Efficient plant regeneration system from leaf base segments of wheat (Triticum aestivum L.) was developed. The factors affecting the callus formation and regeneration capacity of leaf segments of two genotypes; Bobwhite and Pavon 76, were investigated. The highest number of somatic embryos (SE) was obtained on Murashige and Skoog medium supplemented with 2 mg dm^-3 2,4-dichlorophenoxyacetic acid + 1 mg dm^-3 naphthalenacetic acid (14.7 SE per segment). Highest frequency of embryogenic callus (96 %) and somatic embryo formation (24.3 SE per segment) were achieved in the first segments. The highest plantlet regeneration was obtained after transfer of embryogenic calli to regeneration medium supplemented with 1 mg dm^-3 kinetin (6.3 plantlets per segment).

Experiments were carried out to evaluate the effects of 4/2 light-dark cycles (4 h of light followed by 2 h of dark) on the rooting responses of shoots cultivated in vitro of the fruit tree rootstocks GF 677 (peach × almond hybrid), Mr.S. 2/5 (Prunus cerasifera), MM 106 (apple Nothern Spy × Paradise M1) and BA 29 (Cydonia oblonga). Under this light regime rooting percentage of GF 677, Mr.S. 2/5 and MM 106 shoots reached 100 % as in the control treatment (16/8), while in BA 29 shoots, short light-dark cycles increased rooting response by about 65 %. Moreover, the shoots of all rootstocks submitted to the 4/2 cycle showed an appreciable increase in root number and length, and an earlier root emergence of about 4 - 5 d compared to the 16/8 cycle. Finally, rooting percentage of BA 29 shoots submitted to the 4/2 light regime and treated with 0.2 mg dm^-3 indolebutyric acid (IBA), was equal to that reported with 0.4 mg dm^-3 IBA under the 16/8 regime, indicating that the former light regime also amplified the rhizogenic effect of auxin.

Multiple shoot buds could be induced directly from internode explants of Celastrus paniculatus inoculated on Murashige and Skoog's (MS) medium containing different growth regulators. The best response was obtained when 4.44 μM 6-benzylaminopurine (BAP) was incorporated in the medium. Incorporation of indole-3-acetic acid (IAA) and α-naphthalene acetic acid (NAA) did not improve response, rather promoted callusing. Adventitious shoot buds could be multiplied and elongated on MS medium containing 2.22 μM BAP. Rooting of shoots (80 %) was obtained when their bases were dipped in pre-autoclaved indole-3-butyric acid (IBA) solution (2.45 mM) for 10 min followed by their implantation on medium containing 1/4 MS salts, 1.0 % sucrose and 0.6 % agar. Out of 500 plantlets subjected to hardening, 410 were successfully hardened under greenhouse conditions. Twenty plants were established in field while remaining of them were transferred to nursery conditions without any mortality.

Hydroponically grown cucumber plants were exposed to 14-d period of salinity (0, 50, 100 mM NaCl). NaCl caused reduction in the relative water content in the leaves. The Na⁺ content increased and the K⁺ content decreased. The net photosynthetic rate, stomatal conductance and transpiration rate were markedly decreased by all of the salt treatments. Salinity decreased also the maximum quantum efficiency of photosystem 2 (PS 2) determined as the variable to maximum fluorescence ratio, the photochemical quantum yield of PS 2 and the photochemical fluorescence quenching, while the non-photochemical quenching increased. Above results indicate that NaCl affects photosynthesis through both stomata closure and non-stomatal factors.

Supply of aqueous solution of triadimefon (20 mg dm^-3) to unstressed green gram plants increased the contents of soluble proteins, amino acids, nitrate and nitrite, and the activity of nitrate reductase in the leaves and nitrate reductase in nodules. The nitrogenase activity in nodules and roots was also increased. Number and fresh mass of nodules and their nitrate and nitrite contents were also higher than those of the controls. In contrast, the UV-B stress (12.2 kJ m^-2 d^-1) suppressed nodulation and nitrogen metabolism in leaves and roots compared to plants under natural UV-B (10 kJ m^-2 d^-1). Triadimefon-treated plants did not show such severe inhibitions after exposure to elevated UV-B. Thus triadimefon increased their tolerance to UV-B stress.

The effect of sucrose on fruiting, seed production, and seed germination of lesser centaury [Centaurium pulchellum (Sw.) Druce] was examined using explants of flowers and flower buds. Sucrose concentrations in the culture medium ranged from 0.003 to 0.3 M. It has been shown that the number of auxiliary buds, capsules dimension, number of viable seeds per capsule and seed dimensions increased with the increase of sucrose concentrations. The highest values were recorded at sucrose concentrations higher than 0.03 M, except for seeds size, which were larger at sucrose concentration ranging from 0.003 to 0.1 M. The germination of in vitro produced seeds was affected by previous culture history: a higher germination percentage was obtained in seeds that were raised from explants originally grown on medium with sucrose concentrations higher than 0.003 M.

Tobacco leaf disc explants were inoculated with Agrobacterum tumefaciens strain GV2260 carrying p35S GUS-INT to determine the influence of different co-cultivation temperatures (18 - 26 °C), periods (24 - 96 h) and media (solid and liquid) on transformation efficiency. Kanamycin-resistant shoots developed on leaf discs inoculated with Agrobacterium after 4 weeks of culture initiation. Regenerated shoots were excised and rooted in the basal medium supplemented with 100 mg dm ^-3 kanamycin and 250 mg dm ^-3 augmentin. The rooted plantlets were finally transferred to compost and confirmed by GUS assay and PCR analysis. The highest transformation frequency was achieved from the explants co-cultivated with A. tumefaciens in liquid medium for 48 h at 22 or 24 °C.

Floral phenology, pollen quality and seed set of Plantago crassifolia plants, grown in the presence of increasing NaCl concentrations, were studied to test how this Mediterranean halophyte responded to salt stress during the reproductive phase of its life cycle. "Reproductive success" was maximal in plants grown in non-saline conditions, or in the presence of 100 mM NaCl, but it was negatively affected by higher salinities, due to a progressive reduction of pollen fertility, seed set, and seed viability.

The present work describes the changes that take place in phytohormone contents in germinating chickpea (Cicer arietinum cv. Aziziye-94) seeds in response to heavy metal stress. For this aim, endogenous abscisic acid (ABA), gibberellic acid (GA₃), zeatin (Z) and zeatin riboside (ZR) contents were followed for 24, 48 and 72 h in chickpea seeds germinating at the concentrations of 0.1, 1.0 and 5.0 mM Pb or 0.1, 1.0 and 10 mM Zn. The results showed that Pb and Zn significantly delayed and impeded the germination of chickpea seeds. The negative effect of Pb on germination was higher than that of Zn. Further, Pb increased ABA and Z contents while decreased GA₃ content in the germinating seeds. The high concentrations of Zn (1.0 and 10 mM) decreased contents of Z, ZR and GA₃ while 0.1 mM Zn increased the content of the same hormones. The ABA content was enhanced by Zn in all concentrations used.

The effects of NaCl (0, 50, 100, 150 and 200 mM) on growth, water relations, glycinebetaine, free proline, ion contents, stomata number and size of Kochia prostrata (L.) Schard were determined. Shoot and root fresh and dry matter, root and shoot length, relative growth rate, net assimilation rate, relative water content, water use efficiency, soluble sugars and glycinebetaine contents were not changed at low NaCl concentrations, but they were significantly decreased at 200 mM NaCl. The K⁺, Mg²⁺ and Ca²⁺ contents, water potential, chlorophyll a+b and carotenoides contents, and stomata number and size were reduced already at low concentrations of NaCl. In contrast, the Na⁺, Cl^- and proline contents increased several times with increasing NaCl concentration. Kochia prostrata is a salt tolerant species, the optimal growth of this plant occurred up to 150 mM NaCl. The mechanisms of salt tolerance in the plant may be balance among ion accumulation and production of glycinebetaine, proline, soluble sugars for maintenance of pressure potential.

The activities of sucrose phosphate synthase (SPS), sucrose synthase (SUSY), neutral invertase (NI) and soluble acid invertase (SAI) were measured in callus cultures of four Mexican sugarcane cultivars (Saccharum spp.) with a different capacity to accumulate sucrose in stem parenchyma cells. The results indicated that sucrose accumulation in callus was positively correlated to the activity of SPS and SUSY and negatively to the activity of SAI and NI while SPS explained most of the variation found for sucrose accumulation and NI least.

Protoporphyrinogen oxidase (Protox) in the porphyrin pathway is the target site of the peroxidizing herbicides such as carfentrazone-ethyl and oxyfluorfen. In an attempt to develop herbicide-resistant plants, transgenic rice plants were generated via expression of herbicide-insensitive Bacillus subtilis Protox gene fused to the transit sequence for targeting to the plastid using Agrobacterium-mediated gene transformation. Homozygous transgenic rice lines of T₃ generation selected by hygromycin resistance test were examined if they are resistant to the herbicides carfentrazone-ethyl and oxyfluorfen. The homozygous transgenic lines had single copy insertion of B. subtilis Protox gene into their genomes and express its mRNA. Compared to wild-type rice, the transgenic lines were less susceptible to the herbicides when examined with respect to growth, electrolyte leakage, chlorophyll loss and lipid peroxidation. The in vitro Protox activities in transgenic lines were about 56 % higher than those in wild-type rice. With 10 µM concentration of the herbicides in the enzyme assays, Protox activities in transgenic lines were similar to those in non-inhibited wild-type rice. Less amount of protoporphyrin IX was accumulated in transgenic lines than in wild-type rice upon the treatment of the herbicides at 10 µM concentration. Our results indicated that expression of B. subtilis Protox gene was stably transmitted into T₃ rice plants and reduced their sensitivity to carfentrazone-ethyl and oxyfluorfen.

In order to establish an efficient system for in vitro plant regeneration of a short day plant Chenopodium rubrum L. and a long day plant Chenopodium murale L., optimum culture conditions for somatic embryogenesis were investigated. The effects of different growth regulators, their combination and their concentrations on somatic embryos induction in different explant types (root, hypocotyl, cotyledon and leaf) were tested. Somatic embryogenesis was induced in both plants on Murashige and Skoog (MS) medium supplemented with sucrose (3 %), agar (0.7 %) and 1 - 10 μM 2,4-dichlorophenoxyacetic acid (2,4-D) as the sole growth regulator. The largest embryogenic capacity was found in root explants of Chenopodium rubrum on 1 μM 2,4-D and in basal parts of cotyledons in C. murale plants on 10 μM 2,4-D.

Shoot cultures of Alyssum markgrafii O.E. Shulz, endemic nickel hyperaccumulating species of central Balkan, were established and maintained on Murashige and Skoog medium supplemented with 0.2 mg dm^-3 benzyladenine (BA). Nickel in form of NiCl₂ . 6 H₂O was supplemented at 22 different concentrations ranging from 0.0001 to 15 mM but none of them was lethal to cultures. High Ni²⁺ concentrations (10 mM or more) arrested shoot growth which, upon transfer to Ni-free medium, commenced via axillary bud proliferation. Shoots that developed from axillary buds through the subculture manifested increased tolerance to Ni²⁺ expressed as shoot elongation. Shoot multiplication and dry biomass production decreased with increase of Ni²⁺ in medium. Only the accumulation of Ni²⁺ in tissues increased with Ni²⁺ content of the medium. Apart from shoot cultures, high Ni²⁺ accumulation was registered in undifferentiated callus cultured on medium with 0.5 mg dm^-3 BA and 0.5 mg dm^-3 naphthylacetic acid. Highest content of accumulated Ni was 2.37 μg g^-1 (d.m.) in shoots and 2.65 μg g^-1 (d.m.) in callus, both measured on medium with 15 mM Ni²⁺.

Based on the NH₂-terminal sequence of three PR-10 isoforms previously identified in Lupinus albus leaves and a conserved amino-acid region in the PR-10 proteins from leguminosae, a pair of oligonucleotides was designed and used to amplify the corresponding cDNA fragment from a L. albus leaves cDNA library. A fragment of DNA of 200 bp was isolated from the polymerase chain reaction (PCR) mixture and subsequently used to screen the cDNA library. A cDNA coding for a PR-10 protein of 158 amino acid residues was cloned and sequenced. Subsequent studies involving Northern and Western blot analysis have shown that the PR-10 protein isoforms are differentially expressed during the development of the healthy lupin plant. High mRNA and protein contents were detected in roots and hypocotyls of both 7- and 20-d-old plants. In young leaves, the mRNA and protein contents were low and increasead in mature leaves. Tissue printing experiments with root sections suggest that the proteins are extracellular and are mainly associated with the vascular tissues in mature roots.

Experiments were performed to optimize the macronutrients concentrations for in vitro rooting of Ceratonia siliqua micropropagated shoots. Several dilutions of Murashige and Skoog (MS) medium were tested: full-strength MS, half-strength MS (1/2MS), and 1/2MS + full N. The frequency of in vitro rooting was enhanced when the 1/2MS was used (50 % rooted shoots). Mature leaves from 20 - 30 year-old carob trees and from 2 year-old micropropagated plants were collected and the concentrations of macronutrients (N, P, K, Ca, Mg) assessed. Based on the mineral composition of the leaves a new medium was formulated and compared with the previous ones showing an increment of the rooting frequency to 80 %. Moreover, shoots rooted in the new medium did not show symptoms of apical necrosis that occurred in the other tested media.

A modified plant 7SL RNA gene from Arabidopsis thaliana designated AHIIA63M was introduced into potato plants via Agrobacterium-mediated transformation. No transgenic plants could be obtained using pGPTV-based binary vectors where AHIIA63M gene driven by polIII promoter was located close to the polII promoter of the selection gene. Special binary vectors with matrix attachment region (MAR) elements had to be used for transformation to insulate polII and polIII promoters within T-DNA. The level of AHIIA63M RNA in transgenic plants was lower than the levels of transcripts of transgenes driven by RNA polymerase II. The level of AHIIA63M transcript in transgenic potato plants was tissue specific. The highest expression was detected in roots and gynoecium and the lowest in tubers. Moreover, non-specific promoter activity within the MAR element was revealed. This activity contributed to AHIIA63M transcription. This is the first report of expression of a modified 7SL RNA gene in transgenic plants and promoter activity within the MAR element.

We describe the multi-step regeneration system of medicinal plant Schisandra chinensis (Turcz.) Baill. The seeds were pre-treated with 0.005 μM thidiazuron. Subsequently the zygotic embryos of the early heart stage were cultured on medium with 50 μM of 2,4-dichlorophenoxyacetic acid (2,4-D) and after three weeks the embryogenic calli were transferred to a medium with 10 μM of 2,4-D and 4 μM of 6-benzyladenine and were sub-cultured at the 4-week intervals. Abscisic acid (30 μM) and polyethyleneglycol (3 %) significantly influenced the synchronization of development of the somatic embryos (SEs) to the globular stage. The following culture on a medium without growth regulators resulted in full developed cotyledonary stage SEs. Indole-3-butyric acid (0.05 μ) contributed to their rapid conversion to plantlets.

Potted two-year-old lemon trees [Citrus limon (L.) Burm. f.], cv. Verna grafted on sour orange (C. aurantium L.) rootstock, growing in greenhouse, were subjected to drought for 33 d. Control plants were daily irrigated at field capacity. Values of sap flow (SF) were compared with transpiration (E) rates measured gravimetrically. The results underlined the robustness and high sensitivity of the compensation heat-pulse technique for estimating transpiration on a wide range of SF. Good direct correlations between E and SF rates on an instantaneous and daily basis were obtained in both treatments. On a daily basis, a common calibration curve can be used for both irrigation treatments. On an instantaneous basis, changes in SF were matches by similar changes in E in both treatments, although the relationships between these parameters presented different intercepts in each treatment. Sap flow rates were influenced by weather conditions in trees growing in non-limiting soil water conditions. This makes it possible to evaluate the significance of any sap flow measurement in relation to the reference value calculated for the vapour pressure deficit at the time the measurement was taken.

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 effects of three cytokinins, kinetin 4.5 μM (Kin), 6-benzylaminopurine 4.5 μM (BA) and N-phenyl-N'1,2,3- thiadiazol-5-yl-urea 4.5 μM (TDZ), and the effects of different treatment duration on the regeneration of adventitious shoots from quince (Cydonia oblonga Mill.) leaves were studied. In a first experiment, leaves treated with Kin for 0, 8, 16 and 24 d were transferred to BA or TDZ-containing growth medium. In a second experiment TDZ applied for 0, 4, 8, 12, 16 and 24 d was followed by BA. All treatments included 0.5 μM α -naphthaleneacetic acid (NAA). In the sequence Kin-BA, the production of adventitious shoots decreased and reddish-coloured nodular structures (RNS) of meristematic appearance increased with increasing duration of Kin treatment, while somatic embryo formation was optimal at 8 d. In the Kin-TDZ sequence, shoot production was initially pronounced, but it declined with increasing duration of the Kin treatment, while the number of roots, somatic embryos and RNS increased. TDZ-BA treatments induced marked shoot production, which gradually increased with increasing duration of TDZ treatment. The presence of TDZ and a long treatment duration appeared to be very important factors in inducing caulogenesis. Kin appeared to be effective in shoot induction but not in shoot development; the results of this work demonstrate that RNS were adventitious shoots blocked at an early developmental stage on account of insufficient cytokinin activity. BA was less effective than TDZ in inducing shoot regeneration. Finally, both Kin and BA applied after 2,4-D treatment promoted somatic embryo induction.

The effect of NaCl on the growth and activity of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) were investigated in the seedlings of four potato cultivars (Agria, Kennebec; relatively salt tolerant, Diamant and Ajax; relatively salt sensitive). The shoot fresh mass of Agria and Kennebec did not changed at 50 mM NaCl, whereas in Diamant and Ajax it decreased to 50 % of that in the controls. In Agria and Kennebec, SOD activity increased at 50 mM NaCl, but no significant changes observed in Diamant and Ajax. At higher NaCl concentration, SOD activity reduced in all cultivars. CAT and POD activities increased in all cultivars under salt stress. Unlike the other cultivars, in Ajax seedlings, APX activity increased in response to NaCl stress. We also observed new POD and SOD isoenzyme activities and changes in isoenzyme compositions under salt stress. These results suggest that salt-tolerant potato cultivars may have a better protection against reactive oxygen species (ROS) by increasing the activity of antioxidant enzymes (especially SOD) under salt stress.

A protocol of high frequency shoot organogenesis and plant establishment from stem derived callus has been developed for Tylophora indica (Burm. f.) Merrill. - an endangered medicinal plant. Callus was developed on Murashige and Skoog (MS) medium supplemented with 10 μM 2,4,5-trichlorophenoxy acetic acid (2,4,5-T). Multiple shoot induction was achieved from the surface of the callus after transferring onto shoot induction medium. The highest rate (80 %) of shoot multiplication was achieved on MS medium containing 5.0 μM kinetin. The developed shoots rooted best on half-strength MS medium supplemented with 0.5 μM indole-3-butyric acid (IBA). The in vitro raised plantlets with well developed shoot and roots were acclimatized successfully and grown in greenhouse.

Treating androgenic embryos of Aesculus hippocastanum L. with low temperatures (6 °C) improved their germination and regeneration into plantlets. The embryos derived from anther cultures showed better results than those derived from microspore cultures.

We have cloned and characterized the expression of Crocus sativus AGAMOUS1 (CsAG1), a putative C-type MADS-box gene homologous to AGAMOUS (AG) from a triploid monocot species crocus (Crocus sativus L.). The typical domain structure of MIKC-type plant MADS proteins was identified. Phylogenetic analysis of the deduced amino acid sequence indicated that the isolated gene forms a clade with the AGAMOUS homologs from the monocots Hyacinthus orientalis and Phalaenopsis equestris. A differential splicing event altering the amino acid sequence at the C terminus was identified, leading to the formation of two mRNAs differing ten nucleotides in size. The presence of both differentially spliced transcripts was restricted only to mature crocus flowers and particularly to stamens and carpels.

Lead nitrate at concentration of 150 mg dm^-3 inhibits root growth of Lupinus luteus seedlings by bout 20 %, which is accompanied by an increase of K⁺ leakage from the root cells. Non-denaturing isoelectric focusing in polyacrylamide slab gel has shown that lead stimulates the activity of most lipoxygenase isoenzymes and induces one additional isoenzyme with pI 6.9.