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.

Fourteen days-old bean plants, grown on sand with Knop's nutrient solution were subjected to water stress (three days without irrigation). The stress led to a decrease in almost all lipid classes except phospholipids in the primary leaves. The content of palmitic acid increased, and that of the linolenic acid decreased. An increase of hexadecenoic acid in phospholipids was also observed. Rewatering for 24 h led to the recovery of the stressed plants including that of the photosynthetic apparatus, but the changes in the lipid composition were insignificant. The spraying of the plants before and after the water stress with 5 × 10-6 M solution of the phenylurea cytokinin 4-PU-30 alleviated negative effect of water stress on the lipid membrane composition permitting the plants to resist the harmful environment.

Rice (Oryza sativa L.) seedlings inhibited the growth of hypocotyls and roots of cress (Lepidium sativum L.) seedlings when both seedlings were grown together. Two growth inhibiting substances were found in the culture solution in which rice seedlings were hydroponically grown for 14 d. One growth inhibitor was further purified. This suggests that the rice seedlings may produce growth inhibiting substances, acting as allelochemicals to other plants, and release them from their roots into the environment.

The protection compound benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH) was applied to soybean roots or leaves in a dose of 20 cm³ of a solution containing 25 μg g^-1 of the active ingredient. Electrophoretic profiles of chitinase and superoxide dismutase were not altered by the product. Increased activity of two root anionic peroxidases and three differential isoforms of these enzymes were observed in plants with roots treated by BTH, which can be used as biochemical markers of the BTH effect.

Effects of the superinfection with tobacco mosaic virus (TMV) on susceptible tobacco plants infected with potato virus Y (PVY) were determined. Dynamic changes in the TMV and/or PVY contents, the ribonucleases (RNases), the phosphomonoesterase (PME), the phosphodiesterase (PDE) and the glucose-6-phosphate dehydrogenase (G6P DH) activities were studied. The PVY infection caused a substantial reduction in the multiplication of TMV. The content of TMV in the PVY inoculated leaves amounts to 6 and 9 % in the PVY systemically infected leaves when compared with single TMV. Surprisingly, the challenging virus (TMV) enhanced the content of inducing virus (PVY) in the locally inoculated leaves up to 130 - 141 %. In contrast, the reduction of PVY content down to 35 - 40 % by TMV was seen in the PVY systemically infected leaves. The activities of the RNase, the PME, the PDE and the G6P DH were increased (when compared with the healthy plants) during the acute phase of single virus multiplication (PVY or TMV). The increase in the activities of the enzymes in the leaves with mixed infection was at least as high as the sum of the increases of single infections. Moreover, a higher increase than the sum was seen for G6P DH and PDE (by about 20 - 35 %).

Changes in the cytosotic (soluble) and the non-cytosolic (particulate) isozyme composition of hexokinases and in their properties were studied by ion exchange chromatography on DEAE cellulose after the subcellular fractionation both in the healthy and the tobacco mosaic virus (TMV) infected tobacco leaves. Three main isozyme complexes were obtained: one particulate fraction (the particulate hexokinase phosphorylating both glucose and fructose, EC 2.7.1.1), and two soluble fractions (the soluble hexokinase phosphorylating both the glucose and the fructose, and the soluble fructokinase, which phosphorylates primarily fructose, EC 2.7.1.4). The total fructokinase activities were nearly twice higher than the total glucokinase activities (188.6 % of glucokinase activity in healthy plants and 181.3 % in infected plants). The total particulate glucokinase activity was increased to 120.6 % and the fructokinase to 118.9 % in TMV infected tissue when compared with healthy control. The similar pattern of activity was observed for soluble hexokinase isozymes - the sum of soluble glucokinase activity was increased to 175.4 % and of fructokinase activity to 131.2 % in TMV infected tissue. The isozymes isolated both from the healthy control and TMV-infected leaves had the similar elution profiles, displayed Michaelis-Menten kinetics, showed the identical profiles of pH optima and were Mg²⁺ dependent with the highest enzyme activity at equimolar Mg²⁺ and ATP concentration.

In non-acclimated bean plants heat shock induced oxidative damage (increase of free radical concentration and drop of bound thiols, indicating aggregation of proteins) which was regulated by the enhanced activities of peroxidase and superoxide dismutase, as well as by the accumulation of polyphenols and especially of polyamines. In the plants acclimated to high temperature no oxidative damage occurred following heat shock.

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.

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.

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.

Mature and immature cotyledon explants of cowpea were cultured on Murashige and Skoog's (MS) medium supplemented with 0.1 - 2.0 mg dm^-3 benzyladenine (BA). Shoot organogenesis was observed from the minimal greenish calli formed at proximal cutting edges of the immature cotyledon explants after 15 - 20 d of culture. Among whole immature zygotic embryo and seven explant types we tested, single whole cotyledon was suitable for shoot organogenesis. Nearly 67.5 % of the explant types produced adventitious shoots on MS medium containing with 1 mg dm^-3 BA, and the shoot number (10.1) per explant was higher than other explant types. From the histological studies, the shoot primordia originated from the procambial strands of immature cotyledon explants. When the shoots were transferred to 1/2 MS basal medium, formed roots within 20 d of culture. The rooted plants were subsequently transferred to the pots and to the field.

High-frequency regeneration of shoots was achieved at root region of seedlings of Robinia pseudoacacia L. cultured from seeds on medium supplemented with thidiazuron (TDZ, 1.0 μM). The roots of intact seedlings proliferated and formed a compact callus followed by differentiation of numerous shoots. Corresponding cultures on benzylaminopurine-containing medium exhibited much weaker response. Hypocotyl segments also formed shoots at a lower concentration of TDZ (0.1 μM). The shoots formed on TDZ-containing medium were well-developed and readily rooted on hormone-free medium. The obtained plants after acclimation in culture room survived after transfer to soil.

The effect of Pseudomonas fluorescens treatment and Fusarium oxysporum f. sp. cubense inoculation on induction of phenylalanine ammonia-lyase (PAL), peroxidase (POX), chitinase, β-1,3-glucanase and accumulation of phenolics in banana (Musa sp.) was studied. When banana roots were treated with P. fluorescens strain Pf10, a two-fold increase in phenolic content in leaf tissues was recorded 3 - 6 d after treatment. Challenge inoculation with F. oxysporum, the wilt pathogen, steeply increased the phenolic content in P. fluorescens-treated banana plants. Significant increase in POX activity was detected 6 - 9 d after P. fluorescens treatment. PAL, chitinase and β-1,3-glucanase activities increased significantly from 3 d after P. fluorescens treatment and reached the maximum 6 d after treatment. Challenge inoculation with F. oxysporum further increased the enzyme activities. These results suggest that the enhanced activities of defense enzymes and elevated content of phenolics may contribute to bioprotection of banana plants against F. oxysporum.

A rapid micropropagation protocol through induced multiple shoots from the cotyledonary explant of mulberry (Morus alba L) is described. The highest number of shoots (20.3) was obtained when explants from 14-d-old embryos were cultured on Murashige and Skoog (MS) medium supplemented with 7 μM thidiazuron for 45 d. Of the three cultivars used, cv. S-36 was the best followed by cv. K-2 and S-1. The shoots were transferred to MS medium supplemented with 5 μM 6-benzylaminopurine for elongation. The elongated shoots were rooted on half strength MS medium containing 1 - 7 μM indole 3-butyric acid or 1-naphthalene acetic acid. The rooted plants were transplanted to soil with 90 % success. The emerged shoot primordia probably initiated from the pre-existing meristems since the shoot bud show definite vascular connection to the major vascular tissue.

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.

Effects of plant hormones indole-3-yl-acetic acid (IAA), gibberellic acid (GA), benzylaminopurine (BAP), abscisic acid (ABA) and ethrel (ETH) in 5 μM concentration on gas exchange, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO, EC 4.1.1.39) activity, pigment content and yield in cotton (Gossypium hirsutum L. cv. H-777) under drought were studied. At reproductive stage (55 - 60 d after sowing) these hormones were sprayed on shoots one day prior to stress imposition by withholding irrigation. The soil moisture of control plants was kept at field capacity. Net photosynthetic rate (P_N), stomatal conductance (g_s), transpiration rate (E), carboxylation efficiency (CE), water use efficiency (WUE), RuBPCO activity, boll number per plant, seed number per plant and lint mass per plant significantly decreased at drought while chlorophyll (Chl) b content and flower number per plant increased. ABA and ETH significantly reduced gas exchange parameters, Chl a and Chl b content. Detrimental drought effect on P_N, g_s, E, CE, RuBPCO and lint mass per plant was significantly alleviated by BAP and also its effect on seed number and lint mass per plant was significantly alleviated with the ABA treatment.

This study deals with the effects of two cytokinins [kinetin (Kin) and N-(2-chloro-4-pyridyl)-N-phenylurea (CPPU)] and cytokinin antagonists [2-chloro-4-cyclobutyl-amino-6-ethylamino-1,3,5-triazine (ACK1) and N-(4-pyridyl)-O-(4-chlorophenyl)carbamate (ACK2)] in concentration of 1 μM on in vitro cultured Gypsophila. The application of Kin and CPPU stimulated bud opening and increased fresh and dry masses. Cytokinin antagonists reduced the number of sprouted buds and bud fresh and dry masses. In plants treated with CPPU the chloroplasts possessed well developed membrane system, which covered almost the entire chloroplasts volume. In ACK2 treated plants, the plastid apparatus in each cell was represented by two types of chloroplast in which the inner membrane system was differently organized. Cell wall adjacent chloroplasts possessed structure similar to the controls. In inner located chloroplasts part of thylakoids were semi-concentrically arranged and partially destructed.

In vitro regeneration of Melia azedarach L. was studied. Shoots were regenerated from calli initiated from leaflets of in vitro growing plants. The best medium for establishment of cultures was Murashige and Skoog (MS) medium with 4.44 μM benzylaminopurine (BAP) + 0.46 μM kinetin (KIN) + 16.29 μM adenine sulphate (ADE). Regenerated shoots were multiplied in MS + 0.44 μM BAP + 0.37 μM KIN + 3.26 μM ADE. Maximal rooting of 89 % was achieved by culture of regenerated shoots in MS + 12.26 μM indole-3-butyric acid for 3 d and subsequently in MS lacking growth regulators for 27 d. Rooted shoots were acclimatized and successfully transferred to soil.

The greatest growth of wheat and rape plants in vitro was reached on media with 5 or 9 % sucrose, respectively. The highest efficiency for transfer of these plants to ex vitro conditions was found at the same sucrose concentrations. The content of endogenous non-structural saccharides (glucose, fructose, sucrose, starch and fructans) increased with increasing sucrose concentration in the medium up to 10 %.

Wild type of Arabidopsis thaliana plants were cultivated hydroponically in Hoagland and Arnon nutrient solution and treated with copper (5 - 100 µM) for 2, 4, 7 and 14 d. A progressive decrease of the root length and biomass was observed at increasing Cu concentration in the nutrient solution. Roots accumulated higher amounts of Cu than shoots at all Cu treatments. Changes of cell and chloroplast ultrastructure of Cu-treated plants were also observed. Cu application did not induce formation of Cu-phytochelatin complexes. Changes in glutathione and glutathione disulfide content observed in roots and shoots of Cu-treated plants suggest their participation in amelioration of metal-induced oxidative stress.

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.

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.

The effects of 50 mM NaCl and 5, 10, 15 and 20 mM boron on the rate of germination, growth rate, contents of boron, sodium, potassium and chloride, and membrane permeability in maize (Zea mays L.) and sorghum (Sorghum bicolor L.) were studied. Germination rate, lengths of roots and shoots as well as dry matter production in the two tested plants, decreased with the increasing B concentration in nonsaline conditions, and markedly under salinity. Membrane permeability increased by increasing B concentration only under salinity. Increase in B concentration of sorghum was lower under salinity when compared to nonsaline conditions. Contrary to this, increase in B concentration of maize was higher under salinity. Under salinity Na and Cl concentrations increased and K concentration decreased in the both tested plants. Potassium concentration was decreased by B treatments under salinity.

The effect of exogenous brassinosteroids (BR) on the flowering induction of Pharbitis nil was examined. Generally plants treated with brassinolide and castasterone form less number of flowers than control plants, but degree of flowering inhibition was depended on the concentration and the method of BR application as well as the length of the inductive dark period. In plants regenerated from sub-induced apices treated with brassinolide at concentration of 1 and 10 μM the flower formation was inhibited completely.

Plants of maize (Zea mays L.) were waterlogged for 7 d and irrigated (root application) or sprayed (foliar application) with 0, 1, 3 and 6 mg dm-3 of boron. The stability of leaf membranes was assessed by determining leakage of electrolytes from leaf discs exposed to heat (51 °C) and dehydration (40 % PEG). Leaf membranes were more stable to heat than to dehydration. The membranes of waterlogged plants were more injured than those of control plants. Waterlogging reduced contents of dry mass, chlorophyll, soluble proteins, total free amino acids and soluble sugars and leaf relative water content (RWC). Application of boron increased the stability of leaf membranes, chlorophyll, soluble sugars, soluble proteins, amino acids contents, leaf RWC and dry mass accumulation. Foliar boron application was more effective. Application of boron alleviated the deleterious effect of waterlogging.

Distribution of cadmium between roots and shoots of barley was manipulated by the cadmium concentration (0.01 and 0.005 mM Cd²⁺), pH (4.6 and 5.9) as well as treatment duration. The prolongation of treatment increased dry mass and content of cadmium in plants. The cadmium is accumulated mainly in roots. Presence of both, 0.005 mM Cd²⁺ and 100 mM NaCl in medium at pH 5.9 (Cd-NaCl plants) resulted in the most severe growth inhibition of plants, but about one half accumulation of cadmium in roots then in a case of only Cd-treated plants. In the Cd-NaCl plants, the net photosynthetic and transpiration rates were less reduced then in a case of only NaCl-treated plants. The treatments also influenced uptake of Ca, Cd, Cu, K, Mg, Na and Zn predominantly in roots.

A greenhouse pot experiment with different phosphorus supply was conducted to study growth, photosynthesis and free polyamine (PA) content in Plantago lanceolata L. plants in relation to arbuscular mycorrhizal (AM) colonization. Inoculum of Glomus fasciculatum (BEG 53) was used. Inoculated plants had high colonization intensities which were related to the P supply. Non-mycorrhizal (NM) plants showed a typical yield response curve for P availability. Dry masses of mycorrhizal (M) plants were higher at the lowest soil P content than those of NM plants, but the opposite was found at the highest P supply. P contents in M plants were always higher. There were no differences in chlorophyll (Chl) concentrations (except the lowest soil P content) and ratios of variable to maximum Chl fluorescence (Fv/Fm) values between M and NM plants, whereas M plants had higher ratios of leaf area to fresh mass (A/f.m.) at low soil P contents and they had significantly higher CO₂ fixation capacities per unit leaf area. Free putrescine (Put), spermidine (Spd) and spermine (Spm) contents in NM plants were usually highest at the lowest P supply. The ratios of Put/(Spd+Spm) were identical in M and NM leaves. They were significantly higher, however, in NM roots at the two low P doses. It is concluded, that a P nutritional status might exist, below which PA concentrations and ratio are increased drastically, possibly indicating P deficiency or a certain state of plant development with a higher demand for AM symbiosis.

γ-Aminobutyrate (GABA) was the only amino acid out of three amino acid intermediates of GABA shunt that increased significantly after 28 h from the beginning of osmotic stress induced by 20 % polyethylene glycol 6000 in wheat seedlings. At the same time specific activities of glutamate decarboxylase (GAD) and GABA aminotransferase (GABA-T) two enzymes of GABA pathway did not change as compared with the control plants. The response of two GABA-T activities (with pyruvate or 2-oxoglutarate as amino acid acceptor) to aminooxyacetate, 3-chloro-L-alanine and p-hydroxymercuribenzoate prompted us to suggest that at least two isoforms of GABA-T showing different substrate specificity do exist in wheat leaves.

Two wheat (Triticum aestivum L.) genotypes differing in their sensitivity to water deficit (stress tolerant - C306 and stress susceptible - HD2329) were subjected to osmotic stress for 7 d using polyethylene glycol (PEG-6000; osmotic potential -1.0 MPa), at initial vegetative growth. The plants were either supplemented with 1 mM CaCl₂ (Ca²⁺) alone or along with verapamil (VP; calcium channel blocker) to investigate the involvement of calcium in governing osmoregulation. Relative elongation rate (RER), dry matter (DM) production, water potential (Ψ_w), electrolyte leakage (EL), contents of proline (Pro) and glycine betaine (GB) and activities of γ-glutamyl kinase (GK) and proline oxidase (PO) in shoots and roots were examined during stress period. C306 showed relatively higher accumulation of Pro while HD2329 accumulated more GB under stress. RER, DM and Ψ_w were relatively higher in C306 than HD2329. Roots compared to shoots showed lower content of osmolytes but had faster rate of their accumulation. Presence of Ca²⁺ in the medium increased the activity of GK and decreased that of PO while in the presence of its inhibitor, decrease in activity of both the enzymes was observed. Ca²⁺ appeared to reduce the damaging effect of stress by elevating the content of Pro and GB, improving the water status and growth of seedlings and minimizing the injury to membranes. The protective effect of Ca²⁺ was observed to be more in HD2329 than C306.

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.