The effect of high concentrations of the simplest polyphenols on extension growth of maize (Zea mays L.) shoot ooleoptile segments, lettuce (Lactuca sativa L.) roots, and on radish (Raphanus sativus L.) seed germination, was studied. Quinone formation in the process of plant incubation in polyphenol solutions was proved. The data obtained are presumably explained by the important part that is played by the quinoid products of phenol oxidation in the ability ofo- andp-biatomic phenols to inhibit growth.

Chlorflurenol (morphactin) EMD 7301 W (60, 120 and 240 mg I^-1) when applied at five to seven leaf and 10-12 leaf stage induced hermaphrodite flowers in the inflorescences ofRicinus communis. The hermaphrodite flowers were mostly apical in position unlike the apical female flower in the control. With an increase in the time gap between sowing and emergence of the inflorescence there was a reduction of the female structures in the hermaphrodite flowers. The last formed inflorescences had an apical male flower in place of a female. The largest number of inflorescences with an apical male or hermaphrodite flower were produced with 60 mg 1^-1 applied at five to seven leaf stage. The hermaphrodite flowers failed to set fruits.

Preparations of total DNA isolated from algal cells ofChlamydomonas geitleri were characterized by routine methods (UV-spectra, thermal denaturation, sedimentation analysis, centrifugation in CsCl density gradients). In this way, the fundamental physicochemical characteristics, undetermined for this alga up to now, have been attained.
The comparison of the characteristics of the preparations of DNA showed that during isolation it was more convenient to prefer procedures that use the lysis of cells. A mechanical disintegration may sometimes lead to the degradation of the macromolecules of DNA.
The ascertained characteristics of DNA in the alga under study are compared here with the corresponding values of DNA known for the most widely studied volvocal algaChlamydomonas reinhardii as well as for other species of green algae. The greatest difference between the two species comparcd was in the contents of bases G + C. The determined values inChlamydomonas geitleri from 43.4 to 45.4 mol.% are much lower than the values known inChlamydomonas reinhardii (about 65.5 mol.%) or those published for some volvocal algae (60 to 68 mol.%).

The adaptation of Marmur's method, suitable for DNA isolation from plant cell culture, is described.

The effect of nystatin on the fresh-water algaHydrodictyon reticulatum was studied by estimating the electrical resistance of both the membranes and the intracellular fluid. The outflow of potassium ions into the external medium, occurring after addition of nystatin, was determined by flame photometry.
Values of ohmic resistance of membranes treated with nystatin ranged from 0.33 to 1.51 kΩcm², the control values being 8.03-16.73 kΩcm². Values of the resistance of intracellular fluid in nystatin-treated cells lay in the range of 3.21-7.13 kΩcm, those of control cells being 1.10 to 1.91 kΩcm.
The concentration of potassium ions in the external medium increased from 1.35 mM to 4.3 mM after addition of nystatin.

The effects of different osmotic stresses (from 0 to -8× 10⁵ Pa) obtained with NaC or polyethylene glycol 6000 solutions on the germination of flax, sesame and onion seeds were investigated. The effect of presoaking with gibberellic acid (GA³) on the germination of the above mentioned seeds was also studied.
It was found that the rate of seed germination and the final germination percentages as well as the amount of water absorbed by the seeds were considerably lowered with the rise of osmotic stress levels whatever the stress agent used, more considerable reduction was obtained under polyethylene glycol 6000 than under NaCl.
Presoaking with gibberellic acid increased the rate and the final germination percentage of osmotically stressed flax and sesame seeds, while those of stressed onion seeds were slightly retarded.

Chloramphenicol has been found to inhibit nitrate reductase activity in black-gram leaves. It inhibitsin vivo nitrate reductase activity up to 50-67%, and the catalytic property of the enzyme up to a maximum of 70-98%. Modulators, such as KNO₃, NADH and HCO₃ could not protect enzyme inhibition by chloramphenicol. It is suggested that the chloramphenicol inhibition is mainly through its effect on the catalytic process of the enzyme.

The radial transport of organic nitrogen compounds was studied in maize seedling roots in relation to the metabolism of uniformly labelled¹⁴C-amino acids (alanine, arginine, dicarboxylic amino acids and their amides) in the cortex zone. Most active metabolism accompanying transport to the stele was observed for¹⁴C-glutamic acid of "primary" amino acids and for¹⁴C-glutamine of "reserve" nitrogen sources. The transport of¹⁴C-asparagine and¹⁴C-arginine to the conducting bundles is accompanied by weak metabolism. A distinguishing feature of nitrogen metabolism in the stele is intensive decarboxylation of glutamic acid, formed in the course of radial transport and metabolism, to gamma-amino butyric acid. This process is assisted by a highly active glutamate decarboxylase present in the conducting bundles.

Sap flow rate and transpiration dynamics were studied in the course of 3 years in a dominant tree species in the floodplain forest,i.e. in the full-grown oak (Quercus robur L.) tree, using the method of trunk heat balance devised by the authors. The investigations were carried out at a period at which regular and marked fluctuation in a relatively high water table usually occurred, culminating in seasonal flooding. High sap flow rate values in the tree were established under conditions of non-limiting water supply in soil (up to 400 kg per day or up to 39 000 kg per vegetation period) and characteristic daily flow curves (rounded with a large amplitude and with the maximum at noon), corresponding to those described theoretically. Relationships were inferred by means of which tree water consumption can be calculated under these conditions on the basis of data measured at meteorological stations. From these equations it follows that the transpiration of the tree canopy amounted to 80% of the potential evapotranspiration. The amount of the used daily tree water reserve was assessed to be 0.4 mm in the seasonal average. The transpiration coefficient reached in climatically distinct years the values of 400 to 700 of the increase in tree dry matter. The area of the so-called effective tree-crown ground plan approximated to the area determined geodetically. The results obtained are useful for both ecophysiological and hydrological studies. Some of the described procedures are convenient for the evaluation of functional tree dimensions and according to them also of the forest stand structure.

Effects of Na₂CO₃ and NaHCO₃ at equal conductivities (2, 4 and 6 S cm^-1) on germination, seedling growth and some metabolites were studied in two cultivars of green gram (Phaseolus aureus Roxb. cv. Varsha and cv. Pusa Baiskhi) in Petri dishes and sand culture. With increasing conductivity both the salts depressed germination, length of shoot and root and their mass. NaHCO₃ was more depressiv than Na₂CO₃. The contents of chlorophyll, RNA, protein and free amino acids were higher and affected to a lesser extent under salt stress in leaves of cv. Varsha than cv. Pusa Baiskhi. Cv. Pusa Baiskhi was generally more susceptible to salt stress than cv. Varsha.

The stomata and their behaviour towards neutral red uptake in a few arid zone plant species under stress conditions have been inve stigated. Variable patterns of accumulation or non-accumulation and retention of this vital dye, by various cells of leaf epidermis have been observed. The neutral red uptake by the cells of the epidermal strip, coalescence of particles and their movement appear to be connected with the open/closed condition of the stomata.

In an experiment with native maize roots depending on different phosphorus concentration in the external solution (0.001 … 50 mM P), the multiphasic character of the kinetics of phosphate uptake has been stated. The single phases are characterized by the different values of K_m and V_max. In the wide range of concentrations the isotherm of the phosphate uptake has five evident phases. The character of kinetics for the uptake of phosphate is analogical to the kinetics of the enzymatic reactions described by the Michaelis-Menten equation. On the other hand the linear dependence for the inactivated root was determined,i.e. the uptake of phosphate versus different phosphorus concentration in the external solution.
The graphic representation of the logarithmic values for the phosphorus taken up versus the different phosphorus concentration in the external solution gives the biphasic course including concentration less than 1.0 mM P and more than 1.0 mM P. Within the framework of the concentration range the following values of V_max, K_m and ϕ_in were calculated under the conditions if the concentration of phosphorus is less than 1.0mMP: V_max = 1.705 μmol P × g^-1h^-1, K_m = 0.057 mM P and ϕ_in = 0.83,i.e. if the concentration of phosphorus is more than 1.0mM P: V_max = 40 μmol P × g^-1 h^-1, K_m = 16.66 mM and ϕ_in = 20.
According to these results, the phosphate concentration in the external solution influences the activity of the transport mechanisms concerning their conformative changes which discretely change their working regime of membrane transport. This is also demonstrated in the change of values V_max, K_m and ϕ_in.

The inhibitive growth-correlative effect of cotyledons of pea seedlings decreases during their ontogenesis till the age of 14 days. This decrease is associated with an increase in the level of endogenous cytokinins on the one hand and a decrease of endogenous IAA on the other. This is in harmony with the fact that the correlative-inhibiting effect of pea cotyledon upon the growth of its axillary bud can be weakened by exogenous cytokinin and amplified by exogenous IAA.

The action of light on protein synthesis was examined in the cabbage seedlings, a system extensively used in the studies of anthocyanin synthesis. Continuous red and far red light have no effect on total protein content while they cause a marked decrease in the level of free amino acids in cabbage seedlings. The rate of protein synthesis, measured as incorporation of radioaetively-labelled amino acids into proteins, is clearly stimulated by light. Phytochrome involvement in the light stimulation of the incorporation is also demonstrated by the red-far red reversibility of the response. The relative effectiveness of continuous red and far red light upon the incorporation of amino acids into proteins is affected by the nature of the system used to study the incorporation process. When excised cotyledons and short period of incorporation were used, continuous far red was more effective than red. However, when whole seedlings and long period of incorporation were used, red and far red were equally effective. Streptomycin causes a 10- 15% decrease in the rate of incorporation of amino acids into proteins of all cellular fractions, except the plastid fraction where a much higher inhibition (30%) was observed.

Macromolecule syntheses, especially incorporation of radioactive labelled precursors into proteins, RNA and DNA were investigated. Some results on the action of phytohormones applied to dormant seeds and on the influence on water stress conditions by interruption of imbibition even before the radicle protrudes, on germination as well as on RNA and DNA synthesis were analysed. Benzylaminopurine and ethylene, applied in combination, could break dormancy of dormant seeds; a process which is correlated with the onset of DNA synthesis. Interruption of the imbibition during the time of onset of DNA synthesis (after 16 h of imbibition) did not impair the germination, and the protein, RNA and DNA syntheses started after reimbibition at that level which was reached at the interruption point. Only after a break in later phases (after 22 h of imbibition) a weak impairment of germination could be observed.

In the present paper we deal with the possibility of morphogenesis induction in callus tissue cultures of some representatives ofMatricaria andAchillea species. Shoot regeneration from calli ofMatricaria chamomilla andM. inodora has been induced by 0.1 mg l^-1 kinetin or by combination of 0.5 mg l^-1 kinetin and 0.5 mg l^-1 NAA added to Murashige-Skoog culture medium. Rhizogenesis took place without any other addition of auxin. In callus tissue cultures ofAchillea ptarmica cultivated on Murashige-Skoog medium with 1 mg l^-1 2,4-D after a year long cultivation the whole plant has been regenerated without any change of nutrient requirements. In callus tissue ofA. nobilis under the same conditions only roots wore regenerated.

Four soybean cultivars differing in storage potential were subjected to accelerated aging for different periods (2, 4, 6 and 8 days) and tested for germinability and beta-amylase activity. Aging caused a considerable and continuous increase in enzyme activity in both cotyledons and axes of all the four cultivars.

Two isolectins were isolated from the albumin fraction ofArtocarpus integrifolia L. seeds, by precipitation with ammonium sulfate, and DEAE-cellulose and SP-Sephadex C-50 chromatography. The isolectins, when passed through Sephadex G-100 at pH 7.4, had a molecular mass of 43 000 and when subjected to SDS electrophoresis in the presence of β-mercaptoethanol consisted of two subunits with molecular mass of 11 250 and 15 000. When they were tested with human erythrocytes of all the groups of the ABO system there was no blood specificity. The isolectins formed interference arcs by Ouchterlony double diffusion in agarose gel.

It was found that the greatest dehydration rate of detached leaves indicates theTriticum monococcum L. v.vulgare (2n = 14). The indol-3-Acetic acid distinctly decreases the dehydration rate of detached leaves of examined wheat with a different ploidy level (Triticum monococcum, Triticum dicoccum, Triticum spelta andTriticum aestivum).

The increased activity of GOT (E.C.2.6.1.1.) and GPT (E.C.2.6.1.2.) transaminases in maize seedlings found as a marker of genotype opaque-2, was investigated in extirped sprouts of both genotypes, normal and opaque-2. The enzymatic activity was determined in three maize samples from breeding experiments, each sample consisting of a genotype pair, normal and opaque-2, collected from segregating ears of maize plants in the S₁ generation. The seedlings were aseptically grown for 7 days in two variants of cultivation, intact seedlings and sprouts extirped after 4 days of germination.
In the intact seedlings of genotype opaque-2 an increased activity of GOT and GPT, as compared to the intact normal plants, was observed. The extirpation of the sprouts enhanced GOT and GPT activity in the sprouts of both genotypes. However, in extirped sprouts the GOT and GPT activity was found to be still higher in the genotype opaque-2 as compared with the sprouts of normal genotype. Thus it seems that the increased transaminase activity in the sprouts of genotype opaque-2 is genetically determined. The increase does not result from an induction of enzyme synthesis through the supply of amino acids translocated from the endosperm to the sprouts. The absolute level of transaminases in the different breeding samples is dependent on the parenteral lines, the relative level of GOT and GPT activities is higher in the genotype opaque-2.