Immature embryos of Cytisus laburnum L. were cultivated in vitro and four culture media, different techniques of substrate preparation, sucrose concentration and the effect of suspensor removal were tested. The best results were obtained with N6 medium supplemented with 2 mg dm^-3 glycine and set up using a double-layer culture system, in which the top layer had a higher osmotic potential than the bottom one. These conditions allowed normal embryogenic development in up to 45 % of early globular embryos, that were able to develop until a complete maturity. Osmotic potential and mineral nutrients of the medium demonstrated to be crucial for the successful culture and their effects were dependent on embryo age at the time of excision. The presence of an intact suspensor showed to be beneficial only for early globular embryos while older developmental stage embryos were not significantly affected.

Two important enzyme in organic acid metabolism, phosphoenolpyruvate carboxylase (PEPC) and NADP-malic enzyme (NADP-ME), show marked diurnal rhythms in their activities during the establishment of the soybean - B. japonicum symbiosis. The pH of the nutrient solution changes in parallel with NADP-ME activity, being maximal during the night periods, whereas activity of PEPC was highest during the day periods. The results from the experiments with stem girdled plants indicated that the activity of root PEPC is modulated to a great extent by the supply of photosynthates from the shoots. It was also established that succinate application in the nutrient solution during inoculation altered significantly the pattern of assayed enzyme activities. Although our experiments did not reveal the precise mechanism of the involvement of root PEPC and NADP-ME in soybean response to inoculation with B. japonicum, they indicated the pattern of their activity during the first 72 h postinoculation which are critical for establishment and functioning of the symbiosis.

The seedling response to high Cu concentrations (1 and 10 μM CuSO₄ . 5 H₂O) was studied in Aegilops triuncialis, Ae. geniculata, Ae. cylindrica and Haynaldia villosa. The negative effect of Cu on the root growth was recorded at both concentrations, while the shoot growth was inhibited at 10 μM. The most tolerant was Ae. triuncialis, followed by Ae. geniculata. Ae. cylindrica and H. villosa were more sensitive.

Responses of Quercus ilex L. seedlings from three different localities in Italy to experimentally imposed drought stress were analysed. Predawn (Ψ_pd) and midday (Ψ_m) leaf water potential of stressed seedlings decreased on an average until -4.0 and -4.2 MPa, respectively, in the severe water stress. At the end of the severe water stress the relative water content (RWC) was 72.5 - 83.6 % and the photosynthetic rates (P_N) near zero. The critical threshold value of Ψ_pd for complete stomatal closure was from -4.0 to -4.5 MPa. The leaf damage after the severe water stress was significantly greater in seedlings originated from the acorns of climax area (45 % total leaf injured area and 40 % fallen leaves) than in the other seedlings (on an average 20.5 % total leaf injured area and 21 % fallen leaves).

Polyphenol oxidase from the latex of opium poppy was purified to the electrophoretic homogeneity by affinity chromatography using p-aminobenzoic acid as a ligand coupled to Sepharose CL-4B by divinyl sulphone activation method. The purified enzyme was used to prepare the polyclonal antibodies. The purified latex PPO exhibited high diphenolase activity in comparison with almost unmeassurable monophenolase activity. Both of these activities were sensitive to the activation with sodium dodecyl sulphate. Two isoforms (65 and 40 kDa) of latex PPO were separated by the gel filtration. There were no differences in substrate specifity (weak monophenolase and high diphenolase activity) and sensitivity to inhibitors between these isoforms, but they showed differences in electrophoretic mobility.

Activity of antioxidant enzymes was evaluated during somatic embryogenesis and shoot organogenesis from cultured leaf segments of Gladiolus hybridus Hort. The effect of exogenous antioxidants on somatic embryogenesis and shoot organogenesis has also been monitored. Activity of superoxide dismutase (SOD) gradually increased during somatic embryogenesis. while activities of catalase (CAT) and peroxidase (POX) decreased. In contrast, increase in CAT and POX activity and a concomitant decrease in SOD activity were noted during shoot organogenesis. Exogenous application of antioxidants such as glutathione (GSH), α-tocopherol and ascorbate (AA) inhibited somatic embryogenesis but stimulated shoot organogenesis. The frequency of somatic embryogenesis increased with the addition of H₂O₂. However, H₂O₂ inhibited shoot organogenesis.

An approximately 7 % difference in biologically effective ultraviolet-B (UV-B) radiation did not significantly influence leaf length or leaf peroxidase activity of chives (Allium schoenoprasum L.). However, correlation and regression analyses with different climatic parameters revealed that increased UV-B radiation enhanced ascorbate peroxidase activity in chive leaves whereas guaiacol peroxidase was inhibited.

Cowpea (Vigna unguiculata) seeds were put to germinate on filter paper under control (distilled water) and salt stress (100 mM MaCl) conditions. Seeds and seedlings were classified in eight developmental stages (DS), according to their morphological traits. Under control conditions, 7 d after planting, 100 % of the seedlings reached DS VIII (seedlings with radicles measuring more than 5 cm, cotyledons leaving the filter paper, hypocotyls straight and cotyledonary leaves fully open) and under NaCl stress conditions, 11 d after planting only 68 % of the seedlings were at DS VIII. The length of the main root and of shoot has decreased 23 and 44 %, respectively. The two-dimensional electrophoretic patterns of the albumins isolated from stems and leaves were determined in seedlings at DS VIII. In stems 19 proteins (14.6 to 76.3 kDa) had their relative concentration increased by salinity, 8 (31.2 to 65.0 kDa) had their relative concentration decreased by salinity and 9 (16.3 to 39.8 kDa) were apparently synthesised de novo. In leaves, under salt conditions 9 proteins (18.2 to 33.2 kDa) increased in concentration, one (17.1 kDa) decreased in concentration and one (21.2 kDa) was apparently synthesised de novo.

The aim of the present work was to evaluate the feasibility of mannose as a selection system for the future genetic transformation of annatto (Bixa orellana L.). Hypocotyl segments, inverted hypocotyls and immature zygotic embryos were inoculated onto a Murashige and Skoog's medium supplemented with B5 vitamins, 87.6 mM sucrose and mannose in different combinations, 2.8 g dm^-3 Phytagel®, and 4.56 μM zeatin (organogenesis) or 2.26 μM 2,4-dichlorophenoxyacetic acid and 4.52 μM kinetin (somatic embryogenesis). Annatto explants did not regenerate on medium with mannose as the only carbon source when inverted hypocotyls and immature zygotic embryos were used. However, organogenesis (5 % frequency) occurred exclusively in hypocotyl-derived explants nearest to the crown (collar) of the seedlings. No further shoot development was achieved. Therefore the substitution of sucrose by mannose inhibited both organogenesis and embryogenesis, and thus the employment of mannose could constitute an alternative selective agent in protocols for genetic transformation of this species.

N-1-naphthylphthalamic acid (NPA), an auxin transport inhibitor, was found to bind specifically to a crude membrane preparation from sugar beet seedling leaf cell suspension cultures. The dissociation constant (Kd) and binding protein concentration were found to be 1.71 μmol dm^-3 and 220 pmol g^-1(membrane protein), respectively. The amount of specific ³H-NPA binding was significantly increased by adding Mg²⁺ATP to the binding assay solution. Treatment of membrane preparations with acid phosphatase, prior to the NPA binding assay, resulted in lower specific binding. ATP activation and phosphatase inactivation were culture stage dependent. Although a considerable effect could be detected when using cells from day 8 (representing the linear phase), the same treatment did not alter the binding if cells from day 1 (representing lag phase) or day 14 (representing the stationary phase) were used. These observations have strongly highlighted the possible involvement of a phosphorylation and dephosphorylation mechanism in vivo in the regulation of the activity of the NPA binding protein. High phosphatase activity was found in the supernatant, but not in the membrane pellet) after 50 000 g centrifugation. Our present study has indicated that receptor activity could be regulated by a phosphorylation and dephosphorylation mechanism in plants.

A protocol for multiple shoot induction from cotyledonary node explants of Terminalia chebula Retz. has been developed. Germination frequency of embryos (up to 100 %) was obtained on Murashige and Skoog (MS) medium supplemented with 0.5 mg dm^-3 gibberellic acid (GA₃). Maximum number of shoots (6.4 shoots per cotyledonary node) was obtained on half-strength MS + 0.3 mg dm^-3 GA₃+ 1.0 mg dm^-3 indole-3-butyric acid (IBA) + 10.0 mg dm^-3 benzylaminopurine (BAP) after 4 weeks of culture. When the cotyledonary nodes along with the axillary shoot buds were allowed to grow in the same medium upto 19.2 shoots were obtained after 8 - 9 weeks. Best rooting (100 %, 5.5 roots per shoot) was observed when shoots were excised and transferred to half-strength MS medium containing 1.0 mg dm^-3 IBA + 1 % mannitol and 1.5 % sucrose. Survival of rooted plants in vivo was low (35 - 40 %) when they were directly transferred to soil in glasshouse. However, transfer to soil with MS nutrients and 1.0 mg dm^-3 IBA in culture room for a minimum duration of 2 weeks increased the survival percentage of plants to 100 %.

Higher amylase activity in cotyledons of kinetin treated salt stressed (75 mM NaCl) chickpea (Cicer arietinum L. cv. PBG-1) seedlings, as compared to salt stressed seedlings was observed during a growth period of 7 d. The activities of acid and alkaline invertases were maximum in shoots and minimum in cotyledons under all conditions. The reduced shoot invertase activities under salt stress were enhanced by kinetin with a simultaneous increase in reducing sugar content. Kinetin increased the activities of sucrose synthase (SS) and sucrose phosphate synthase (SPS) in both the cotyledons and shoots of stressed seedlings. Kinetin appears to increase the turnover of sucrose in the shoots of stressed seedlings.

Pisum sativum L. cv. Phenomen plants were grown in pots in greenhouse and their growth, and ATP and chlorophyll (Chl) a and b contents were assessed after 9-d exposure to sodium arsenate [0.04 and 0.07 mmol kg^-1(soil)], or to lead acetate [2.0 and 4.0 mmol kg^-1(soil)], or zinc acetate [5.3 and 9.3 mmol kg^-1(soil)]. The luciferin-luciferase method was used for ATP analyses. Soil pollution reduced significantly the growth, but the low toxicant concentrations elevated the cotyledon and shoot ATP concentrations per fresh matter content. The ATP/Chl ratio was increased in the zinc-treated seedlings as compared with the respective controls. The ATP concentration and a number of growth parameters were negatively correlated, and thus the high ATP content might contribute to the significantly reduced growth of seedlings.

Twenty clones of the breeding population of Hevea brasiliensis were evaluated for phenetic diversity. The test-clones included six clones developed in Nigeria, ten Malaysian clones, two clones from Indonesia and a clone from each of Brazil and Sri Lanka. Data collected on fifteen seed characters in 1998 and 1999 were utilized for multivariate analysis. Cluster analysis of data matrix of clonal mean seed characters was conducted to produce principal component axes, dendrograms and Tocher's clusters in 1998, 1999 and the combined data. There was taxonomic isolation of the recent collection from Brazil (IAN 710) from the other clones that are either members or descendants of the Wickham collection of 1876. There was a continuum of phenetic diversity from the highly divergent to the closely related pairs of clones. The highly divergent clones are expected to produce heterotic progenies in crosses while crosses among clones with close phenetic similarity should be avoided. This will guide against inbreeding depression and genetic erosion.

We have analyzed the stress-associated proteins in a high-rubber-yielding guayule (Parthenium argentatum Gray cv. 11591) leaves. Protein profiles in leaf fractions, resolved by SDS-PAGE and visualized by Coomassie Brilliant Blue staining, were different under various stresses. Changes in 25, 34 and 74 kDa polypeptides were noticed in response to low night temperature treatment while 24, 40, 47 and 81 kDa proteins responded to low irradiance. 23, 50, 75 and 82 kDa proteins were altered in response to drought stress. Certain proteins may play a significant role in the acquisition of tolerance in parenchyma cells of guayule leaves and might be useful markers to study adaptation in guayule plants.

Valerophenone synthase homologue of chalcone synthase (CHS) is the first key enzyme described to be involved in the biosynthesis of bitter acids, the compounds produced in hop lupulin glands valuable for the taste of beer. The complete sequence of a novel homologue of CHS chs 4 was isolated from hop. Protein predicted from chs 4 cDNA has 43.45 kDa and length 395 amino acids. It was found by the analysis of chs 4 flanking sequences that this gene is in the cluster with other CHS homologues - chs 3 and vps. The intron identified in chs 4 has been found to be homological to vps and chs 3 introns. Expression of chs 4 was partially characterized using reverse transcription polymerase chain reaction and it was found that chs 4 is specifically expressed in the glandular tissue of hop cones likewise vps. The predicted protein sequence CHS 4 was compared with other CHS-like proteins.

Random amplified polymorphic DNA (RAPD) markers were used to analyze genetic fidelity of micropropagated teak (Tectona grandis L.) clones with respect to subcultural passage. Of the twenty primers screened, no variation in RAPD profiles was noticed in the in vitro clones of fifth, tenth, fifteenth and twentieth passage in comparison to the in vivo mother plants. Only one micropropagated plant of twenty-fifth subcultural passage, however, differed from the in vivo ones. It revealed the appearance of a new polymorphic DNA fragment (molecular mass 379 kb) in case of primer OPB-08. This primer, manifesting detectable variation, may be utilized as a diagnostic marker for assessing genetic fidelity of micropropagted teak plants.

Chromosome structure and chromatin organisation of a two-chromosome model cereal Zingeria biebersteiniana (Claus) P. Smirnov were studied: nuclear DNA content was determined by microdensitometric analysis after Feulgen staining; Feulgen absorption at different thresholds of absorbance in interphase nuclei also provided evidence on the organisation of chromatin, allowing quantitative estimation of condensed chromatin within interphasic nucleus. The DNA methylation pattern of Z. biebersteiniana metaphase chromosomes was examined with a specific monoclonal antibody. 5-methyl-cytosine residues are present in several chromosome sites and differences may be present between corresponding regions of homologues. Chromosome banding pattern reveals large bands in the centromeric regions of each chromosome, showing constitutive heterochromatin; by fluorochromes staining pericentromeric blocks are evidenced. After the cold and 9-aminoacridine pre-treatments and after aceto-carmine and aceto-orceine staining, respectively, the metaphase chromosomes were analysed by image analysis system revealing a segmentation of the chromosome body that resembles Giemsa/Reverse banding in animal chromosomes.

Chlorophyll a (Chl a) content and chlorophyllase (Chlase) activity from leaves of wild type (WT) and the ethylene-insensitive mutant (eti 5) of Arabidopsis thaliana (L.) Heynh during temperature stress and plant recovery have been studied. The plants were subjected to temperatures of 4 °C (LT) and 38 °C (HT) for 24 h. Chl a gradually decreased somewhat during stress and in the first day of recovery, especially in HT-treated plants. At the end of the experimental period (1 d stress and 10 d recovery) Chl a content was lower in eti 5 plants than in WT ones. The Chlase in WT was more affected than in eti 5 plants during the temperature treatment and the recovery period.

The effects of different concentrations (10^-7 to 10^-2 M) of cadmium chloride on root growth, cell division and nucleoli in root tip cells of Allium sativum L. were investigated. At lower concentrations of Cd²⁺ (10^-7 to 10^-6 M), Cd²⁺ did not influence the root growth, even had a stimulation effects during a short treatment. The results showed that the rate of root growth per day at the treatment groups (10^-4 to 10^-2 M Cd²⁺) decreased with increasing duration of the treatment and increasing Cd²⁺ concentration. Cd²⁺ induced c-mitosis, anaphase bridges, chromosome stickiness and on nucleoli, causing some particles of similar silver-stained material scattered in the nuclei and making the silver staining reaction at the periphery of the nucleolus weaker.

Capsaicin, a possible allelochemical, caused growth inhibition of roots and shoots of alfalfa (Medicago sativa), cress (Lepidium sativum), lettuce (Lactuca sativa), crabgrass (Digitaria sanguinalis), timothy (Phleum pratense) and ryegrass (Lolium multiflorum), and suppressed their germination. Increasing the dose of capsaicin increased the inhibition. The concentrations for 50 % inhibition of the root growth were 2.7, 0.32, 2.1, 0.27, 0.29 and 0.57 mM for alfalfa, cress, lettuce, crabgrass, timothy and ryegrass, respectively, and the concentrations for 50 % inhibition of the shoot growth were 17, 0.87, 6.7, 2.3, 1.4 and 6.2 mM for alfalfa, cress, lettuce, crabgrass, timothy and ryegrass, respectively. Germination percentage was inhibited 50 % at the concentrations 82, 88, 68, 4.8, 22 and 11 mM for alfalfa, cress, lettuce, crabgrass, timothy and ryegrass, respectively. Thus, effectiveness of capsaicin on the plant growth differed with species and targets, and suggests that capsaicin may act as an allelochemical to other plants.

Dunaliella salina V-63 was cultivated in different concentrations of NaCl (0.5, 1.0, 2.5, 3.0, or 4.0 M) and at two irradiances (170 or 220 μmol m^-2s^-1). Concentration-dependent suppression of growth was observed above 1 M NaCl, and elevated salinity induced formation of salt-containing vacuoles. However, the changes in the chloroplast ultrastructure following changes in salinity and irradiance (increase of invaginations and protuberances, numerous grana with low number of thylakoids, less number of starch grains, etc.) appeared to be of primary importance.

Isozymic profiles of different micropropagated banana (Musa spp.) cultivars (Giant Governor, Dwarf Cavendish, Robusta, Champa, Kachakel and Chatim) of West Bengal, India were assessed at different subcultural passages. Variation with respect to the banding pattern was noticed only in esterase but not in peroxidase and acid phosphatase. Of the six cultivars, four showed variation both at isozymic and yield level. Two cultivars (Kachakel and Chatim) maintained their esterase profile and genetic stability even after twenty subcultural passages.

Activities of phosphofructokinase (PFK), fructose-1,6-bisphosphate aldolase (FBP aldolase) and pyruvate kinase (PK) increased progressively in the roots of flood-tolerant SSG-59-3 cultivar during flooding. In contrast, only a slight change in activities of PFK and FBP aldolase was discerned in the roots of flood-sensitive S-308 cultivar during initial stages of flooding followed by a decline in the activities of these enzymes. Although the activity of hexokinase (HK) was transiently elevated in roots of both the cultivars during flooding, the magnitude of increase was much more in SSG-59-3 than in the S-308. In leaves of SSG-59-3, HK activity increased during 12 h of flooding whereas only a minor change occurred in the case of S-308. Flooding resulted in depressed activities of PFK and PK in leaves of S-308 but that in SSG-59-3 rose following imposition of waterlogged conditions. Activity of FBP aldolase in leaves of tolerant cultivar also showed a steady enhancement during flooding. The total and reducing sugars content decreased in leaves and roots of the S-308 during flooding but in SSG-59-3 the amount was more or less comparable to that in corresponding non-flooded plants.

Experiments were conducted under field conditions to assess the growth, physiological and biochemical responses of wheat plants (Triticum aestivum L.) to supplemental UV-B radiation (7.1 kJ m^-2) and enhanced ozone (0.07 μmol mol^-1) separately and in combination. Enhanced UV-B radiation and O₃ reduced biomass, yield, photosynthetic rate, chlorophyll, carotenoid and ascorbic acid contents and catalase activity, whereas increased total phenol content and peroxidase activity. Contents of flavonoids increased due to UV-B treatment. The interactive effects were, however, less than additive.

The activity of chlorophyllase in wild type (WT) was higher than in ethylene insensitive mutant (eti 5) of Arabidopsis thaliana (L.) Heynh plants during the vegetative period. Chlorophyll content in eti 5 leaves was higher than in WT but the difference decreased by the end of the experimental period.