 2.5 GHz EMR exposure. The temperature of the plants was not changed by the EMR exposure. These findings confirm the frequency-dependent non-thermal effects of EMR on the EP of plants.

Plant mitogen activated protein kinase (MAPK) cascades comprise a complex network playing a major role in regulating extracellular stimuli as well as developmental processes. The present study involves cloning four MAPKs (ClMPK1, 3, 4 and 5) from Curcuma longa. All four ClMPKs have fully canonical motifs of MAPK and each is represented by a single copy in the turmeric genome. The analysis of exon-intron junctions revealed conserved nature of ClMPKs across different plant groups. The RT-qPCR analysis showed their expression in mature plant tissues. The transcript analysis using the RT-qPCR shows that the four ClMPKs were differentially regulated by cold, salinity, and drought stresses. ClMPK4 showed a significant upregulation in the presence of NaCl, polyethylene glycol, and mannitol. The time-course expression analysis revealed a marked accumulation of ClMPK1 and ClMPK4 transcripts after mechanical wounding or applications of abscisic acid, H₂O₂, methyl jasmonate, and salicylic acid. ClMPK5 showed a unique and pronounced expression in response to hexavalent chromium (Cr^VI).

To investigate the physiological mechanisms of salt stress mitigated by exogenous sucrose, Arabidopsis thaliana seedlings grown on Murashige and Skoog medium were treated with 3 % (m/v) sucrose combined with 75, 150, and 225 mM NaCl for 3 d. Our results show that increased salinity significantly decreased the survival rate, fresh mass, content of proteins, chlorophyll a (Chl a), and chlorophyll b (Chl b), and activities of antioxidant enzymes, whereas enhanced the content of malondialdehyde. However, the treatment with sucrose significantly enhanced salt stress tolerance in the Arabidopsis seedlings by decreasing lipid peroxidation and increasing the activities of superoxide dismutase, peroxidase, and catalase, the content of proteins, Chl a, Chl b, anthocyanins, and the transcription of genes involved in anthocyanin biosynthesis. Thus, sucrose might reduce ROS-induced oxidative damage by enhancing activities of antioxidant enzymes and the content of anthocyanins, thereby preventing membrane peroxidation and denaturation of biomolecules.

Recent studies have shown that the expression of genes related to the synthesis of flavonoids, such as the phenylalanineammonia lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI), and stilbene synthase (STS) genes were induced in response to different signaling molecules and Botrytis cinerea inoculation in grapevine leaves. Therefore, in the present study, the nucleotide and deduced amino acid sequences of STS genes from cultivars Campbell Early and Kyoho were compared. The deduced amino acid sequences of VlKSTS12, VlKSTS11, VICESTS13, and VlKSTS1 showed 100 % homology to VlCESTS12, VlCESTS11, VICESTS24, and VlKSTS13, respectively, in Campbell Early and Kyoho. In addition, the maximum transcription was observed 6 h after chemical treatments. In Campbell Early, the transcription of PAL, CHS, and CHI was higher in leaves treated with ethephon than in those treated with hydrogen peroxide, methyl jasmonate, and salicylic acid. The PAL, CHS, and CHI genes were more induced in Campbell Early than in Kyoho. The mRNA content of STS genes started to increase at 6 h and peaked at 48 h after the treatments. In Kyoho leaves, the expression of STSs was highly up-regulated at 1 h and peaked at 6 h after the treatments. The expression of the STS genes was induced in both the cultivars in leaves inoculated with B. cinerea. STS11 and STS12 showed differential expression patterns from STS1, STS24, and STS13 in Campbell Early leaves inoculated with B. cinerea.

In order to identify target region amplification polymorphism (TRAP) markers linked to three physiological traits in wheat (Triticum aestivum L.), the segregating F₄ population from the cross between drought-sensitive (Yecora Rojo) and drought-tolerant (Pavon 76) genotypes was made. The parents and 150 F₄ families were evaluated phenotypically for drought tolerance using two irrigation treatments [2.5 and 7.5 m³(H₂O) m^-2(soil)]. Using 40 different TRAP primer combinations tested for polymorphism in parental and F4 family genotypes, the results revealed that quantitative trait locus (QTL) for chlorophyll content was associated with TRAP 5, TRAP 14, and TRAP 20 and explained 18, 16, and 23 % phenotypic variation, respectively. The genetic distance between chlorophyll content QTL and TRAP 5, TRAP 14, and TRAP 20 were 12.3, 19.8, and 13.6 cM, respectively. QTL for flag leaf senescence was associated with TRAP 2, TRAP 3, TRAP 15, and TRAP 16 and explained 33, 27, 28, and 23 % phenotypic variations, respectively. The genetic distance between flag leaf senescence QTL and TRAP 2, TRAP 3, TRAP 15, and TRAP 16 were 9.4, 14.7, 18.1, and 17.3 cM, respectively. QTL for cell membrane stability was associated with TRAP 8, TRAP 9, and TRAP 37 and explained 27, 30, and 24 % phenotypic variation, respectively. The markers TRAP 8, TRAP 9, and TRAP 37 had genetic distances of 17.0, 10.0, and 9.0 cM, respectively. Therefore, these TRAP markers can be used in breeding for drought tolerance in wheat.

This study was carried out to understand the mechanism of protection of plants under cold stress by exogenous 24-epibrassinolide (EBR). The eggplant (Solanum melongena L.) seedlings were pretreated with five concentrations of EBR (0, 0.05, 0.1, 0.2 and 0.4 °M) and then exposed to day/night temperatures of 10/5 °C for 8 d. The results show that EBR, especially 0.1 °M EBR, dramatically alleviated growth suppression and a decrease in chlorophyll content and photosynthetic rate caused by the cold stress. In addition, EBR also decreased malondialdehyde content and O₂ ^.- production rate induced by the cold stress, and increased the activities of superoxide dismutase, guaiacol peroxidase, catalase, and ascorbate peroxidase, and proline content. The results of the present study suggest that exogenous EBR could improve cold tolerance of eggplant by regulating photosynthesis and antioxidative systems.

The effect of UV-B irradiation at temperatures of 22 and 4 °C on flash induced oxygen yields, photochemical activity, and energy transfer in pea thylakoid membranes in the absence and presence of scavengers of reactive oxygen species (ROS) was studied. Three different scavengers were used: dimethyl sulfoxide (DMSO), histidine (His), and n-propyl gallate (nPG). As result of the UV-B treatment of isolated membranes, the flash oxygen yields were considerably affected - the amplitudes decreased and the oscillation pattern was lost. The analysis of the flash oxygen yields and initial oxygen burst showed alterations of a number of oxygen evolving centers in the S0 state as well as changes of decay kinetics of the oxygen burst under continuous irradiation. ROS scavengers exhibited more or less expressed protective effects, nPG being the most effective against UV-B induced damages of the flash oxygen yields. At both the temperatures, photosystem II (PS II) mediated electron transport was more sensitive to the UV-B treatment in comparison with photosystem I (PS I). The analysis of 77 K fluorescence spectra showed that the fluorescence ratio F735/F685 increased by the UV-B treatment probably due to a redistribution of excitation energy between both photosystems most likely caused by partial unstacking and due to a decrease of PS II fluorescence resulting from reaction center-type quenching. The nPG was the most powerful scavenger which protected the oxygen evolution capacity of PS II in the absence and presence of an exogenous electron acceptor to the highest extent.

BABY BOOM (BBM), initially identified in Brassica napus, can enhance the shoot regeneration capacity in tissue culture and is involved in the conversion from the vegetative to embryogenic state. This study aimed to isolate BBM orthologue genes from Rosa canina and analyse their functions. Two full-length cDNAs, designated RcBBM1 and RcBBM2, were isolated from R. canina by the rapid amplification of cDNA ends (RACE). The predicted amino acid sequences of the two RcBBMs contained the bbm-1 motif and the motifs typically conserved in the eudicotANT (euANT) lineage. Phylogenetic tree analysis showed that the RcBBMs were most closely related to the BBM orthologue genes identified in Glycine max and Medicago truncatula. The transcripts of the RcBBMs were detected in young roots, calluses, and protocorm-like bodies (PLBs), whereas they were undetectable in stems, leaves, and flowers. RcBBM1-GFP and RcBBM2-GFP fusion proteins were both localized in the nucleus. 35S::RcBBM1 and 35S::RcBBM2 transgenic Arabidopsis thaliana lines exhibited enhanced shoot regeneration capacity in tissue culture, but did not undergo spontaneous somatic embryogenesis. The results suggest that RcBBMs may be candidate genes for improving the shoot regeneration efficiency of R. canina.

Two types of hairpin RNA (hpRNA) constructions were designed using a chimeric gene formed from two genes, the coat protein (CP) gene or the silencing suppressor gene, from the Cucumber mosaic virus (CMV) and the Potato virus Y (PVY_N), respectively; one type generated a single hairpin structure, whereas the other formed a two-hairpin structure. Four constructs, pDCPSH (double CP gene fragments, single hairpin), pDCPDH (double CP gene fragments, double hairpins), pHC2bSH (two silencing suppressor gene fragments, single hairpin), and pHC2bDH (two silencing suppressor gene fragments, double hairpins), were individually introduced into tobacco plants. A transcript analysis demonstrates that the small interference RNA (siRNA) processing efficiency was greater with the double-hairpin construct than with the single-hairpin construct, although the expression of their target genes were similar. A viral resistance assay shows that the transgenic tobacco plants effectively resisted a mixed infection of CMV and Potato virus Y (PVY^N) and that pDCPDH exhibited the highest silencing efficiency. The accumulation of siRNA in the inoculated transgenic plants expressing different hairpin structures was similar. A genetic analysis reveals that viral resistance in the transgenic plants was stably inherited from the T₀ to T₁ generation. A transcript analysis and a viral resistance assay indicate that the double-hairpin structure of the same target sequences tended to produce more siRNA before the virus inoculation and thus strengthened RNA-mediated viral resistance.

Interaction between aluminum (Al) and boron (B) in Al accumulator species has not been characterized so far. In this work, tea [Camellia sinensis (L.) O. Kuntze] plants were cultivated hydroponically and treated with adequate (control) or low B supply (-B) without or with 300 μM Al (-B+Al) for 14 weeks. Growth of B-deficient plants was completely resumed by Al supplementation or even surpassed control plants regarding shoot biomass. Net photosynthetic rate was negatively influenced by the low B supply, and the Al treatment increased it up to the level of the control plants that was reflected in the higher content of saccharides. The activity of ascorbate peroxidase (APX) in the younger leaves decreased at the low B supply accompanied with an increased H₂O₂ content. The Al treatment increased the APX activity up to the level of the control plants simultaneously with the reduction of H₂O₂. Activities of superoxide dismutase (SOD) and peroxidase (POD) increased in the low B plants and the Al treatment augmented this effect. The content of malondialdehyde (MDA) in the leaves increased by low B but declined upon the Al treatment. In the Al-treated plants, the activity of nitrate reductase (NR) and the content of free α-amino acids exceeded those of the control plants, and nitrite concentration diminished. The shoot and root B content of the B-deficient plants supplemented with Al was similar with the B-sufficient ones. The results demonstrate that the up-regulation of C and N metabolism, the activation of antioxidative defense, and the enhancement of B uptake and transport were mechanisms for growth amelioration of the B-deficient plants by Al supplementation in tea.

Two of the abundant transcripts encoding type 2 metallothionein (MT) proteins designated as MET2a and MET2b were selected in our previous study due to their high abundance (16.05 %) in the suppression subtractive hybridization library and their involvement in fruit development and maturation. The present study involves the isolation of the full-length cDNA encoding MET2a and MET2b from the ripening oil palm fruit mesocarp, examining their expression pattern compared to the other two previously reported type-3 MT members (MT3-A and MT3-B) in various oil palm organs including different vegetative and reproductive tissues. The full-length cDNA sequences of MET2a and MET2b were 571 and 553 bp and they were designated as EgMT2a and EgMT2b, respectively. The sequences of the EgMT2a and EgMT2b were then compared for sequence similarities in the database using both BLASTN and BLASTX programs. Their sequences were homologous (67-77 %) with several type-2 MTs in plants. All four MT encoding genes were differentially expressed in the ripening oil palm mesocarp tissues, but undetectable in the vegetative tissues examined. All MT genes examined were significantly up-regulated in the mature developmental stages of oil palm fruit mesocarp, except for EgMT2b which was expressed only at 17 weeks after anthesis. The type 2 MT proteins are related to a greater degree to the late fruit-ripening stage than the type 3 MT proteins consistent with their reported functions in homeostasis or detoxification. The findings in the present study contribute to better understanding the molecular mechanisms involved in fruit ripening in oil palm.