Papaverine hydrochloride, which is an alkaloid found in opium, inducedc-metaphase,c-anaphase, non-congression, diagonal anaphase, chromosome and chromatid bridges, lagging of chromosomes, micronuclei and multinucleated cells in root tips ofAllium cepa. It is the only one amongst the alkaloids of opium which caused a high increase in MI after a long period of treatment with some low concentrations.

Effects of exogenous application of auxin, GA3, abscisic acid, ethrel, methionine and α-alanine to the cut ends of the pedicels of flower buds, flowers and fruits on their abscission behaviour were studied. Fruit pedicels required more time for abscission compared with flower and flower bud pedicels. NAA inhibited abscission of all types of pedicels and the inhibition was maximum in matured fruit pedicels and minimum in flower bud pedicels. Flower pedicels were more sensitive towards the abscission promotive effects of GA3, abscisic acid and ±-alanine and the flower bud pedicels towards ethrel and methionine. The duration of Stage-I of abscission was maximum in cut pedicels of fruit and minimum in those of flower buds. Biochemical analyses revealed greater quantities of endogenous amino acids in the epicalyx of flowers with the exception of methionine and aspartic acid which were found to be present in higher quantities in the epicalyx of flower buds. Levels of IAA-like compounds were maximum in the epioalyx of flower buds and minimum in the epicalyx of flowers. Higher levels of abscisic acid were found in the epicalyx of matured fruits and the epicalyx of flower buds showed a minimum amount of abscisic acid-like compound.

A number of phenolic compounds have been tested for ability to inhibit the cytokinin-induced synthesis of betacyanin inAmaranthus caudatus cotyledons. Under the conditions employed, the compounds responded thus: (1) no inhibition with up to 1 mg ml^-1 (quercetin 3-rhamnosylglucoside and chlorogenic acid), (2) partial or no inhibition up to 0.1 mg ml^-1 with greater inhibition at 1 mg ml^-1 (phloridzin, arbutin, caffeic acid, p-hydroxybenzoic acid and 3,4-dihydroxyphenylalanine) and (3) partial or no inhibition up to 0.1 mg ml^-1 with complete, inhibition at 1 mg ml^-1 (o-coumaric,m-coumaric,p-coumaric, protocatechuic and ferulic acids and phenylalanine). The results show that if theAmaranthus betacyanin bioassay for cytokinins is to give reliable results, then certain contaminating phenolics must be removed beforehand; some difficulties involved in this are briefly discussed.

The rate of RNA synthesis in shoot apices of the short-day (SD) plantChenopodium rubrum was compared in three successive dark periods required for flowering.³²P label was used for fractionation of RNA on slabs of polyacrylamide gels on mioroscopic slides. Incorporation of³²P and³H-uridine into apices was followed using histoautoradiography under identical conditions for oomparison. The lowest rate of synthesis was found on the seoond day of induction. A slight increase was usually observed in the third dark period, possibly linked with the first anatomical and/or morphological changes whioh have appeared due to mduction. Most of the label was found in ribosomal BNA in this case. After the plants wero transferred from light to darkness RNA synthesis in the shoot apex decreased within three hours. There was good agreement between results obtained by eleotrophoresis and by histoautoradiography. All previous observations which have been obtained using cytophotometry and histoautoradiography were confirmed.
The rate of synthesis of BNA in shoot apices is paralleled by that in primordial leavea. The marked rise of RNA synthesis during the inductive period, found in some planta requiring only single inductive cycle, was not established inChenopodium. A different pattern of RNA synthesis between plants flowering after one and after several dark periods, is suggested in discussion.

The cytogenetic effect of two radiolytic cytosine products, i.e. of isobarbituric acid and of dialuric acid has been studied on a system of resting meristem ofVicia faba L. on chromosomal level. Both compounds produced in a concentration 10^-3 and 10^-4 M chromosomal aberrations with a relatively low frequency, about 4 aberrations per 100 anaphases after 12 h of treatment. Among the aberration types chromosomal and chromatid breaks and minutes pre-dominated.

The cells of some pea, tobacco and haplopappus callus strains reveal considerable variability in nuclear morphology (polymorphous nuclei, differences in nucleolar size and number, enlarged chromocentres) and chromosome counts. The specific features in the nuclear morphology of callus cells are related with some pecularities in the reproduction activity of these cells (amplification, amitosis, fragmentation, various deviations from normal mitosis) under cultural conditions including both the definite action of the culture system and the absence of the regulatory control by the intact organism.

The influence of pretreatment with some cations on anaerobic nitrite production (in an assay medium lacking nitrate) by excised primary roots of pea (Pisum sativum L., ov. Raman), detached from six-day-old seedlings germinated in distilled water, was investigated. When the excised roots were precultivated in one-salt-solutions of KNO3, then these roots produced at 9 mM and 15 mM NO3- concentrations under anaerobic conditions significantly more NO2-, than those precultivated in a nutrient solution containing besides K+ ions also Ca2+ and Mg2+ ions, and they produced nitrite for a longer time. The KNO3 dependent increase in anaerobic NO2- production was counteracted most by Ca2+ and to a lesser extent by Mg2+; Na+ was without effect. NH4+ at higher concentrations (12 and 15 mM) significantly depressed nitrite production both by roots precultivated in a solution containing besides NH4+ only K+, and by roots precultivated in a full nutrient solution containing K+, Ca2+ and Mg2+, however at lower NH4+ concentrations (0.6 and 2mMNH4+; 15mMNO3-) the decrease was more conspicuous in the KNO3 solution than in the full nutrient solution. Nitrate reductase level was not influenced by this pretreatment. When 6% and 7.5% n-propanol, which increases membrane permeability and causes mixing of storage and metabolic nitrate pools in the cells, was added to the assay medium lacking nitrate, anaerobic nitrite production increased and the differences caused by the precultivation disappeared. These results show that higher K+ concentrations in unbalanced one-salt-solutions of KNO3 can cause higher membrane permeability by accentuating Ca8+ deficiency, which results in a faster penetration of NO3- from the storage pool to the sites of its reduction and in an easier penetration of NO2- out of the roots, and that higher NH4+ concentrations can change nitrate compartmentation and diminish the metabolic NO3- pool which results in a slower nitrate reduction. Besides that, lower NH4+ concentrations in KNO3 solutions (15mMNO3-) probably partially counteract the K+ dependent increase in membrane permeability.
The results obtained show that there is no simple, direct relationship between the so-called metabolic pool of nitrate (i.e. anaerobic nitrite production) and the level of nitrate reductase, but that the velocity of nitrate reduction can be influenced by nitrate compartmentation in the cell.

Hormone-directed transport is shown in a detached adult leaf ofPelargonium zonale, after a local application of solution (0.1 ml) of various groups of phytohormones (GA3 -BAP-AIA-ANA-2,4-D). Importance of isolated leaf as a simplified experimental system is underlined by the positive results obtained with³⁵S (or³²P).
The idea of competition between two attractive foliar centers, induced by hormones is illustrated:
i) with regard to the concentration of the same hormone (higher effect at 25 mg than at 2.5 mg.l-1 with GA₃ for example);
ii) when two different hormones are competitive on the same leaf. In this respect, GA3 appears to be the most effective hormone tested on this material.
Finally, the idea of a hormone-directed transport, independent of the antisenescence effect is supported by the fact that an orientated translocation remains induced after general pretreatment with an alternative hormone (BAP and GA₃, for instance).

Several improvements of the method of sap flow rate determination in full-grown trees elaborated by the authors are described. The method is based on heat balance with direct electrical heating of the xylem. The accuracy of the relationship for the calculation of flow rate was improved, the influence of unevennesses of flow in different annual rings was reduced. A method of extrapolation of the results obtained by measuring an individual xylem segment against the whole tree and of interpolation to a unit segment was elaborated, a simplified method of connecting the electrodes supplying the thermal input to the segment is described and an indicator of the relative water content of the xylem was derived.

The ultrastructure of differentiating epidermal cells of maize root (within the distance of 1 and 2 mm from the root body apex) were studied under conditions of non-lethal and lethal osmotic stresses of nutrient medium containing polyethylene glycol 4000, as well as regeneration of their ultrastructure following rehydration. The structural response to water deficit of the cells investigated was dependent on both the stress duration and the stage of their ontogenic development. Following non-lethal stress, in younger cells investigated (1 mm), condensation of nuclear chromatin, decrease of polyribosomes and increased density of free ribosomes in cytoplasm, reduction of mitochondrial cristae and occurrence of intramitochondrial inclusions, less compact dictyosomes were observed. Pastid structure remained unchanged. Microtubules were lacking in treated cells. In the more differentiated cells (2 mm) protoplast retreat from cell walls was also observed as well as a general decrease of ribosomes and ER elements in parietal cytoplasm, an increased number of intramitochondrial inclusions and mitochondrial membrane fragmentation. In these cells, Golgi apparatus was also lacking. The ultrastructure regeneration of the more differentiated cells was less pronounced. Lethal osmotic stress would cause more severe structural damage in all the cell components investigated.

The study deals with the absorption and translocation of Ca²⁺ by án intact plant of pumpkinCucurbita pepo L. and with the effect of various concentrations of 2,4-dinitrophenol (DNP) on these processes. The absorption of Ca²⁺ was reduced by the application of this inhibitor, but not completely stopped. The translocation of Ca²⁺ into shoots was affected more expressively: it was almost completely inhibited by higher DNP concentrations. The uptake of Rb⁺ is aubstantially more influeneed than that of Ca²⁺: higher inhibitor concentrations caused its complete cessation.

Crystal-containing organelles in cells of virus infected plants lying at chloroplasts and mitochondria are identical with single membrane-bound microbodies containing crystals of catalase described in healthy plants. Massive complex inclusions caused by turnip mosaic virus very frequently contain the same microbodies with crystal inclusions; that phenomenon may be related to some pathophysiological changes of virus infected plants. Comparable proteinaceous crystals, but not lying within microbodies limited by a membrane, may also be found in cytoplasm of infected cells. These crystals are sometimes surrounded by a substance resembling the microbody matrix. Disintegrated cytoplasm of virus infected cells may also contain the same crystals lying free in "empty spaces". Cytopathological effects responsible for this phenomenon and possible artifacts as well are discussed.

The syndrome of a new apricot disease - "witches broom" is described. Diseased trees have an abnormally high number of lateral, thin shoots, which again have many abnormal secondary shoots at a very narrow angle. Witches broom shoots are without any blossom buds. We may assume therefore that the apricot witches broom - according to the syndrome - may be listed among the group of witches broom diseases which are caused by a mycoplasma like organism. Some of the witches broom shoots are characterized by very small leaves.

CCC in either absence or presence of salinity slightly and irregularly affected the shoot dry weight, but consistently increased the seed cotton yield. The extent of such positive effect upon yield tended to be larger in the presence rather than in the absence of salinity when using CCC as a seed-soaking medium alone, but the reverse if applied as a spray after seed-soaking.

The presence of synthetic auxins (2,4-D at a concentration as low as of 0.5 to 5.0 mg I^-1, NAA at least at 5 mg I^-1) in the cultivation medium was essential for the induction of callogenesis in anther cultures ofZea mays L. The application of IAA was ineffective. Kinetin induced bursting, darkening and a rapid anther necrosis, but at an appropriate concentration ratio with 2,4-D it stimulated pollen maturation at the same time.

Sodium azide, reported to be a strong mutagen in barley, revealed a very weak mutagenic activity inArabidopsis.

Jerusalem artiohoke (Helianthus tuberosus L. cv. D-19) dormancy is normally broken by a 16-week treatment with 4 °C. A thermoperiod of 2 °C-12 h, 8 °C-12 h allows one to reduce this time to 12 weeks. Anoxy applied at 24 °C is effective after 4 weeks. By coupling anoxy and low températures varying daily between 2 °C - 12 h and 8 °C - 12 h, the breaking of dormancy is obtained after a one-week treatment.

Various types of meiotic anomalies in Mi generation such as multivalents, fragments, bridges, mioronuclei, polyads and in particular the multispindle formation, were observed after seed X-ray irradiation inCapsicum annuum L. As the dose increased there was a gradual increase in the number of aberrations.

Net photosynthetic CO₂ uptake (P _N ) and transpiration (E) rates through adaxial and abaxial leaf surfaces were measured gasometrically on the area of maize leaf blades of different insertion levels in the phase of male florescence and in the phase of spadices development. The distribution pattern of gas exchange on the area of all measured leaf blades found in the phase of male florescence (significantly lower value in the basal parts) was changed in the phase of spadices development: P_N andE of abaxial surfaces of older leaves,i.e. 9th, 10th (under which the spadices were growing) and 11th, rapidly increased in the basal parts in comparison with the middle ones and positively influenced the gas exchange of the whole leaves. It appears that P_N may be maintained or increased in the older leaves in the phase of spadices development to prevent shortage of photosynthates.

Mitochondria from dwarf and tall light-grown peas have been separated from contaminating chloroplasts and other organelles on discontinuous sucrose gradients. A comparison between activities of the mitochondria from the two cultivars of light-grown pea seedlings was made. It was observed that both respiratory control (R.C.) indices and phosphate to oxygen (P : O) ratios were superior in mitochondria from the tall cultivar than the dwarf cultivar. The results are discussed in relation to energy status and possible gibberellic acid content in the two cultivars.

Uridine incorporation into the shoot apex of the short-day plantChenopodium rubrum was investigated during a 16 h period of darkness and the following transfer to light. Uridine incorporation during this single inductive cycle was compared to incorporation under non-inductive conditions of continuous light. After transfer of the plants from light to darkness RNA synthesis was reduced to about half after the first two hours. This occurred not only when the plants were precultivated in continuous light but also after an interruption of the dark period by light for 31/2 h. The low level of uridine incorporation was maintained for the whole duration of the dark period. Incorporation regained its initial level after exposure of the plants to light irrespective of the duration of the preceding dark period. After this immediate rise of uridine incorporation in plants transferred from darkness to light a slight temporary decrease was observed in light. In darkness the decrease of incorporation into the nucleoli was still more marked than the reduction of overall incorporation. After the termination of the dark period incorporation into the nucleolus rose slowly and extranucleolar incorporation was relatively enhanced during the first 10 h of light in induced plants. The fluctuations of RNA synthesis observed in the shoot apex during photoperiodic treatment may be regarded as a necessary condition for the transition from the vegetative to the reproductive state.

An electrophoretically homogeneous lactate dehydrogenase was isolated from soybean seedlings, the specific activity of which was approximately 1800 times higher than the crude extract. From the dependence of the rate of reaction catalyzed by lactate dehydrogenase on substrate concentration, Michaelis constants and Hill coefficients were determined for four natural substrates,i.e. lactate, pyruvate, NAD and NADH. The enzyme from soy-bean plants is non-competitively inhibited by oxalate and mesoxalate,i.e. by the compounds analogous to the substrate. At pyruvate concentrations above 0.8 mM, the rate of reaction catalyzed by lactate dehydrogenase from soy-bean plants decreases, fructose diphosphate and ATP function as inhibitors as well. The inhibition by ATP is pH dependent, which seems to be of importance for the regulation of enzyme activityin vivo.