Seedlings of two cultivars of zucchini (Cucurbita pepo L.) Courgette d'Italie (CI) and Courgette d'Alger (CA) were pre-treated with various concentrations of cadmium, copper and zinc for 30 d. High accumulation of heavy metals especially in the roots was showed. Peroxidase activity was affected according to the type of metal added, concentration, and the plant cultivar used. In leaves and roots of the CI control plants peroxidase activities were 50 and 17 % higher than in the CA control plants. Treatment with Cd (5 µg g^-1), Cu (200 µg g^-1), and Zn (500 µg g^-1) increased peroxidase activities in CA but decreased it in CI both in leaves and roots. Heavy metals tested lead also to some qualitative changes characterized by appearance of new isoforms of peroxidase. The results show the possibility to use the activities of peroxidase as biomarkers for Cd, Cu and Zn stresses.

A reliable protocol for plant regeneration from mature embryo derived calli of nine barley (Hordeum vulgare) cultivars has been developed. The auxins 2,4-dichlorophenoxyacetic acid, picloram and dicamba proved effective in inducing callus from mature embryos of most of the barley cultivars. The induced primary callus was loose, friable and translucent. It ultimately yielded creamy white and compact callus after 2 - 3 transfers on fresh medium of the same composition. Callus induction and regeneration capacity were highly cultivar dependent. Addition of a high concentration of picloram (4 mg dm^-3) promoted regeneration in 3 cultivars (Tallon, Grimmett and Sloop). In cv. Arapiles, abscisic acid and betaine were crucial in generating morphogenic callus from the mature embryos. Plants regenerated from these calli were hardy and developed roots readily when transferred to hormone free medium.

The effect of benzothiadiazole (BTH) on protein synthesis was studied in sugar beet plants. Extracellular proteins induced by 0.025 % BTH were examined and their pattern was compared with that induced by sodium salicylate, chitosan, paraquat, AgNO₃, and by tobacco necrosis virus. BTH induced synthesis of at least 9 acidic and 6 basic proteins; three of them appeared as acidic chitinase isozymes, three as acidic β-1,3-glucanase isozymes, three as basic chitinase isozymes, and one as a basic β-1,3-glucanase isozyme. One of the basic chitinase isozymes was found also in control plants. The most of the newly formed proteins was also induced by the other inducers under study regardless of the necrotic or symptomless reaction of plants. The benzothiadiazole proved to be an efficient inducer of proteins in sugar beet.

The increase in water use efficiency (the ratio of photosynthetic to transpiration rates) is likely to be the commonest positive effect of long-term elevation in CO₂ concentration (CE). This may not necessarily lead to decrease in long-term water use owing to increased leaf area. However, some plant species seem to cope better with drought stress under CE, because increased production of photosynthates might enhance osmotic adjustment and decreased stomatal conductance and transpiration rate under CE enable plants to maintain a higher leaf water potential during drought. In addition, at the same stomatal conductance, internal CO₂ concentration might be higher under CE which results in higher photosynthetic rate. Therefore plants under CE of the future atmosphere will probably survive eventual higher drought stress and some species may even be able to extend their biotope into less favourable sites.

Activities of host ribonucleases and glucose-6-phosphate dehydrogenase were studied in three cultivars (Monosvalof, Steffi and Rimini) of sugar beet differing in their resistance to beet necrotic yellow vein virus (BNYVV). No differences were found in the susceptibility of cultivars to BNYVV between mechanically inoculated and Polymyxa betae (a natural fungal vector of the virus) infected plants, but the culmination of reproduction curves of BNYVV in mechanically inoculated plants was observed one week earlier than in plants inoculated by means of P. betae. The activities of ribonucleases corresponded with virus multiplication. In roots, activities of ribonucleases reached a maximum at day 7; in leaves, maximum activity was found at day 21 in cv. Monosvalof, and at day 14 in cv. Steffi. The relatively resistant cultivar Rimini showed much lower activities. The activity of glucose-6-phosphate dehydrogenase was only slightly increased at the time of culmination of the BNYVV reproduction curve in cvs. Monosvalof and Steffi.

The effect of 50 to 200 mM NaCl on two lines (CP with solid stem and CV with hollow stem) of ×Haynaldoticum sardoum was studied. NaCl significantly reduced root and shoot fresh and dry masses, root length and less markedly shoot length of CP and CV plants. The sodium accumulated in the leaves in relation to the concentration of NaCl and length of the treatment; CP leaves contained twice as much sodium as CV leaves. The leaf chlorophyll a/b ratio was not affected by NaCl. NaCl decreased the leaf water and osmotic potentials. The pressure potential increased due to the increased concentration of dissolved solutes in the leaf, particularly sodium. The proteinase and exopeptidase activities increased during NaCl treatment.

Water relations of two rapidly expanding species in deforested localities, Calamagrostis epigeios and Calamagrostis arundinacea, were compared. After short- or long-term water stress, water content and specific leaf area were more reduced in C. epigeios than in C. arundinacea. After short-term stress, osmotic potential was similar in both species, but after long-term stress, it was much lower in C. epigeios plants. Abscisic acid and proline contents were higher in stressed plants of C. epigeios than in those of C. arundinacea.

Increasing soil acidity (from pH 6.5 to pH 2.0) decreased chlorophyll (Chl)a andb contents, dry matter accumulation by plants and the transpiration coefficient. Chl stability to heat significantly increased with increased soil acidity. The Chla/b ratio was increased significantly at pH 5 and 4 and decreased at pH 3 and 2. SprayingSorghum shoots with kinetin solutions counteracted the above adverse effects on Chl content and dry matter accumulation. Kinetin-treated plants showed a lower transpiration coefficient than the untreated plants.

Addition of 0.5 and 2.5 gm^-3 of metribuzin into Hoagland nutrient media, either alone or in combination with NaCl, induced significant decreases in nitrate-, amino-, ammonia-, and total soluble-N contents, whereas significant increases in these nitrogen fractions were apparent in maize and castor bean seedlings and plants treated with high concentrations (5 and 10 g m^-3) of the herbicide, again either alone or in combination with NaCl. Protein- and total-N contents increased and decreased at low and high concentrations of the herbicide, respectively. The contents of chlorophyllsa andb, as well as carotenoids of both castor bean and maize seedlings and plants treated with low concentration of herbicide, either alone or supplemented with NaCl, were unaffected, whereas at high concentrations of the herbicide a significant decrease in chloroplast pigments was found. Nitrate reductase activity (NRA) was increased significantly at low concentrations of the herbicide alone and decreased significantly at high levels. Inclusion of NaCl into the herbicide media induced significant decreases in NRA of both castor bean and maize seedlings and plants. Unlike NRA changes, protease activity was increased significantly with high concentrations (5 and 10 g m^-3) of metribuzin and decreased significantly with its low (0.5 and 2.5 g m^-3) concentrations.

Whole sugar beet (Beta vulgaris L. cv. Ras poly) plants were grown in the greenhouse from the same seed stock used for an in vitro shoot tip culture. In vitro produced sugar beet plants exhibited a high content of chlorophylls a and b, carotene, and total and soluble sugars. On the other hand, total protein content of in vivo plants was higher than that of in vitro plants. No differences were found by SDS-PAGE analysis in the nature and contents of soluble proteins of in vitro propagated plants and greenhouse-grown plants. Surfaces of epidermal cells were larger and palisade and spongy paranchyma tissues were thicker in leaves of regenerants than in leaves of seedlings. Vascular tissues in leaf petioles in regenerants were flat and more differentiated than in seedlings. Closed and undeveloped stomata were found on the abaxial leaf surface of regenerants, whereas in seedlings the stomata were open.

Micropropagation and Agrobacterium-mediated transformation were developed in Kalmia latifolia cv. Ostbo Red. The transformation of Kalmia latifolia plants was carried out by an Agrobacterium tumefaciens strain containing the nptII and gusA genes in its T-DNA. Shoots were regenerated on kanamycin selection medium and the expression of the gusA reporter gene was verified by fluorogenic β-glucuronidase (GUS) assay in a few vegetative generations after regeneration. The presence of the gusA gene in regenerated kanamycin resistant plants was detected by polymerase chain reaction.

Recently, evidence has increased for both long- and short-distance transport of polyamines (PAs) in living organisms, but the mechanisms involved and physiological significance of PAs translocation are still not well understood. This review deals with various aspects of polyamine uptake and transport in higher plant tissues.

Expression of the β-glucuronidase (GUS) reporter gene driven by the CaMV 35S, rolC, nos and mas promoters was assessed in the tips of 12 independent clones of transgenic sugar beet (Beta vulgaris) roots. Three questions were addressed: 1) expression pattern specific for a given promoter, 2) expression pattern variability, and 3) relationship between gene expression and cell differentiation. Characteristic patterns of tissue-specific expression were distinguished for each promoter. Striking differences, however, were found between some clones, bearing the same construct. Statistical analysis of the pattern variability proved that the variability is significantly lower within the construct than between constructs. rolC-GUS clones exhibited the lowest and CaMV 35S clones the highest pattern variability. Comparisons between the four promoters showed consistent GUS activity in areas playing a key role in tissue determination (the elongation zone) where cells switch from frequent mitosis and mostly isodiametrical growth, typical for the promeristem, to rapid elongation and differentiation. All of the clones were highly GUS-positive in the elongation zone of stele. Activity was commonly localised in the stele of the maturation zone for CaMV 35S, rolC and mas-GUS clones. CaMV 35S-GUS clones were highly active in the promeristem.

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.

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.

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.

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.

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.

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.