The photoacoustic spectroscopic studies of purple pigmented leaves revealed the occurrence of anthocyanins and betalains in some local weed species growing on soils with low moisture levels. The pigmentation intensities were higher in C₄ plants than in C₃ plants. An inverse correlation was observed between pigmentation intensities and soil moisture levels.

Five cultivars and the half diallel set of 10 F₁ hybrids of flue-cured tobacco (Nicotiana tabacum L.) were grown in two seasons. Highly significant differences were assessed between genotypes as concerns flowering time, plant height, number of leaves, leaf length and width and yield per plot. High to moderate values for heritability in the broad sense were obtained in all cases. Hybrids, in general, flowered earlier, were taller, had fewer but shorter and wider leaves and slightly increased yield when compared with the mean value of all parents. The variance associated with general combining ability (GCA) was highly significant in all characters. The estimates of SCA were significant in most cases. High GCA/SCA ratios which largely exceeded the unity were obtained for most attributes. The negative and positive alleles were unequally distributed in the parents for all the studied traits. A small number of effective genes was obtained for all characters except plant height, where one to two groups of genes were distinguished

In an open gas exchange system with a thermocouple psychrometer the transpiration rate of the first leaf in 8-day plants of spring barley was measured in dependence on the water saturation deficit (ΔW _sat). The plants were cultivated in Richter's nutrient solution, either complete, or deficient in nitrogen or phosphorus. The cuticular transpiration (as measured in the dark) was unaffected by N and P deficiency. The N deficiency reduced the transpiration rate by increasing stomatal resistance since full water saturation of the leaf (67% rate of the control variant) up to stomatal closing at Δ W_sat = 14%. The P deficiency does not affect the transpiration rate at initial phases of wilting, but the stomata close only at a higher Δ W_sat (25%) than those in the control.

A lectin was isolated fromCanavalia brasiliensis Mart. seeds by combining solubility fractionation with affinity chromatography on Sephadex G-50. The lectin showed a carbohydrate specificity for D-mannose (D-glucose) binding and a requirement for Ca²⁺ and Mn²⁺. All the hemagglutinating activity was found in the cotyledons and the presence of the lectin was followed during the first 15 days of plant germination, through the activity against rabbit erythrocytes, the presence of the "lectin peak" in Sephadex G-50 affinity chromatography, presence of the "lectin bands" in SDS-polyacrylamide gel electrophoresis and the "lectin arcs and rockets" in immunoelectrophoresis in agarose gel. On application of all these methods the lectin showed a differentiated metabolism, disappearing more slowly than the other high molecular weight proteins of the seed.

In five-day-old etiolated pea seedlings an increase in IAA content and in L-tryptophan aminotransferase (TAT) and L-tryptophan dehydrogenase (TDH) activities in the apical part of the epicotyl was found 12 h after root excision, which was followed by a decrease up to 48 h. In ten-day-old seedlings a continuous decrease in IAA, TAT and TDH levels in the apical part of the epicotyl was recorded up to 48 h after root excision. This indicates a growth-correlative effect of the root becoming evident in dependence on plant ontogenesis in changes of IAA content and activities of the above enzymes catalysing IAA synthesis.

Proteins diffusing from tobacco pollen grains exhibit different phosphohydrolytic activities. Molecular sieving produces nuclease fractionation into forms I, II and III with apparent molecular masses ≥ 60 × 10³, 32.9 × 10³ and 24.6 × 10³, respectively, and separation of principal forms II and III from phosphatase and major part of 5'- and 3'-nucleotidase activities. These forms did not differ in the mode of substrate attack and were combined for further enzyme characterization.
The preparation had 3'-nueleotidase activity even after further purification by DEAE-cellulose chromatography. The enzyme is an endonuclease with preference for single stranded molecules. The endolytical cleavage of native DNA occurs simultaneously in both strands and generates limit products of about 58 pairs of nucleotides. DNA duplex polymers are also cleaved by a terminally-directed, exonuclease-like process. The products of DNA degradation are oligonucleotides and 5'-mononucleotides. In the presence of NaCl, both endolytical and exonucleaselike activities on bihelical DNA are inhibited and the proportion of mono-to oligonucleotides produced increases. The enzyme can rapidly convert superhelical plasmid DNA to a nicked open circular form, and then to a unit-length linear molecule.
On the basis of these properties and of those found earlier (sugar-unspecificity, acidic pH optimum, activation by Zn²⁺ ions), the extracellular nuclease of tobacco pollen can be classified as plant nuclease I (EC 3.1.30.x).

The effects of PEG 6000 priming on germination performance of aged wheat seed lots have been studied. A correct application of osmopriming treatment indicated a relationship between the pattern of water absorption, the reactivation of mitotic activity and the start and synchronization of germination. The possibility of controlling pregerminative events by means of this treatment is discussed on the physiological basis of seed germination.

A number of amino acids have been tested for their ability to inhibit the cytokinininduced synthesis of betacyanin inAmaranthus caudatus cotyledons. Under the conditions employed there was not any serious inhibition of pigment synthesis at amino acid concentrations belowca. 20 μg ml^-1. Amino acids such as methionine, γ-aminobutyric acid and leucine did not give rise to serious inhibition belowca. 200 μg ml^-1. At amino acid concentrations ofca. 2000 μg ml^-1, inhibitions of pigment synthesis was in all instances complete.

This paper deals with the verification of a test of crop seedlings for the determination of the salt tolerance. There is a typical concentration of NaCl in the culture medium above which an enhancement of the free proline content is induced (critical point, critical concentration). The determination of this critical concentration in 19 cultivars of crop plants has proved that plants grown in aride areas (i.e. Hordeum, Triticum durum) have a critical concentration that is by about 50 to 80 mmol l^-1 of NaCl higher than that of plants grown in more humid regions (i.e. Triticum aestivum). The critical concentration is not influenced by pH changes of the external solution. Calcium application leads to an enhancement of tolerance. The different increases of growth and fresh mass of salt sensitive and salt tolerant plants selected by this test system proved the aptitude of the critical concentration in culture medium for proline augmentation as a test parameter.

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.

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%.

A pot culture experiment was performed to evaluate salt tolerance potential ofSesbania aculeata Poir. The plant can tolerate salinity levels up to electrical conductivity (ECe), 10 mS cm^-1 and at 15 mS cm^-1 thero is about 40% reduction in dry matter production. The analysis of inorganic constituents in different plant parts revealed that the plant has the capacity to regulate sodium uptake under saline conditions and chloride uptake always exceeded that of sodium. The potassium: sodium ratio is also maintained at a fairly constant level in leaflets while it is reduced in leaf rachis, stem and roots. Salt stress caused accumulation of calcium and magnesium in all plant parts. A considerable decline in phosphorus uptake was observed due to salinity. Iron was found to be accumulated more in salt stressed roots only. Nitrogen accumulated in both roots and leaves while considerable proline accumulation was observed in leaves of salt stressed plants. The amount of soluble sugars was increased in roots and leaves due to salt stress, while starch content of roots decreased. Those changes induced by salinity are discussed in relation to salt tolerance capacity of the plant.

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.