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.

Plant regeneration through indirect somatic embryogenesis was attempted from the immature cotyledon-derived explant of Cassia angustifolia Vahl. - a valuable leguminous shrub. The highest frequency (90.5 %) of somatic embryos was obtained on a Murashige and Skoog (MS) medium augmented with 10.0 μM 2,4-dichlorophenoxyacetic acid (2,4-D) and 1.0 μM benzyladenine (BA) with the production of a maximum of 22.8 embryos per explant, of which 35.3 % germinated on the same medium after 6 weeks of culture. A half strength MS medium without plant growth regulators facilitated better conversion of embryos into complete plantlets compared to a full strength MS medium. Regenerated plantlets were successfully acclimatized in sterile Soilrite and transferred to field conditions with a 70 % survival rate. Histological studies performed at different stages of embryogenesis revealed the mode of differentiation of embryos from the callus. The content of chlorophylls (a + b) and carotenoids, and the net photosynthetic rate (P_N) in the regenerated plantlets were tested during different periods of acclimatization.

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.

Stems of angiosperm trees are affected by gravity. Young poplar stems show primary growth in the top internodes and differential cambium activity in the basal internodes after inclination with some tension wood formed after 45 min. This study was conducted in order to characterize the early changes in poplar gene expression during the early stages of the gravitropic response. Using microarray technology, the expression of 15 000 genes was examined. Approximately 3.1 % of these genes exhibited significant expression changes within the first 45 min of gravity stimulation. Approximately 73 % of the identified genes were found to have a known or predicted molecular function. Many of these genes were involved in secondary wall formation (cellulose synthesis and lignification), cytoskeleton development, signaling, and stress response. Some identified genes seem to play a role in sensing gravitational signals during tension wood formation. A large number of the identified arabinogalactan (AGP) and transcription factor genes were involved in cell wall biosynthesis suggesting that these genes are particularly active in the first phases of signal transduction during tension wood formation.

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.

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.

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.

The effect of esculetin and some related coumarins (coumarin, 7-hydroxycoumarin and scopoletin) on growth of pumpkin (Cucurbita maxima Duch.) seedlings and the activities of pumpkin glutathione S-transferases (GSTs) were investigated. Coumarin and esculetin affected the growth of seedlings. The hypocotyls of affected seedlings became weak and bent at the mid region, roots became very soft with brownish discoloration, and finally seedlings died. Among the compounds tested, only esculetin inhibited CmGSTU3 and CmGSTU2 activities measured with 1-chloro-2,4-dinitrobenzene (CDNB) and at a concentration of 22 µM, it inhibited the activity of CmGSTU3 by 50 %.

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.

Information on plant responses to combined ozone and cadmium stresses are scarce and limited to herbaceous species. In this research, two poplar clones (I-214 and Eridano), differently sensitive to O₃, were grown for 5 weeks in pots supplied with 0, 53.5, and 160.5 mg(Cd) kg^-1 (soil d.m.) and then exposed to 15-d O₃ fumigation (0.06 mm³ dm^-3, 5 h a day). The effects of the two stressors, alone or in combination, on Cd, Ca, Fe, and Zn accumulation in above-nad below-ground organs, photosynthesis, leaf pigments, and accumulation of H₂O₂ and NO were investigated. Cadmium induced a reduction in stomatal conductance and a significant accumulation of H₂O₂ and NO in both clones nad negatively affected the carotenoid content in I-214. Ozone, on the other hand, counteracted Cd accumulation in the above-ground organs and significantly increased the xanthophyll de-epoxidation state indicating photoinhibition in O₃-treated plants. Surprisingly, O₃ alone or in combination with Cd decreased H₂O₂ accumulation in I-214. The NO production was generally stimulated by Cd, whereas it decreased following O₃ exposure in I-214. The overall data indicate that Cd and O₃ induced clone specific responses. Moreover, when they were applied in combination, antagonistic rather than synergistic effects were observed.

The present study was carried out to examine the effects of seed soaking in 1 mM ascorbic acid (AA) or 1 mM proline on the growth, content of photosynthetic pigments and proline, relative water content, electrolyte leakage, antioxidant enzymes and leaf anatomy of Hordeum vulgare L. Giza 124 seedlings grown in greenhouse under 100 or 200 mM NaCl. The plants exposed to the NaCl stress exhibited a significant reduction in growth, relative water content, leaf photosynthetic pigments, soluble sugars, as well as alterations in leaf anatomy. However, the treatment with AA or proline ameliorated the stress generated by NaCl and improved the above mentioned parameters. NaCl increased electrolyte leakage, proline content, and activities of antioxidant enzymes (SOD, CAT, and POX). The antioxidant enzymes and leaf anatomy exhibited considerable changes in response to AA or proline application in the absence or presence of NaCl.

Carbendazim (methyl-2-benzimidazole carbamate) promoted root growth of chickpea (Cicer arietinum L.) seedlings subjected to polyethylene glycol (PEG, osmotic potential -0.5 MPa) induced water stress. The relative water content, membrane stability index, 2,3,5-triphenyltetrazolium chloride reduction and contents of some osmolytes (proline, sucrose, glucose and fructose) enhanced significantly while the contents of lipid peroxides and hydrogen peroxide diminished effectively by addition of 0.05 % carbendazim into PEG solution.

Black gram [Vigna mungo (L.) Hepper] cv. IPU 94 plants grown in sand culture with deficient zinc (0.1 µM Zn) nutrition and those deprived of normal (1 µM) Zn supply at the initiation of flowering, showed decrease in dry matter production and especially seed yield. These plants showed a decrease in the size of anthers and stigmatic heads, pollen producing capacity of the anthers and stigmatic exudations. Zn deficiency caused structural alterations in exine and retarded germination of pollen grains and tube growth. The pollen extracts and stigmatic exudates of the Zn-deficient plants showed increase in activity of acid phosphatase isoforms and inhibition of esterase isoforms. Zn deficiency led to decrease in number of pods, seeds per pod and seed mass, altered seed coat topography and reduced seeds germinability. Low seed yield under Zn deficiency is attributed to a role of Zn in pollen function, as also in pollen-pistil interaction conducive to fertilization and development of seeds.

The dynamics of biomass accumulation, production of flavonoids and consumption of carbon, nitrogen and phosphate were investigated in Glycyrrhiza inflata Batal cell suspensions cultivated in flasks. Biomass accumulation exhibited a "S"-shape curve in each culture cycle, with the greatest values obtained on day 21 (16.4 and 232.4 g dm^-3 of dry and fresh mass, respectively). Similarly, flavonoids production also got to a peak of 95.7 mg dm^-3 on day 21. Sucrose was decomposed to reducing sugars which were almost used up on day 22. Nitrate and phosphate in the medium were almost exhausted on day 18 and 10, respectively, while ammonium still maintained at concentration 100 mg dm^-3 when the cells were harvested. Consequently, the proportion of ammonium to nitrate in the medium should be optimized for higher flavonoid production.

A micropropagation protocol through multiple shoot formation was developed for Thlaspi caerulescens L., one of the most important heavy metals hyperaccumulator plants. In vitro seed-derived young seedlings were used for the initiation of multiple shoots on Murashige and Skoog (MS) medium with combinations of benzylaminopurine (BA; 0.5-1.0 mg dm^-3), naphthaleneacetic acid (NAA; 0-0.2 mg dm^-3), gibberellic acid (GA₃; 0-1.0 mg dm^-3) and riboflavin (0-3.0 mg dm^-3). The maximum number of shoots was developed on medium containing 1.0 mg dm^-3 BA and 0.2 mg dm^-3 NAA. GA₃ (0.5 mg dm^-3) in combination with BA significantly increased shoot length. In view of shoot numbers, shoot length and further rooting rate, the best combination was 1.0 mg dm^-3 BA + 0.5 mg dm^-3 GA₃ + 1.0 mg dm^-3 riboflavin. Well-developed shoots (35-50 mm) were successfully rooted at approximately 95 % on MS medium containing 20 g dm^-3 sucrose, 8 g dm^-3 agar and 1.0 mg dm^-3 indolebutyric acid. Almost all in vitro plantlets survived when transferred to pots.

A highly reproducible system for efficient plant regeneration from protoplast via somatic embryogenesis was developed in cotton (Gossypium hirsutum L.) cultivar ZDM-3. Embryogenic callus, somatic embryos and suspension culture cells were used as explants. Callus-forming frequency (82.86 %) was obtained in protoplast cultures from suspension culture cells in KM₈P medium with 0.45 µM 2,4-dichlorophenoxyacetic acid (2,4-D), 0.93 µM kinetin (KIN), 1.5 % glucose and 1.5 % maltose. Protocolonies formed in two months with plating efficiency of 14 %. However, the callus-forming efficiencies from other two explants were low. The calli from protoplast culture were transferred to somatic embryo induction medium and 12.7 % of normal plantlets were obtained on medium contained 3 % maltose or 1 % of each sucrose + maltose + glucose, 2.46 µM indole-3-butyric acid (IBA) and 0.93 µM KIN. Over 100 plantlets were obtained from protoplasts derived from three explants. The regenerated plants were transferred to the soil and the highest survival rate (95 %) was observed in transplanting via a new method.

The growth and the content of endogenous cytokinins (CKs) of current-year-old shoots from juniper plants (Juniperus communis L.) growing over and off ore site were compared. The juniper shoots from ore site (M plants) had higher metal content and exhibited delayed growth. Less bases and nucleosides of Z- and iP- type CK and more iP-conjugates were present in the M shoots. These changes were probably due to inhibited CK export from the roots and/or altered CK metabolism forming less biologically active CKs.

Somatic embryos were obtained from immature zygotic embryos of Cedrela fissilis Well. (Meliaceae), after a culture period of 12 months, with regular subcultures every 6-8 weeks. Callus was developed on explants in 2 months on Murashige and Skoog (MS) medium containing 2,4 dichlorophenoxyacetic acid (2,4-D) or picloram (PIC). When the calli were transferred to fresh medium, embryogenic tissue appeared on MS + 45 µM 2,4-D, or 22.5 µM 2,4-D + 0.4 µM 6-benzyladenine (BA), or 20.7 µM PIC after 6 months. Sub-culture of embryogenic tissue in MS medium supplemented with 4.5 µM 2,4-D resulted in the differentiation into somatic embryos after further 4 months. Repeated secondary somatic embryogenesis was achieved by regular subculture on this medium. Maturation and conversion of somatic embryos into plantlets was achieved on MS medium without plant growth regulators and the conversion frequency was approximately 12.5 %. The plantlets were successfully acclimatized in pots with soil. Histological studies showed that somatic embryos had no detectable connection with the mother explants and that somatic embryos in advanced stages were bipolar with shoot and root apical meristems, they contained vascular system and showed typical characteristics of a somatic dicotyledonous embryo.

Hydroponics were used to study the impact of acidity on growth, nutritive properties and metabolic changes in kikuyu grass (Pennisetum clandestinum Hochst). Four treatments (pH 6.0, 5.0, 4.0, and 3.0) were compared for effects on biomass, leaf and root length, crude protein, amino acid content and key enzymes of sugar metabolism. Reduction in biomass, root and leaf length, amino acid contents, glucose-6-phosphate dehydrogenase (G6PDH) and pyruvate kinase (PK) content was observed only at pH 3.0, in association with increased leaf proline content. Kikuyu grass is able to grow normally under mild acidity (down to at least pH 4.0).

A greenhouse experiment was conducted to assess the effect of 25, 50, 75, and 100 mM NaCl on growth, ion accumulation, seed yield, and seed oil content in 67-d-old plants of Foeniculum vulgare Mill. Increasing NaCl concentration caused a significant reduction in fresh and dry masses of both shoots and roots as well as seed yield. Na⁺ and Cl^- in both shoots and roots increased, whereas K⁺ and Ca²⁺ decreased consistently with the increase in NaCl concentration. Plants maintained markedly higher Ca²⁺/Na⁺ ratios in the shoots than those in the roots, whereas that of K⁺ /Na⁺ ratios remained almost uniform in both shoots and roots. Proline content in the shoots increased markedly at the highest NaCl concentration. Oil content in the seed decreased progressively with increase in salinity.

Thermotolerance of pearl millet (Pennisetum glaucum cv. ICMV-94133) and maize (Zea mays cv. Golden) was assessed at germination and vegetative stage. Final percentage of germinated seeds and rate of germination (number of days to 50 % germination) decreased due to high temperature (45 °C) similarly in the both species. In contrast, at the vegetative stage, high temperature (38/27 °C) caused a significant reduction in shoot dry mass of maize, whereas this attribute remained almost unchanged in pearl millet. Relative growth rate and net assimilation rate (NAR) increased significantly in pearl millet due to high temperature, but in contrast, in maize NAR was slightly reduced. Concentrations of N, P, and K in the shoots of both species increased at high temperature, but N accumulation was more pronounced in pearl millet than in maize. High temperature caused a marked increase in both shoot and root Ca²⁺ concentration in maize, but it did not affect that of pearl millet. S concentration in the shoots of maize decreased significantly due to high temperature, whereas that in pearl millet remained unaffected. Shoot Na⁺ concentration of both species was not significantly affected by high temperature. High temperature caused a significant increase in uptake of N, P, and K⁺ in pearl millet, but the uptake of Ca²⁺, Mg²⁺, Na⁺ and S remained unaffected in this species. In contrast, in maize, a significant increase in uptake of K⁺ and Ca²⁺, and a decrease in uptake of N, S, Mg²⁺, and Na⁺ were found at high temperature. Overall, maize showed lower tolerance to high temperature compared with pearl millet.

The localization, biotransformation, and chemical speciation of copper in root tips of cucumber (Cucumis sativus) were investigated using synchrotron-based micro X-ray fluorescence (μ-XRF) and micro X-ray absorption near edge structure (μ-XANES). The highest content of Cu was found in root cap and meristematic zone whereas low Cu content in elongation and maturation zone. There was a dramatic increase of Cu content in root cap and meristematic zone after treatment with 100 μM CuSO₄ for 72 h. The μ-XANES analysis revealed that most of Cu in root tip was bound with alginate, citrate, and cysteine-like ligands whereas rarely deposited in form of CuO. From root cap to maturation zone, the proportion of Cu bound with alginate-like ligands increased whereas that bound with citrate-like ligands decreased. The proportion of Cu bound with cysteine-like ligands increased from root cap to elongation zone but sharply declined in maturation zone. The results suggested that Cu was chelated by S ligands in the cell walls which protect protoplasm against possible damage caused by Cu excess.

Actin is the most abundant protein in eukaryotic cells and is a key cytoskeletal component controlling cell morphology and motility. In this study, four MiACT genes were isolated from mango by homological cloning and designated as MiACT1, MiACT4, MiACT7, and MiACT9. Sequence alignments and phylogenetic analysis demonstrated that the four MiACT genes of mango were highly similar to each other at the nucleotide and amino acid levels. All of four MiACT proteins showed high similarity to the known actin proteins from other species. Reverse transcription polymerase chain reaction revealed that the four MiACT genes were constitutively and stably expressed in all organs tested. Application of plant growth regulators and four stress treatments had a remarkable effect on the expression of MiACT4, MiACT7 and MiACT9, whereas expression of MiACT1 was unresponsive. In contrast, the expression profiles of the four MiACT genes were not regulated by diurnal rhythms. Moreover, the expression of MiACT1 was not affected by heavy metal treatments and the transcript level of MiACT1 was rather stable in different days during the post-harvest period either under treatment or not. Our results suggest that the four actin genes play important roles throughout the entire life cycle of mango; the constitutively and stably expressed MiACT1 is the best candidate as an internal standard for differential gene expression analysis in mango.

A quantitative trait loci (QTL) approach was applied to dissect the genetic control of the common wheat seedling response to osmotic stress. A set of 114 recombinant inbred lines was subjected to osmotic stress from the onset of germination to the 8^th day of seedling development, induced by the presence of 12 % polyethylene glycol. Root, coleoptile and shoot length, and root/shoot length ratio were compared under stress and control conditions. In all, 35 QTL mapping to ten chromosomes, were identified. Sixteen QTL were detected in controls, 17 under stressed conditions, and two tolerance index QTL were determined. The majority of the QTL were not stress-specific. In regions on five chromosome arms (1AS, 1BL, 2DS, 5BL and 6BL) the QTL identified under stress co-mapped with QTL affecting the same trait in controls, and these were classified as seedling vigour QTL, in addition to those expressed in controls. Tolerance-related QTL were detected on four chromosome arms. A broad region on chromosome 1AL, including five QTL, with a major impact of the gene Glu-A1 (LOD 3.93) and marker locus Xksuh9d (LOD 2.91), positively affected root length under stress and tolerance index for root length, respectively. A major QTL (LOD 3.60), associated with marker locus Xcdo456a (distal part of chromosome arm 2BS) determined a tolerance index for shoot length. Three minor QTL (LOD < 3.0) for root length and root/shoot length ratio under osmotic stress were identified in the distal parts of chromosome arms 6DL (marker locus Xksud27a) and 7DL (marker locus Xksue3b). Selecting for the favourable alleles at marker loci associated with the detected QTL for growth traits may represent an efficient approach to enhance the plants' ability to maintain the growth of roots, coleoptile and shoots in drought-prone soils at the critical early developmental stages.

The changes in the activities of antioxidant enzymes and amounts of proteins, phenols, and flavonoids in regenerating and non-regenerating calli during organogenesis of Sterculia urens were monitored. Maximum growth of calli and the most efficient regeneration of shoots occurred on Murashige and Skoog (MS) medium supplemented with 0.5 mg dm^-3 benzylaminopurine (BAP) + 2 or 4 mg dm^-3 naphtalene acetic acid (NAA). Peroxidase (POD), catalase, and superoxide dismutase activities increased in the regenerating calli but decreased in the non-regenerating calli. Six POD isoenzymes were detected. Protein content decreased in the non-regenerating calli and increased significantly during regeneration of shoots from callus. Total phenols and flavonoids increased in the non regenerating calli. SDS-PAGE analysis revealed a role of many proteins in organogenesis.

During the first year of hybrid poplar development, we assessed radial growth dynamics quantified by the proportion of secondary xylem tissue within the stem area, the vessel area percentage, the content of both lignin and cellulose, the lignin monomeric composition, and the macromolecular properties of cellulose. The intraannual radial growth dynamics in the proportion of secondary xylem tissue was fitted by the Gompertz regression line whereas changes in the vessel area percentage were fitted maximally by a cubic regression line. Under constant temperature and photoperiod, this study revealed that nonlinear patterns of radial growth dynamics are the result of a developmental programme which drives cambial activity and ageing. The increased proportion of guaiacyl units found may be important for the greater stability of the lignin structure in the first year of hybrid poplar development. The tensile strength of juvenile wood was ensured by the trade-off between a slight increase in the degree of polymerization of cellulose and a slight decrease in the content of cellulose during ageing.

A gene (named BcFLC1) homologous to the AtFLC gene, which encodes a floral repressor, was isolated from the nonheading Chinese cabbage (Brassica campestris L. ssp. chinensis) cv. NJ074. The gene showed high similarity to AtFLC. For studying the gene function, we designed to introduce the BcFLC1 gene into Arabidopsis thaliana. The results showed that BcFLC1 had effects on flowering time similar to AtFLC. We also found that Arabidopsis cold-tolerance was enhanced by BcFLC1 overexpression. Under low temperature stress, the BcFLC1 transgenic plants exhibited stronger growth than wild-type plants. The elevated cold tolerance of the BcFLC1 over-expressing plants was also confirmed by the changes of electrolyte leakage and malonyldialdehyde and proline content.

The effects of Al, Cd and pH on growth, photosynthesis, malondialdehyde (MDA) content, and some antioxidant enzyme activities of the two soybean cultivars with different Al tolerance were determined using a hydroponic culture. There were six treatments as follows: pH 6.5; pH 4.0; pH 6.5 + 1.0 µM Cd; pH 4.0 + 1.0 µM Cd; pH 4.0 + 150 µM Al; pH 4.0 + 1.0 µM Cd + 150 µM Al. The results showed that the low pH (4.0) and Al treatments caused marked reduction in the growth (root and shoot length and dry mass), chlorophyll content (SPAD value) and net photosynthetic rate. Higher malondialdehyde content, superoxide dismutase (SOD) and peroxidase (POD) activities were detected in the plants exposed to both Al and Cd than in those exposed to Al treatment alone. An expressive enhancement of SOD and POD was observed in the plants exposed to 150 µM Al in the comparison with the control plants, especially in Al-sensitive cv. Zhechun 2 which had also significantly higher Al and Cd content than Al tolerant cv. Liao-1. Cd addition increased Al content in the plants exposed to Al + Cd stress, and cv. Zhechun 2 had relatively lower Al content. The present research indicated that Al and Cd are synergistic in their effects on plant growth and some physiological traits.

The effects of zirconium ascorbate (Zr-ASC), a water-soluble complex of Zr, were examined on wheat seedlings (Triticum aestivum L. cv. MV. 20). Hydroponically grown plants were exposed to 10, 33, 55, 100 and 550 µM Zr-ASC (Zr₁₀, Zr₃₃etc.). After 9 d of treatment inhibition of germination, retarded root and shoot growth, and increased activities of antioxidant enzymes (guaiacol peroxidase, ascorbate peroxidase, and glutathione reductase) showed that Zr-ASC was only harmful at and over a concentration limit of 100 µM. Chlorophyll (Chl) content of plants was only decreased by Zr₅₅₀. Zr-ASC at lower concentrations was beneficial for plant development: Zr₁₀ and Zr₃₃ enhanced root elongation, Zr₅₅ induced about 30 % increase in the total Chl content, while the activity of antioxidant enzymes was not elevated indicating that no oxidative stress was generated by the intracellularly accumulated Zr⁴⁺ ions.

The apple (Malus domestica Borkh) rootstock M 4 shoots were grown in vitro for 4 weeks on Murashige and Skoog (MS) medium containing three NaCl concentrations (35, 100 and 200 mM) in combination with two CaCl₂ concentrations (5 and 10 mM). Inclusion of 10 mM CaCl₂ in the medium, in the presence of 35 mM NaCl, significantly increased the number of shoots and the fresh mass compared to 5 mM CaCl₂. The number of shoots, length of shoots, and the fresh mass of cultures were very low in the presence of 100 and 200 mM NaCl, independently of CaCl₂ concentration of the medium. By increasing NaCl and CaCl₂ concentrations in the culture medium, contents of N, Na, Cl, proline and soluble sugars in plantlets increased, whereas K, Mg, B, Zn and chlorophyll content decreased in comparison to the control.