The effect of leaf temperature on the post-illumination burst of CO₂ (PIB) in 15 day-old primary bean leaves (Phaseolus vulgaris L.) was studied by means of infrared gas analysis in a closed gas exchange system. The amplitude and kinetic of PIB was different with its own characteristic course for different temperature steps. The temperature optimum for the PIB at 21% O₂ near the carbon dioxide compensation concentration Λ (150 mg m^-3) was 33 °C while that for net photosynthetic rate (P _N) at 21% O₂ and 600 mg m^-3 CO₂ was 24.5 °C. The PIB was observed to 12…33 s after the darkening of leaves. No PIB was observed at 2% O₂. The applicability of PIB as an estimate of photorespiration rateR _p has been proved by comparing it with extrapolation of the relationship betweenP _n and CO₂ concentration to zero.

Alterations in protein pattern were observed in the callus tissues ofVigna unguiculata (L) Walp. up to tenth passage from its initiation. A gradual increase in quantity of protein was found up to sixth passage of culture. Decrease in the quantity of protein after eight months of culture might be correlated with the cytodifferentiation of the tissues. It has been recorded that with the initiation of morphogenesis there is an increase in the number and intensity of protein bands at the anionic end of the polyacrylamide gel.

To induce mutation in tomatillo (Physalis ixocarpa Brot.) commonly grown for its fruit value, seeds were treated with three alkylating agents (dimethyl sulphate, diethyl sulphate and methyl ethane sulphonate) and gamma rays. Seven viable and five chlorophyll mutant types were screened both from M₁ and M₂ generations. The isolated mutant lines are described and evaluated with reference to their beneficial value.

Using differential staining of cell walls the anatomy of microsporogenesis was investigated on cross-sections of anthers of fertile plants of the sweet pepperCapsicum annuum L. cv. Severka, as well as of its sterile analogues. The lignin-like staining as observed in the microsporocyte primary walls of fertile plants disappears with their getting independent in the course of meiosis. On the contrary, in sterile plants the stain increases in intensity, the thick-walled microsporocytes usually form a continuous block up to the period of tetradogenesis, and so far as microspores originate, they are not dissociated outwards. Moreover, in sterile anthers the external tapetum is usually not differentiated.

The changes in cell division rate were studied in different components of the shoot apex ofChenopodium rubrum during short-day photoperiodic induction and after the inductive treatments. Induced and vegetative apices were compared. Accumulation of metaphases by colchicine treatment was used to compare the mean cell cycle duration in different components of the apex. A direct method of evaluating the increase in cell number obtained by anticlinal or periclinal divisions was applied if the corresponding components of induced and non-induced apices had to be compared. The short-day treatment prolonged the cell cycle more in the peripheral zone than in the central zone and still more in the leaf primordia. The importance of changing growth relations for floral transition was shown particularly if the induced plants were compared with the vegetative control with interrupted dark periods. Induced plants transferred to continuous light showed further changes in the rates of cell division. The cell cycle was shortened more in the central zone than in the peripheral zone,i.e. there was a further shift in growth relations within the apical dome. The cell cycle in the leaf and bud primordia was also shortened if compared with the vegetative control, the acceleration being stronger in the bud primordia. There was a subsequent retardation in cell division in the leaf primordia formed during and after the inductive treatment if the plants were fully induced. An inhibition of the oldest bud primordia was observed in fully induced apices, as well.

In biological experiments the ionizing radiation is usually defined by the type, energy and total absorbed dose, as well as by the dose rate. If radiation generated by a physical particle accelerator is employed, we consider it necessary to supplement these data with the value for frequency of pulses of the ionizing radiation jet. As follows from our experiments, this parameter expressively affects the relative biological effect of ionizing radiation.

Relationships between seed protein patterns of 16 species ofArachis were studied by means of immunochemical methods (immunoelectrophoresis and double diffusion). The broad similarity of these patterns suggests that protein patterns are conservative in this genus from an evolutionary viewpoint. The differences which have evolved support recent schemes for classifying the genus, particularly the breakdown into sections. It also suggests thatA. villosa andA. correntina should probably be recognized as distinct species. The strong relationship indicated betweenA. hypogaea andA. batizocoi supports the hypothesis that the latter may be source of one of the genomes ofA. hypogaea. The possibility thatA. cardenasii might be the source of the other genome did not receive such strong positive support.

In two clones ofTradescantia (4430 and 02) differing in the sensitivity to the mutagenic action of alkylating agents, equimolar doses of [¹⁴C] methyl methanesulphonate (MMS) elicited a similar degree of protein, RNA and DNA alkylation and a similar amount of DNA-7-methylguanine and DNA-3-methyladenine in cells of inflorescence. Moreover, in the same clones and tissues the same doses of nonlabelled MMS produced a similar amount of DNA single strand breaks and/or alkali labile sites as measured in alkaline sucrose gradients. None of the DNA lesions followed is therefore decisive for explanation of the different mutagenic sensitivity ofTradescantia clones.

Uptake of phosphate ions by 1 mm segments of isolated maize root cortex layers was studied. Cortex segments (from roots of 8 days old maize plants) absorb phosphate ions from 1 mM KH₂PO₄ in 0.2 mM CaSCO₄ at the average rate of 34.3 ±3.2 μg P_i g^-1 (fr. m.) h^-1,i.e. 0.35± 0.02 μmol P_i g^-1 (fr. m.) h^-1. Phosphate uptake considerably increases after a certain period of "augmentation",i.e. washing in aerated 0.2 mM CaSO₄. This increase is completely blocked by the presence of 10 μg ml^-1 cycloheximide.
The relation of uptake rate to phosphate concentration in the medium was shown to have 3 phases in the concentration range of 0.02 - 40 mM. Transition points were found between 0.8-1 mM and 10-20 mM. Following K_m and V_max values were found: K_m[mM] : 0.37 - 3.82 - 27.67 V_max[μg P_i g^-1 (fr. m.) h^-1] : 3.33 - 39.40 - 66.67
We have found no sharp pH optimum for phosphate uptake. It proceeds at almost constant rate till pH 6.0 and then the uptake rate drops with increasing pH. At low phosphate concentrations (1 mM) the lowest uptake rate was found at 5 and 13 °C, while the uptake is higher at 5 °C than at 13 °C at phosphate concentrations higher than 1 mM. At these concentrations uptake rate at 35 °C is lower than at 25 °C.
Phosphate uptake considerably decreased in anaerobic conditions. DNP and iodoacetate (0.1 mM) completely blocked phosphate uptake from 1 mM KH₂PO₄, while uptake from 5 and 10 mM KH₂PO₄ was left unaffected by these substances. The inhibitors of active - SH groups NEM and PCMB inhibited phosphate uptake: 10^-3 M NEM by 81.6%, 10⁴ M NEM by 42% and 10^-4 M PCMB by 42%.

Supply of KNO₃, NH₄Cl or NH₄NO₃ to the maize seedlings increased total chlorophyll and carotenoids (over zero nitrogen control) amounts per fresh matter unit of the primary leaves. The increase was most apparent when the pigment level in control plants started declining,i.e. between days 14 and 16. Supply of inorganic nitrogen increased pigment synthesis in excised leaf segments from dark grown seedlings, although the increase during a 24 h incubation was not as high as with either glycine or glutamine. Salicylic acid at 0.01 to 1 mM concentration increased and at 10 mM lowered the pigment biosynthesis. The increase at lower concentrations of salicylic acid was unaffected by KNO₃ but it was suppressed by NH₄Cl. When 12-day seedlings were transferred to the dark, total chlorophyll and carotenoids declined appreciably, but the supply of inorganic nitrogen protected them from decline to same extent. Thus inorganic nitrogen, especially the nitrate, is more important in protecting from degradation of chlorophyll and carotenoids than in increasing their biosyntheses.

IsolatedN. tabacum andV. faba protoplasts were used as a model to examine the DNA-fuchsin changes during the dedifferentiationin vitro. Using the pattern recognition method for the evaluation of cytophotometric data obtained we have established: 1) the major fraction of cells of the original tobacco and bean leaf tissue is in G₁-period of the cell cycle; 2) the significant decrease to 1C DNA-fuchsin content in nuclei in the first hours of cultivation and then a reconstitution of 2C pool followed by entering of these cells into S-period of mitotic cycle; 3) only 2% of tobacco and 4% of bean mesophyll cells contain 4C DNA.

The seed protein patterns of 12Arachis species were compared by polyacrylamide gel electrophoresis (PAGE), similarities between patterns were measured by the Jaccard index. Results obtained confirm the close relationships established between members of the genus on morphological grounds and support the more recent classification schemes.A. villosa andA. correntina could well be regarded as distinct species on grounds of protein differences whileA. macedoi andA. villosulicarpa (although members of the same section, Extranervosae) show considerable differentiation of their protein patterns. Surprisingly, the formA. ×batizogaea showed less similarity in protein pattern to those of its parental species than might have been expected. The principle value of seed protein pattern data appears to be in distinguishing species within sections.

Proteins from two species of the genusArtocarpus (A. integrifolia L. andA. incisa L.) were compared by ammonium sulphate fractionation, molecular sieve chromatography and SDS-polyacrylamide gel electrophoresis, with special attention to the lectins. The protein content and hemagglutinating activity were markedly different in the two seeds. The protein pattern obtained by both molecular sieve chromatography and SDS-polyacrylamide gel electrophoresis were quite different. The only similarities found were the elution volume of the lectins in the Sephadex G-100 column and the lectin bands (11 500 and 15 000 daltons) in SDS-polyacrylamide gel electrophoresis.

Foliage and tuber fresh matter and chlorophyll content in cvs. Atom alue, Multa, Kufri, Desiree and Patrones were decreased with the increase in soil acidity. However, tuberization was enhanced at pH 5.5 and decreased significantly at pH 4.5 in all cultivars tested. At pH 4.5 the specific mass of all the cultivars was slightly increased. The highest content of reducing sugars and proteins was found at pH 5.5. No definite pattern was observed in total glycoalkaloids content under different acidic range.

Stem tips ofSpinacia oleracea were isolated and grown in sterile culture, with Sandoz 9789 added to the medium. Although the herbicide provoked a complete loss of all chloroplast pigments, developed shoots were able to flower, in response to long days; in short days flowering was inducible by adding gibberellins. Sandoz 9789 decreased the elongation of stems by up to 30%; the percentage of flowering plants in culture was also decreased. However, among those plants that flowered, the majority were male, so that Sandoz 9789 produced a shift of the sex ratio toward maleness.

A new undescribed yellows-type disease ofGypsophila paniculata L. was found. Since a stunted growth is the predominant symptom the disease has been termed stunting. Electron micrographs of ultrathin sections revealed numerous mycoplasma-like organisms in diseased phloem tissues. Attempts to maintain the diseasedGypsophila plants for further investigation of this disease failed for the present in spite of all applied modifications in nutrient media.

The effect of macroelements on nitrogen assimilation, level of nitrate reductase (NR), glutamine synthetase (GS) and glutamate dehydrogenase (GDH) and content of nitrate nitrogen were studied in 17 day-old pea seedlings. The highest inhibition of NR was found at deficiencies of Mg and Ca while deficiency of K was less effective. The level of GS was decreased only in roots exclusively at deficiency of Mg. On the other hand, the deficiency of Mg and Ca increased the level of GDH. The lowest level of endogenous nitrate was found at deficiency of K. Present results show that assimilation of nitrate by plants was decreased by Mg and Ca deficiency while assimilation of ammonium was not affected.

Four strains of the phytopathogenic bacteriumCorynebacterium fascians (Tilford)Dowson were selected from our isolates and deposited in the Czechoslovak National Collection of Type Cultures (CNCTC) of the Institute of Hygiene and Epidemiology in Prague. Two very virulent (Cor 83/82 "UPR" and Cor 82/81 "UP") and one avirulent (Cor 81/80 "CP1b") pelargonium strains, producing acid from rhamnose, were isolated from fasciations onPelargonium zonale W. One avirulent celery strain ofC. fascians (Cor 80/80 "CF4a") was isolated from a root expiant ofApium graveolens L. growing on a nutrient mediumin vitro. Morphological, cultural, physiological and biochemical characteristics of these selected Czechoslovak isolates were compared with the American patented strain cotype ATCC 12974.

A closed gas exchange system has been designed for connection to the Hewlett-Packard programmable calculator controlled data acquisition system to provide a complete process of measuring and control. The system enables routine measurements of photosynthetic and dark respiration rates at different irradiances and different carbon dioxide and oxygen concentrations and leaf temperatures, and also a simple and rapid automatic control of irradiance according to the actual photosynthetic rate.

Willows were rapidly propagated by repeated division of cultured rooted shoots into a larger number of nodal segments. Rapid clonal propagation of mountain-ash and black locust was achieved by induction of shoots from axillary buds and a multiple shoot culture was used for rapid multiplication. Excised shoots were rooted in an agar medium with a low concentration of auxin and rooted plantlets were transplanted to soil.