In vitro bulblet formation was studied using solid, liquid and bioreactor culture (immersion and periodic immersion in liquid media using ebb and flood) in order to develop a cost effective method for the mass propagation of Lilium oriental hybrid 'Casablanca'. Although the percent of bulblet formation was higher in solid culture, the increased growth rate and production of large number of bulblets in bioreactor makes it suitable for mass propagation. Four times per day and 15 min of medium supply was optimal for bulblet formation in ebb and flood bioreactor. Bulblet formation was also found to be effective in 16-h photoperiod. It was also observed that bulblet formation in the medium with 1.0 mg dm^-3 BA and 0.3 mg dm^-3 NAA was higher than in the medium without growth regulators, but formation of abnormal bulblets was higher in medium with BA and NAA.

The pattern of NADH- and NAD(P)H-specific nitrate reductase (NRs) activities in Indian mustard (Brassica juncea L. Czern. and Coss.) was monitored throughout growth stages. NAD(P)H:NR (EC 1.6.6.2) activity was maximum at early stages of growth (30 days after sowing, DAS), then declined gradually reaching to almost zero at 90 DAS. Contrary to this, NADH:NR (EC 1.6.6.1) activity was low at 30 DAS, then gradually increased till 90 DAS and thereafter, it became constant. The decrease in NAD(P)H:NR activity and increase in the NADH:NR activity were associated with the seasonal decrease in nitrate content in the soil.

Phenylmethylsulphonyl fluoride (PMSF), a well known inhibitor of both thiol- and serine-type proteases, in aqueous solutions either alone or with the plant growth regulators, methyl ester of jasmonic acid (MeJA) and N⁶-benzyl-aminopurine (BAP), significantly inhibited the growth of excised Cucurbita pepo L. (zucchini) cotyledons. SDS-PAGE analysis of the protein profiles showed that PMSF suppressed the gradual decline of the main 20 - 25 kDa polypeptide group and the low molecular mass polypeptides (below 15 kDa) while leupeptine was not able to affect the electrophoretic pattern of cotyledon proteins. On the other hand, in the presence of PMSF, the content of the polypeptides with higher molecular mass including the 97.4 kDa polypeptide and the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (55 kDa) decreased. Besides, when applied together with MeJA, PMSF prevented the appearance of the jasmonate-induced polypeptides (JIPs; 69, 60 and 43 kDa) thus suggesting that JIPs are synthesized from aminoacids released during the breakdown of cotyledon storage proteins.

Seed storage proteins of Ebenus cretica were fractionated to albumins, globulins, prolamins and glutelins according to their solubility in water, 0.5 M NaCl solution, 55 % propanol-2 and 0.125 M sodium borate (pH 9.0) containing 0.5 % SDS (sodium dodecyl sulfate) solution, respectively. Glutelins consist of the major (about 81 %) fraction of the total extracted proteins. Analysis by SDS-PAGE revealed that the total extracted protein patterns from different racemes of the same plant were similar, while those from seeds of different plants were different. In addition, distinct differences were observed within protein patterns of alkaline extractable glutelin fractions and salt soluble globulin fractions. In E. cretica four ecotypes (A - D) were distinguished by SDS-PAGE of total extracted seed proteins. The last method was more simple and rapid than others and was suggested for screening analysis.

Effect of free radical scavengers and metal chelators on polyethylene glycol (PEG, osmotic potential -1.5 MPa) induced oxidative damage in detached rice leaves was investigated. PEG treatment resulted in a decrease in relative water content and an increase in proline content, and lipid peroxidation. PEG treatment also decreased chlorophyll and protein contents. Free radical scavengers (ascorbate, sodium benzoate, reduced glutathione, and thiourea) retarded and metal chelators [2,2'-bipyridine (BP), 8-hydroxyquinoline, and 1,10-phenanthroline] prevented PEG-induced oxidative damage. Furthermore, the protective effect of BP was reversed by adding Fe²⁺ and Cu²⁺, but not by Mn²⁺ or Zn²⁺. The protective effect of BP is most likely mediated through chelation of iron. It seems that oxidative damage induced by PEG may require the participation of iron.

The relationship between nutrient composition, crop biomass, and glutamate dehydrogenase (GDH) isoenzyme pattern was investigated in soybean (Glycine max) and maize (Zea mays) by monitoring the nutrient induced isomerization of the enzyme from the seedling stage to the mature crop. GDH was extracted from the leaves of the plants, and the isoenzymes were fractionated by isoelectric focusing followed by native polyacrylamide gel electrophoresis. The isomerization V_max values for soybean GDH, similar to maize GDH increased curvilinearly from 200 - 400 μmol mg^-1 min^-1 as the inorganic phosphate nutrient applied to the soil decreased from 50 - 0 mM. In soybean, combinations of N and K, P, or S nutrients induced the acidic and neutral isoenzymes, and gave biomass increases 25 - 50 % higher than the control plant. GDH isoenzymes were suppressed in soybean that received nutrients without N, K, or P and accordingly the biomass was about 30 % lower than the control. Treatment of maize with NPK nutrients increased the GDH V_max values from 138.9 at the vegetative to 256.4 μmol mg^-1 min^-1 at the reproductive phase, and suppressed the basic isoenzymes, but induced both the acidic and neutral isoenzymes thereby inducing seed production (27.0 ± 1.4 g per plant); whereas both the acidic and basic isoenzymes were suppressed in the control maize, and seeds did not develop. Simultaneous induction of the acidic, neutral, and basic isoenzymes of GDH indicated the occurrence of senescence. Therefore in maize and soybean, the induction of the acidic and basic isoenzymes of GDH led to the enhancement of biomass.

The effect of organic (Fe-EDTA and Fe-EDDHA) and inorganic (FeCl₃) iron substances on rooting of the rootstock GF-677 (Prunus amygdalus × Prunus persica) in vitro was studied. Full rooting (100 %) was observed in explants nourished with Fe-EDDHA, while less rooting was found in the absence of iron or in the presence of FeCl₃. On the contrary, no root formation was observed in explants nourished with Fe-EDTA, which showed extremely lower chlorophyll and high iron contents at the end of the experiment.

The plant growth retardant, paclobutrazol at 8.5 or 17.0 μM concentrations effectively inhibited the stem elongation and primary leaf expansion of bean seedlings. Although the retardant reduced the relative water content in well-watered plants, the water and pressure potentials remained high in the primary leaves. K⁺, Na⁺, Mg²⁺ and Ca²⁺ contents in the primary leaves of the paclobutrazol-treated plants were not significantly different from those in the control. The stomatal density increased on both surfaces but the length of guard cells was not reduced significantly on the adaxial epidermes of the paclobutrazol-treated primary leaves. The inhibitory effect of paclobutrazol on the abaxial stomatal conductances became more pronounced with time during the light period but the adaxial surfaces displayed similar or slightly higher conductances than those of the control. The transpiration rate on a unit area basis did not change significantly or increased in the treated leaves thus the reduced water loss of paclobutrazol-treated plants was due to the reduced leaf area. Stomatal conductances of the adaxial surfaces responded more intensively to exogenous abscisic acid and the total leaf conductance decreased faster with increasing ABA concentration in the control than in the paclobutrazol-treated leaves. Paclobutrazol, an effective inhibitor of phytosterol biosynthesis, not only amplified the stomatal differentiation but increased the differences between the adaxial and abaxial stomatal conductances of the primary leaves.

The effect of maize root exudates on the toxicity of lead and manganese to arbuscular mycorrhizal fungus (AMF) Glomus intraradices was studied in vitro by observation of intraradical hyphae regrowth from colonised root segments. Higher heavy metal (HM) concentrations strongly reduced the hyphal growth, however, the inhibitory effect was to a large extent eliminated by the addition of maize root exudates to the media. However, the capacity of exudates to ameliorate HM toxicity was limited and did not operate when a threshold HM concentration was reached.

The ascorbate system, one of the major antioxidant systems, has been studied in two bryophytes; a moss, Brachythecium velutinum (Hedw.) B., S. & G., and a liverwort, Marchantia polymorpha L. The moss and liverwort gametophytes contain ascorbate both in the reduced and oxidized form; utilize ascorbate in removing hydrogen peroxide by means of ascorbate peroxidase and reconvert to ascorbate its oxidation products by means of dehydroascorbate reductase and monodehydroascorbate reductase. Ascorbate oxidase activity was measured in the cytosolic fraction suggesting a localization of the enzyme different from more evolved organisms. The ascorbate content was maintained in the moss after drought stress while it declines in the liverwort, which seems more sensitive to water stress. Since ascorbate recycling is more efficient in the moss than in the liverwort, this seems to suggest a correlation between efficiency of ascorbate recycling and water stress tolerance.

The histological events during adventitious bud and somatic embryo development in explants from Picea omorika seedlings cultivated in vitro have been examined. Meristematic activity in the superficial layers of cotyledons led to bud primordia formation. Bud primordia had characteristic zonal organization with needle primordia arising on the flanks of the meristem. Somatic embryo initial was formed on the cotyledon surface after an unequal transversal division of a cell. The smaller, apical cell gave rise to apical dome and later on secondary, filamentous suspensor while the larger vacuolated cell presented primary suspensor.

The effects of ethephon, an ethylene generating compound, and 2,5-norbornadiene (NBD), an inhibitor of ethylene action, on peroxidase (POD; EC 1.11.1.7), catalase (CAT; EC 1.11.1.6), polyphenol oxidase (PPO; EC 1.14.18.1) activities and proline content in salt-stressed spinach leaves were investigated. POD and PPO activities were increased by NaCl + ethephon + NBD combination and reduced by NBD. Also, ethephon increased the CAT activity while ethephon + NBD reduced CAT activity. NaCl + ethephon increased proline content. The antagonistic effect of ethephon and NBD was seen on POD and PPO activity and proline accumulation, but was not on CAT activity.

To test whether different nitrogen form (nitrate or ammonium) in substrate can alter the response to elevated partial pressure of CO₂ (pCO₂) plants of perennial ryegrass (Lolium perenne cv. Bastion) were grown from seeds in growth chambers under pCO₂ of either 35 Pa (ambient, CA) or 70 Pa (elevated, CE) in a hydroponic system (with nutrient and pH control) for 24 d. Nitrogen was supplied as ammonium, nitrate or an equimolar mixture of both N forms. Under CE plants grew faster than their counterparts under CA during the first 14 d but after 23 d of cultivation stimulation disappeared. Despite the strong positive effect of mixed forms of N on plant growth, the beneficial effect of CE was similar to that in the other two N treatments. However, the almost alike final growth response to CE had different underlying mechanisms in different N treatments. Plants supplied with nitrate as a sole source of nitrogen had lower leaf mass ratio but much higher specific leaf area compared to plants supplied with ammonium. The decrease in the content of leaf organic N (per unit of structural dry mass) under CE was found only in leaves of plants supplied with ammonium on day 14. Nevertheless, the available form of N evidently contributes to changes of leaf N content under CE. The high levels of N and non-structural saccharides in plants supplied with ammonium at CE suggest that the CO₂ response of these plants was controlled by factors other than amount of available carbon and nitrogen.

Eryngium foetidum L. plants were regenerated from mature leaf and petiole explants through direct organogenesis without intervening callus phase. From leaf explants, adventitious multiple shoots raised on Murashige and Skoog (MS) medium supplemented with 4.43 μM benzylaminopurine (BAP) and 0.57 μM indole-3-acetic acid (IAA), whereas in petiole explants shoot regeneration occurred at 8.86 μM BAP and 0.57 μM IAAA. 80% of the leaf explants and 44% of petiole explants produced shoots after four weeks of culture. The regenerated plants were rooted on MS medium supplemented with 2.46 μM indole-3-butyric acid and 2.88 μM gibberellic acid. The plants were successfully established in the soil and showed 70.9% survival in the field.

The effects of 2-aminopurine, olomoucine, 6-dimethylaminopurine (inhibitors of cyclin-dependent kinases; CDK), and sodium vanadate (a potent inhibitor of protein phosphatases) on DNA endoreduplication were investigated during elongation and differentiation of the primary roots in Pisum sativum. When compared with the untreated control plants, at least one additional round of DNA replication was evidenced to occur within most cells, the majority of which have attained 4C DNA level, and a considerably greater portion of cells represented the endopolyploid state with nuclear DNA content approximating the 8C value. It is concluded that cellular commitment to DNA endoreduplication may appear not only as a consequence of suppression imposed directly upon CDK activity, but also as an indirect output connected with the decreased activity of cdc25 protein phosphatase, an enzyme necessary to turn the switch on for appropriate conformation of the CDK/cyclin B complex. By calculating the absorption profiles of Feulgen-stained nuclei, specific phosphorylation-dependent changes in chromatin condensation of endopolyploid cells have been revealed. It is proposed that acquisition of a certain critical level of chromatin condensation constitutes a prerequisite for additional rounds of DNA synthesis in plants.

Regeneration of Plumbago rosea L., a rare medicinal plant, via somatic embryogenesis in callus cultures derived from leaf explants was described. Optimum callus formation was achieved on semi-solid Murashige and Skoog (MS) medium supplemented with 0.25 mg dm^-3 kinetin and 2.0 mg dm^-3 1-naphthaleneacetic acid (NAA). Somatic embryogenesis was achieved upon transferring the 4-week-old callus to a medium containing 1.0 mg dm^-3 kinetic (Kn), 0.5 mg dm^-3 gibberellic acid (GA₃) and 0.1 mg dm^-3 NAA. Embryo maturation and germination was achieved on the half-strength MS basal salts supplemented with 0.01 - 0.25 mg dm^-3 Kn and 2 % (m/v) saccharose. An average of 50 - 60 plantlets were obtained from 150 mg of embryogenic callus within 4 week of subculture. Out of the 50 plantlets about 28 survived in the greenhouse.

Eleven monosomics in cotton that were obtained in the progenies of three disomic desynaptic plants were cytologically characterized. The transmission of the monosomes in progeny was shown in the 26 monosomic plants. In 23 plants the frequency of monosomics was ranged between 14.29 and 41.67 %. Three monosomics usually occurred in much lower frequencies (from 3.03 to 5.00 %). Various transmission rates indirectly pointed out different monosomes as a specific chromosomes of cotton genome. Three telochromosomes and one isochromosome were isolated from the progenies of the four monosomics. Using translocation test it was recovered that seven monosomes of different monosomics are homologous to one of the chromosomes of six translocation lines of our collection.

Nodal explants excised from 18 to 20-year-old female plants of Simmondsia chinensis if cultured on Murashige and Skoog's medium supplemented with 20 μM N⁶-benzyladenine (BA) differentiated an average of 2.7 ± 0.4 shoots in 11.5% explants. The percentage of nodal explants inducing multiple shoots enhanced significantly if in vitro raised shoots were used as source of explants. Nearly 100% cultures differentiated an average of 4.7 ± 2.0 shoots per explant on the same medium. Nearly 85% of the shoots induced roots when a pulse treatment of 50 μM indole-3-butyric acid (IBA) was given prior to their transfer to semi-solid MS medium containing 10 μM IBA + 0.5% activated charcoal + 1 μM BA. Plantlets were gradually hardened in Soilrite and acclimatized to soil.

RAPD analysis in selected cultivars of Kapoori and Bangla betel vines (Piper betle L.) were carried out in order to ascertain the relatedness of the two to each other. On the basis of the data from 10 RAPD primers, it was found that the Kapoori cultivars were more heterogeneous (mean SI = 0.521) while the Bangla cultivars were mostly similar to each other (mean SI = 0.884). Within each type, the overall polymorphism of RAPD bands was more than 70 %. When RAPD band data for both types of cultivars were considered cumulatively, the two were clearly separated from each other. In fact only six bands out of a total of 60 bands were found to be common to cultivars of both types. Bands specific to only one of the two types have potential for developing betel vine cultivar-specific probes and SCAR-markers.

Wheat (Triticum aestivum L.) plants were subjected to mild water stress during grain filling at milk (early, medium, and late) and dough (early, soft, hard) stages. The grains harvested from stressed plants were subjected to low temperature stress of 10 °C for 24 h in presence or absence of 1 mM CaCl₂, and embryos were examined for oxidative injury. The embryos of grains water stressed at milk and soft dough stages showed lowest contents of H₂O₂ and malondialdehyde and highest membrane stability index, ascorbic acid content, and activities of catalase, ascorbate peroxidase, and superoxide dismutase as compared to control embryos or water-stressed at other stages. Presence of Ca²⁺ in the medium reduced H₂O₂ and malondialdehyde content and increased ascorbic acid content, and catalase, ascorbate peroxidase and superoxide dismutase activities.

The morphological and anatomical aspects of direct and indirect somatic embryogenesis in pea were described. Direct embryos were induced from shoot apical meristems of 3 to 5-d-old pea seedlings, embryogenic callus originated from immature pea zygotic embryos or shoot apices. Auxin (picloram, 2,4-dichlorophenoxyacetic acid) was necessary to induce somatic embryos. The developmental stages typical for pea zygotic embryos were detected. Globular and heartshaped somatic embryos were morphologically similar to their zygotic counterparts; in contrast, torpedo and cotyledonary somatic embryos displayed great morphological variation, which affected mainly cotyledons (size, shape, number). Based on anatomical sections, possible ways of somatic embryo formation and localization of initiation sites within primary explant tissue have been proposed. The multicellular origin of somatic embryos is supposed in both systems of pea somatic embryogenesis under investigation.

The effect of mercury and cadmium, in the form of HgCl₂ and CdCl₂ respectively, on proline accumulation and two key proline biosynthesizing enzymes, Δ¹-pyrroline-5-carboxylate synthetase (P5CS) and Δ¹-pyrroline-5-carboxylate reductase (P5CR), was investigated in Phaseolus aureus Roxb. and Triticum aestivum L. The 5-d-old seedlings were exposed to 0.05, 0.1, 0.2 or 0.4 mM concentrations of the metals in Hoagland solution for 12 and 36 h. T. aestivum exhibited considerably greater accumulation of proline than P. aureus in response to the metal treatment. Among the two metals, Hg induced greater accumulation of proline than Cd. The activity of P5CS increased significantly in response to the metal treatment, particularly in T. aestivum in which the activity of the enzyme in the control was much higher than that was in P. aureus. The activity of P5CR on the other hand mostly decreased in response to the metal treatment. The study indicated a strong dependence of the metal induced proline accumulation on the constitutive P5CS content of the plants.

Effect of the benzothiodiazole (BTH) pre-treatment was monitored during the acute infection stage in the susceptible and the hypersensitive tobacco plants infected with the tobacco mosaic virus (TMV). Dynamic changes in the contents of chlorophyll, the total proteins, and the pathogenesis related proteins (PR-proteins), and activities of ribonucleases (RNase), phosphomonoesterase (PME), phosphodiesterase (PDE), and glucose-6-phosphate dehydrogenase (G6P DH) were studied. Neither the protein nor the chlorophyll contents were significantly changed by the TMV infection and/or the BTH treatment. The BTH pre-treatment caused a substantial reduction in the multiplication of TMV in the locally-infected leaves of the hypersensitive cultivar Xanthi-nc (to 15.1%). A lesser decrease (to 50.3%) was observed in the locally-infected leaves of susceptible cultivar Samsun. But in the systemically-infected leaves of this cultivar, only a 4-d delay in the multiplication of TMV was found. In the locally-infected leaves of both cultivars, the activities of the RNase, PME, PDE and G6P DH were sharply increased during the acute phase of TMV multiplication (when compared with the healthy plants) and the curves of these activities correlated with the multiplication curves of TMV. The BTH alone also strongly enhanced the activities of these enzymes early after application. Only low additional increases in some enzymes and even slight declines in the others were observed when the inoculation of leaves of cultivar Xanthi-nc followed the pre-treatment with the BTH. No inhibition of the enzymes was observed when the direct effect of different concentration of the BTH (1 - 1000 μM) was examined in vitro during a measurement of the activity. The analysis of intercellular proteins by PAGE under native conditions shows the similar spectrum of the proteins extracted from either the BTH-treated or the TMV-infected tobacco cv. Xanthi-nc.

Multiple shoots of Spilanthes acmella Murr. were induced from hypocotyl segments obtained from 1-week-old seedlings on Murashige and Skoog's (MS) medium containing benzyladenine (BA), isopentenyl adenine, and naphthaleneacetic acid (NAA). High frequency shoot proliferation (95 %) and maximum number of shoots per explant (10 ± 0.6) were recorded with 0.5 mg dm^-3 BA in combination with 0.1 mg dm^-3 NAA. A proliferation was achieved by repeatedly subculturing the nodal segments on shoot multiplication medium. About 95 % of the in vitro shoots developed roots after transfer to half strength MS medium containing indole-3-butyric acid (1.0 mg dm^-3). 95 % of the plantlets were successfully acclimatized and established in soil. Transplanted plantlets showed normal flowering without any morphological variation.