Two cultivara ofCicer arietinum L. with different sensitivity to drought in the early vegetative stage were compared for their capacity to accumulate proline when subjected to water stress. Both shoots and roots of the two selected cultivara accumulated proline under water stress and this effect increased with increase of water stress level. A high positive correlation between free proline and water saturation deficit (WSD) was recorded while these two factors were negatively correlated to the dry weight of the shoot. Also effects of duration of stress on proline accumulation patterns in relation to drought resistance have been shown.

In pea alcohol dehydrogenase (PADH) four isoenzymes were detected with the same mobility in one-and two-day germinating seeds; in three-and four-day seedlings the isoenzyme fastest moving towards the anode was lacking. These isoenzymes did not differ in substrate specificity to ethanol, propanol, butanol, and allyl alcohol, but only three of them reacted with isobutanol, and two with cyclohexanol.
On germination of seeds in actinomycin D at a concentration of 30 μg ml^-1 two isoenzymes disappeared and the activity of the other two was considerably lower.

The induction of gametogenesis in the studied homothallic alga by the transfer to a nitrogen-Less medium leads to an adaptation of the cell population until a dynamic equilibrium is attained. Throughout the adaptation, the homeostatic forces regulating the number of the cells in the population assert themselves on the basis of internal nitrogen circulation. Part of the induced cells which perform no conjugation is probably destroyed by lysing, whereas the cells being just in the pre-Induction phase as well as those having passed the phase without being induced to gametes, continue their cycles by means of the released nitrogenous substances. The conditions which in some cells cause the induction of gametogenesis, produce a partial spontaneous synchronisation in other cells. The course of the cell cycles in parts of the culture may be determined according to the pulses of the increasing number of the zygotes within the whole cell population, if the cell cycles have run at a certain degree of synchrony. The culture conditions which induce gametogenesis cause a quick decrease of the biosyntheses of the RNAs while the biosyntheses of the DNAs are almost maintained at the original level. During the dynamic equilibrium of the population, the average content of the RNAs per cell remains very low, whereas the average content of the DNAs per cell virtually does not change (compared with the original state).

The optimum conditions for cell suspension culture experiments have been characterized by respiration,p-Phenylenediamine oxidase and growth of cell suspension ofNicotiana tabacum for 15 days in stationary culture. Change of 3,4-Dihydroxybenzoic and 4-Hydroxybenzoic acids both present at 10^-4 M in culture medium were studied in short term experiments. An oxidation product of 3,4-Dihydroxybenzoic acid characterized by an absorption maximum at 280 nm was isolated after 1 h of incubation. The 4-Hydroxybenzoic acid did not change when incubated for 4 h under the same conditions.

Alfalfa witches' broom manifested by an expressive increase in the number of stems and dwarfing of the affected plants was found in Czechoslovakia. The disease is not saptransmissible and was transmitted by grafting to healthy alfalfa plants. The disease occurrence is sporadic. The symptoms observed in comparison with those described in Australia and USA are mild and inconspicuous. Electron micrographs of ultrathin sections showed the presence of numerous mycoplasma-like organisms (MLO) in diseased but not in healthy phloem tissues.

Growth correlations in the shoot apical meristem during transition to flowering were studied in a quantitative long day plant,Brassica campestris L. cv. Ceres, requiring only one long day for floral initiation. During photo-inductive exposure of the plants, an overall increase in cell number could be observed at the shoot apex concomitant with promotion of leaf initiation. Release from apical dominance and decline in relative growth rate of leaf primordia are reported as early effects of photo-induction. With the onset of floral differentiation, production of new leaf primordia had stopped altogether. Maximum increase in RNA concentration could be noticed in axillary meristems following photoperiodic treatment, whereas in vegetative plants the highest RNA concentration was found in leaf primordia. The significance of these changes occurring during transition to flowering is discussed.

Proteolytic activities were studied in cotyledons of germinated and mature dry seed and axis of mature dry seed ofVigna unguiculata (L.) Walp. cv. Seridó using the following substrates: hemoglobin (pH 3.5), casein (pH 6.0), LPA (pH 7.0), and BAPA (pH 7.6). During the germination period (six days) examined, the total activities of LPA-ase and BAPA-ase decreased progressively in cotyledons corresponding to protein depletion. Consequently, the specific activities of the above proteases remain practically constant. In the case of caseinase and hemoglobinase, total activities increased in the cotyledons up to the third day of germination. Thereafter there was a decrease in these activities (total) but an increase in specific activities. Higher values than in the cotyledons for all the activities were obtained with the axis of mature dry seed. A 25 to 50 % ammonium sulfate fraction of a buffered extract from mature dry seed was used as source of enzyme for all the substrates used. Sephadex G-100 chromatography of the 25 to 50 % (NH⁴)²SO⁴ fraction gave two main peaks which correspond to relative molecular mass of 100 000 and 60 000 and contained all the activities.

Effect of 2,4-dinitrophenol (DNP) was studied onNigella sativa to note the changes in mitosis, DNA, RNA and protein synthesis. The chemical affected division frequency considerably and chromosomal abnormalities like sticky bridge, fragmentation, micronucleietc. were recorded. By using precursors of nucleic acid and protein synthesis, it was found that DNP also inhibited DNA, RNA and protein synthesis. The decrease in division frequency can be correlated with the DNA synthesis.

Polyacrylamide gel electrophoresis was used to study the differences in patterns of the isoperoxidase spectrum in leaf tissues of the genome series (2n, 3n, 4n) of twoNicotiana tabacum L. cultivars,i.e. in the growth stage of the 5th-6th and 10th-11th leaf, and in the stage of elongation growth. Mutual comparisons of the cultivars showed that the variability and difference in patterns between the cultivars in later growth stages was more important. In both cultivars only one rapidly migrating main band of isoenzymes was registered within the range of Rm 0.45-0.77; only in the stage of elongation growth on the 2n and 4n levels two bands were recorded. No association between the number of genomes and the number or distribution of isoperoxidases was found.

Sucrose synthetase was purified about 130-fold from morning-glory (Pharbitis nil Choisy cv. Murasaki) callus cells, and the properties of sucrose synthesis and cleavage activities of the enzyme were compared.
The enzyme preparation gave a single band by disc electrophoresis. The molecular mass of the enzyme was estimated to be 4.2 × 10⁵ by gel filtration. The enzyme preparation gave two bands by SDS disc electrophoresis, suggesting the molecular mass of about 3.8 ×10⁴ and 7.0 × 10⁴.
The pH optima of sucrose synthesis and cleavage activities of the enzyme were different from each other, giving pH 9.0 and pH 6.5 respectively. MgCl², MnCl² and CaCl² activated the sucrose synthesis activity about two times the normal rate and conversely inhibited the sucrose cleavage activity.
F-6-P was not replaced by fructose. UDP was the only valuable substrate as a nucleotide diphosphate.
The enzyme showed the negative ecoperativity effect of UDPG suggesting to be an allosteric enzyme. The Km values of sucrose and fructose were calculated to be 167 mM and 5 mM, respectively. UDP suggested substrate inhibition. The apparent equilibrium constant varied between 1 to 3.
Based on these results, the role of the enzyme in the sucrose metabolism of morning-glory callus cells will be discussed.

Results obtained by comparison of similarity of seed protein spectra of 15 species of the genusAllium (in 22 samples) by means of immunochemical methods more or less correspond to the contemporary division of this genus. Species belonging to the sectionCepa (according to Vvedenskiy) andPhyllodolon have very similar spectra, which suggests that they either should be allocated to one sectionCepa or to two subsections (Cepa andPhyllodolon). Species belonging to the subgenusRhizirideum considerably differ in seed proteins. The investigated species of the subgenusMelanocrommyum show the most distinct spectrum of all the other analyzed representatives, less marked differences were found in the case of the representatives of the subgenusAllium.

Esterase isoenzyme patterns were studied in seeds of 6 cultivars ofAllium cepa L. and of14 species ofAllium, namelyAllium aflatunense B. Fedtsch.,A. altaicum (Pall.) Reyse,A. Cristophii Trautv.,A. fistulosum L.,A. jajlae Vved.,A. Karsianum Fom.,A. nutans L.,A. porrum L. cv. Gigant,A. praemixtum Vved.,A. pskemense Vved.,A. ramosum L.,A.rotundum L.,A. schoenoprasum L.,A. stipitatum Regel. The cultivars differ in their isoenzyme patterns, the cultivar Kaštická stands apart from all the other cultivars, probably due to the high alkalinity of its seed extract. The examined species, arranged according to their mutual similarity of isoenzyme patterns, form several groups corresponding to individual sections of the genus. Our results corroborate the recognizing of the sectionCepa and the subsectionPhyllodolon. The maintaining ofA. jajlae andA. rotundum as well described species fits better with our results, than degrading them to subspecies ofA. scorodoprason.
Our results agree in main features with those obtained by the immunological method. Some few differences appear concerning individual species. It is evident that esterase isoenzyme patterns can be used in chemotaxonomy ofAllium on an infrageneric level, and, at least inA. cepa, also on an infraspecific level.

In the seeds ofAllium altaicun (Pall.)Reyse a set of enzymes was found, metabolizing choline esters, composed of active choline esterases and choline acetyltransferase. Choline esterase cleaving acetylcholine occurs in five isoenzymes. The enzyme preparation hydrolyses strongly acetylthiocholine and sinapine, but weakly butyrylthiocholine (20%) in comparison with acetylthiocholine. The hydrolysis of the substrates mentioned is inhibited by physostigmine and neostigmine, but it is not inhibited by the specific inhibitor of acetylcholine esterase (BW 284 C51). In addition to hydrolytic activity a strong catalytic activity of choline acetyltransferase was also observed during the synthesis of sinapine from sinapic acid and choline. The detection of the mentioned enzymes in some representatives of theAllium genus indicates that choline esterases are more widely distributed in monocotyledons than previously assumed.

The induction of gametogenesis has its beginning in the most diluted cell suspension after the transfer of the cells to a nitrogen-less medium. Here, the highest percentage frequencies of zygotes are formed within the same period of time in comparison with the less diluted cell suspensions. The zygotes formed in the mostly diluted cell suspensions mature relatively very slowly and germinate very irregularly. The induction of gametogenesis retards in the denser cultures probably due to the strongest homeostatic forces trying to return the cell population to its initial stage. In our experiments up to now, the effects of the changing irradiance of the cells inside the suspension were not separated from the effects of the changing number of the cells in the given volume of the culture. Neither were the ratios of distilled water to the amount of the zygotes, nor to the vegetative cells constant. Thus, it is necessary to consider the mentioned effects as the result of an interaction of both factors under consideration. Each of the cell populations behaved as an autonomous whole. Also the populations, starting after the transfer to a nitrogen-less medium of the same culture density, may sometimes differ significantly in the observed characteristic features at various phases of their growth. The discontinued supply of nitrogen obviously causes a change of the cell metabolism in favour of the nitrogen-less substances, especially in the more diluted cell suspension. This work completes and explains some earlier results obtained from the study of the life cycle inChlamydomonas geitleri.

GA₃ as well as SA increase the protein content of the stem and the leaves at 1 day under both 8- and 24-h photoperiods. A new protein band with Rm 0.47 seems to be associated with floral bud initiation as it develops within 1-3 days in the stem as well as in the leaves of plants exposed to inductive treatments regardless of whether the induction is caused by 8-h photoperiods or by treatment with GA₃ of SA under 24-h photoperiods. Another band with Rm 0.23 developed only in the stem of water-as well as GA₃- or SA-treated plants under 8-h photoperiods. It may possibly be associated with extension growth.

Leaf inclination of three upper leaf pairs of a plant was used as a visual parameter for estimation of leaf (plant) water status inM. perennis. Negative correlation was found between leaf angle and leaf water saturation deficit (WSD). Large angles (between 130 and 80-90°) indicated WSD below approx. 12%, narrow angles expressed negative water balance of the plant and indicated usually strong or moderate water stress. The correlation may be expressed by two regression lines differing in slope. Some differences were observed between three leaf pairs investigated: At the same water deficits, leaves of the first pair (from apex) were inclined to a less degree than leaves of the other two leaf pairs. Leaves of the third pair wilted the most rapidly, therefore their WSD were highest at moderate and strong water stress of the plant. The approximation method tested is suitable for judgment of the plant water status inM. ptrennis and may be used in ecological investigations in forest ecosystems.

The two final products of radiolytic degradation of cytosinei.e. parabanic and oxaluric acids were investigated as regards their cytogenetic effects. Broad bean (Vicia faba L.) root meristem was used as experimental material. While the oxaluric acid was not able to induce chromosomal aberrations to a greater extent, the parabanic acid acts as a clastogenic compound. When applied on a resting broad bean root meristem at concentration from 10^-3 to 10^-2 M it induces chromosome and chromatid aberrations, especially breakages. Their frequency reaches 9-12% at the highest tested concentration. The same concentrations of the parabanic acid increases mitotic index of the first cell generation of primary root.