Life span of the second leaf of wheat(Triticum aestivum L., cv. Grana) plants was studied from day 8 to day 50 of plant age in a variant with nitrogen (+N) and in a variant in which plant senescence was induced by the omission of nitrogen from the nutrient solution (-N). Seed protein was the sole source of nitrogen for these plants. Specific leaf mass (SLM) in the -N variant, and specific leaf area (SLA), the mass of fresh leaf, soluble protein content and total nitrogen content in the +N variant peaked by day 22 of plant age (that is by day 19 of leaf age). Dry matter content, leaf length and leaf area, and SLM in the +N variant peaked by day 29 of plant age (that is by day 26 of leaf age). The ontogeny of the second leaf in the variant with enhanced senescence was shorter by at least 14 days. Plants from this variant showed typical symptoms of N deficiency, that is yellowing of leaves, tip burn, and lack of tillering. However, the growth and biochemical characters studied did not indicate an earlier onset of the senescence of the second leaf of -N plants. Both +N and -N variants reached their peaks (with the exception of an earlier peak by day 12 in case of total nitrogen content in the -N variant) on the same day of leaf age. Thus the first part of the leaf life span from leaf growth initiation to full expansion was of the same length in both the control and N-def icient plants. The stage of the proper senescence of the second leaf of -N plants was very short; the leaf completely died away within 7 days after senescence onset.

This study examined whether 'Risnod2' and 'Risnod27' non-nodulating mutants of pea (Pisum sativum L.) provided with increasing concentrations of nitrate could achieve a growth and nitrogen accumulation comparable to their parental N₂-fixing cv. Finale. In the cv. Finale, nodule number, nodule dry mass accumulation, total C₂H₂-reducing activity of nodulated roots (TAR) and estimated N₂ fixation were considerably inhibited at 5.0 and 10.0 mM root medium NO₃ ^- concentrations. In contrast a 0.63 mM level stimulated both the nodule dry mass and TAR. The cv. Finale N₂-fixing plants grown on 0 to 2.5 mM NO₃ ^- levels had higher shoot N concentrations than the Nod^- mutants, but within the 5.0 to 10.0 mM levels the Nod^- mutants approached or even overtopped the N concentration of the cv. Finale plants. Compared with a high positive correlation found in the Nod^- mutants, shoot N concentration in the cv. Finale was negatively correlated with the root medium NO₃ ^- concentration. The pattern of nitrogen content in shoot dry mass was very similar to that seen in the shoot dry mass accumulation. The Nod^- mutants grown on the 5.0 and/or 10.0 mM NO₃ ^- level had plant dry mass, shoot nitrogen concentration, shoot nitrogen content, and root/shoot dry mass ratio comparable with those of the nodulating cv. Finale grown on the same nitrate levels.

Chickpea (Cicer arietinum L. cv. 235) plants were grown in sand culture at moisture equal to 45-50% of sand saturation capacity under greenhouse conditions. 60 d after sowing, pots were divided into four lots, leaving one as control and sand moisture content of others was brought to 25-30% (S₁), 12-15% (S₂) and 5-6% (S₃) of sand saturation capacity, by withholding the water supply and then maintaining the required levels gravimetrically till the harvest. Relative water content of leaves and nodule water content were measured as indices of water stress. With increase in the severity and duration of water stress nitrogenase activity and nitrogen and leghemoglobin content of the nodules decreased and the ratio of leghemoglobin components I and II were changed. Nodules developed under limited water availability showed decreased branching, breakdown of the endodermis, greater compactness and decreased vacuolation of cells in the central symbiotic tissue as compared to the control.

The effects of nitrogen applied at increasing levels of 0, 4, 8, 16 and 32 mM N (KNO₃ or NH₄Cl) were studied in faba bean (Vicia faba) nodulated byRhizobium leguminosarum bv.viceae RCR lool. Nitrogenase activity was higher at 4 and 8 mM N than the zero N treatment (control), but 16 and 32 mM N significantly reduced the efficiency of nodule functions. Nitrate reductase activities (NRA) of leaves, stems, roots, nodules and nodule fractions (bacteroid and cytosol) were increased with rising the NO₃ ^- or NH₄ ⁺ levels. NRA decreased in the order of nodules>leaves>stems>roots. Cytosolic NR was markedly higher than that recorded in the bacteroid fractions. Nitrate levels were linearly correlated to NRA of nodules. Accumulation of NO₂ ^- within nodules suggests that NO₂ ^- inhibits nodule's activity after feeding plants with NO₃ ^- or NH₄ ⁺.

Agrobacterium tumefaciens induced transgenosis by treatment of germinatingArabidopsis thaliana seed embryos has been achieved with differentAgrobacterium strains including the strain LBA4404, which was ineffective in seed transformation experiments of the other authors. The frequency of transgenosis was increased several times by application of acetosyringone to the growingA. tumefaciens suspension cultures. The DNA demethylating agent 5-azacytidine partly restored the distorted Mendelian segregation ratios in the offspring of transgenic plants.

A simple equipment was developed to cultivate young cereal plants under enhanced CO₂ concentration. Cultivation system permits growing of about 40 barley seedlings for about 2 to 3 weeks. The system consists of two identical growth chambers (volume about 30 dm³), gas conditioning circuit and measuring circuit with an infra-red CO₂ analyser. Capabilities of the whole equipment were tested by growing barley plants under 330 and 1000 cm³ (CO₂)m^-3 and in combination with high or low nitrate level.

Decapitated pending vines are the most responsive parts of vanilla plants. Inflorescence localization along training vines showed a decreasing gradient from the decapitated end to the base in sun locality and was irregular and showed opposite gradient in shade locality. Soluble and ionic peroxidase activities, determined in the leaves and in the internodes, showed a marked peak during the end of June and a gradient along training vines which was inverse to the gradient of inflorescence localization and opposite between sun or shade conditions, supporting the utility of peroxidases as spatial and temporal biochemical markers of flowering processes.

Esterase isoenzyme spectra of different organs of seedlings and field-grown plants of fiber flax (Linum usitatissimum L., cv. Belinka) were studied by electrophoresis in polyacrylamide gel for estimating ontogenetic variability of gene expression. Formation of individual isoesterases depended on the type of tissue and the stage of its development. Isoesterases characteristic of exclusively one or some tissues of the same developmental stage were revealed simultaneously with basic esterase isoforms active in all analysed parts of seeds, seedlings and field-grown plants. The revealed changes of esterase isoenzyme spectrum during germination show tissue and time specificity of the endogenous regulation of genes controlling their formation.

Plants regenerated from callus cultures derived from leaf discs and mesophyll protoplasts ofPetunia hybrida cv. Rose of Heaven exhibit a high frequency of genetic and chromosomal variation. Of twelve leaf disc-derived plants examined, only three had the normal diploid chromosome number (2n=14) while seven were tetraploid and two were aneuploid (16 and 27 chromosomes). Of seventeen plants derived from two protoplasts, none had the diploid chromosome number. Most had 28 chromosomes, one 29, two 27, one 26 and one had variable numbers (14-28) in different root tip cells. In all cases aneuploidy was associated with developmental abnormality. In addition, heritable differences in growth, morphology and flower pigmentation were observed in callus-derived tetraploids and diploids, including one diploid which differed from parent plants in at least four characters. These results are discussed in terms of the importance ofPetunia in genetics research and for studies of somaclonal variation.

The interaction between native and introduced fungi and their effect on plant growth and mineral uptake were studied. The host plants wereLygeum spartum andAnthyllis cytisoides, the introduced fungus wasGlomus fasciculatum. The four soils used were selected from disturbed and contaminated by mining activities areas. Inoculated and uninoculated plants were grown in the unsterilized and sterilized soils (with and withouth native microflora, respectively). Plants inoculated withG. fasciculatum were higher and had higher tissue P concentration than uninoculated plants, especially inA. cytisoides. However, this inoculation was not effective in unsterilized substrates, suggesting a competition between introduced and native fungi. Concentration of mineral elements other than P varied depending on the host plant and soil. Decrease in Fe, Cu, Mn, Zn and Pb was observed in mycorrhizalA. cytiosides plants and a slight increase in Zn concentration was noted in mycorrhizalL. spartum plants. The study showed that the type of soil and their populations of native endophytes have a considerable effect on plant response to mycorrhizal symbiosis, especially in disturbed soils.

Transpiration rate, stomatal frequency, growth, contents of pigments, saccharides, total nitrogen, proteins and some nutritive elements (K, Ca, Mg, P) of radish plants were significantly lowere dwith the rise in salinization levels using NaCl. Spraying radish shoots with proline solution (200 g m-³) counteracted the above adverse effects, especially at low and moderate salinity.

The C₄ speciesFlaveria trinervia is obviously better adapted to saline environments than the C₃ speciesF. pringlei. Treatment with 100 mM NaCl diminished crop growth rate inF. pringlei by 38% but not inF. trinervia. Under saline conditions, more assimilates were invested in leaf growth inF. trinervia but not inF. pringlei. Electrolyte concentration inF. trinervia in control and salt treated plants is lower than inF. pringlei. Fluorescence data do not indicate a damage of PS 2 charge separation in both species. Whether the C₄ photosynthetic pathway inF. trinervia is responsible for the improved salt tolerance compared toF. pringlei remains an open question.

In six rice cultivars the relative amounts of 55, 26-28 and 15 kDa polypeptides were mostly lower in plants grown for 15 d under low irradiance than in plants grown under saturating irradiance. This decline in the polypeptides, especially in those related to light-harvesting chlorophyll proteins, was accompanied with a decrease in the whole chain electron transport and the photosystem 2 activity.

The content of lead in greening etiolated barley leaves remained the same, regardless the time of incubation of excised leaves in the presence of lead ions (8-24 h). The lead deposits have not been detected within mesophyll cells, but were found in intercellular spaces of mesophyll, in guard cells and in cuticle covering stomata. This suggests that lead may be transported in the leavesvia transpiration stream. Lead reduced the content of chlorophyll, especially chlorophyllb content and the average number of grana, whereas in the presence of kinetin the content of chlorophyll increased. In the combined treatment (lead + kinetin) kinetin diminished the inhibitory effect of lead on the chlorophyll content. The number of chloroplasts in mesophyll cells remained unchanged after lead treatment, whereas kinetin alone or applied together with lead increased the average chloroplasts number. The thylakoids system in chloroplasts of kinetin and kinetin + lead treated plants was similar to that observed in control, although the grana number was smaller. Both lead and kinetin increased the content of condensed chromatin in nuclei.

The effects of salinity (0, 50, 100, 150, and 200 mM NaCl) and heat-shock (42°C) and their interactions on germination, seedling growth, and some relevant metabolic changes of two cultivars (cv. Giza 155 and cv. Stork) of wheat (Triticum vulgaris L.) were studied. Germination studies indicate that plants tolerated salinity up to 100 mM NaCl. The lengths of roots and shoots and their water content, as well as fresh and dry matter yield of cv. Giza 155 seedlings remained more or less unchanged up to 100 mM NaCl and of cv. Stork up to 50 mM NaCl. Salinity induced progressive increase in soluble carbohydrates, soluble proteins and proline in cv. Giza 155 and in soluble proteins, proline and other free amino acids in cv. Stork. However, under the higher salinity levels, in cv. Giza 155 increase in soluble carbohydrates was accompanied by lose in other free amino acids, whereas in cv. Stork an opposite effect was obtained. Heat-shock treatment (42°C for 24 h) induced a significant decrease in the final germination percentage, the shoot and root lengths, fresh matter yield and the water content. The dry matter yield of the two cultivars was considerably increased as compared with the corresponding treatments with NaCl only. Heat-shock treatment resulted in a significant increase, in the amount of soluble carbohydrates and proline in salt treated seedlings of both cultivars. The pattern of changes in amino acids was opposite to that of soluble proteins, indicating that the increase in soluble proteins was at the expense of other amino acids in cv. Giza 155 andvice versa in cv. Stork.

Several factors influencing reliability of the quantitative fluorimetric β-glucuronidase (GUS) assay in transgenic plant tissue have been investigated. We obtained linear dependence of fluorescence on both the duration of hydrolysis and the extract concentration. The stability of the enzyme in the homogenate was fairly high, the same as the stability of the substrate solution and of the final reaction product. The modification of the extraction/incubation buffer was proposed, resulting in several times higher activity in comparison with original procedure.

Interspecific hybrids from the crosses betweenBrassica campestris, B. carinata, B. juncea andB. napus were obtained throughin vitro ovary and ovule culture. F₁ hybrids were studied morphologically and flow cytometry was used to estimate 2C nuclear DNA content both in parentalBrassica species and their hybrids. It was found that in comparison with the A genome, the B and the C genomes ofBrassica contained 26.9 % and 43.9 % more DNA, respectively. This finding may be used to distinguish interspecific hybrids containing various genome combinations. It was concluded that flow cytometric analysis of nuclear DNA content might be useful tool inBrassica breeding.

Parameters of water relations were measured throughout the season in phenologically identical leaves of rose plants grown in a heated greenhouse. The increase in osmotic potential observed from spring to early autumn seems to result from the decrease in the non-osmotic water fraction, and, conversely, its decrease from early autumn to winter seems to be due to an increase in the non-osmotic water fraction. These observations support the hypothesis that the non-osmotic water fraction may be correlated to starch concentration in rose leaves.

The slot-immunobinding assay (SIBA) was adapted for detection of plum pox virus (PPV) and compared with DAS-ELISA. SIBA was easy to perform and as sensitive as DAS-ELISA in detection of various PPV isolates in herbaceous and woody plants, but not in aphids (Myzus persicae).

The accumulation of nitrogen and potassium by plant cells at undesirable concentrations manifests itself in changes in the osmotic phenomenon and finally in the transport process. Temperature gradient is another factor influencing the transport phenomenon. We have followed the changes in the electric diffusion potential and the heat transfer under the influence of these two factors on transport properties of roots of plants grown under conditions of either salinity or nutrient deficiency on the transport of KG solution through segments of the first node roots and of the primary root. Physical causes of the accumulation of the above mentioned ions were then studied by means of a mathematical model. The results obtained showed that high KNO₃ concentration in nutrient solution caused an inhibition of volume and heat flows, stimulated osmotic flow, and reduced electrical polarization of root cells. Cell polarization was slowed down when temperature gradient was increasing and enhanced when temperature gradient was decreasing. This indicates that the pressure difference between the exterior and the interior of root cells was levelled off by osmotic water flow but not by potassium ion flow.

There exist two main mechanisms of allelopathy: 1) direct transfer of metabolites between neighbouring plants during their life and 2) accumulation and transformation of bioactive substances in the environment with their subsequent influence on higher plants. The latter mechanism is similar to that causing soil sickness or soil toxicity. Allelochemicals affect all functions of the living system: photosynthesis, respiration, mineral nutrition, transpiration, immunity, and growth. The initial biochemical effect of allelochemicals seems to be on the synthesis of protein mediated by RNA/DNA. Knowledge of the mechanisms of concrete signals during realization of hereditary codes would serve as a powerful tool for the improvement of crop plant development and productivity.

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.

A low activity of peroxidase (POD, EC 1.11.1.7) was found in crude extracts fromin vitro plants ofSyngonium podophyllum cv. Butterfly sealed in the multiplication vessels. Removal of the lids from the vessels increased the POD activity. A greater increase in the POD activity was measured whenin vitro plants were transplanted into a weaning growth medium. The POD activity was further promoted by removal of the phenolic substances from the extracts by polyvinyl-polypyrrolidone (PVPP).

Growth parameters (leaf area, length of shoot and root, water content and dry matter accumulation), contents of reducing sugars and saccharose as well as activities of α- and β-amylases of castor bean and maize seedlings and adult plants supplemented with 0.5 μg g^-1 and 2.5 μg g^-1 of metribuzin either alone or in combination with 50 μg g^-1 NaCl, were increased significantly whereas at high concentrations (5 and 10 μg g^-1) of herbicide, an opposite response was apparent. On the other hand, polysaccharide content and invertase activity of castor bean and maize seedlings and adult plants were significantly decreased in response to low concentrations (0.5 and 2.5 μg g^-1) of metribuzin and increased significantly at high concentrations (5 and 10 μg g^-1) of the herbicide either alone or in combination with 50 μg g^-1 NaCl. Total carbohydrate contents of castor bean and maize seedlings and whole plants treated with herbicide either alone or in combination with NaCl did not change significantly. Growth parameters, carbohydrate fractions contents and activities of enzymes in both castor bean and maize seedlings and whole plants treated with herbicide alone were consistently higher than those values detected in plants treated with herbicide in combination with NaCl.

Hypocotyls of seedling plants of the sunflower inbred line HNK-81 were used as a source of protoplasts. Optimal conditions of isolation and culture of protoplasts were established. Using the method of individual culture in microdrops, a 77% final plating efficiency was achieved. Cytokinins, especially zeatin, showed a significant influence on the formation of globular embryo-like structures, but these failed to develop into mature embryos. Calli obtained in liquid media containing auxins and cytokinins grew on agar solidified media without growth regulators.

InAlysicarpus vaginalis (L.) DC. nitrogen, ascorbic acid, proline and epicuticular wax (ECW) contents were higher in the plants growing in the coastal region whereas the protein, soluble sugars and starch contents were lower. The higher contents of proline, nitrogen and ascorbic acid recorded in the plants of the saline habitat are a physiological adaptation to overcome the salt stress. The higher ECW content in the plants of the saline habitat specially in the summer months seems to be an adaptation in these plants to survive in the saline habitat.

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.

Changes in the content and subcellular localization of ribonuclease isoenzymes were determined in mesophyll protoplasts prepared fromNicotiana tabacum L. cv. Samsun from healthy and potato virus Y (PVY) infected plants. Intact chloroplasts, mitochondria and soluble cytosolic proteins were obtained after protoplast disintegration by means of differential centrifugation. The 1 000g pellet from healthy protoplasts contained 7.3 %, the 15 000g pellet 13.5 % and 15 000g supernatant 82.1 % of the total activity of ribonucleases. The 1 000g pellet from infected protoplasts contained 10.4%, the 15 000g pellet 10.0% and 15 000g supernatant 89.6 % of the total activity of ribonucleases. The activity of these enzymes in infected protoplasts was enhanced in crude homogenate to 137.0 % (P<0.001), in 1 000g pellet to 194.8 % (P<0.001), in 15 000g pellet to 101.3 % (NS), and in 15 000g supernatant to 149.4 % (P<0.001) of that in healthy noninoculated protoplasts.