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.

Nitrate reductase level in leaves of pea plants is higher than in roots despite of the lower content of endogenous nitrate. Addition of ammonium ions to nutrient solution containing nitrate decreases nitrate reductase level in leaves estimatedin vivo while its level estimatedin vitro is increased.
Glutamine synthetase (GS) level in roots decreases during short (24 and 48 h) and long (14 d) term cultivation of seedlings in solutions containing ammonium ions. This decrease occurs in leaves only after the long term influence of ammonium ions. Level of this enzyme is higher in plants grown in the presence of nitrogen (ammonium and nitrate) as compared to those grown without the nitrogen.
Level of glutamate dehydrogenase in roots is increased after both short and long term cultivation of plants in the presence of ammonium ions.

Nitrate depletion from the media by intact corn seedlings grown under solution culture was measured over a period of time. Two methods were assessed to differentiate corn genotypes for nitrate uptake ability: (1) Nitrate uptake per day per plant basis. (2) Nitrate uptake per day per gram root dry matter basis. The former method was found to be superior as it gave significant and positive correlations with dry matter, nitrate, and reduced nitrogen accumulation in stem, leaf and roots. Nitrate uptake was found to vary with plant age. Root mass and efficiency of roots appear to contribute to the total nitrate uptake ability of the genotype. Corn genotypes studied exhibited marked differences in nitrate uptake ability.

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.

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.

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.

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 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.

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.

The effect of plant tissue culture medium with different concentrations and combinations of growth regulators (kinetin, indol-3-ylacetic acid, 2,4-dichlorophenoxyacetic acid) was evaluated on mitosis ofAllium sativum meristem root tip cells. Different combinations of growth regulators at low concentrations had no effect on induction of mitotic aberrations or inhibition of mitotic activity. Inhibition of mitotic activity, a tendency to chromosome stickiness and clumping and a slight increase in the frequency of mitotic aberrations were observed at higher concentrations. It may be proposed that plant tissue culture media have no direct effect on induction of mitotic aberrations in plant tissue culturesin vitro.

The growth of root, hypocotyl and cotyledons was measured in apple seedlings cultured for nine days from embryos isolated from seeds after various periods of after-ripening. Greening of the cotyledons was taken into account and the chlorophyll content determined as well.
Embryonal dormancy results in anomalies already appearing in the early stage of development. They are manifested by differentiated greening and uneven growth of cotyledons, as well as by hypotrophy of root or hypocotyl. The frequency of those anomalies in the population decreases during the removal of dormancy, and therefore it may be accepted as the criterion of its depth.

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.

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.