Pistia stratiotes is used for the epuration of domestic sewage in the Biyem Assi phytopurification station. During the process, Fe²⁺, Mn²⁺, Zn²⁺ and Pb²⁺ are absorbed in substantial amounts by the plant. These metals modify the H⁺/K⁺ exchange system at the root level. H⁺ efflux is inhibited by Fe²⁺ and by Zn²⁺ and enhanced by Mn²⁺ and Pb²⁺. K⁺ influx is inhibited by Fe²⁺, by Zn²⁺ and by Pb²⁺ and enhanced by Mn²⁺. It is shown that the purification capacity ofPistia stratiotes can vary with the composition of the heavy metals in the surrounding medium.

Increasing salinity of growth medium induced a reduction in growth and transpiration rate. The concentrations of chlorophylls and carotenoids were increased in most cases in broad bean leaves while in pea plants they remained more or less unchanged with the rise of salinization up to 80mM NaCl. Thereabove a significant decrease in these contents was observed. A stimulation of the net photosynthetic rate of pea was observed at the lowest levels of NaCl but at the highest levels inhibitory effect was recorded. In broad bean all salinization levels inhibited photosynthetic activity, but dark respiration of both plant species was stimulated. The content of Na⁺ in the roots and shoots of both species increased at increasing salinity. In broad bean, Ca²⁺ concentration in shoots and K⁺ and Ca²⁺ contents of roots increased at increasing salinization, while in pea plants, the content of K⁺ and Ca²⁺ was almost unaffected by salinity. Salinity induced an increase in the content of these ions in pea roots. Mg²⁺ content in shoots and roots of both broad bean and pea decreased at increasing salinity except in roots of pea, where it was generally increased.

The regeneration ability of primary explants derived from mericlones of two commercial Bohemian hops was investigated. It was found that these hops are able to regenerate shoots by direct organogenesis on media containing BAP or zeatin at concentrations 0.5-2 mg dm^-3. The highest regeneration of shoots was achieved from either petioles or internodes at frequencies 21% and 52%, respectively, on the medium containing zeatin (2 mg dm^-3), while relatively low amount of regenerated shoots (1.3%) was observed for leaf blade explants. On the other hand, more efficient rooting occurred on the leaf blades then on other explants. A similar pattern of regeneration we observed for HLVd-infected mericlones of clone Osvald 31 even though viroid concentration inin vitro cultures was about 8-fold higher than in field-grown plants and was 31.1 pg mg^-1 of fresh mass in the average. These results suggest that HLVd infection did not impair organogenesis. We found that high 2,4-D concentration pretreatment (11 mg dm^-3) did not promote somatic embryogenesis. Although this treatment suppressed direct organogenesis, the inhibition was not complete and in low frequency the shoot regeneration was seen. Sensitivity of hop explants to antibiotics commonly used inAgrobacterium-mediated transformation was assayed. It was found that kanamycin (100-200 mg dm^-3) suppressed efficiently callogenesis, root formation and shoot proliferation. An estimation of effect of kanamycin (200 mg dm^-3) and ticarcillin (500 mg dm^-3) on morphogenesis was performed using regeneration medium. The inhibitory effects observed suggest that these conditions could be used inAgrobacterium transformation/selection system.

Potato spindle tuber viroid (PSTVd, severe strain) was isolated from tobacco plants transformed with a dimeric infectious expression construct which was maintained for a long time inAgrobacterium tumefaciens. Afterin vitro hybridization of PSTVd to complete minus transcripts of PSTVd (lethal), the resulting heteroduplexes were analyzed by electrophoresis under native conditions. Electrophoretic analysis revealed an appearence of electrophoretically distinguishable heteroduplexes, suggesting an accumulation of mutated sequence variants of PSTVd had occurred in the plant transformants. TGGE analysis of PSTVd cDNA, re-cloned from the original expression vector pCB1413 to plasmid pUC18 confirmed the accumulation of mutations in the cDNA and the instability of this sequence inA. tumefaciens maintained at 4°C for 2.5 years. One of these point mutations was identified by sequencing the PSTVd cDNAs isolated from the individualE. coli colonies. This transition (GC→AT) was localized at the position of 81 in the PSTVd genome, causing the change of C to U in PSTVd plus RNA. Transformation of tobacco with the freshly prepared expression vector containing the dimeric sequence of PSTVd lethal KF440-2 lead to the propagation of PSTVd electrophoretically identical to that derived from the original sequence and maintained in the tomato by a conventional infection.

The effect of combinations of different concentrations of copper (Cu) and mercury (Hg) ions with different constant temperatures (T) onPhaseolus vulgaris plants was studied. Criteria investigated included shoot and root length, dry mass, chlorophyll content (Chl) and stability index (CSI), and contents of soluble (SS) and hydrolysable saccharides (HS), soluble proteins (SP) and total free amino acid (AA). Each of the factors (T, Cu and Hg) significantly affected the parameters tested with exception of T effect on Chlb content as well as on Chla/b ratio. Bifactorial interactions (T×Cu) or (T×Hg) were also significant, except the interaction (T×Hg) in shoot elongation, Chlb content and Chla/b ratio. Statistical treatment of the data lead to three findings: (1) temperature was dominant in affecting CSIa, shoot AA and root SS, (2) Cu and Hg had the predominant effect on growth parameters and Chl content, and (3) interactions (T×Cu and T×Hg) were dominant in affecting CSIb, shoot SP, and root HS.

Different behaviour of small groups of stomata on a single leaf blade (stomatal patchiness) is reviewed. The occurrence of stomatal patchiness depends on plant species, age, leaf position, environmental conditions,etc. The possibility of errors in conventional evaluation of stomatal and non-stomatal (biochemical) limitations of photosynthesis resulting from patchy stomatal closure is analysed. The consequences of stomatal patchiness for leaf and plant photosynthesis and water economy are discussed. A brief survey of the techniques currently used for detection and quantification of stomatal patchiness is presented.

Crenatin (3, 4, 5, tri-hydroxybenzyl alcohol, 4-glucoside) isolated from chestnut, was studied for its ability for improvement of rooting in the bean rooting test. Crenatin itself had a positive effect on number of roots. Moreover it enhanced the number of IAA-induced roots. In addition, a retardation of the apical bud growth was observed.

Electrophoretic separation of seed alcohol dehydrogenase (ADH) fromNicotiana tabacum on 12% starch gels at pH 7.8 produced only one band with an apparent R_f of 0.65, which confirmed earlier reports. The same was found with pollen ADH. However, in polyacrylamide gel isoelectric focusing, seed ADH separated into three distinct bands with apparent pI of 5.33, 5.42 and 5.50. The pI 5.33 isoenzyme was found to be the essential form inN. sylvestris seeds. The analysis of charge properties ofN. tomentosiformis seed ADH showed only one isoenzyme with pI of 5.56. These results present further evidence thatN. tabacum has arisen from a cross between aN. sylvestris predecessor and an ancestral type ofN. tomentosiformis. The presence of the pI 5.42 form inN. tabacum is consistent with the reported formation of heterodimeric ADH in tobacco hybrids.

The constitutive expression of peroxidase isoenzymes which are capable of oxidizing 4-hydroxystilbenes was studied during the growth cycle of suspension cell cultures from grapevine (Vitis vinifera L. cv. Monastrell) berries. the results showed that the growth of suspension cell cultures is accompanied by the constitutive expression of the peroxidase isoenzymes HSPrx 1 and HSPrx 2, previously characterised by their properties for oxidizing 4-hydroxystilbene, the expression of these isoenzymes being characteristic of Monastrell vines brought to a resistant state. However, although the differential catalytic properties of these grapevine isoenzymes are also shown by the horseradish peroxidase, no immunological relationships have been found between the peroxidases from either source.

The influence of N, P, K supply on the contents of dry mass, chlorophyll (a+b), vitamin C, saccharides and the activities of peroxidase (E.C. 1.11.1.7), catalase (E.C. 1.11.1.6), and acid phosphatase (E.C.3.1.3.2) in leaves of celery plants during their growth stages was investigated. A correlation between the amount of N, P, K and the chemical composition and catalytic activities of enzymes was found.

Cell nuclei were isolated from leaf tissues of wild banana (Musa balbisiana, M. acuminata ssp.banksii andM. acuminata ssp.errans) and of the two vegetative clones of diploid cultivar "Pisang Mas". Relative fluorescence intensity was measured on propidium iodide-stained nuclei by flow cytometry. Nuclei isolated fromGlycine max with known nuclear genome size were used as internal standard to determine nuclear DNA content ofMusa in absolute units. The results of the study showed that the size of nuclear genome ofMusa is smaller than previously estimated. In general, it is smaller in comparison with many other angiosperms. Furthermore, it was found that nuclear DNA content ofM. balbisiana (genome BB) is significantly lower than that ofM. acuminata subspecies and cultivars (genome AA). This finding should permit estimation of genome composition in triploidMusa clones with expected hybrid composition. Flow cytometry is proposed as a useful technique with potential applications in taxonomy, breeding and biotechnology ofMusa.

Sclerotium rolfsii andSclerotium bataticola could utilize protein and produce extracellular proteinase. In protein-deficient media no extracellular proteinase was detected. In protein-containing media addition of glucose stimulated enzyme synthesis; in absence of glucose addition of ammonium to the protein-media decreased enzyme activity. The rate of protein hydrolysis was higher in media contained glucose but not ammonium. The rate of glucose depletion from the culture filtrates was faster in treatments received protein with glucose or with glucose and ammonium, and addition of sulphur showed slight decrease in glucose utilization.

A salt mixture resistant (SMR) cell line ofVigna radiata (L.) Wilczek was isolated by selection on agar solidified PC-L2 medium supplemented with NaCl, KCl and Na₂SO₄ (8∶1∶1) equimolar to 300 mol m^-3 NaCl, a concentration inhibitory to the wild-type non-selected cells (salt mixture sensitive, SMS). This line retained its resistance after subculture for 3 passages (3 months) on normal medium. The SMR line grew significantly better than SMS line at all the levels of salts, though less in saline medium than the SMR on normal medium. The growth of SMR line was significantly higher than that of SMS line under KCl stress. However, both the lines responded similarly to Na₂SO₄ at a concentration higher than 100 mol m^-3. The SMR line was found to be more sensitive to NaCl than SMS line. The SMR line under salt mixture stress maintained lower levels of Na⁺ and higher levels of K⁺ than SMS line. The SMR line failed to regenerate shoots, although rhizogenesis was observed on PC-L2 medium containing salt mixture (300 mol m^-3).

The effect of shortwave (250 nm) UV radiation (UV-C) on the level of peroxidase activity and peroxidase isoenzyme patterns in leaves of resistant ([Vitis vinifera x Viris riparia] x Vitis rupestris andVitis rupestris) and susceptible (Vitis vinifera) grapevine species toPlasmopara viticola (downy mildew) was studied. The results show that although UV-C did not produce significant changes in peroxidase activity in susceptible species, and only minor changes in resistant species, treatment with UV-light induces an acidic isoperoxidase (isoperoxidase A₁), capable of oxidising 4-hydroxystilbenes in resistant species. It was named HSPrx 2. Since peroxidase is apparently the enzyme responsible for ε-viniferin synthesis from resveratrol in grapevines, a close relationship between this peroxidase isoenzyme and ε-viniferin synthesis which occurs in grapevine leaves after UV-C treatment must be expected.

In the topmost leaves of low-irradiance (LI) tolerant CO 43 and LI susceptible IR 20 rice cultivars, the contents of chlorophyll (chl)a andb and carotenoids and the Hill reaction activity increased under LI. The increase was greater in cv. CO 43 than that in cv. IR 20, and in Chlb than in Chla. The contents of soluble proteins and reducing sugars and nitrate reductase activity of the leaves decreased while the content of non-reducing sugars increased due to shading. The decrease in reducing sugars was greater in cv. CO 43 than in cv. IR 20. On the other hand, the decrease in soluble proteins and nitrate reductase was much less in cv. CO 43 as compared with cv. IR 20.

Biomass, relative growth rate (RGR), organic and inorganic solute contents in control and NaCl (50-100 mM) affected roots or calli of the wild tomato genotypeLycopersicon pennellii and theLycopersicon esculentum wilty mutantflacca were compared. Under NaCl-stress, the RGR of calli fromL. pennellii was higher than that of the mutantflacca, while the root biomass of the former was lower than that of the latter. Constant water contents were found in calli and roots, irrespective of the genotypes and NaCl concentrations. Taking into account the solute contents of the apoplasm, Na⁺ accumulation was similar in the sensitive tissues (calli fromL. flacca, roots ofL. pennellii) and the tolerant ones (calli fromL. pennellii, flacca roots). Decreased K⁺ and Mg²⁺ and increased proline contents were found in both sensitive tissues. In comparison with sensitiveL. pennellii roots, salt sensitiveflacca calli showed increased total organic acid and amino acid contents.

Phosphorylase from tubers ofDioscorea dumentorum was fractionated by (NH₄)₂SO₄ precipitation and further purified to apparent homogeneity. Two forms of phosphorylase, Dd₁ and Dd₂ were obtained with different K_m, optimum temperatures and pH values. They obeyed Michaelis-Menten kinetics, they were activated by AMP, Mg²⁺ and Ca²⁺ but inhibited by ATP, ADP, ADP-glucose and Na₂SO₄. The molecular masses found for Dd₁ and Dd₂ were 102 000 and 195 000 respectively. SDS gel electrophoresis indicated that Dd₂ is a dimer and Dd₁ is a monomer. Both phosphorylase forms contained pyridoxal-5'-phosphate as their prosthetic group, which was essential for their activity. Dd₂ is more active in starch synthesis while Dd₁ is more active in starch degradation. The affinity of the enzyme forms for P_i is not a measure of the rate of glucan degradation. The decline in activities of the enzymes between pH 5.5 and 7.5 was due to unsuitable ionic forms of the enzymes and not due to irreversible denaturation. Both forms of phosphorylase showed double displacement reaction mechanism in direction of phosphorolysis, while in direction of synthesis, sequential mechanism was indicated. Indoleacetic acid activated the enzyme forms in direction of starch degradation but acted as an inhibitor in direction of glucan synthesis. The results of this study suggest that Dd₂ may have some synthetic function while Dd₁ has a degradative role. The effect of pH on the phosphorylase activity suggests histidine as the amino acid residue around the active site that might be involved in enzyme catalysis.

Addition of either abscisic acid (ABA) or kinetin at 10^-6 M to salinized media (20-120mM NaCl) induced remarkable effects on growth ofPhaseolus vulgaris plants. Whereas ABA inhibited the plant growth and the rate of transpiration, kinetin induced stimulation of both parameters. Moreover, ABA increased proline and phosphorus concentrations in the salinized plants whilst kinetin decreased them.
ABA induced stimulation of the transport of K, Ca and Cl from root to shoot, accumulation of K, Na and Cl in root cells and inhibits the transport of Na and accumulation of Ca. Kinetin appeared to inhibit the transport and accumulation of Na and Cl, transport of K, and stimulates the accumulation of K and Ca as well as the transport of Ca. The highest influence of both ABA and kinetin was mostly observed when these hormones were used in combination with the highest concentration of NaCl (120 mM) in the medium.

The germination percentage of chick-pea (Cicer arietinum) Seeds was greatly reduced by temperatures of 30°C and 35°C. This thermoinhibition was overcome by ethylene (ethrel). Both ABA and PEG diminished ethylene production and germination percentage in a parallel way. FC, MGBG and CHA stimulated both ethylene production and germination. AVG reduced ethylene production to some extent but did not inhibit germination. CoCl₂ and PG completely prevented both ethylene production and germination; this effect was reversed by ethylene but not by its immediate precursor ACC. NBE prevented both germination and ethylene production. Our results suggest that high ethylene production rates are not essential for germination of chick-pea seeds but that certain quantities of ethylene may be required.

The effect of four bacterial and six fungal species on nodulation and growth ofVicia faba cv. Giza 3 inoculated withRhizobium leguminosarum biovarviceae strain RCR 1001 were assessed in a pot experiment.Bacillus cereus, Pseudomonas fluorescens, Aspergillus niger andA. quadriliniatus either alive cells or sterile filtrate significantly promoted nodulation, growth and nitrogen accumulation. Heat-killed cells had no effect.

Growth analysis indicated that carbon gain in the alpine succulentSedum album tended to take place early during the growing season. Leaf water potential remained unchanged for a considerable length of time after the imposition of water stress in the field. Induction of crassulacean acid metabolism (CAM) by protracted water stress occurred before any signs of stress could be observed in the leaves, and appeared to be influenced by a complex interaction of environmental conditions including temperature and duration of sunshine. Increased levels of proline and betaine towards the end of the growing season appeared to reflect seasonal changes.

Meristems from 25-90-year-old oak (Quercus robur L. andQ. petraea Matt.) trees and seed embryos were pretreated with polyvinyl pyrrolidone, ascorbic acid, cysteine and citric acid solutions. Tissues were cultured mostly on a WPM medium supplemented with different combinations and concentrations of growth regulators. All the different pretreatments showed a positive effect against the otherwise very rapid and harmful browning of the explants but ascorbic acid (100 mg dm^-3) proved to be the most effective. Shooting was induced from seed embryos and meristems originating from adult trees. Rooted plantlets were obtained from explants of seed embryos.

Water and osmotic potentials were measured in young and mature styles of selfcompatible (SC) and selfincompatible (SI) species ofSolanaceae. For mature flowers, the stylar water and osmotic potentials were considerably lower in SI speciesNicotiana alata andPetunia hybrida than in SC speciesN. sylvestris andN. tabacum. Stylar water content (in % fresh mass) was also significantly lower in SI species (N. alata, P. hybrida, diploid clones of potato) than in SC species (N. acuminata, N. glauca, N. paniculata, N. sylvestris, N. tabacum). For flower buds younger than 2 d before anthesis, no differences in stylar water potential betweenN. alata (SI) andN. tabacum (SC) were observed. During further flower bud development the stylar water potential inN. alata decreased more expressively than inN. tabacum. Pollen culture in media with various concentrations of sucrose or polyethylene glycol revealed that optimal water potential for pollen tube growth was lower inN. alata than inN. tabacum. The differences were similar as for differences in stylar water potential. The results are considered in relation to possible involvement of stylar water potential in unilateral interspecific incompatibility inSolanaceae.