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.

ALBINO3, a homologue of PPF1 in Arabidopsis, encodes a chloroplast protein, and is essential for chloroplast differentiation. In the present study, ALBINO3(-) transgenic plants exhibited a significant decrease in both the number of rosette leaves at bolting and the days before bolting, suggesting the important roles of ALBINO3 in regulating flowering during non-inductive short-day photoperiods. ALBINO3 mRNA was apparently accumulated in shoot apical meristem and floral meristems around the shoot apical meristem in wild-type plants. ALBINO3 might be predominantly involved in inducing the floral repression pathway by activating the expression of TFL1, and by suppressing the expression of LFY, respectively, in the shoot apical meristem. Moreover, the function of ALBINO3 in regulating flowering transition depended on the expression of CO and GA1, because ALBINO3 might function in the downstream integration of the photoperiod-dependent and the photoperiod-independent pathways. These results suggest that ALBINO3 may have an important integrative function in the flowering process in Arabidopsis.

Transformation and high efficient regeneration of transgenic plants from the trimmed etiolated shoot/root region (TESRR) of Anliucheng sweet orange [Citrus sinensis (L.) Osb.] seedling was reported. A visual green fluorescent protein (GFP) marker gene was introduced to evaluate transformation efficiency by using the explants from TESRR and epicotyls. The transformation protocol was: infection 20 min, co-culture 3 d, selection culture 30 d, and rooting 15 d. Out of a total of 288 sprouted shoots obtained from TESRR, 34 shoots (11.8 %) yielded GFP expression. In contrast, only 2 (3.0 %) of the 67 sprouted shoots from epicotyl transformation yielded GFP expression. In all plants showing the green fluorescence an expected 500 bp GFP fragment was proved by PCR analysis. Southern blot analysis further confirmed the integration of GFP gene into citrus genome. Transgenic plantlets were obtained within 80 d using the TESRR, compared within 150 d by using epicotyls.

Tocopherol cyclase (TC, encoded by gene VTE1) catalyzes the penultimate step of tocopherol synthesis. In this study we used wild type and transgenic tobacco plants overexpressing VTE1 from Arabidopsis to examine the role of tocopherol in ozone sensitivity. Wild type plants responded to an 4-h exposure to 300 nmol mol^-1 ozone by severe leaf necrosis while the transgenic lines exhibited limited injury. Compared with the wild type, VTE1-overexpressing plants had lower increase in hydrogen peroxide, malondialdehyde contents and ion leakage, and lower decrease of net photosynthetic rate 48 h following the ozone exposure. Transgenic plants also better maintained the structural integrity of the photosynthetic apparatus.

This report describes an efficient plant regeneration system for the medicinal plant Lythrum salicaria via direct adventitious shoot development from leaf and stem explants. Leaf explants were much more responsive to regeneration than stem segments. Of the hormonal combinations tested, those involving thidiazuron (TDZ; 0.1, 0.3 or 0.5 mg dm^-3) were more effective than the combinations of other hormones and 0.1 mg dm-3 TDZ combined with either indole-3-acetic acid (IAA) or indole-3-butyric acid (IBA) was the most productive. Rooting was readily achieved when multiple shoots were singled out and cultured on medium containing different auxins. IAA was the most effective on root development in terms of both the number of roots per shoot and the frequency of rooted shoots. More than 90 % of the regenerants survived after hardening for four weeks at gradually decreased air humidity.

The aim of this research was to determine whether exogenous abscisic acid (ABA) applied immediately after ex vitro transfer of in vitro grown plants can improve their acclimatization. Tobacco (Nicotiana tabacum L.) plantlets were transferred into pots with Perlite initially moistened either by water or 50 µM ABA solution and they were grown under low (LI) or high (HI) irradiance of 150 and 700 µmol m^-2 s^-1, respectively. Endogenous content of ABA in tobacco leaves increased considerably after ABA application and even more in plants grown under HI. Stomatal conductance, transpiration rate and net photosynthetic rate decreased considerably 1 d after ex vitro transfer and increased thereafter. The gas exchange parameters were further decreased by ABA application and so wilting of these plants was limited. Chlorophyll (a+b) and β-carotene contents were higher in ABA-treated plants, but the content of xanthophyll cycle pigments was not increased. However, the degree of xanthophyll cycle pigments deepoxidation was decreased what also suggested less stress in ABA-treated plants. No dramatic changes in most chlorophyll a fluorescence parameters after ex vitro transfer suggested that the plants did not suffer from restriction of electron transport or photosystem damage.

RAPD markers linked to beet necrotic yellow vein virus (BNYVV) resistance genes were identified in two Beta vulgaris accessions Holly-1-4 and WB42 using bulked segregant analysis. The polymorphism revealed by the RAPD markers in the F₂ generations of WB42 was higher than that of Holly-1-4. The segregation distortion at marker loci was slightly lower in the B. vulgaris × B. maritima cross than in the B. vulgaris × B. vulgaris cross. For Holly-1-4, a RAPD marker was identified in a long distance from the resistance gene of Rz ₁ . However, a RAPD marker tightly linked with Rz ₂ gene in repulsion phase was detected with an approximate distance of 0.036 rf. This marker was not generation specific and showed high repeatability. The distance between Rz ₁ and Rz ₂ genes was estimated as 0.464 rf. After the Rz ₂ Rz ₂ and Rz ₂ rz ₂ genotypes were identified using ELISA values and repulsion phase RAPD markers, comparison of their ELISA means revealed lack of the gene dosage effects. Nevertheless, under the field or severe infection conditions, the difference between ELISA mean values of the Rz ₂ Rz ₂ and Rz ₂ rz ₂ genotypes might be more than that observed in this study and the gene dosage effects of Rz ₂ allele might be important.

Following leaf application of salicylic acid (SA), calcium chloride, hydrogen peroxide and 6-benzylaminopurine (BA), Manila grass (Zoysia matrella) plants were exposed to day/night temperature of 7/2 °C for 120 h in a growth chamber. The lower content of malondialdehyde (MDA) and H₂O₂ and higher activities of ascorbate peroxidase (APX), guaiacol peroxidase (POD) and catalase (CAT) during exposure to low temperature in pre-treated plants in comparison with control plants demonstrated that these compounds improved the chilling tolerance of Manila grass.

Rice overexpressed thaumatin-like protein gene and the proteins from the leaf blades of 2-week-old transgenic rice seedlings were fractionated into cytosolic and membrane fractions, and separated by two-dimensional polyacrylamide gel electrophoresis and stained with Commassie brilliant blue. Among of 440 detected proteins, 5 proteins were up-regulated and 5 proteins were down-regulated by the overexpression of thaumatin-like protein. In the sense thaumatin-like protein transgenic rice and/or in rice inoculated with Xanthomonas oryzae pv. oryzae (Xo7435), 2-cys peroxiredoxin, thaumatin-like protein and glycine cleavage H protein were up-regulated, while oxygen evolving complex protein 2 was down-regulated. These results suggest that thaumatin-like protein-mediated disease resistance of rice against bacterial blight disease is the results of changes in proteins related to oxidative stress and energy metabolism in addition to changes in proteins related to defence.

Pea (Pisum sativum L., cv. Scinado) seedlings were exposed to low doses of ultraviolet-B (UV-B; 4.4 and 13.3 kJ m^-2 d^-1) or UV-C (0.1 and 0.3 kJ m^-2 d^-1) radiation for 14 d. Aminocyclopropane carboxylic acid (ACC), indoleacetic acid (IAA) and abscisic acid (ABA) contents were quantified by gas chromatography coupled to mass spectrometry (GC-MS). The accumulation of ACC upon irradiation was dose-dependent. ABA content was reduced and IAA content increased upon UV-C treatment whereas the UV-B doses used did not cause significant changes in ABA and IAA contents.

The ZEITLUPE (ZTL) protein is involved in the control of circadian period, hypocotyl elongation and flowering time in Arabidopsis thaliana. The aim of the present work was the identification of the InZTL gene and localization of its mRNA in the model short-day plant Ipomoea nil. The deduced InZTL protein of 622 amino acid residues contained a LOV domain at the N-terminal part, followed by an F-box domain and six carboxy terminal kelch repeats. Amino acid sequence of InZTL showed 84 % homology with Mesembryanthemum crystallinum ZTL (McZTL) and 83 % with Arabidopsis thaliana ZTL (AtZTL). Fluorescence in situ hybridization (FISH) to InZTL mRNA showed its high accumulation in the vascular bundles as well in the guard cells of the cotyledon. Immunolocalization of ZTL protein indicated a similar distribution pattern of ZTL protein as InZTL mRNAs.

The induction of defence compounds and enzymes involved in the phenylpropanoid pathway were studied in the ripe and green chilli fruits inoculated with Colletotrichum capsici and Alternaria alternata. Total phenols and the activity of phenylalanine ammonia lyase (PAL), peroxidase (PO), polyphenol oxidase (PPO) and catalase (CAT) increased in the inoculated ripe and green chilli fruits compared to the corresponding healthy fruits. Total phenols and the activities of the enzymes were at the maximum 2-3 d after inoculation and thereafter declined sharply in ripe chilli fruits, whereas slowly in green chilli fruits. In comparison with ripe chilli fruits, green chilli fruits were more resistant as they showed higher accumulation of total phenols and also higher activities of enzymes.

Transgenic Podophyllum peltatum plants were successfully produced by Agrobacterium tumefaciens-mediated transformation. Embryogenic callus was co-cultivated with Agrobacterium tumefaciens harboring a binary vector pBI 121 carrying β-glucuronidase (GUS) and neomycinphosphotransferase (NPT II) gene. GUS-histochemical analysis revealed that, 50 µM acetosyringone treatments during Agrobacterium infection and 3 d co-cultivation with Agrobacterium showed enhanced transformation efficiency. Percentage of GUS positive callus increased rapidly as the subculture time proceeded on selection medium containing 100 mg dm^-3 kanamycin. Kanamycin resistant somatic embryos were formed from embryogenic callus after cultivation with 11.35 µM abscisic acid (ABA) for 3 weeks and then on hormone-free selection medium. Somatic embryos were germinated and converted into plantlets on medium containing 2.89 µM gibberellic acid (GA₃). The integration of GUS and NPT II gene into transgenic plants was confirmed by polymerase chain reaction and Southern analysis.

The effects of exogenous abscisic acid (ABA) on lead tolerance in rice (Oryza sativa L.) seedlings were investigated. Pre-treatment with 0.1 g m³ ABA for 2 d restricted amount of Pb translocated from roots to shoots, decreased malondialdehyde and H₂O₂ contents in leaves, and alleviated Pb-induced decrease in plant growth and leaf chlorophyll content. Further, ABA pre-treatment adjusted leaf antioxidative enzyme activities (increased ascorbate peroxidase and catalase activities while decreased superoxide dismutase activity) and so alleviated oxidative stress.

To better understand the mechanisms involved in aluminum toxicity and tolerance in plants, microarray technology was used to evaluate changes in gene expression in Arabidopsis thaliana under Al stress. With the use of Affymetrix Arabidopsis ATH1 Genechip, a comparison of RNA expression profiles was made between control and Al-treated Arabidopsis seedlings. A total of 256 genes were identified as Al-responsive. Ninety-four genes were shown to be up-regulated and 162 were down-regulated; comprising 1.1 % of the 24 000 Arabidopsis genes. Real-time RT-PCR was used to confirm the microarray data. The analysis showed that a large number of transcription factors and several putative signaling components were up-regulated by aluminum. Chloroplast structural and photosynthetic genes were, in general, down-regulated. A number of previously identified Al-responsive genes, e.g. GST, Auxin-regulated, Peroxidase, and Chitinase, were up-regulated by Al-stress, whereas Wali 3 and Wali 4 were down-regulated. We also identified several up-regulated genes involved in vacuolar signaling, sorting and docking. Three genes were also up-regulated by Al-stress, Ras GTP-binding protein, ABC-cassette binding, and the AtELP1 receptor genes, have previously been documented as responsive to drought and/or oxidative stress and may play important roles the detoxification of Al ions by transportation and storage into root vacuoles. Ultrastructural changes in the roots tips cells of Arabidopsis were evaluated using transmission electron microscopy and energy-dispersive X-ray analysis with scanning electron microscopy and results showed Al accumulation in the root tips of Arabidopsis.

Inter-simple sequence repeat (ISSR) markers were used to assess the genetic stability of long-term micropropagated plantlets of London plane tree (Platanus acerifolia Willd.). Twenty micropropagated plantlets were chosen from a clonal collection of shoots that originated from a single mother shoot. This clonal collection had been maintained under in vitro culture conditions for at least 8 years, as achieved by axillary branch multiplication. Out of 38 ISSR primers screened, 16 primers were found to produce clear reproducible bands resulting in a total of 103 distinct bands with an average of 6.44 scorable bands per primer. Of these 103 bands, 86 were monomorphic across all 20 of the plants tested and 17 showed polymorphisms (16.5 % polymorphism). Based on the ISSR band data, similarity indices between the plantlets ranged from 0.92 to 1.00. These similarity indices were used to construct an UPGMA dendrogram and demonstrated that all 20 micropropagated plants grouped together in one major cluster with a similarity level of 91 %. A total of 1771 scorable bands were obtained from the full combination of primers and plantlets and only 51 (2.88 %) were polymorphic across the plantlets which indicates that this micropropagated line of P. acerifolia is genetically stable.

Effect of long term soil salinity (control-S₀ and three levels S₁ to S₃) was studied in two maize (Zea mays L.) genotypes, PEHM 3 (comparatively tolerant) and Navjot (susceptible) at vegetative and anthesis stages during summer-rainy season. Salinity stress decreased relative water content (RWC), chlorophyll (Chl) and carotenoid (Car) contents, membrane stability index (MSI), potassium and calcium contents, and increased the contents of superoxide radical (O₂ ^.-), hydrogen peroxide (H₂O₂), thiobarbituric acid reactive substances (TBARS), proline, glycinebetaine, total soluble sugars, and sodium, and Na⁺/K⁺ and Na⁺/Ca²⁺ ratios in both the genotypes. Contents of zinc, copper, manganese and iron increased up to S₂. Though under S₀ PEHM 3 had higher content of all the metals, Navjot recorded higher content of Zn at all salinity levels and contents of all metal ions at S₂ and S₃. Activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and glutathione reductase (GR) increased upto S₂ in both the genotypes, and upto S₃ in PEHM 3 at the two stages. Salinity induced decrease in RWC, Chl, Car, MSI, K⁺ and Ca²⁺ was significantly greater in Navjot, which also recorded higher Na⁺ content and Na⁺/K⁺ and Na⁺/Ca²⁺ ratios than PEHM-3. PEHM-3 recorded higher contents of proline, glycine-betaine, total soluble sugars, K⁺, Ca²⁺, activity of SOD, APX, CAT, GR, and comparatively lower O^{2 .-}, H₂O₂ and TBARS contents compared to Navjot.

In this study we examined the genetic diversity and geographic scale of genotype distribution within the model legume species Medicago truncatula widely distributed in pasture and marginal agricultural lands in Greece and other Mediterranean countries. Thirty one Medicago truncatula and Medicago littorialis accessions were chosen on the basis of their geographical distributions and studied using 9 polymorphic simple sequence repeats (SSR) markers. The number of alleles per locus varied between 3 and 7. A total of 42 alleles were detected with a mean value of 4.66 alleles per locus. Geographic origin was not related with genotypic similarity among accessions. However, there were instances of close genetic relatedness between accessions from neighboring locations in a geographic compartment. In conclusion, the presented data revealed extensive M. truncatula genotype dispersal in Greece pointing to the significance of preserving local genetic resources in their natural environment.

In over 80 % of the angiosperms, the female gametophyte is comprised of seven cells, two of which are the synergid cells. These cells are considered pivotal in assuring successful fertilization. The synergid cells direct pollen tube growth toward the female gametophyte, and facilitate the entrance of the tube into the embryo sac. Once the pollen tube enters the synergid cell, its growth is arrested, the tip of the tube breaks, and two sperm cells are released. This sequence of events is also synergid dependent. In addition, separation of the cells of the male germ unit, orientation of the two sperm cells in the degenerating synergid, and fusion of the egg and central cell with sperm cells may also be related to synergid cells. Synergid structure has been widely studied, but development and function of these cells during angiosperm fertilization remains elusive. Recent molecular approaches have provided an enhanced understanding of the role of synergid cells in fertilization. The present review summarizes the results of current studies regarding the role of synergids in angiosperm reproductive function.

Crocus sativus corms were grown in Perlite and watered by half-strength modified Hoagland nutrient solution containing 0, 50, 100, 150, 200 mM NaCl. Growth parameters and contents of proteins, proline, polyphenols, minerals and saccharides were studied in fibrous roots, contractile roots, corms and leaves. All plants remained alive and did not display any sign of foliar damage even at 200 mM NaCl. However, the salinity decreased growth, relative water content and increased contents of proline and Na⁺ in all organs. Total protein content was increased in corms and contractile roots but decreased in fibrous roots. Changes in protein pattern were also observed. Polyphenol content was increased by salinity in all organs except the leaves. As salinity increased, content of soluble saccharides decreased except in the contractile roots.

An efficient, highly reproducible system for plant regeneration via somatic embryogenesis was developed for Cenchrus ciliaris genotypes IG-3108 and IG-74. Explants such as seeds, shoot tip segments and immature inflorescences were cultured on Murashige and Skoog (MS) medium supplemented with 2.0-5.0 mg dm^-3 2,4-dichlorophenoxyacetic acid (2,4-D) and 0.5 mg dm^-3 N⁶-benzyladenine (BA) for induction of callus. Callus could be successfully induced from all the three explants of both the genotypes. But the high frequency of embryogenic callus could be induced only from immature inflorescence explants. Somatic embryos were formed from nodular, hard and compact embryogenic calli when 2,4-D concentration was gradually reduced and BA concentration increased. Histological studies of somatic embryos indicated the presence of shoot apical meristem with leaf primordia. Ultrastructural details of globular and scutellar somatic embryos further validated successful induction and progression of somatic embryogenesis. Shoots were differentiated upon germination of somatic embryos on MS medium containing 2,4-D (0.25 mg dm^-3) and BA or kinetin (1-5 mg dm^-3). Roots were induced on 1/2 MS medium containing charcoal (0.8 %), and the regenerated plants transferred to pots and established in the soil showed normal growth and fertility.

A protocol for somatic embryogenesis in Azadirachta indica A Juss. has been standardized using in vivo leaflets. Experiments were carried out to examine the effect of various auxins, cytokinins, sucrose, inorganic and organic salts on subsequent somatic embryo induction and maturation. Embryogenic calli were induced on Murashige and Skoog (MS) medium supplemented with 1.5 mg dm^-3 kinetin and 1.5 mg dm^-3 indole-3-acetic acid and subsequently all the stages of somatic embryo development (globular, cordate, torpedo and cotyledonary) were observed. Maturation of these embryos was accomplished with the same growth regulators after three subcultures. The histological study of somatic embryos showed resembles to zygotic embryos. The matured somatic embryos were transferred onto half strength MS-medium devoid of growth regulators for their germination (82 %). Plantlets were acclimatized in the field with a survival rate of 80-83.5 %.

A highly efficient protocol for plant regeneration from cotyledonary node of two chickpea (Cicer arietinum L.) cultivars ICCV-10 and Annigeri used phenylacetic acid (PAA). The Murashige and Skoog (MS) medium supplemented with 2.0 mg dm^-3 6-benzylaminopurine (BAP) and 1.0 mg dm^-3 PAA was used for induction of bud formation. Buds were elongated on MS medium supplemented either with only 0.75 mg dm^-3 gibberellic acid (GA₃) or 0.2 mg dm^-3 GA₃ + 0.6 mg dm^-3 PAA. The elongated shoots were then transferred onto rooting medium containing 1 mg dm^-3 PAA. The frequency of multiple shoot induction and rooting was higher in Annigeri as compared to ICCV-10. The complete plantlets with well-developed roots were transferred to pots containing sterilized soil and sand in the ratio 3:1 where they survived (74 %) and set normal seeds.

The objective of this work was to test whether Ca²⁺, a second messenger in stress response, is involved in ABA-induced antioxidant enzyme activities in Stylosanthes guianensis. Plants were sprayed with abscisic acid (ABA), calcium channel blocker, LaCl₃, calcium chelator, ethylene glycol-bis(β-amino ethyl ether)-N,N,N', N'-tetraacetid acid (EGTA), and ABA in combination with LaCl₃ or EGTA. Their effects on superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities and chilling resistance were compared. The results showed that ABA decreased electrolyte leakage and lipid peroxidation but increased maximum photochemical efficiency measured as variable to maximum fluorescence ratio (F_v/F_m) under chilling stress. Treatment with LaCl₃ or EGTA alone and in combination with ABA increased electrolyte leakage and lipid peroxidation, decreased Fv/Fm, suggesting that the block in Ca²⁺ signalling decreased chilling resistance of S. guianensis and the ABA-enhanced chilling resistance. ABA-induced SOD and APX activities were suppressed by LaCl₃ or EGTA. The results suggested that Ca²⁺ is involved in the ABA-enhanced chilling resistance and the ABA-induced SOD and APX activities in S. guianensis.

Plant β-glucosidases catalyze the hydrolysis of glycosidic linkages and play a vital role in defense against pathogens and stress. The present work investigated the relationship between leaf development and β-glucosidase protein content in Olea europea L. (cv. Picual) leaves. The total chlorophyll content increased with leaf age in current-season leaves. Immunoblot analysis revealed that the content of 61 kD protein of β-glucosidase also increased with leaf age, and that the enzyme existed in three isoforms (pI 5.8-6.2). Statistical analysis indicated a strong correlation between chlorophyll and β-glucosidase protein contents.

Recent developments in knowledge about the interactions between lichens and heavy metals at different levels, from populations to cells and from ecology to molecular biology are reviewed. Sources of heavy metals, mechanisms of heavy metal accumulation and detoxification by lichens are discussed. Special emphasis is placed on ultrastructural changes as well as physiological parameters such as membrane integrity, pigment composition, chlorophyll a fluorescence, photosynthesis, respiration, contents of ATP, amino acids, ergosterol, ethylene, non-protein thiols, activity of antioxidant enzymes and expression of stress proteins.

Barley seedlings were pre-treated with 1 and 5 µM H₂O₂ for 2 d and then supplied with water or 150 mM NaCl for 4 and 7 d. Exogenous H₂O₂ alone had no effect on the proline, malondialdehyde (MDA) and H₂O₂ contents, decreased catalase (CAT) activity and had no effect on peroxidase (POX) activity. Three new superoxide dismutase (SOD) isoenzymes appeared in the leaves as a result of 1 µM H₂O₂ treatment. NaCl enhanced CAT and POX activity. SOD activity and isoenzyme patterns were changed due to H₂O₂ pre-treatment, NaCl stress and leaf ageing. In pre-treated seedlings the rate of ¹⁴CO₂ fixation was higher and MDA, H₂O₂ and proline contents were lower in comparison to the seedlings subjected directly to NaCl stress. Cl^- content in the leaves 4 and 7 d after NaCl supply increased considerably, but less in pre-treated plants. It was suggested that H₂O₂ metabolism is involved as a signal in the processes of barley salt tolerance.

We have investigated the effects of cadmium on the microtubular (MT) cytoskeleton in the root tip cells of Allium sativum L. using indirect immunofluorescence microscopy. Cd affected the mechanisms controlling the organization of MT cytoskeleton, as well as tubulin assembly/disassembly processes. Cd induced the formation of abnormal MT arrays, consisting of discontinuous wavy MTs or short MT fragments at the cell periphery. Cadmium caused irregular nuclear disorder in cells where the MT organization and function was disturbed. Furthermore, with increased Cd concentration and duration of treatment the MTs depolymerized more severely, the frequency of abnormal cell increased and the mitotic index decreased progressively. The above findings showed that MT cytoskeleton is one of target sites of Cd toxicity in root tip cells.

An experiment was conducted with two contrasting pigeon pea (Cajanus cajan L.) genotypes, ICPL 84023 (tolerant) and ICP 7035 (susceptible), to study the physiological and molecular basis of waterlogging tolerance in relation to oxidative stress and antioxidant enzyme activities. Waterlogging resulted in visible yellowing and premature senescence of leaves, and greater decline in relative water content, chlorophyll content, and membrane stability index in ICP 7035 than in ICPL 84023. Superoxide radical and hydrogen peroxide contents increased at day 4 and 6 of waterlogging probably due to activation of NADPH-oxidase. O₂ ^.- production was inhibited, by diphenylene iodonium chloride, a specific inhibitor of NADPH oxidase and expression of NADPH oxidase-mRNA was increased under waterlogging condition in ICPL 84023. ICP 7035 showed higher contents of ROS in control condition and after recovery, however, during waterlogging the O₂ ^.- production was higher in ICPL 84023. Activities of antioxidant enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase and catalase increased under waterlogging more in ICPL 84023 than in ICP 7035. Cu/Zn-SOD and APX-mRNA expression in 24-h waterlogged plants showed enhanced expression in ICPL 84023 compared to ICP 7035. The cloning and sequencing of APX gene of tolerant and susceptible genotypes yielded cDNAs of 622 and 623 bp, having 95 % homology with each other and 92 % with the corresponding sequences of Vigna unguiculate APX-gene.

In this communication, we report the binding of abscisic acid responsive elements (ABREs) of rice Osem, namely motif A and motif B, with a cognate trans-acting factor present in the nuclear extract of tobacco leaf. The binding is specific as both the complexes were disrupted with an excess of homologous non-radioactive DNA like motif A or motif B themselves or with cis-elements of rice Rab16A, motif I (ABRE) and motif IIa (non-ACGT ABRE-like sequences). Four tandem repeats of ABRE from wheat Em (4X ABRE) or two tandem repeats of Em ABRE, plus two copies of coupling element (CE1) from barley HVA22 (2X ABRC), also showed specific complexes, that were competed out by an excess of homologous competitors like motif I, motif IIa, motif A, motif B, 4X ABRE and 2X ABRC, but not by the unrelated 4X DRE sequence. Elution of the protein from all the complexes showed a single 26 kDa polypeptide band. Introgression of two of the above synthetic promoters 4X ABRE and 2X ABRC, each fused with minimal promoter of cauliflower mosaic virus 35S (CaMV 35S), could induce the expression of the reporter gene β-glucuronidase (gus) in transgenic tobacco in response to high NaCl concentration, dehydration or abscisic acid, but not at the constitutive level, proving that they can be used as efficient stress-inducible promoters. Our work shows both in vivo and in vitro activity of the promoters from monocot genes in the model dicot plant tobacco.