The present investigation has been performed to evaluate nitrate reductase (NR) and nitrogenase activities as well as growth and mineral nutrition of wheat plants grown under drought stress and inoculated with different Azospirillum strains (NR^- and NR⁺). Fresh, dry mass and water content decreased with decreasing soil moisture content, which was accompanied with low soluble sugars and soluble protein content and increase in the total amino acids content. Azospirillum inoculation with either bacterial strain (NR^- and NR⁺) significantly increased the above characteristics even at 40 % moisture content. NR activity decreased in both the shoots and roots by decreasing soil moisture content. NR⁺ strain exhibited increased root NR activity compared with uninoculated plants or inoculated with NR^- strain. However, plants inoculated with NR^-strain increased NR activity in the shoot more than in the root of the same plant and in the shoot of control plants. Inoculation with either NR^- and NR⁺ Azospirillum strains gave higher nitrogenase activity than uninoculated control plants. The low N supply (0.5 mM) did not affect nitrogenase activity. NR^-strain was less effective than NR⁺strain in promoting total N-yield, spike numbers and their mass per pot. Azospirillum inoculation exhibited no significant changes in wheat Mg²⁺ content. However, K⁺ and Ca²⁺ have shown significantly increased values. Azospirillum beneficial effect on plant N balance and growth are most probably composed of multiple mechanisms and beneficial NR is one of them. The importance of Azospirillum NR⁺strains for increasing wheat resistance to water stress is also supported by the obtained data.

Multiple shoots were initiated from nodal and shoot tip explants collected from mature trees of Morus alba L. cultivars Chinese White, Kokuso-27 and Ichinose, and M. multicaulis Perr. cultivars Goshoerami and Rokokuyaso after 2 weeks of culture. Nodal explants were more responsive than shoot tip explants. Murashige and Skoog basal medium was found to be most suitable medium and 6-benzylaminopurine was the most effective cytokinin for shoot induction. Explants collected between April and September evoked better response than the explants collected between October and March. Shoots were multiplied by transferring nodal explants excised from in vitro raised shoots onto a medium containing cytokinins. Sucrose was the most suitable carbon source examined for shoot multiplication. An increase in shoot multiplication rate was noticed upto 4 - 5 subcultures. Nodal explants rooted on an auxin-supplemented medium. The acclimatized plants were successfully transplanted in the field.

Influence of various saline media on Chlorella fusca growth, contents of photosynthetic pigments, and activity of the nitrate reductase (NRA) was determined. KCl, CaCl₂, and MgCl₂ in concentrations relative to NaCl as 1:1, 2:1, and 3:1 promote cell number, dry mass, and contents of photosynthetic pigments. The activity of NR was enhanced by Mg²⁺ and K⁺ and in some cases by Ca²⁺ at all ratios applied.

The possibility was examined whether the pool of sequence variants of HLVd which accumulated as progeny of "thermomutants" induced upon heat-treatment of hop could initiate infection of non-host solanaceous plants. It was found that HLVd microevolution led to the appearance of HLVd population in tomato. This viroid population was maintained at levels detectable by molecular hybridisation, showing the highest concentration in apical leaves. HLVd was further transferred from tomato to Nicotiana benthamiana, where distinct HLVd sequence variants appeared and were stably maintained at low levels. Our results show that replication of HLVd under heat stress resulted in the production of viroid quasispecies, potentially important for viroid evolution in so-called non host plants.

The modified nucleotide content of the ribosomal RNAs in wheat is greatly influenced by light. The rRNAs of etiolated seedlings contain far fewer modified derivatives. The modified nucleotide composition characteristic of green plants develops gradually as a result of irradiation. In the course of the experiments changes in the state of modification of 5.8S and 18S rRNAs were examined during the greening of etiolated wheat seedlings. Three types of minor nucleotides, O^2'-methyladenosine, O^2'-methylguanosine and pseudouridine were found in the 5.8S rRNA of green wheat leaves, none of which was detected in etiolated wheat. The minor nucleotides appeared in the 5.8S rRNA only after 48 h irradiation. The sequences of 5.8S rDNA, TTS1, ITS2 and 18S rDNA were also determined and the presence of the hyper-modified nucleotide 1-methyl-3-(α-amino-α-carboxypropyl)-pseudouridine was detected in green wheat 18S rRNA. This minor component was not demonstrable in etiolated wheat 18S rRNA, but appeared after irradiation for 48 h.

Black plum (Syzygium cuminii) explants were grown in vitro on Murashige and Skoog medium. Among the various saccharides tested, the best caulogenic response was afforded by sucrose both in terms of explant response and shoot developing potential. Within monosaccharides, mannose was totally inhibitory as on the medium supplemented with this the shoot buds failed to develop, while, fructose and xylose completely inhibited the opening as well as the elongation of shoot buds. Glucose and galactose did not completely inhibit the caulogenic response. Among disaccharides, other than sucrose, maltose totally inhibited the elongation of the developed shoot buds while lactose supported it to a limited extent. Sugar alcohols, though not as good as sucrose, proved better sources of carbon and energy than the other tested sugars. Sucrose at concentration 4 % proved to be the best in developing 4.2 shoots per explant.

Potted tomato plants (Lycopersicon esculentum Mill. cv. Amalia) were submitted to three different treatments: control (C) plants were maintained at day/night temperature of 25/18 °C; preconditioned plants (PS) were submitted to two consecutive periods of 4 d each, of 30/23 and 35/28 °C before being exposed to a heat stress (40/33 °C lasting 4 d) and non-preconditioned (S) plants were maintained in the same conditions as the C plants and exposed to the heat stress. The inhibition of plant growth was observed only in PS plants. Heat stress decreased chlorophyll content, net photosynthetic rate and stomatal conductance in both PS and S plants. However, PS plants showed good osmotic adjustment, which enabled them to maintain leaf pressure potential higher than in S plants. Furthermore, at the end of the recovery period PS plants had higher pressure potential and stomatal conductance than in S plants.

In a fructose-containing medium in which rye root-microsomal membrane vesicles had reached the equilibrium of uptake of fructose, the presence of both Mg²⁺ and ATP caused the efflux of fructose from the vesicles. Among nucleotides examined, ATP caused the largest efflux of fructose. The efflux of fructose dependent on Mg²⁺ and ATP was quite insensitive to a protonophore, carbonylcyanide m-chlorophenylhydrazone (CCCP), which actually abolished MgATP-dependent proton accumulation in the vesicles, while it was largely inhibited by vanadate, which inhibits ATP-binding cassette transporters (ABCTs). The Michaelis-Menten constant (Km) of the efflux of fructose was 0.4 mM. It was observed that fructose stimulated the ATPase activity of the vesicles and that vanadate markedly decreased the fructose-stimulated ATPase activity.

To examine the ion accumulation and membrane lipid metabolism in response to salinity we compared two tomato cvs. Pera and Hellfrucht Fruhstamm (HF), considered to be salt-tolerant and sensitive respectively. Na⁺ and K⁺ accumulation was significantly higher in roots of cv. Pera after 24 h and 72 h of 100 mM NaCl. While in cv. HF, a temporary increase in K⁺ accumulation at 24 h was accompanied by a sustained increase in Na⁺ content. Both cultivars enhanced incorporation of [³²P]orthophosphate into phosphatidylinositol 4,5-bisphosphate at 24 h and 72 h of NaCl. In parallel to the increase of phosphatidylinositol 4,5-bisphosphate a decrease in phosphorylation of phosphatidic acid and phosphatidylcholine were observed in the sensitive cv. HF. Structural and signal lipid changes in response to salinity were more evident in the sensitive cv. HF. Salt tolerant cv. Pera accumulated Na⁺ ions in the roots without considerable modifications in lipid metabolism.

Five cultivars of Plantago ovata Forsk. (medicinal plant) have been developed by different agricultural universities in India. Genetic variability of these cultivars was estimated using RAPD markers. The data were correlated to morphological characters and a dendrogram was obtained from Jaccard's coefficient.

An effort has been made to assess the role of reactive oxygen species in germination and subsequent growth of Amaranthus lividus under elevated temperature. Transfer of A. lividus seeds from 25 to 45 °C for 4, 8 and 12 h, during early imbibitional period reduced percentage of germination, relative germination performance, relative growth index and seedling length. Heat shock during early germination decreased also the activities of free radical scavenging enzymes like catalase, peroxidase and superoxide dismutase, increased the accumulation of superoxide, hydrogen peroxide and induced lipoxygenase mediated membrane lipid peroxidation. Membrane injury index and relative leakage ratio revealed a rise with concomitant reduction in membrane protein thiol content in heat shock raised seedlings. The results indicate that heat shock in A. lividus seeds induced an excessive generation of ROS and led to an oxidative membrane damage, causing early growth impairment.

Here we studied whether early development of Silene latifolia is accompanied with changes in acetylation of nucleosomal histones H4. Using acid-urea-triton polyacrylamide gel and immunoblotting with specific antisera the histone acetylation in relationship with transcriptional activity, measured by [¹⁴C]-uridine incorporation, was analysed in dry and germinating seeds, seedlings, and adult leaves. We show that quiescent and germinating seeds, until the root tip is released from testa, are characterised by an absence of transcriptional activity and by a low H4 acetylation level: only mono-acetylated isoforms were present. During the postgermination period and early plantlet development, a high increase of transcriptional activity started and a sharp H4 hyperacetylation, up to the penta-acetylated isoform, was detected. We conclude that epigenetic modification by nucleosomal histone deacetylation plays a role in maintenance of global genome silencing in quiescent seeds.

An antiviral factor (AVF) was separated by removing virus particles from extracts of tobacco mosaic virus (TMV) infected leaves using calcium phosphate gel and by column chromatography on DEAE cellulose. AVF was not found in the extracts from healthy plants. The AVF restricted the virus infectivity "in vivo" and significantly decreased the activity of key enzymes of metabolic pathways tending to the purine and pyrimidine nucleotides biosynthesis of viral- RNA (glucose-6-phosphate dehydrogenase, ribonucleases, phosphomonoesterase and phosphodiesterase). No inhibition of these enzymes was observed "in vitro" when the effect of different concentrations of AVF (0.25 - 250 µg cm^-3) was examined.

F-actin distribution was studied in mitotic cells of embryogenic suspension culture of Norway spruce [Picea abies (L.) Karst.]. Actin was present in dividing cells of embryo head during whole mitosis. Transient co-localization of actin microfilaments with preprophase band of microtubules was observed. Weak actin staining occurred with non-kinetochor microtubular fibers in metaphase spindle. F-actin was not localized with kinetochore microtubular fibres in metaphase as well as with shortening kinetochore fibres in late anaphase. On the other hand, abundant actin microfilaments array was formed in the area of late anaphase spindle in equatorial level of the cell between separating chromatids. F-actin was also present in phragmoplast area in telophase.

Contrasting rice genotypes differing in leaf mass ratio (LMR) and leaf nitrogen content were screened. A strong inverse relationship was observed between ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) content and its efficiency estimated as the ratio of net photosynthetic rate (P_N) to Rubisco content. Similarly, an inverse relationship between the specific activity of fully activated Rubisco and its content was observed. This suggests that a down regulation of Rubisco may occur if the efficiency of the enzyme is superior. Genotypes IET 12989 and IET 13567 recorded higher P_N together with lower Rubisco content in comparison with other genotypes measured. These genotypes showed low LMR and low nitrogen content and hence could be considered as efficient nitrogen users.

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.