Selenium (Se) is essential for health of humans, animals, and plants. Especially wheat is a major source of Se in the terrestrial food chain. In this study, an element analysis was optimized and the content of Ca, Mg, K, S, P, Fe, Se, Mn, Cu, Zn, and Mo in leaves, roots, and seeds were measured during growth of wheat (Triticum aestivum L. cv. Manu) in Hoagland nutrient solution with 5 and 15 μM Na₂SeO₄. Se was transported to all investigated tissues and accumulated in the seeds in proportion to used amounts. The supplementation of Se, independently of concentration, weakly modified the micro- and macro-elements content in the seedlings. In the flag-leaf stage, an increase of the Mo and S content in the shoots and the S and Cu content in the roots was found. Moreover, in the generative phase, a decrease in Ca and Fe in the roots was registered. Increased Se in the nutrient solution strongly stimulated the Se accumulation in the seeds.

Exposure to low temperatures is one of the most important factors that generate abiotic stress in plants, and the rapid accumulation of soluble sugars belongs to significant metabolic responses to cold stress. The accumulation of soluble sugars may be at least partially triggered by an increased rate of starch degradation. The analysis of transcript profiles and starch degrading enzyme activities in leaves of two potato cultivars was performed during a 12-h exposure to 2 °C. An induction of β-amylase expression and activity as well as an accumulation of reducing sugars were observed in cv. Desiree. No accumulation of reducing sugars and no significant changes in the β-amylase activity were initially observed in cv. Russet Burbank. Surprisingly, an increased α-amylase activity was observed in the last hours of the experiment, which was accompanied by an increased amount of reducing sugars. The results indicate that the leaves of Desiree and Russet Burbank potatoes growing under cold stress may degrade starch via different pathways.

Self-grafted and pumpkin rootstock-grafted cucumber plants were subjected to the following four treatments: 1) aerated nutrient solution alone (control), 2) nutrient solution with 10 mM Ca(NO₃)₂ (Ca), 3) nutrient solution with 90 mM NaCl (NaCl), and 4) nutrient solution with 90 mM NaCl + 10 mM Ca(NO₃)₂ (NaCl+Ca). The NaCl treatment decreased the plant dry mass and content of Ca²⁺ and K⁺ but increased the Na⁺ content in roots and shoots. Smaller changes were observed in pumpkin rootstock-grafted plants. Supplementary Ca(NO₃)₂ ameliorated the negative effects of NaCl on plant dry mass, relative growth rate (RGR), as well as Ca²⁺, K⁺, and Na⁺ content especially for pumpkin rootstock-grafted plants. Supplementary Ca(NO₃)₂ distinctly stimulated the plasma membrane (PM) H⁺-ATPase activity which supplies the energy to remove excess Na⁺ from the cells. The expressions of gene encoding PM H⁺-ATPases (PMA) and gene encoding a PM Na⁺/H⁺ antiporter (SOS1) were up-regulated when Ca(NO₃)₂ was applied. The pumpkin rootstock-grafted plants had higher PM H⁺-ATPase activity as well as higher PMA and SOS1 expressions than the self-grafted plants under NaCl + Ca treatment. Therefore, the addition of Ca²⁺ in combination with pumpkin rootstock grafting is a powerful way to increase cucumber salt tolerance.

C-repeat binding factor (CBF), also called the dehydration-responsive element binding factor 1 (DREB1), can be induced by low-temperature (LT), and plays an important role in abiotic stress tolerance in higher plants. In present study, two new homologous genes of CBF from Prunus mume (PmCBFb and PmCBFc) have been identified and characterized. The complete coding sequences of PmCBFb and PmCBFc were 714 and 723 bp, respectively. They encoded putative proteins of 237 and 240 amino acids. Neither of them had introns. Genome PCR sequencing showed that PmCBFb was arranged in tandem with PmCBFa (another CBF/DREB1 homolog in P. mume) within a region of nearly 4 kb. Promoter prediction analyses indicated that multiple types of cis-elements related to abiotic stress and irradiance existed in the putative promoter region of PmCBFb. LT treatment of seedlings showed that the expression of PmCBF genes were induced by 2 °C within 30 min, and their expression reached a peak after 8-12 h. In addition, PmCBFa and PmCBFb appeared more sensitive to LT than PmCBFc. However, the exact roles of PmCBF genes in plant cold tolerance need to be further investigated.

Endogenous salicylic acid (SA) functions in plant response to an aluminum stress were assessed. We used different Arabidopsis thaliana genotypes including snc1 with a constitutively high content of SA, sid2 and nahG (transgenic lines) both with a low content of SA, SA insensitive mutant npr1-1, and snc1/nahG (i.e., the nahG expression in the snc1 background) with a similar SA content as in wild type (WT) plants. Results show that the snc1 plants displayed obvious growth retardation of roots and shoots under the Al³⁺ stress, whereas the sid2, nahG, and npr1-1 plants exhibited alleviated symptoms in comparison with the WT plants. The Al³⁺ content increased in all the tested genotypes with the increasing AlCl₃ concentration applied, but no significant variations were detected among the tested genotypes. The snc1 had much higher superoxide dismutase and peroxidase activities, and a lower catalase activity and the ratio of reduced to oxidized glutathione accompanied by higher accumulations of H₂O₂ and malondialdehyde compared with the WT plants. These changes were largely reversed by the introduction of nahG; the sid2, nahG, and npr1-1 plants were less affected than WT plants in all the above-mentioned parameters. The Al³⁺ stress significantly enhanced malate exudation in all the tested genotypes, but no significant correlation was observed between the SA-involved response to the Al³⁺ stress and the malate exudation. Based on these data, it was concluded that the SA-related functions in Arabidopsis response to the Al³⁺ stress were associated with the control of oxidative stress, but not of malate exudation.

Plant growth regulators (PRG)-assisted phytoremediation is a technique that could enhance the yield of heavy metal accumulation in plant tissues. So far, a small number of experiments have helped identify three groups of plant hormones that may be useful for this purpose: auxins, cytokinins, and gibberellins. Studies have shown that these hormones positively affect the degree of accumulation of metallic impurities and improve the growth and stress resistance of plants. This review summarizes the present knowledge about PGRs' impact on phytoextraction yield.

Transcription factors play vital roles in stress signal transduction and gene expression modulation. The sequence analysis shows that MdCBF1 from Malus domestica Borkh. cv. Fuji contained an AP2 core domain of 56 amino acids. By comparison of deduced amino acid sequences of CBF related proteins, we deduced that MdCBF1 is a CBF transcription factor gene which belongs to AP2/EREBP family, DREB-A1 subfamily. Further, we reported that transgenic Arabidopsis thaliana plants expressing the MdCBF1 gene exhibited stronger growth than wild type plants under freezing stress. The analysis of RT-PCR for stress-responsive genes implied that MdCBF1 over-expressing plants had a higher expression of COR15a, RD29A, and RD29B genes than wild type plants. Collectively, our results indicate that MdCBF1 might play an important role in the response of transgenic Arabidopsis plants to freezing stress.

MYB transcription factors (TFs) are known to have important functions in regulating the biosynthesis of secondary metabolites in plants. In this study, LeMYB1, a member of the MYB gene family of Lithospermum erythrorhizon, was cloned via the rapid amplification of cDNA ends. The alignment of the predicted translations of LeMYB1 with other MYB proteins revealed that LeMYB1 contained an N-terminal R2R3 repeat and a high degree of amino acid identity to NtMYBJS1 which is involved in jasmonic acid signalling and phenylpropanoid biosynthetic pathway regulation. To determine the expression pattern of LeMYB1, its promoter was cloned and the sequence analysis was performed. The results revealed a number of potential regulatory motifs related to tissue-specific gene expression and abiotic and biotic stress responses. Real-time PCR results suggest that LeMYB1 was induced transiently during the early stage when L. erythrorhizon cells were transferred from a B5 growth medium to a M9 production medium for shikonin formation. Exogenous methyl jasmonate (MeJA), an effective inducer of shikonin biosynthesis, induced the rapid LeMYB1 expression. In contrast, a treatment with ibuprofen (IBU), an inhibitor of jasmonate biosynthesis, significantly inhibited the LeMYB1 expression. Another inhibitor of shikonin formation, 2,4-dichlorophenoxyacetic acid (2,4-D), also markedly repressed the expression of LeMYB1. Tissue-specific expression analysis showed that LeMYB1 mRNA was predominantly accumulated in roots where shikonin was synthesized. Thus, the LeMYB1 gene may be a valuable member of the R2R3-MYB family in L. erythrorhizon and is possibly involved in the regulation of shikonin biosynthesis.

ApKUPs are typical high-affinity potassium (K⁺) transporters of Alternanthera philoxeroides which are involved in its response to K⁺ starvation and abiotic stresses. In this study, the overexpression of ApKUP3 gene in rice resulted in enhanced K⁺ nutrition and drought tolerance of transgenic plants. Compared with wild-type (WT) plants, the transgenic plants showed a better growth performance and a strengthened K⁺ accumulation under different K⁺ supplies. The ApKUP3 overexpression in the rice plants also enhanced tolerance to a drought stress, as evidenced by a reduced leaf water loss and an increased total leaf chlorophyll content, stomatal conductance, net photosynthetic rate, and activities of superoxide dismutase, peroxidase, and ascorbate peroxidase (APX). Moreover, the transcription of genes involved in the antioxidation defense system were higher in the transgenic plants than in the WT plants upon the drought stress.

Indian mustard (Brassica juncea L. cv. Vitasso) plants exposed to 10, 30, 50 and 100 µM of Cd for 5 d in hydroponic culture were analysed with reference to the distribution of Cd²⁺, the accumulation of biomass and antioxidants and antioxidative enzymes in leaves. Cd induced a decrease in plant biomass. The maximum accumulation of Cd occurred in roots followed by stems and leaves. Cd induced a decrease in catalase (CAT) and guiacol peroxidase (GPX) activities but an increase in ascorbate peroxidase (APX) and monodehydroascorbate reductase (MDHAR) activities. Enhancement in dehydroascorbate reductase (DHAR) activity was also at 10 µM Cd. Glutathione reductase (GR) activity showed pronounced stimulation after all treatments, but glutathione S-transferase (GST) and glutathione peroxidase (GPOX) activities decreased. The effectiveness of ascorbate-glutathione cycle (AGC) was determined by the ratio of ascorbate to H₂O₂. This ratio decreased in the Cd-treated leaves which indicated that the cycle was disordered.

This study was carried out to better understand the role of 24-epibrassinolide (EBR) in thermotolerance of melon (Cucumis melo L.). The melon seedlings were pretreated with various concentrations of EBR (0, 0.05, 0.1, 0.5, 1.0, and 1.5 mg dm^-3) as foliar spray and then exposed to a high temperature (HT) stress. Exogenous EBR (0.5-1.5 mg dm^-3) alleviated HT-caused growth suppression. In parallel, 1.0 mg dm^-3 EBR attenuated the decrease in chlorophyll content, net photosynthetic rate, stomatal conductance, maximum quantum efficiency of photosystem (PS) II, quantum yield of PS II, and photochemical quenching of chlorophyll a fluorescence in HT-stressed plants, and inhibited transpiration rate and non-photochemical quenching. Furthermore, exogenous EBR also significantly reduced the content of malondialdehyde (MDA) and increased the content of soluble proteins and free proline, and activities of antioxidant enzymes including superoxide dismutase, guaiacol peroxidase, catalase, and ascorbate peroxidase under the HT stress. The results show that protective effects of EBR against the HT stress in the melon seedlings were most likely mediated through the improvement of photosynthesis and the stimulation of antioxidant capacity.

Sulfur dioxide (SO₂) is a well-known and widespread air pollutant but it also acts as signaling molecule in various processes in animals. However, there is limited information on the role of SO₂ in plants except of its toxicity. Here we studied the role of SO₂ on stomatal movements in sweet potato (Ipomoea batatas) leaves. SO₂, generated by Na₂SO₃/NaHSO₃ solutions, was applied on epidermal strips. We found that the SO₂ donor induced stomatal closure in a dose-dependent manner. Rapid increases in endogenous hydrogen sulfide and nitric oxide content levels were observed in leaves after the treatment with the SO₂ donor. The SO₂-induced stomatal closure was reversed by the H₂S scavenger hypotaurine and the NO-specific scavenger cPTIO. Our results indicate that the SO₂-induced stomatal closure was likely mediated by the H₂S and NO signaling pathways.

This paper compares the changes in water content, chlorophyll a fluorescence and leaf ultrastructure during dehydration and rehydration in two desiccation tolerant plants Xerophyta viscosa and X. retinervis. Both species showed decreasing quantum efficiency of photosystem 2 (F_v/F_m) with decreasing water content. Extreme water loss observed after 25 d of dehydration resulted in considerable damage of leaf tissue ultrastructure. After rehydration, both species need several days to reconstitute their photosynthetic machinery.

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.

The main task of annually grown fibrous roots is to supply aboveground organs with water and nutrients. The key for this function, the development and mortality of primary tissues during a root lifespan is still poorly understood, especially in plants grown under field conditions. The goal of this study was to investigate the differentiation and maturation of fibrous roots from the initial appearance until the senescence and death. We monitored the histogenesis and anatomy of first order fibrous roots of black cottonwood (Populus trichocarpa Torr. & Gray) sampled at a known age. The daily examination of the first order fibrous roots revealed that only primary tissues were differentiated during the first seven days after their initiation and were maintained during the root lifespan. We observed all stages of exodermis and endodermis formation regulation a fibrous root water and nutrients uptake capacity. A cytological analysis, examined if any cellular symptoms of autophagy could be detected in senescent roots, indicated that vacuolar cell death was involved in root mortality. Our results are the first report strongly suggesting that programmed cell death (PCD) could be engaged in the senescence of ephemeral fibrous roots. The anatomical results advance our understanding of how roots absorptive ability is related to precise timing of tissue development during primary growth and of fibrous root senescence after fulfilment of its tasks.

Homogeneous low phosphorus availability was reported to regulate root architecture in Arabidopsis via auxin, but the roles of auxin in root architecture plasticity to heterogeneous P availability remain unclear. In this study, we employed auxin biosynthesis-, transport- and signalling-related mutants. Firstly, we found that in contrast to low P (LP) content in the whole medium, primary root (PR) growth of Arabidopsis was partially rescued in the medium divided into two parts: upper with LP and lower with high P (HP) content or in the reverse arrangement. The down part LP was more effective to arrest PR growth as well as to decrease density of lateral roots (DLR) than the upper LP, and effects were dependent on polar auxin transport. Secondly, we verified that auxin receptor TIR1 was involved in the responses of PR growth and lateral root (LR) development to P supply and loss of function of TIR1 inhibited LR development. Thirdly, effects of heterogeneous P on LRD in the upper part of PR was dependent on PIN2 and PIN4, and in the down part on PIN3 and PIN4, whereas density of total LRs was dependent on auxin transporters PIN2 and PIN7. Finally, heterogeneous P availability altered the accumulation of auxin in PR tip and the expression of auxin biosynthesisrelated genes TAA1, YUC1, YUC2, and YUC4. Taken together, we provided evidences for the involvement of auxin in root architecture plasticity in response to heterogeneous phosphorus availability in Arabidopsis.

LeAN2 encoding an anthocyanin-associated R2R3-MYB transcription factor was isolated from tomato. The expression of LeAN2 in tomato was induced by low temperature and oxidative stress. Green fluorescent protein was fused to LeAN2 and the complex was expressed transiently in onion epidermal cells. Green fluorescence was observed only in the nucleus. Overexpression of LeAN2 under the control of the CaMV35S promoter in tobacco induced expression of several anthocyanin biosynthetic genes and the content of anthocyanin was markedly higher in transgenic tobacco compared with wild type plants. Transgenic tobaccos conferred tolerance to chilling stress by maintaining a higher chlorophyll content, net photosynthetic rate, and maximal photochemical efficiency of PS II compared to the wild type plants. Furthermore, the transgenic plants showed lower ion leakage, a lower content of reactive oxygen species, and a higher content of non-enzymatic antioxidans under the chilling stress. They also showed an enhanced resistance to the oxidative stress induced by methyl viologen based on a decreased chlorophyll content loss, lower ion leakage, and an enhanced maximal photochemical efficiency of PS II. These results indicate that overexpression of LeAN2 resulted in an increased anthocyanin accumulation and enhanced resistance to the chilling and oxidative stresses in transgenic tobacco.

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.

Low temperature is the main limiting factor for cultivation expansion, fast growth, and high yield of Eucalyptus species. To investigate the mechanism of their cold tolerance, a cDNA subtraction library representing the cold-induced genes of Eucalyptus dunnii was constructed using suppression subtractive hybridization (SSH) technique. A gene encoding a calmodulin-binding protein (CaMBP) was identified from the SSH library, and the expression pattern of CaMBP under cold stress was further evaluated through reverse transcription - quantitative polymerase chain reaction (RT-qPCR). The expressions of EguCBF1a and EdCaMBP increased already after 4 h of the cold stress, supporting the idea that the CaMBP gene may have a function in the survival of Eucalyptus during winter. A full-length mRNA sequence of 1 808 bp was obtained via a rapid amplification of cDNA ends method, and the sequence was subsequently deposited to GenBank (accession No. JX401571). The CaMBP cDNA of E. dunnii contained a single open reading frame of 1 362 bp, a 5t' untranslated region of 175 bp, and a 3t' untranslated region of 268 bp. Multiple sequence alignment and phylogenetic analysis indicated that CaMBP of E. dunnii shared 56 to 84 % identities with the CaMBPs of other plants and was similar to that of Ricinus communis, Medicago truncatula, and Gossypium hirsutum.

Shoot and root mass of tobacco plants treated with only 0.05 µM boron was decreased by 25 and 50 %, respectively, when compared to plants sufficiently supplied with B (2 and 5 µM). Leaf B content of 0.05 µM B-treated plants decreased (about 80-90 %) when compared to 2 µM B treated plants; this drop of B content were not as marked (about 25-45 %) in roots. Leaf and root nitrate contents in B-deficient plants were 45-60 % and 35-45 % lower, respectively, than those from 2 and 5 µM B treated plants. It is suggested that B deficiency might decrease nitrate uptake rather than nitrate reductase activity in tobacco plants.

A pot experiment was conducted in a greenhouse to assess the tolerance of Agropyron cristatum plants to cadmium contaminated soils (0, 5, 10, 25, 50, 100, 150, and 200 mg kg^-1) for 100 d. Results indicate that Cd in concentrations of 5-50 mg kg^-1 had no significant impact on growth, relative membrane permeability (RMP), lipid peroxidation measured as malondialdehyde (MDA) content, and chlorophyll (Chl) content relative to the control. Exposure of these plants to high concentrations of Cd (100-200 mg kg^-1) caused a small reduction in growth and Chl content and a slight enhancement of RMP and MDA content compared with the control. In addition, superoxide dismutase (SOD) and peroxidase (POD) activities show an increasing trend with the increase of Cd content in soil. The Cd content in the roots was 4.7-6.1 times higher than that in the shoots under all Cd treatments suggesting that the plant can be classified as a Cd excluder. The translocation factor was low and similar at 25-200 mg kg^-1 Cd treatments. In summary, A. cristatum plants tolerated Cd stress and might have potential for the phytoremediation of Cd contaminated soils.

Trehalose was supplied to wheat (Triticum aestivum L.) seedlings just before a high temperature (40 °C) treatment and some physiological parameters were measured during the heat stress and recovery. The application of trehalose decreased the net photosynthetic rate (P_N) of wheat seedlings under the heat stress, but to a small extent increased the dry mass (DM) and leaf water content (LWC) after recovery from the heat stress. The trehalose-induced decrease in PN under the heat stress was not associated with a stomatal response. The heat stress slightly decreased the maximal efficiency of photosystem II (PS II) photochemistry (the variable to maximum chlorophyll a fluorescence ratio, F_v/F_m) similarly in the trehalose treated or non-treated plants. Under the heat stress, the actual efficiency of PS II photochemistry (Φ_PSII) and the efficiency of excitation energy capture by open reaction centers (F_v'/F_m') were lower in the trehalose-pretreated seedlings, whereas they were higher after the recovery. The patterns of changes in nonphotochemical quenching (NPQ) were contrary to those of ϕ_{PS II} and F_v'/F_m'. The chlorophyll content was lower, whereas the β-carotene content and the degree of de-epoxidation (DEPS) of xanthophyll cycle pigments were higher in the trehalose-pretreated wheat seedlings under the heat stress. These results suggest that exogenous trehalose partially promotes recovery of wheat by the increase of NPQ, β-carotene content, and DEPS.

Salt decreases the uptake of Zn and other minerals and causes nutritional disorders in plants. Zn is an essential micronutrient for all organisms and it is reasonable to hypothesize that Zn status is essential for maintaining salt tolerance in plants. In this study, the physiological and molecular mechanisms of Zn-based alleviation of salt stress in wheat seedlings were investigated. Our results indicate that sufficient Zn nutrition maintained antioxidative enzyme activities and decreased a reactive oxygen species over-accumulation in wheat seedlings. Our data also reveal that sufficient Zn nutrition improved the expression of Na⁺/H⁺ antiporter genes, TaSOS1 and TaNHX1, thereby decreasing the Na⁺ accumulation and subsequently improving salt tolerance in wheat seedlings.

To determine the effects of phosphorus nutrition on chilling tolerance of photosynthetic apparatus, tomato (Lycopersicon esculentum Mill. cv. Kenfengxin 2002) plants were raised under different P contents and subjected to 7 d of chilling at 9/7 °C. After chilling (2 h or 7 d) plant growth, P content in tissue, gas exchange and chlorophyll fluorescence were measured. Decreasing P concentration [P] in the nutrient solution markedly reduced plant growth and the chilled plants exhibiting higher optimum [P] than the unchilled plants. Decreasing [P] significantly decreased light saturated net photosynthetic rate (P_Nsat), maximum carboxylation velocity of Rubisco (V_cmax), maximum potential rate of electron transport contributed to Rubisco regeneration (J_max), quantum efficiency of photosystem (PS) 2 (ΠPS2) and O₂ sensitivity of P_Nsat (PS_O2) and this trend was especially apparent in chilled plants.

Rice chromosome single segment substitution line (SSSL) W23-19-06-06-11 with the genotype Rf3Rf3/Rf4Rf4, a strong restorer line for wild-abortive (WA) cytoplasmic male sterility (CMS), was recently identified from the SSSL library. To investigate the genetic mode of Rf genes and the genetic relationship among WA, yegong (Y), and dwarf-wildabortive (DA) CMS systems, the plants derived from three BC3F2 populations involving W23-19-06-06-11 and the three CMS lines, that carried the Rf3Rf3/Rf4Rf4, Rf3Rf3/rf4rf4, and rf3rf3/Rf4Rf4 genotypes and WA-, Y-, and DA-CMS cytoplasm, were selected and their pollen and spikelet fertility were evaluated. The results show that the genetic effect displayed a trend of Y-CMS > WA-CMS > DA-CMS in the genetic background of W23-19-06-06-11, the effect of Rf4 appeared to be slightly larger than that of Rf3, and their effects were additive for the three CMS systems. Two pairs of dominant genes governed the fertility restoration in pollen and spikelet in the W23-19-06-06-11 which indicates that the genetic mode of the Rf genes was a qualitative character for the three CMS systems.

Amino acids (AAs) play significant roles in metal binding, antioxidant defense, and signaling in plants during heavy metal stress. In the present study, the essential amino acids (EAAs), non-essential amino acids (NEAAs), as well as the enzymes of proline and cysteine biosynthetic pathways were studied in contrasting arsenic accumulating rice genotypes grown in hydroponic solutions with addition of arsenate (As^V) or arsenite (As^III). Under a mild As stress, the total AAs content significantly increased in both the rice genotypes with a greater increase in a low As accumulating rice genotype (LAARG; IET-19226) than in a high As accumulating rice genotype (HAARG; BRG-12). At the equimolar concentration (10 μM), As^III had a greater effect on EAAs than As^V. Conversely, As^V was more effective in inducing a proline accumulation than As^III. Among NEAAs, As significantly induced the accumulation of histidine, aspartic acid, and serine. In contrast, a higher As concentration (50 μM) reduced the content of most AAs, the effect being more prominent during As^III exposure. The inhibition of glutamate kinase activity was noticed in HAARG, conversely, serine acetyltransferase and cysteine synthase activities were increased which was positively correlated with the cysteine synthesis.

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.

Tobacco leaf discs were transformed with a plasmid pBIBnNHX1, containing the selectable marker neomycin phosphotransferase gene (nptII) and Na⁺/H⁺ vacuolar antiporter gene from Brassica napus (BnNHX1), via Agrobacterium tumefaciens-mediated transformation. Thirty-two independent transgenic plants were regenerated. Polymerase chain reaction (PCR) and Southern blot analyses confirmed that the BnNHX1 gene had integrated into plant genome and Northern blot analysis revealed the transgene expression at various levels in transgenic plants. Transgenic plants expressing BnNHX1 had enhanced salt tolerance and could grow and produce seeds normally in the presence of 200 mM NaCl. Analysis for the T₁ progenies derived from seven independent transgenic primary transformants expressing BnNHX1 showed that the transgenes in most tested independent T₁ lines were inherited at Mendelian 3:1 segregation ratios. Transgenic T₁ progenies could express _BnNHX1 and had salt tolerance at levels comparable to their T₀ parental lines. This study implicates that the BnNHX1 gene represents a promising candidate in the development of crops for enhanced salt tolerance by genetic engineering.

Fatty acid ω-3 desaturase (FAD) is the key enzyme catalyzing the formation of trienoic fatty acids. We utilized an Arabidopsis FAD7 gene and the seven independent transgenic rice plants harbouring 1 to 3 copies of this gene were generated. The expression of FAD7 mRNA was different among independent transgenic lines regardless of the copy number. The total linolenic acid (18:3) contents reduced by about 7 - 32 % in transgenic rice plants but the linoleic acid (18:2) content increased accordingly. With or without wounding treatments, the jasmonate content was higher in transgenic lines than in wild-type rice plant. The transgenic lines overproducing jasmonate also showed increased expression of PR1b mRNA and allene oxide synthase inresponse to wounding.

Androgenic lines of Brassica juncea cv. PR-45 raised by anther culture, were screen for genetic variation. 393 androgenic plants were transferred to pots to study the R₀ generation. These plants showed substantial variation for different characters. Seed progenies of 27 lines of R₀ plants were sown in the field to study R₁ generation. Androgenic plants within lines were significantly homogeneous for the various agronomic characters studied. Two lines were shorter (18 - 20 %) than the control plants, with a remarkable feature of early maturation. Three lines showed 27 - 31 % higher yield than the parent cultivar.