Plants of Vigna mungo raised from seeds presoaked in salicylic acid (0.0, 0.01, 0.1 and 1.0 mM) and nodulated with the cowpea strain of Rhizobium leguminosarum were analysed 15 and 30 d after sowing. The foliar nitrate and nitrite contents were varying but soluble protein and total nitrogen contents were lower in treated than control plants. Nitrate reductase activity was increased at the two lower concentrations of 0.01 and 0.1 mM but was inhibited at the highest concentration used (1.0 mM). The number of nodules, their leghemoglobin and protein contents and nitrogenase activity of roots were reduced.

Decrease in seed viability and germination rate may be caused by biochemical changes associated with seed ageing. Different biochemical assays were conducted to investigate the changes occurring at the ageing of Bambusa bambos seeds. A reduction in the total content of food reserves such as sugars, proteins and lipids were recorded. Decreased activity of peroxidase, acid phosphatase, alkaline phosphatase were also noticed during accelerated ageing. A substantial increase in total free amino acids and the activity of amylases confirms the degradation of stored biomolecules in seeds during ageing.

Growth and Na⁺, K⁺, Cl^-, proteins, sugars and proline concentrations were measured in three triticale genotypes M2A, DF99 and Asseret grown on nutrient solution with or without 75 mM NaCl. In saline conditions, leaf area of the three triticales was reduced by 50 % and dry to fresh mass ratio increased. Total protein concentration was diminished by 10 %. K⁺ concentration decreased whereas Na⁺ and Cl^- accumulated in roots and shoots of salt-stressed plants. This ion accumulation was greater in roots of Asseret than in roots of the other triticales. Soluble sugar concentration increased in M2A and Asseret and decreased in DF99. Proline concentration increased in M2A and DF99 and decreased in Asseret. Osmotic adjustment was essentially realized by Na⁺ and Cl^- uptake. Non-reducing sugars and proline contributed too, but to a lesser extent.

Water and K⁺ fluxes were examined in detopped plants ofZea mays L. (cv. White Horse Tooth), which were grown and exuded on half-strength Long Ashton nutrient solution containing the appropriate concentration of Zn²⁺ at 20 °C. In light-grown plants, 100 and 500 μM Zn²⁺ increased both water and K⁺ fluxes in detopped maize plants whereas 1 000 μM Zn²⁺ inhibited both fluxes. In the dark-pretreated plants, 1 000 μM Zn²⁺ in the medium stimulated K⁺ flux. The fluxes of K⁺, Zn²⁺, Ca²⁺ and Mg²⁺ were usually higher in detopped plants than in intact ones. At 1 000 μM Zn²⁺ in the exudation medium, Zn²⁺ concentration was higher in the xylem exudate of dark-pretreated plants than in roots of plants maintained in light. The results are discussed in relation to the influence of Zn²⁺ on the membrane permeability and transport in plants.

Cytokinin content in xylem sap was higher in plants grown under local supply of fertilizers as compared to those grown under homogenous distribution of nutrients in soil. The separate assay of cytokinins in xylem exudate from split root system showed that roots, which were in contact with fertilizer mainly contributed to cytokinins transported from roots to shoots.

The decrease in inorganic phosphate concentration in bean (Phaseolus vulgaris L. cv. Złota Saxa) roots induced decrease in respiration rate. The decrease observed in ATP pool in phosphate deficient (-P) roots was greater than it would result from the decline in respiration and possible involvement of alternative pathway, suggesting an increased energy utilization for growth and ion uptake. Indeed, relative growth rate was higher in -P plants until 12 d of culture and later dropped to the rate similar to the control. Net nitrate uptake rate was higher in -P plants than in +P plants at the beginning of phosphate starvation, then during the prolonged culture it decreased rapidly in -P plants and after 19 d it was 8 times lower than that in the control. The decline in ATP production during prolonged phosphate starvation influenced NO₃ ^- uptake more than root growth.

Leaves of 15 - 30-d-old plants of sunflower and jute were harvested at 10.00 or 23.00 (local time) and measured immediately, or those harvested at 10.00 were incubated for one hour in sunlight either in water or 5 mM methionine sulfoximine (MSX) solution and then for three hours in dark either in water or 15 mM KNO3 solution. Nitrate feeding during dark incubation, in general, increased nitrate reductase (NR) and nitrite reductase (NiR) activities, and NADH and soluble sugar contents. Increase in tissue nitrate concentration in MSX fed but not in control samples suggested reduction of nitrate in dark. NADPH-dependent NR activity increased considerably upon feeding with nitrate in dark. Concomitantly, NADPH phosphatase activity was also increased in nitrate treated, dark incubated leaves. It is proposed that nitrate regulates dark nitrate reduction by facilitating generation of NADH from NADPH by NADPH phosphatase. High amounts of ammonia accumulated in MSX treated, but not in control leaves, upon dark incubation. Relative activities of NR and NADPH phosphatase, and amounts of soluble sugar and NADH were low in MSX fed samples compared to that of control. So, high amount of ammonia might partially repress NADPH phosphatase and consequently deprive NR of reducing equivalents.

Accumulation of the pathogenesis-related (PR) proteins localised in intercellular spaces of barley primary leaves, chlorophyll content, structure of chloroplasts, and photosynthesis were examined during natural and in vitro induced leaf senescence (cultivation of whole plants in the dark or detached leaves under nutrient deficiency). Some of PR proteins accumulated during natural senescence, but their accumulation pattern was different from those of pathogen-induced as well as during in vitro-induced senescence, which indicate different molecular bases of these processes. Photosynthetic rate and chlorophyll content indicate that natural senescence of barley primary leaves began from 15th day after sowing. In 35-d-old first leaves, the chloroplasts showed typical characteristics of senescence as significant decrease of size, greater grana, and prominent plastoglobuli. The chloroplasts contained more grana under in vitro induced senescence and they had reduced length in the dark. Correspondingly, accumulation of PR proteins was detectable on about the 15th day but the content of some PR proteins increased in later stages of senescence.

Plants of peanut (Arachis hypogaea L.) were subjected to 7-d and 14-d waterlogging and sprayed with 10 and 100 mg 1^-1 of gibberellic acid (GA₃). Waterlogging decreased the leaf area (A), net photosynthetic rate (P_n), chlorophyll content (Chi) and temporarily the leaf water potential (Ψ_w) and increased stomatal diffusive resistance (r_s) of both leaf surfaces. Application of GA₃ increased A and P_n and significantly decreased the r_s of both leaf surfaces but did not affect Ψ_w or Chl. Thus GA₃ partially alleviated the effects of waterlogging on A, r_s and P_n.

A precursor in tetrapyrrole biosynthesis, 5-aminolevulinic acid (ALA), was applied via presowing soaking in Vigna catjung, V. mungo, and V. radiata. ALA increased plant growth and influenced dry matter accumulation in leaves, stems, and pods through increased chlorophyll content and photosynthetic CO₂ absorption. At harvest, ALA treated plants had increased number of pods per plant, seeds per pod, 100 seed dry matter, biological yield, and the harvest index. Therefore, pretreatment of seeds with optimal concentration of ALA is recommended for improving the growth and productivity of tropical legumes.

Sodium chloride tolerant cell lines of finger millet were isolated from embryogenic cultures growing on MS medium supplemented with picloram (2 mg I^-1), kinetin (0.1 mg l^-1) and sodium chloride (1 %) at the end of 6 passages. The sodium chloride tolerant cell lines showed better growth in comparison with control at all concentrations of sodium chloride tested, with optimum growth at 0.25 % NaCl. When the tolerant lines were grown for 3 passages in absence of NaCl, the growth was lower than that of the tolerant lines tested immediately at the end of 6 passages of selection. NaCl tolerant calli had more Na¹ in comparison with control and they regenerated plants in presence of 1 % NaCl, while the control lines failed to differentiate. When screened in a hydroponics system with 1 % NaCl, the tolerant plants grew to maturity while the control plants failed to grow.

The effects of ethylene on postharvest horticultural produce are a major limiting factor in their orderly and efficient marketing. Nitric oxide and nitrous oxide have recently been shown to inhibit ethylene action and synthesis in higher plants and their potential for commercial use to extend the storage and marketing life of fruits, vegetables and flowers is reviewed.

Nodulation was inhibited in plants of green gram (Vigna radiata, cvs. ADT-1 and CO-5) exposed to different levels of simulated acid rain using a mixture of H2SO4, HNO3 and HCl (6:3:1) of pH 2.5, 4.0 and 5.5 in comparison with control (pH 7.0). Protein content of leaves increased in cv. CO-5 but decreased in cv. ADT-1 whereas the nitrate content of leaves increased in cv. ADT-1 but lowered in cv. CO-5. Nitrate reductase activity was increased in the nodular roots of cv. ADT-1 but was decreased in leaves. In cv. CO-5 it was increased in leaves but was insignificantly reduced in the nodules at pH 2.5. The nodule nitrogenase activity increased at pH 4.0 and 2.5 in cv. ADT-1.

Nitrate content, activities of nitrate reductase and glutamine synthetase, soluble protein content, and proportion of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) protein in total proteins were measured in leaves of Beta vulgaris L. plants affected by nickel, cadmium, and molybdenum in concentrations of 10^-4, 10^-2, and 1 mM. The most harmful effect on the above mentioned parameters had Cd, less harmful Ni, whereas Mo stimulated the investigated parameters. The proportion of RuBPCO protein showed a high tolerance to heavy metals.

Expression of the gene 4 for cytokinin synthesis in two clones of transgenic tobacco plants resulted in slightly higher(ca. 10 - 20 %) levels of endogenous cytokinins -zeatin, zeatin riboside and isopentenyladenosine. This was associated with changes in photosynthetic processes on chloroplast and leaf level. In comparison with nontransformed plantlets a higher degree of grana stacking was found in both clones of transgenic plants which indicated a higher proportion of photosystem 2 lightharvesting complex in thylakoids. This was supported by a decreased chlorophylla/b ratio in the separated grana fraction. The rate of leaf net photosynthetic rate (measured as CO₂ uptake) wasca. 25 % higher in both clones than in nontransformed plants. Also the rates of dark and light respiration, and CO₂ compensation concentration were higher in transgenic plants. On the other hand, parameters of water relations (water, osmotic and pressure potentials, stomatal and cuticular transpiration rates) were not significantly affected in transgenic tobacco plants.

Energetic aspects of the relation between transpiration and respiration during the dark period were evaluated. One-year old seedlings of three trees, one bush and one annual plant were grown in controlled conditions. Experiments were performed under uniform environment during the day and two regimes of air relative humidity (RH) during the night, low (50 - 65 %) and high (95 %). For all investigated plant species the dark transpiration rate (E), the free energy of respiratory substrate, the entropy production and the free energy balance (FEB) of the dark respiration were higher at low than at high RH. E was linearly related to the FEBr ² ranged between 0.63 and 0.90)

Investigations were carried out to determine the sites of lead uptake within the frond and the root ofLemna minor. With the sodium rhodizonate four regions favoured in lead uptake were distinguished: the frond region between the base and the node, the basal part of the root, and the regions at the proximal and distal ends of the root cap. For analysis in electron microscope only the root regions were chosen. The highest rate of lead uptake was found in the basal part of the root. Lead was present in the apoplast of this region after 5 min of exposure and was observed in the stelar cells after 30 min of incubation. Lead deposits were detected mostly in the cell walls adjacent to the plasma membrane and in the lumen of several endomembrane compartments - the endoplasmic reticulum (ER), dictyosomal vesicles, nuclear envelope and the vacuoles. Lead induced changes of cell ultrastructure; an increase in the number of membraneous structures, swelling of ER cisternae and distortion of the dictyosomal cisternae were observed after 2 to 6 h of exposure.

Dynamics of CO₂ evolution at low pressure was studied in barley, maize, pea, wheat and pine seedlings using the gas exchange system with laser photoacoustic spectrometer. The CO₂ evolution from plant surfaces to environment increased with decreasing air pressure. Simultaneously the changes in activities of phosphoenolpyruvate carboxylase, glucose-6-phosphate dehydrogenase, glyceraldehyde phosphate dehydrogenase, alcohol-dehydrogenase, isocitrate dehydrogenase, malate dehydrogenase in pea and maize leaves were observed. The response depended on plant species used as well as on air pressure and period of its action

Shoot and root fresh and dry matters and their Cu content were determined in 7-d-old seedlings of Triticum aestivum L. cv. Alkora treated with Cu (10,20, 40 µg cm-3) and Si (500 µg cm-3). Si significantly reduced the toxic effect of Cu on fresh and dry matter production of wheat seedlings. Moreover, plants treated with Cu and Si absorbed less Cu from the solution and had higher water content in shoots and roots than that treated with Cu only.

Indoor experiments demonstrated that allelopathic potential of rosette and flowering plants of qort is an important factor explaining the growth reduction of its associated species. Aqueous tissue extracts of flowering plants exhibited strong inhibitory effects on the germination percentage and radicle growth rate of the tested species as compared with those of vegetative plants. Under laboratory conditions, this inhibition was in agreement with toxicity assessments of soil samples collected from the rhizosphere of T. resupinatum L., where shoot and root dry mass of the tested species were significantly reduced. Detoxification of allelochemicals by presence of activated carbon can eliminate the inhibitory effects of the different extracts. This technique clarifies the occurrence of allelopathic interference by qort on seed germination and seedling growth, and hence suspects the allelopathic potential of qort in the growth reduction of associate species under field conditions along with competition.

Pot experiments were conducted to evaluate the possible interaction of salinity (osmotic potential -0.3, -0.9 and -1.2 MPa) and occurrence of Azospirillum lipoferum or exogenous gibberellic acid (GA₃) (100 µg g^-1) on growth and some physiological parameters of maize. ¹⁵N-uptake as well as the percentage of nitrogen derived from ¹⁵N-fertilizer were decreased by increasing the NaCl concentrations and completely inhibited at concentrations corresponding to osmotic potentials -0.9 and -1.2 MPa. The percentage of nitrogen originating from N₂ fixation was significantly correlated to the total counts of Azospirillum cells that colonized the histosphere. At high NaCl concentrations although no significant changes in N % in shoot dry mass either in inoculated or uninoculated plants were observed, the total N-yield [mg(N) pot^-1] was decreased. Fresh and dry shoot mass significantly increased by Azospirillum inoculation. Azospirillum and GA₃ treatments were positively correlated with most of the parameters analysed. Azospirillum inoculation or GA3 application at NaCl concentrations up to -1.2 MPa significantly increased the chlorophyll, K, Ca, soluble saccharides and protein contents as compared with control plants.

Developing fruits on lower nodes were major reproductive sink for photosynthates in bell pepper (Capsicum annuum L.). The removal of these fruits resulted in faster growth of other fruits on upper nodes. Sink manipulated plants have the higher rate of net photosynthetic rate at the later stages of plant development.

A reliable protocol for the regeneration of onion through repetitive somatic embryogenesis was established. Embryogenic callus was derived from mature seeds on Murashige and Skoog (MS) medium supplemented with 2 mg dm-3 2,4-dichlorophenoxyacetic acid (2,4-D). Somatic embryos aroused on the surface of calli cultures and formed plantlets after the removal of 2,4-D or its substitution with 1 mg dm-3 kinetin (Kin). Reculturing the somatic embryos on 2,4-D containing medium led to secondary embryos formation. The embryogenic cultures which were preserved for five months on maintenance medium containing 2 mg dm-3 2,4-D + 0.5 mg dm-3 Kin have retained their ability for regeneration, while those kept on 2,4-D only, failed to form plantlets. Electrophoretic analysis of total soluble proteins revealed that the competence for successful conversion of somatic embryos into plantlets is associated with the expression of new set of proteins (112, 58 and 30 kD). The regenerated plants were successfully transferred to the soil.

Differences in anatomy and morphology of the kiwifruit leaves and leaf petioles might play a considerable role in the sex-determination. Three months after bud break (June), the kiwifruit leaves of both male and female plants, grown on the vegetative and generative shoots showed different leaf area (128.6 ± 13.45 cm2 in male and 104.5 ± 4.02 cm2 in female plants) and shape. The most frequently leaf shape was determined as "folium cordatum" and "folium rotundato-cordatum". Higher values of total leaf thickness of the female leaves (190 ± 3.84 µm) in comparison to male leaves (174 ± 3.52 µm) were estimated, resulting in the thicker adaxial leaf epidermis and especially in thicker palisade parenchyma in female leaves (136 ± 2.76 µm in comparison to 104 ± 1.61 µm in male leaves). Typically bifacial leaves were observed in both male and female leaves. Anomocytic stomata in hypostomatic leaves were found. The reticulate venation appears to be the main type of leaf venation. Stalked stellate multicellular trichomes on the abaxial leaf side were frequently observed in the leaves of both sexes. No important differences between male and female plants were found in the structures of vascular system in leaves and leaf petioles. Thus leaf thickness and surface morphology of adaxial leaf epidermis can be considered as important structural parameters in the sex determination.

The immature zygotic embryos of reciprocal maize hybrids (CHI-31 x GF1 and CHI-31 × GE2) were used as the initial material for induction of somatic embryogenesis in vitro. Histological analysis of somatic embryogenesis revealed high developmental variability. The arising formations were classified into 5 groups: A) somatic embryos phenotypically similar to zygotic embryos, B) polyembryos, C) formations with radicle but without meristematic plumule, D) formations with radicle without differentiated plumule, and E) formations with plumule without radicle. The formatioms A and B regenerated directly into plants. Plant regeneration from formations E required preculture on the rooting medium. Formations C and D failed to develope into plants possibly because of early loss of meristematic cell character during the embryo axis differentiation. The reverse sequence of radicle and plumule differentiation in somatic embryos in comparison with zygotic ones was noted. The epigenetic character of the scutellum, coleoptile, coleorhiza and leaves primordia development was discussed.