The ribulose 1,5-bisphosphate activity and its relative content in pea (Pisum sativum L., cv. Bordi) seedlings grown either under white or red light were investigated. Plants grown under red light had a lower ribulose 1,5- bisphosphate carboxylase (RuBPCO) activity as compared to plants grown under white light, if expressed on a fresh mass. These activities were very similar under both lights, as calculated on protein basis, although the relative content of RuBPCO was higher in the red one. The activity of RuBPCO under red light corresponds to the lower rate of net photosynthesis. The results are discussed in respect to possible presence of RuBPCO inhibitor in pea plants growth under red light.

Cotyledons ofXanthium strumarium, organs with low sensitivity to photoperiodic treatment show a higher free indol-3-ylacetic acid level (by about 35 %) than the first pair leaves, organs with high sensitivity to photoperiodic treatment. This was seen in plants of three different age groups : A. with the first pair of leaves of 15-20 mm in length; B. with the first pair of leaves having finished their growth and C. with the third leaf of 30-40 mm in length.
Changes in free IAA level during the inductive dark period were similar in both cotyledons and leaves of the first pair. The level of IAA rose in the first half of the dark period, began to decrease in the latter half, reaching nearly initial level at its end.
Application of IAA (10^-4 - 10^-2M) to the cotyledons reduced their already low photoperiodic sensitivity resulting in inhibition of flowering (almost 70 % using 10^-4M IAA).
Elevated free IAA level is assumed to be one of the causal factors of low photoperiodic sensitivity of cotyledons.

Decrease in leaf irradiance to 50 % due to shading of plants in glasshouse only during clear summer days did not induce significant changes in growth parameters, characteristics of water relations and epidermal conductance of two cyclamen cultivars. Thus the possibility of acclimation of plants to non-stable changes in environmental conditions was not proved.

Leaves of drought-resistant and drought-sensitive genotypes of maize (Zea mays L.) were sprayed with ethephon to determine its effect on water and osmotic potentials. With both sufficient and limited water supplies, ethephon decreased the water potential, but not the osmotic potential, of the drought-sensitive maize. It had no effect on the water and osmotic potentials of the drought-resistant maize under either water regime. The results showed that the response of a genotype of maize to ethephon depends upon its susceptibility to drought.

The contet of phenols, o-dihydroxyphenols and peroxidase activity in healthy andCurvularia andropogonis (Zimm.) Boedijn infected leaves ofJava citronella were determined. As a result of infection, the content of phenols and peroxidase increased two- and four-fold, respectively in necrotic lesions compared to healthy leaves. In surrounding tissue of lesions, their increase was one-and half fold only. The peroxidase activity decreased with the maturity of the necrotic lesions. Necrotic lesions produced in response to infection appear to be the consequence of higher accumulation of phenols and their oxidation by peroxidase.

Potassium (K⁺) and nitrogen (N) supply affect stomatal apertures within the daylength conditions. There is a negative proportion between potassium supply and stomatal pore area: the smallest pores were to be found in the plants with K⁺ surplus, whereas the plants in K⁺ shortage had the largest pores. This is interpreted as a reaction of the plant to get more ions by an increased transpiration stream. With different nitrogen concentrations in the supply solution a similar proportion could be found, with the exception of the condition "N shortage in shortday", and further testing is necessary. The ionic supply has a parallel effect in both daylengths.

Arabidopsis thaliana tumors were induced by octopine strain ofAgrobacterium tumefaciens B6S3 and its derivatives with modified T-DNA. Flowering shoots appeared sponta-neously onin vitro cultivated tumors and set seeds. R₁ and R₂ progeny of octopine synthesizing plants segregated in opine synthesis activities 3:1 and 15:1. Octopine synthase activity showed absolute linkage with agropine synthesis in most lines. In R₃ and R₄ progenies, the fraction of octopine synthase and agropine synthesis positive plants was lower than expected, but Mendelian segregation was restored if plants were cultivated on medium with 5-azacytidine. The most probable mechanism of disapearance of opine synthesis is cytosine methylation. The effect of 5-azacytidine lasted for at least next two generations.

Samples of the same kind (rape leaves, wheat crowns, onion bulbs or spruce needles) killed by a slow freeze-thaw cycle or by immersion in liquid nitrogen showed a similar time course of leakage. Leakage was accelerated in treatments when the sample, immersed in water, was killed by heating for 5, 15 or 30 min in a boiling water bath. The longer the boiling, the sooner the maximum conductivity (L_km) was obtained. The L_km did not depend on the way of killing but in samples killed by freezing, it was achieved after a longer leakage time. The leakage rate decreased from onion to rape, wheat and spruce. The relative conductivity [%] allowed a better comparison of various treatments and of samples of different kinds of tissues than the specific conductivity [μS cm^-1].

Callus cultures were initiated from the bud apices of 10-40-year-old Scots pines (Pinus sylvestris L.) at different seasons and maintained on modified MS medium without subculturing. Separate sets of experiments were used for analyses of carbohydrate content, ethylene production, amino acid composition, protein patterns andin vitro translation. In each case the change in the colour of the calli was recorded and the fresh mass of the samples measured. The onset of tissue browning was found to be associated with changes in protein pattern, amino acid content, ethylene production and the occurrence of sucrose and accumulation of starch.In vitro translation experiments using poIy(A)⁺ RNA isolated and purified from the calli indicated that the switch in metabolism accompanying browning is paralleled by activated protein synthesis. Thus, the development of brown colour does not as such seem to be harmful to the tissue. The later, more intense tissue browning and deterioration which is reflected in a reduced capacity for protein synthesis and changes in the free amino acid pool and protein pattern is probably a secondary phenomenon.

The effect of water stress induced by application of polyethylene glycol 6000 during seed germination and seedling growth ofOryza sativa L. cv. IAC 165 was analysed. The seed germination was inhibited by the decrease in the water potential of the medium, the inhibition being greater under white light than under continuous darkness. When the seedling was submitted to water stress (-0.51 MPa) white light inhibited growth of root, coleoptile-and leaf, while under no stress conditions white light caused increase in growth of root and leaf and only inhibition of coleoptile growth.

The content of auxin-, inhibitors-and gibberellin-like substances in freeze-dried humic acids was studied. The results indicate the existence of growth-promoting substances in humic acids, possibly corresponding to IAA or its precursors. Inhibitory activity is more marked during germination than during the growth process. The inhibitory effect caused by high concentration of humic acids could be due to an auxin-like action rather than an input per se of growth inhibitors. A significant amount of both free and conjugated gibberellin-like substances were observed.

Aminopeptidase, carboxypeptidase and proteinase activities were measured in endosperms from unripe and ripe seeds of ×Haynaldoticum sardoum. Aminopeptidase and proteinase activities were high during the early maturation stages and then decreased. In contrast, carboxypeptidase activity increased with maturation.
Localization studies demonstrated that aminopeptidase and carboxypeptidase activities were present in the three tissues examined (pericarp, green layer plus aleurone, and starchy endosperm). Proteinase activity against gliadin was located in the pericarp and in the green layer plus aleurone, but was absent in the starchy endosperm.
The presence of proteolytic activities in the outer kernel layers might be correlated to the hydrolysis of transitory protein reserves during the senescence of the seed coatś.
Aminopeptidase and carboxypeptidase activities located in the starchy endosperm could participate in the breakdown of protein reserves during the early phases of seed germination.

The equilibrium density of chloroplasts from barley (Hordeum vulgare L. cv. Hassan) was analyzed by sucrose gradient centrifugation. Natural and detachment-induced leaf senescence were associated with a decrease in density and an increase in heterogeneity of the chloroplast population. Treatments (with growth regulators and light) which retarded or accelerated senescence, respectively, retarded or accelerated chloroplast density decrease. Accelerators as well as retardants of senescence decreased the heterogeneity of the chloroplast population.

Influx and efflux of inorganic phosphate was determined in freshly cut and "aged" slices of sweet potato tubers, in the presence or absence of abscisic acid. Slices aged in the phytohormone took up considerably less phosphate than did the control slices. No difference in the rates of uptake of phosphate by the fresh tissue was observed. Kinetics of uptake of the aged untreated slices, proved to be bi-phasic. This was not the case for the treated slices. Neither the treated nor the untreated uptake curves for the fresh slices were bi-phasic. Efflux of phosphate from the slices aged in abscisic acid was greater than from the untreated slices. The results strongly suggest an effect of abscisic acid on the cell membrane.

Regeneration abilities of buds on shoot segment explants isolated from adult trees of oak (Quercus robur), aspen (Populus tremula), black locust (Robinia pseudacacia), Japan pagoda tree (Sophora japonica), and English walnut (Ailanthus glandulosa) were studied during the growing season. Optimum BAP concentrations for the regeneration of oak bud meristems were dependent on the date of sampling. Axillary shoots could be induced from winter and summer buds of oak and aspen on Dustan and Short media supplemented with activated charcoal and BAP at concentrations from 0.5 to 2 mg 1^-1. More intensive rooting of segments of newly formed shoots was observed on MS medium diluted to one half and supplemented with 2 % sucrose and 0.2 mg 1^-1 of IBA.Populus tremula formed longer axillary shoots on DS media supplemented with 0.5 mg 1^-1 of BAP and 1 mg 1^-1 of GA₃.
Regeneration capacities of black locust, Japan pagoda tree, and English walnut were higher. In addition to the induction of multiple shoots from buds, shoots could also be obtained from calluses formed on basal segment parts. Asparagine and glutamine at a concentration of 25 mg 1^-1 stimulated the percentage of differentiated stems on callus surface. Inhibitory effects of substances which accumulated in buds in the second half of the growing season could be reduced by means of pulse treatments in 50 mg 1^-1 BAP solutions or using short-term dipping into 0.1 % AgNO₃ solution.

Organogenic callus cultures ofPapaver somniferum L. were studied with the aim of describing the morphology of the callus and observing the changes occurring during differentiation and induction of organogenesis. The morphology of the cells and the formation of meristemoid areas were studied on a light microscopic level. Histological evidence showed that from the inner meristematic centres, protracheal elements are differentiated, from the surface meristematic centres meristemoids are formed and therefrom green leaf-like organoids.

Phaseolus coccineus storage globulins were extracted from mature cotyledons, purified and characterized. Three major proteins were separated. A component showing erythroagglutinating activity was thoroughly purified by thyroglobulin-Sepharose chromatography. The relative molecular masses of the three fractions are Mr = 330, 178, and 500 kDa as determined by polyacrylamide gel electrophoresis (PAGE). They correspond to the proteins found in other systems and classified as phytohaemagglutinin (PHA), vicilin and legumin, respectively. Electrophoretic analyses under denaturating conditions (SDS-PAGE) evidenced the major subunits for the three proteins. Isoelectrofocusing of the isolated proteins indicated a large heterogeneity for vicilin.

The study deals with the effect of indol-3-ylacetic acid (IAA) on endogenous rhythm of flowering inChenopodium rubrum L. ecotype 374. Phase setting of the rhythm and length of its period were not affected, its amplitude decreased or changed insignificantly depending on the time and the site of IAA application. The intervals of significant inhibitory effect of IAA applied to apical buds terminated later than after IAA application to photoreceptive organs. The inhibitory effect did not correlate with the level of IAA uptake. Results obtained support the hypothesis that both photoreceptive organs and apical buds are the sites of inhibitory effect of applied IAA.

In the long-term cultivated callus cultures ofMatricaria recutita L. the identical concentration changes in the biosynthesis of glutathione, glutamate, aspartate, total thiols and proteins were detected within the subculture. The level of oxidized glutathione during the growth of callus culture was low with the highest value 10.66 nmol g^-1 on the 13th day of subculture. The ratio GSH/GSSG which significantly influences the redox processes in a cell, and the activity of glutathione reductase increased from the 8th day. Ascorbate formation was detected on the 17th day, although no relation between the ascorbate synthesis and the concentration of glutathione and glutathione reductase was found.

Continuous treatment with spermidine or 1-aminocyclopropane-1-carboxylic acid stimulated ethylene production and ethylene-forming enzyme activity and accelerated chlorophyll breakdown in detached tobacco leaves. The treatments also induced the production of eleven major acidic pathogenesis-related proteins, which were also produced during the hypersensitive reaction to tobacco necrosis virus. A delay between the onset of the stimulated ethylene increase and the detection of PR-proteins was found; ethylene production was stimulated after a few hours of treatment, whereas one, three and all the eleven PR-proteins were detected by polyacrylamide gel electrophoresis of fluid extracts after 2, 4 and 6 days of treatments, respectively. The possible causal relationship between stimulation of ethylene production and PR-protein accumulation is discussed.

The growth of primordia of marginal buds (marginals) which differentiate on leaf margins is correlatively inhibited on intactBryophyllum crenatum plants. Following leaf isolation, the marginals are released from this correlative inhibition, which process is accompanied within 2 to 10 h after leaf isolation with a decrease in the content of endogenous IAA in the leaf blade. This decrease can be enhanced by transversal cutting of the leaf blade into three parts which also results in enhanced subsequent growth of the marginals. The growth which follows after the release of the marginals from correlative inhibition is accompanied in cut leaf blades with an increased content of endogenous IAA in the period from 12 h to 7 d after leaf isolation when compared with uncut leaf blades. The highest content of endogenous IAA was recorded in the middle section, and the lowest IAA content in the basal section of the leaf blade.