Carob tree (Cerafoma siliqua L.) micropropagated shoots were rooted on half-strength Murashige and Skoog medium, supplemented with different types and concentrations of sugars, in order to determine the effects of sugar composition and concentration on in vitro rooting and in vivo establishment of the plantlets. Among the various sugars tested, the best rooting response was obtained with 145 mM sucrose, both in terms of rooting frequency and index of rooting. The use of filter-sterilized rather that autoclaved fructose increased root number and root length. Sugar treatment during rooting slightly influenced plantlet survival and growth during acclimatization. A reduction in the glucose concentration during rooting was beneficial for plantlet acclimatization.

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 thickening that appeared on maize roots under the influence of 6-benzylaminopurine and α-naphthylacetic acid (concentration 10^-5, 10^-6, 10^-7 and 10^-8 M) were analysed. The changes in length and width of maize roots at the edge of elongation zone after 24,48 and 72 h of treatment were studied. The growth in length of cells at the edge of elongation zone stopped abruptly but the growth in width slowly continued. So, the growth of cells in length and width under the influence of growth regulators was not simultaneous. They had distinct time limits.

The seeds of two barley (Hordeum vulgare L.) cultivars (a drought resistant cv. Tokak-137/57 and a drought sensitive cv. Erginel-90) were imbibed either in distilled water (control) or in a solution containing 40 mg dm^-3 paclobutrazol (PBZ) and air dried. Seeds were germinated and grown in a glasshouse for 21 d and seedlings were subjected to salt stress by treating them with 100 and 200 mM NaCl for 12 d. The height of shoots was significantly decreased and root length was increased in PBZ-treated plants prior and after NaCl stress for 12 d leading to an increase in root to shoot ratio. Leaf chlorophyll and carotenoid contents in PBZ treated plants were increased in controls and especially in plants subjected to salt stress. PBZ induced increase in superoxide dismutase (SOD) activities was higher in cv. Tokak-157/37, than in cv. Erginel-90. However, an increase in SOD activity was not accompanied by an increase in peroxidase activity.

We have assayed different combinations of nutrient media and growth regulators to induce callus and plant regeneration from explants of root, shoot and leaf, complete seed, and isolated mature embryo of barley (Hordeum vulgare L. cv. Hassan). The best results were obtained with mature embryo in J25-8 medium supplemented with 2.0 mg dm^-3 2,4-dichlorophenoxyacetic acid where about 75 % developed friable calli. Some 80 - 85 % of these calli regenerated barley plants in the same J25-8 medium supplemented with 1.0 mg dm^-3 indole-3-butyric acid and 0.1 mg dm^-3 kinetin.

Role of superoxide dismutase isozymes and other antioxidant enzymes was studied in relation to leaf age in sunflower (Helianthus annuus L. cv. ACC 1508) at pre-flowering and grain filling stages. Relative water content (RWC) did not change much in leaves of different age and at the two stages. Protein content declined continuously from the youngest to the oldest leaf, while chlorophyll (Chl) and carotenoids (Car) contents increased down to 7^th/9^th leaf and declined in subsequent older leaves. Protein, Chl and Car contents were higher at pre-flowering than at seed filling stage. Superoxide dismutase (SOD), its isozymes, and ascorbate peroxidase (APO) and catalase (CAT) activities were highest in the 9^th leaf and declined in subsequent older leaves. SOD and APO activities were higher at seed filling, except in oldest senescent (13^th, 15^th) leaves. Among SOD isozymes, Cu/Zn-SOD and Mn-SOD activities accounted for most of the total SOD, and only marginal activity was observed for Fe-SOD. Peroxidase activity increased from youngest to the oldest leaf at pre-flowering stage and down to 13^th leaf at seed filling stage.

Seasonal changes in foliage nitrogen (N) and carbon (C) concentrations and δ¹⁵N and δ¹³C ratios were monitored during a year in Erica arborea, Myrtus communis and Juniperus communis co-occurring at a natural CO₂ spring (elevated [CO₂], about 700 μmol mol^-1) and at a nearby control site (ambient [CO₂], 360 μmol mol^-1) in a Mediterranean environment. Leaf N concentration was lower in elevated [CO₂] than in ambient [CO₂] for M. communis, higher for J. communis, and dependent on the season for E. arborea. Leaf C concentration was negatively affected by atmospheric CO₂ enrichment, regardless of the species. C/N ratio varied concomitantly to N. Leaves in elevated [CO₂] showed lower δ¹³C, and therefore likely lower water use efficiencies than leaves at the control site, regardless of the species, suggesting substantial photosynthetic acclimation under long-term CO₂-enriched atmosphere. Leaves of E. arborea showed lower values of δ¹⁵N under elevated [CO₂], but this was not the case of M. communis and J. communis foliage. The use of the resources and leaf chemical composition are affected by elevated [CO₂], but such an effect varies during the year, and is species-dependent. The seasonal dependency and species specificity suggest that plants are able to exploit different available water and N resources within Mediterranean sites.

Substitution of wheat (Triticum aestivum L.) chromosomes 7A, 1D, 3A, 3B, 3D, 4A and 4D of cultivar Cappelle Desprez by their homologues of cultivar Bezostaya-1 increased the seedling tolerance to high concentrations of copper (1 μM CuSO_4⋅ 5 H₂O). Substitution of chromosome 1A had negative effects on seedling tolerance.

Plant regeneration through indirect somatic embryogenesis was attempted from leaf, internode, node and shoot-tip derived callus of Leptadenia reticulata. Somatic embryos at the highest frequency was induced on Murashige and Skoog (MS) medium supplemented with 8.87 μM benzyladenine (BA) and 2.46 μM indole-3-butyric acid (IBA). From different explants, only shoot-tip and node explant derived calli induced somatic embryos. Transfer of the embryogenic callus to suspension cultures of the same concentration of growth regulators facilitated the development of embryos. Suspension cultures with reduced concentration of BA (2.22 μM) either alone or in combination with 0.49 μM IBA fostered maturation of embryos. Half-strength MS solid medium with 1.44 μM GA₃ and BA (0.22 or 0.44 μM) facilitated conversion of embryos into plantlets at higher rate compared to that on with BA alone. About 77 plantlets were recovered from 10 mg callus. Plantlets transferred to small cups and subsequently to field survived in 80 %. All the plantlets established in the field exhibited morphological characters similar to that of the mother plant.

Shoot formation from seedling explants of Pinus heldreichii was induced by pulse treatment with benzyladenine at different concentration, followed by culture on medium lacking plant growth regulators. After treatment with 222 μM benzyladenine (BA) an average of 4.6 shoots per explant was obtained. Shoots, detached from explants, rooted with a frequency of about 10 %, and rooted plantlets were successfully transferred to ex vitro conditions.

The contents of three major steviol glycosides (SGs) (stevioside and rebaudiosides A and C) in vegetative and generative organs during ontogeny of Stevia rebaudiana Bertoni were analysed with HPLC. Plant organs contained different amounts of the SGs, which declined in the following order: leaves, flowers, stems, seeds, roots. The highest content of the SGs was found in upper young actively growing shoot sections, whereas lower senescent shoot sections exhibited the lowest amount of such compounds. During ontogeny a gradual increase in the SG content was observed in both mature stevia leaves and stems, and this process lasted up to the budding phase and the onset of flowering.

Fatty acid content and composition of chloroplast membranes, ethylene production associated with thylakoid lipids degradation as well as photosynthetic electron transport involving photosystems 1 and 2 were used to determine the effects of increasing Cd concentrations in the growth medium [0, 14, 28, and 42 mg (Cd) kg^-1(sand)] on the photosynthetic performance of barley plants (H. vulgare L., cv. CE9704). High concentrations of Cd triggered serious disturbances of the chloroplast membranes. Ethylene production increased whereas a drop of 18:3 fatty acid content occurred, indicating that Cd mediates lipid peroxidation in the thylakoids. The enhanced ethylene production could be used as an early indicator of Cd-induced membrane degradation, yet at very high concentration (42 mg kg^-1) Cd decreased ethylene production.

Understanding the molecular basis of polarity induction in plant cells is a research aspect that extends from signal perception and transduction to morphogenesis. A gradient of cytoplasmic ion fluxes generated through ion channels plays a crucial role in subsequent events leading to polar growth. Convincing evidence is now available implicating temporal and spatial distribution of Ca²⁺ in cytoplasm, generated by localized activity of calcium channels, as the early biochemical events associated with polarity induction. Ion channel antagonists are common tools for studying ion channel structure and function. Coupled with a fluorescent dyes, calcium channel antagonists (phenylalkylamine and dihydropyridine), have been used to localize L-type calcium channels. Additionally, the advent of Confocal Laser Scanning Microscopy has made possible the visualization of Ca²⁺ channels in plant cells. Persisting problems of dye loading and their cellular compartmentation have been addressed by developing a variety of experimental protocols. Present article highlights the current state of our understanding of these concepts, methodologies and their applications in different aspects of plant development.

A reliable method of plant regeneration has been achieved from decapitated mature embryo axes (DCMEA) explants. Shoots appear directly from explants of genotype T-15-15 when cultured on Maheswaran and Williams (EC₆) basal medium supplemented with N⁶-benzylaminopurine (BAP) and indole-3-acetic acid (IAA) at various combinations. The shoots elongated on half strength Murashige and Skoog (MS) medium fortified with 3 μM gibberellic acid. Elongated shoots were rooted with 80 - 85 % efficiency on half strength MS medium with 0.5 μM indole-3-butyric acid. Survival of plants in the pots was 75 - 80 %. This protocol was used in Agrobacterium mediated transformation. The DCMEA explants were treated independently with two A. tumefaciens (LBA 4404) strains harbouring a binary vector carrying the green fluorescent protein (GFP) and β-glucuronidase (GUS) reporter genes, respectively. Both the strains contained neomycin phosphotransferase selectable marker gene. After co-cultivation, the explants were cultured on EC₆ basal medium supplemented with 5 μM BAP and 1 μM IAA. The selection of putative transformants was on a medium containing 50 mg dm^-3 kanamycin. Expression of GUS and GFP gene was confirmed by histochemical assay and fluorescence microscopy, respectively. The elongated shoots expressing GFP reporter gene were rooted and transferred to pots for hardening. The integration of GFP gene into the genome of putative transformants was confirmed by Southern blotting.

A simple protocol for mass multiplication of Crataeva nurvala, a medicinal tree, from seedling-derived explants is described. Six different types of explants (cotyledonary nodes, epicotyl nodes, hypocotyl segments, first pair of leaves, cotyledons, and root segments) developed shoots on Murashige and Skoog's (MS) basal medium or the same supplemented with different concentrations of 6-benzylaminopurine (BAP). Among the explants tested for caulogenic potential, only the epicotyl and cotyledonary nodal explants developed shoots on MS basal medium, while on BAP (0 - 2.0 mg dm^-3) adjuvated media all the explants exhibited caulogenesis. The optimum concentration of BAP varied for these explants. The shoots could be rooted on half strength MS with 0.02 mg dm^-3 α-naphthalene acetic acid to get plants, which have been transferred to soil. The explants from in vitro regenerated shoots also possessed a similar caulogenic potential.

Explants of four F₁ hybrids (OMR 36-41/1, OMR 36-41/2, OMR 36-41/4 and OMR 36-41/5) and two cultivars (Rayong 1 and Rayong 60) of cassava (Manihot esculenta Crantz) were subjected to different combinations of 2,4-dichlorophenoxyacetic acid (2,4-D), 1-naphthaleneacetic acid (NAA), kinetin (KIN) and N⁶-benzylaminopurine (BAP) to induce somatic embryogenesis, organogenesis and micropropagation. Shoot apices of the F₁ hybrids exhibited higher frequency (62 - 74 %) of proliferation of somatic embryos than the cultivars (21 - 43 %) in Murashige and Skoog basal medium supplemented with 8 mg dm^-3 2,4-D and 0.5 mg dm^-3 NAA. Nodal explants of regenerated plantlets were rapidly micropropagated with 90 % efficiency on a medium containing 0.1 mg dm^-3 NAA and 0.05 mg dm^-3 BAP irrespective of explant source.

Multiple shoots were induced from the cotyledonary nodes derived from seedling of Sesbania rostrata on Nitsch (1969; N) medium supplemented with various concentrations of benzyladenine (BA). 1 mg dm^-3 BA proved to be the best, eliciting 5.8 ± 1.0 shoots per explant in 100 % cultures. The elongation of shoots was best at 2.0 mg dm^-3 BA. The shoot proliferation capacity increased to 7.5 shoots per explant following transfer of explants to the fresh shoot multiplication medium (MS + 1.0 mg dm^-3 BA), after an initial incubation of 30 d. To further enhance number of shoots per explant an alternative strategy of cultivation of mother explant on fresh shoot multiplication medium after excision of shoots was adopted. Following the repeated harvesting of shoots an average of 33 shoots per explant could be obtained. The in vitro regenerated shoots produced roots when transferred to half-strength MS medium supplemented with 3 % sucrose and 1 mg dm^-3 IBA. The developed plantlets were planted in the soil and transferred to the field after an acclimatization period of 3 - 4 months. These plants produced flowers and fruits in the field and exhibited the development of prominent and more organized stem nodules as compared to the in vivo raised plants of the same age.

Tobacco (Nicotiana tabacum L. cv. BY-2) cell lines tolerant to 700 μM Ni in which unselected cells can not grow, were selected. The Ni-tolerant cells were also more tolerant to Co, but not to Cd than unselected cells. Ni concentrations in Ni-tolerant cells were always higher than those in medium. Since buthionine sulfoximine did not affect their Ni-tolerance, it is suggested that phytochelatins are not involved in Ni-tolerance of Ni-tolerant cells. On the other hand, histidine contents in Ni-tolerant and unselected cells, which were treated with Ni, were higher that those treated without Ni, and the degree of the elevation of histidine contents by Ni-treatment was higher in Ni-tolerant cells than in unselected cells. Additionally, exogenous histidine reduced the inhibitory effect of Ni on the growth of unselected cells. In addition, the cells that were tolerant to histidine-analogue, had higher contents of histidine and Ni-tolerance. These results suggest that histidine is involved in Ni-tolerance and the detoxification of Ni in symplast in Ni-tolerant cells.

A rapid and efficient procedure is outlined for in vitro clonal propagation of an elite cultivar of jewel orchid (Anoectochilus formosanus). Multiple shoot proliferation was induced in shoot tip explants on Hyponex (H3) media supplemented with 1 mg dm^-3 benzyladenine or 1 - 2 mg dm^-3 thidiazuron (TDZ). Addition of activated charcoal (1 g dm^-3) to the TDZ containing medium promoted multiple shoot formation (11.1 shoots per explant). However, the regenerated shoots had slow growth rate and failed to elongate. This problem was overcome by transferring the shoot clumps to a hormone free H3 medium supplemented with 2 % sucrose and 0.5 g dm^-3 activated charcoal. Rooting was induced in 100 % of the regenerated shoots in the same media. The plantlets were acclimatized and established in greenhouse.

Efficiency of pretreatment as foliar spray of indole-3-acetic acid, gibberellic acid and kinetin, each ranging from 0.1 to 10.0 μM concentration, in restoring the metabolic alterations imposed by NaCl salinity was investigated in Vigna radiata (L.) Wilczek. Glycolate oxidase, superoxide dismutase, catalase and peroxidase activities increased under stress in leaves and roots also. Malondialdehyde content and total peroxide content also increased under stress. All the three hormones used were able to overcome to variable extents the adverse effects of stress imposed by NaCl to these parameters.

Application of NaCl (electrical conductivity 4.0 mS cm^-1) resulted in about 52, 50 and 55 % reduction in total nitrogen contents in mung bean [Vigna radiata (L.) Wilczek] leaf, root and nodule, respectively. In nodule, nitrogenase activity was reduced by about 84 % under stress as compared with the control set. Glutamine synthetase activity was reduced by about 31, 16 and 23 %, glutamate oxoglutarate aminotransferase activity was reduced by 78, 57 and 42 % and glutamate dehydrogenase activity was reduced by 9, 8 and 42 % in leaf, root and nodule, respectively, under salt stress. The pretreatment with indole-3-acetic acid, gibberellic acid and kinetin, each ranging from 0.1 to 10 µM, in restoring the metabolic alterations imposed by NaCl salinity was investigated in mung bean. The three phytohormones used were able to overcome to variable extents the adverse effects of stress imposed by NaCl solution.

The effect of radiation quality (350 - 740 nm) and darkness (D) on in vitro rooting, and chemical composition of the peach rootstock GF 677 was studied. Shoot explants were exposed for four weeks to cool white (control) (W), red (R), blue (B), green (G) or yellow (Y) radiation from fluorescent tubes. Some of the explants were kept in D during the rooting stage and others were maintained only for the first 2- or 4-d under R, B, G, Y or D, and subsequently were transferred to W. W was the most effective radiation source for adventitious root formation of GF 677 explants. Rooting was inhibited in those plants that remained in continuous D, and R reduced root growth in all treatments. The 2- or 4-d exposure to D, Y or B followed by W helped adventitious root development similarly as did W. G significantly increased Fe concentration in roots.

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.

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.

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.

Treatment of intact potato (Solanum tuberosum L., cv. Nevskii) tubers with 24-epibrassinolide (EB) resulted in prolonged deep dormancy, increased production of ethylene and higher contents of free and bound abscisic acid (ABA) in buds. EB at the most efficient concentration 0.021 mg dm^-3, applied immediately after tuber harvest, inhibited sprouting by 36 - 38 d, increased ethylene formation after 1 and 7 d of storage by almost 300 and 150%, respectively, and increased the content of both free and bound ABA during the whole period of storage (on average by about 80%). Electron microscopic and morphometric studies showed that EB brings about a decrease in cell volume in tunica and all types of meristems and an increase in the number of vacuoles, accompanied by a decrease in their volume.

Dog rose (Rosa canina L.) plants in the bloom stages of flowering were sprayed by indole-3-acetic acid (IAA) in concentrations of 0.06 and 0.60 mM and gibberellic acid (GA₃) in concentrations of 0.60 and 1.50 mM. Ascorbic acid, total sugar, reducing sugar and carotenoid contents gradually increased, while the protein content remained unchanged and the content of phenolic substances decreased during hypanthium development. Ascorbic acid, total sugar, reducing sugar and carotenoid contents increased in hypanthium sprayed by GA₃ and IAA. However, IAA and GA₃ applications (except low concentrations) decreased contents of phenolic substances. IAA and GA applications might be a good way to produce the high quality hypanthium in R. canina.

Carbon translocation was affected by shade in different tropical tree species differing in successional status and degree of shade tolerance. Plants of the early-successional shade-intolerant species Cecropia pachystachya and Schizolobium parahyba and of the late-successional shade-tolerant species Myroxylon peruiferum and Hymenaea courbaril were grown under full sun (FS) and natural shade treatments (NS) and assessed for [¹⁴C]-sucrose translocation. Most of the ¹⁴C was retained in the fed leaf after a 24 h translocation period. Under FS, the growing apical part of the plant was the most intense sink for most species. Shade affected growth and sink intensity differently in early and late successional species. Growth was more markedly affected in the early species. Whereas these continued to invest carbon into the growing apical part of the plant under shade conditions, the late successional species invested relatively more into other sinks.

The effects of Cu²⁺ on growth, chlorophyll and other ion contents ofKoeleria splendens originated from Cu-contaminated soil have been investigated in nutrient solution. The most evident Cu²⁺ effects concern the root growth, especially the root length. Since in plants grown under lower Cu²⁺ concentrations (4 and 8 μM) root elongation, biomass, chlorophyll, Mg²⁺, Fe²⁺, Ca²⁺ and K⁺ content were increased compared with the control, the development of an adaptive mechanism ofK. splendens to Cu²⁺ is suggested. High Cu²⁺ concentration (160 μM) caused a significant reduction in root length and biomass as well as a decreased rate of chlorophyll biosynthesis. The reduction of growth can be correlated with the toxic effect of Cu²⁺ on photosynthesis, root respiration and protein synthesis in roots. 160 μM Cu²⁺-treatment had a negative influence on the concentrations of Ca²⁺, Fe²⁺, Mg²⁺ and K⁺ and a positive influence on the Cu²⁺ concentration in the plant tissues. Loss of nutrients similar to the senescence response suggests that excess of Cu²⁺ leads to the progressive senescence of the plants. Our results demonstrate the existence of an adaptive mechanism ofK. splendens under low Cu²⁺ concentrations, while high Cu²⁺ quantities cause disturbances in plant function.

Rhododendron shoot regeneration was accomplished using either flower explants (each consisting of ovary with pedicel) of Rhododendron cvs. Nova Zembla and Irina or leaves isolated from in vitro grown Rhododendron catawbiense Michx. Multiple shoot tip clumps were obtained on Anderson's medium containing 0.5 to 1.5 mg dm^-3 thidiazuron (TDZ) in combination with 12 to 15 mg dm^-3 N⁶-[2-isopentenyl]adenine (2iP) and 1 to 3 mg dm^-3 indole-3-butyric acid (IBA). After 16 weeks on the regeneration media, explants with shoot tip clumps were transferred for shoot elongation to Anderson's medium with 3 mg dm^-3 2iP. Two months later, the shoots have reached 5 to 40 mm in length and were fit for subcultivation.