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.

Two cultivars ofCicer arietinum L. with contrasting sensitivities to water stress, cv. C 214 (relatively resistant) and cv. 130 (susceptible) were compared for their protein content and soluble nitrogen (sol-N) under water stress. During water stress shoots of the cv. C 214 showed an increase (over the control) in both protein and sol-N content. The total nitrogen (total-N) also increased in the cv. C 214 while remaining almost unaffected in the cv. G 130. Cultivar C 214 shoots recorded lower protein/sol-N ratios. The results have been discussed in relation to resistance to water stress.

Complexes of water soluble proteins (albumins) were investigated in three cultivarsof Phaseolus vulgaris, viz: Yeltruská Saxa, Vainica Saavegra B, and Krupnaya sakharnaya. The first two cultivars exhibit haemagglutinating activity against rabbit erythrocytes, but have different elution profiles on Sephadex G-100. Their individual peaks have a different subunit composition, as revealed by SDS gel electrophoresis, as well as a different immunoelectrophoretic pattern, although proteins I and II of the specificity Veltruská Saxa are present in both cultivars. The cultivar Krupnaya sakharnaya expressively differs from the preceding lectin cultivars; it has no erythroagglutinating activity, its albumin complex has a high-molecular component, absent in the preceding ones, and has no lectin peak in the region of molecular mass of 100 000 to 200 000. Immunoelectrophoresis gave no evidence of protein I and II of the specificity Veltruská Saxa.

Esterase variation in shoot and root systems of ten-days seedlings of spring barley mutant lines was investigated. By an electrofocusing method it was found that some regions of the esterase activity were specific for the first leaf and for the root system of seedlings. Results showed the absence of close relationships between the morphological and esterase variation. Low negative correlations were only obtained for the root system parameters.

Both root and hypocotyl growths of lettuce, tomato, red cabbage and cucumber were inhibited when the seedlings were grown in Petri dishes together with 1 to 6 fruits ofWashingtonia filifera. This inhibition, in the case of lettuce hypocotyl, was not reversed completely even after the addition of 50 mg l^t-1 GAs. Effect ofW. filifera fruits on the light-induced synthesis of anthocyanin in red cabbage seedlings revealed that the presence of one fruit was enough to reduce the production of anthocyanin three times less than that of control. Water-soluble extract of the fruits when subjected to high temperature increased its growth inhibiting ability several times that of the untreated control.

The paper deals with the distribution of alpha and beta-glucosidases in the germinating pollen grains ofPortulaca grandiflora. Both these enzymes are localized in the pollen wall and the cytoplasmic granules. The latter are distributed throughout the pollen cytoplasm, pollen tube and stigma hair. In non-germinating pollen grains, enzymes are concentrated in the pollen wall. Stigma hair sheaths are completely free from enzymes. The functional significance of these enzymes in the hydrolysis of phenolic glycosides and polysaccharides is discussed.

Root primordia initiate in poplar stems in the secondary growing parts, that is in the parts where the elongation growth is terminated and the leaves are mature. Their initiation is connected with the occurrence of unusual biseriate, rarely multiseriate rays. A small cell group in the secondary phloem is initiated by cell division of the ray. It gradually enlarges by continuing cell division, by the addition of cells adjacent to the cell group and by cambial activity. Thus, a hemispherical root primordium is formed, for which a permanent occurrence of reserve lipids is characteristic. In stems several years old the intraprimordial mitotic activity is rhythmically renewed together with the cambium function renewal. Latent root primordia slightly enlarge with the passing years, whereas mainly the cells localized in their centre divide. Further organization and root histogenesis was not observed either in older root primordia. Adjacent to root primordia, cambial initials produce the secondary xylem elements increasingly. Xylem protuberances are thus formed under root primordia. Primordia initiation is most frequent within the first year of stem development, though they can also initiate in later years.

Ribulose-1,5-bisphosphate carboxylase activity (RuBPC), chlorophyll (chl) and protein (prot) concentrations and chlorophyll/protein (chl/prot) ratios were determined in five differentPopulus clones together with their maximal net CO₂ uptake rates (P_max). A classic reference clone (Populus ×euramericana "Robusta" (Dode) Guinier) was compared with four recently selected euramerican and interamerican crossings. Chl/prot ratio and RuBPC activity varied among the different clones, while chl a/chlb ratio showed only a very low coefficient of variation (1.7%) for the five clones. Poplar clone "Robusta" could be distinguished from the recent faster growing clones based on the different biochemical characteristics. A significant correlation was found between both total chl concentration and chl/prot ratio with P_max for the five clones.

The net photosynthetic rate (F), transpiration rate (Q) and water use efficiency (F/Q) of oilseed rape (Brassica campestris L. cv. Span) was studied under a range of atmospheric conditions by gas exchange techniques. The plants were at the full bloom/pod initiation stage of development at the time of measurement. The environmental conditions consisted of various levels of photosynthetically active radiation (100 to 2800 (μmol m^-2 s^-1 PAK: 400-700 nm), air temperature (10 to 42°C) and vapour pressure deficit (0.7 to 2.1 kPa VPD). The peak values ofF were recorded at 1600 μmol m^-2 s^-1 PAR, 20°C air temperature and 1.2 kPa VPD of air in the chamber.
Q increased with increasing PAR, air temperature and VPD. However, theF/Q remained high and almost constant from 600 to 1600 μmol m^-2 s^-1 PAR, but declined at the low and high photon flux densities.F/Q decreased progressively with increase in air temperature and VPD of air in the chamber.

Protein content, total and specific peroxidase activity and isoperoxidase patterns were determined in crude protein preparations from individual parts of field-grown wheat (Triticum aestivum L., cv. Jubilar). Protein content in roots, leaves, and stalks increased at the beginning of ontogenesis and then decreased from 6th, 9th, and 10th development phase (according to Feekes), respectively. Steady increase of the protein content in the ears was observed.
Highest peroxidase activity was found in the roots; it diminished from the onset of ontogenesis till maturity of the plants. In the leaves and stalks a slight decrease of peroxidase activity till the 10th development phase and then an increase till maturity was found. The ears exhibited a gradual increase of peroxidase activity. The course of specific peroxidase activity was found to be very similar to that of total activity.
Isoperoxidase patterns did not change significantly. In the leaves, a decrease of activity of C₄ and C₅ isoperoxidases was recorded. In the stalks, C l isoenzyme emerged at the end of ontogenesis. A gradual increase of A₁ and A₅ isoperoxidase intensity took place both in the leaves and stalks.

Roots obtained from 4-day maize seedlings were allowed to absorb uniformly labelled¹⁴C-suorose only with their middle part while the apical and basal parts did not contact the medium. The amino acids and their amides produced in the cortex at the expense of nitrates and the¹⁴C-sucrose carbon moved radially to the stele where they were selectively distributed in the polar directions of transport. "Primary" amino acids moved predominantly in the apical direction while amides and basic amino acids were transported mainly in the opposite direction. When the nutrient medium was devoid of nitrogen sources, the amino acids entering the stele from the cortex were transported mostly to the root tip, indicating a significant role of young tissues in consuming organic nitrogen compounds when they are in short supply in the root.

Dependence of the growth of this alga culture on temperature displays a wide interval of temperatures (from 4 °C to 30 °C) and the dependence of the sexual reproduction only a narrow one (from 18 °C to 25 °C). The optimum temperatures for both the processes are not so different (round 23 °C). Dependence of both the processes on irradiance displays a wide interval of irradiances in both eases (from 4 W m^t-2 to 80 W m^t-2 PhAR and higher). The optimum irradiances for these processes are very different (approx. 50 W m^t-2 PhAR for the growth and approx. 10 W m^t-2 PhAR for the sexual reproduction) under the experimental conditions used.

Callus tissues originating fromZea mays root meristem, induced for rhizogenesis callus, meristematic and differentiated maize root cells for isolation of nuclei and acid-soluble chromosomal proteins were used. Cytological investigations proved that rhizogenesis begins with the formation of meristematic centres, followed by root differentiation about 5-12 days after the treatment with α-naphtalene acetic acid (NAA). When applying electrophoresis in 15% polyacrylamide gel, differences between the electrophoretic profiles of acid-soluble chromosomal proteins, isolated from root cells and from callus tissues, were established. The main differences concern histone H1 and probably H4. There are no differences between electrophoretic patterns of acid-soluble chromosomal proteins of nonorganized callus and callus induced for rhizogenesis. The possible explanation of these results is discussed.

The effects of various ammonium salts and amino acids on nitrite reductase (NIR) induction in isolated pea roots cultured in media containing nitrate or nitrite and either exogenous sucrose or no sugar were investigated. Thg aim of these investigations was to determine if the NIR level is subject to end-product control. The results showed that even though some ammonium salts and casamino acids can depress NIR level under certain conditions this inhibition cannot be interpreted in terms of direct end-product inhibition of NIR synthesis because their effects were dependent on the character (anion) and toxicity of the respective ammonium salt, on the presence of exogenous sucrose in the induction medium, and on the inducer of NIR. NH₄HCO₃ inhibited NIR induction at those concentrations which were toxic to the roots, ammonium phosphates hampered NIR induction only in roots exposed to nitrite in media containing sucrose, while casamino acids slightly depressed NIR induction only in roots exposed to nitrate and exogenous sucrose. The results further show that the basal (noninduced) NIR level changes little even under strongly toxic conditions.