Stimulation of flower formation was ohserved in the female plants ofCannabis sativa raised from seeds treated with gamma rays. These plants produced seeds, of smaller size. One of 195 plants formed sterile hermaphrodite flowers with reduced female structures and increased number of anthers.

The study deals with the changes in metabolic processes of galactose breakdown in tobacco mosaic virus infected tobacco tissues treated with a 1.0 × 10^-4 M solution of 2,4-D (2,4-dichlorophenoxyacetic acid). At the time of maximum virus reproduction the plants infected exhibited a considerable increase in galactokinase and galactose-1-phosphate uridyltransferase activities. The activity of both galactose metabolizing enzyme systems investigated was not affected markedly by 2,4-D, but its increase was induced preferentially by virus biosynthesis.

Starch formation was studied by means of plant anatomy in segments of maize and pea leaves, deprived of starch, floating overnight in the dark (1) on solutions of various saccharides, (2) on sucrose solutions containing auxin-type growth regulators and (3) on suorose solutions with antibiotios (proteosynthesis inhibitors). A comparison was made of mesophyll tissues of the two species used, of spongy and palisade parenchyma in pea leaves and-especially-of mesophyll and vascular bundle sheath in the leaves of maize. Although the effects of the given treatments were striking, the response of the particular tissues was considerably uniform. If the given sugar appeared as utilizable for starch formation, it was effective equally in all tissues under study. It was not possible to distinguishin situ the different ways of staroh synthesis by means of the application of growth substanoes. No striking differences in the effect of antibiotics upon staroh formation were seen in-normally-starch containing and starch lacking tissues.

The plant growth regulator 2-ohloroethylphosphonic acid inhibited the elongation of growth inPhaseolus aureus seedlings. In comparison to the control, the polyphenol oxidase and peroxidase activity of treated seedlings was low up to 24 and 48 h of germination, respectively and that of phenylalanine ammonia-lyase and tyrosine ammonia-lyase was slightly less at 120 h and that of α- and β-glucosidases were less at 48 and 72 h, respectively. At other stages of germination, it greatly stimulated the activities of these enzymes.

The reversal of the cytogenetic effects of 5-fluordeoxyuridine, which are the gradual decrease of the mitotic index and the induction of chromosomal fragments was followed after addition of different concentrations of thymidine. Thymidine in the concentration 10⁴ M reversed both the effects of FUdR completely. The concentration of thymidine 10⁵ M partly reversed both the decrease of the mitotic index and the induction of chromosomal fragments. Uridine also caused some decrease of the cytogenetic effects of 5-fluordeoxyuridine.

FUdR 10^-4 M was applied together with [³H] TdR on the growing barley embryos cultivated in the nutrient solution. Samples were fixed 1-4 h after the onset of the treatment and microautoradiograms were prepared. All the mitoses were unlabelled, while more than 150 autoradiographic grains were found above labelled interphase nuclei; no cells that terminated S phase at the onset of the treatment passed through entire G₂ and reached mitosis during the 4 h duration of the treatment. Chromosomal fragments in anaphases appeared the first hour after the onset of the treatment. Their frequency increased from the first to the second hour and remained almost constant from the second to the fourth hour. FUdR induces chromosomal fragments in barley root meristems also in G₂ phase of the mitotic cycle.

Fifteen soybean cultivars were evaluated in two water supply conditions, inducing or not a drought stress. Main canopy traits were measured several times during the reproductive period and, at maturity date, the yield components were estimated. Using principal components analysis, the main physiological functions involved in soybean drought tolerance are described: leaf cells enlargement and assimilates transport. These processes could be a good basis on which to define new selection criteria for soybean drought tolerance.

Four soybean cultivars differing in storage potential were subjected to accelerated aging for different periods (2, 4, 6 and 8 days) and tested for germinability and beta-amylase activity. Aging caused a considerable and continuous increase in enzyme activity in both cotyledons and axes of all the four cultivars.

Two isolectins were isolated from the albumin fraction ofArtocarpus integrifolia L. seeds, by precipitation with ammonium sulfate, and DEAE-cellulose and SP-Sephadex C-50 chromatography. The isolectins, when passed through Sephadex G-100 at pH 7.4, had a molecular mass of 43 000 and when subjected to SDS electrophoresis in the presence of β-mercaptoethanol consisted of two subunits with molecular mass of 11 250 and 15 000. When they were tested with human erythrocytes of all the groups of the ABO system there was no blood specificity. The isolectins formed interference arcs by Ouchterlony double diffusion in agarose gel.

It was found that the greatest dehydration rate of detached leaves indicates theTriticum monococcum L. v.vulgare (2n = 14). The indol-3-Acetic acid distinctly decreases the dehydration rate of detached leaves of examined wheat with a different ploidy level (Triticum monococcum, Triticum dicoccum, Triticum spelta andTriticum aestivum).

The increased activity of GOT (E.C.2.6.1.1.) and GPT (E.C.2.6.1.2.) transaminases in maize seedlings found as a marker of genotype opaque-2, was investigated in extirped sprouts of both genotypes, normal and opaque-2. The enzymatic activity was determined in three maize samples from breeding experiments, each sample consisting of a genotype pair, normal and opaque-2, collected from segregating ears of maize plants in the S₁ generation. The seedlings were aseptically grown for 7 days in two variants of cultivation, intact seedlings and sprouts extirped after 4 days of germination.
In the intact seedlings of genotype opaque-2 an increased activity of GOT and GPT, as compared to the intact normal plants, was observed. The extirpation of the sprouts enhanced GOT and GPT activity in the sprouts of both genotypes. However, in extirped sprouts the GOT and GPT activity was found to be still higher in the genotype opaque-2 as compared with the sprouts of normal genotype. Thus it seems that the increased transaminase activity in the sprouts of genotype opaque-2 is genetically determined. The increase does not result from an induction of enzyme synthesis through the supply of amino acids translocated from the endosperm to the sprouts. The absolute level of transaminases in the different breeding samples is dependent on the parenteral lines, the relative level of GOT and GPT activities is higher in the genotype opaque-2.

On the basis of earlier data it was suggested that the induction of cytokinin autonomy might be accompanied by disorders in plastid function and a decrease in cytokinin utilization. In the work presented below the formation of chlorophyll and the isozyme patterns of nine enzymes, some of which are known to be localized in plastids, were compared in tobacco callus tissues differing in their hormonal requirements. Tissues either not requiring cytokinin or both auxin and cytokinin for their growth, contained a lower amount of chlorophyll than the cytokinin-and auxin-dependent strain. The number of isozymes of glucose-6-phosphate and NADP-malate dehydrogenase (i.e. enzymes which are known to be located in plastids) was reduced from four in the cytokinin-and auxin-dependent strain to two and one in the two cytokinin-autonomous strains, respectively. The fully habituated tissue contained an additional isozyme of NADP-malate dehydrogenase. The total number of isozymes of the remaining enzymes (NAD-malate dehydrogenase, peroxidase, esterase and a-and β-galactosidase) either was decreased or not changed in the cytokinin autonomous strains. The exception was an additional anodic peroxidase in one strain. The number of these isozymes in tissue habituated with respect to both auxin and cytokinin either remained the same or increased. Tobacco callus strains with altered requirements for growth regulators contained some new isozymes which were not present in any other strain and some isozymes present in other strains were absent. These differences are discussed in relation to the possible role of plastid function disorder associated with habituation.

IAA-oxidase activity increased in the stem as well as in the leaves of plants treated with GA₃, SA and GA₃ + SA during the early stages under inductive and non-inductive photoperiods, the activity being the highest in GA₃ + SA-treated plants. An isoenzyme of IAA-oxidase with Rm 0.15 developed in the stem as well as in the leaves subsequent to 1 or 2 inductive treatments. As this band persisted till the end of the experiment, it may be associated with the initiation as well as development of floral buds. Another band (Rm 0.30) appears to be associated with the phenol (SA) as it developed in the stem as well as in the leaves of SA- and GA₃ + SA-treated plants under both photoperiods. A band with Rm 0.60 developed in the leaves but not in the stem of GA₃-, SA- and GA₃ + SA-treated plants under both photoperiods.

The application of 2,4-dichlorophenoxyacetic acid at a concentration of 1.0 × 10^-3 M toCucumis sativus brings about a decrease in the activity of carbohydrate catabolizing enzymes in the leaves of experimental plants. On the contrary, in CMV infected plants the activity of sucrase, glucokinase, fructokinase, phosphoglucoisomerase and glucose-6-phosphate dehydrogenase are enhanced at the same time. The application of 2,4-D to virus infected plants promotes this effect further, so that the activities of the enzymes investigated are twice as high as those in the control.

In field-grown sugar beet plants (Beta vulgaris L. cv. Dobrovická A), each of66 successive leaves produoed in the course of the vegetation period was different with respect to its photosynthetic capaoity (P_c), life span, duration of leaf area expansion, and longevity after its maximum leaf area (A_max) has developed. The proportionality between the seasonal changes in these characteristics was not the same if the sequential senescence of leaves was taken into account. With aging of individual leaves, P_c increased with the leaf area expansion having attained the peak value between 75% to 100% of A_max The rate of ontogenetic changes in P_c of each leaf was specified by the rate of its growth and development so that even at comparable ages the successive leaves constituted a series of different physiological units.
The seasonal changes in quantum irradiance (PAR) were found to be responsible for differences in the growth characteristics between the successive leaves: Leaf expansion period was related with daily integrals of the incoming PAR (Io), while leaf longevity, after the A_max had been attained, was closely linked with PAR intercepted by the canopy (I). P_c expressed per the total leaf area of the plant was significantly correlated withI, while P_c calculated per unit leaf area of the plant was related toI _o Leaf potential to adapt P_c correspondingly to changes in PAR was greatest during leaf blade expansion; after the leaf had ceased to expand, changes in P_c were independent of differences in leaf irradiance.
The results stress, at least for field conditions, the inadmissibility of the extrapolation of attributes from one leaf to the other ones sequentially senescing on the plant.

N, P, K, Ca, and Mg contents, chlorophyll content, gibberellin-like substance content, photosynthetic and respiration rates, Hill reaction activity, and specific leaf area of different parts of the leaf blade of maize (Zea mays L.) were determined. Parts with highest values of the determined components and processes were marked in the longitudinal and transverse profiles of the leaf blade. The established gradients of substance contents and of the functional activity were related to the growth stage of the leaf.

The results of studies performed on winter rape leaves (Brassica napus L. var.oleifera L., cv. Górczański) indicated that independently of the plant cultivation conditions and of the leaf growth rate, all leaves showed significant increase in desiccation tolerance at the beginning of leaf expansion. The increase in tolerance was correlated with the formation of a central vacuole in the mesophyll cells. Therefore, the high desiccation tolerance of vacuolised cells in comparison to the non-vacuolised ones is supposed to be due to the higher ability of the former to avoid cytoplasm dehydration. Development of frost tolerance in the leaves during autumn does not seem to be causally related to desiccation tolerance changes.

Shoots have been produced in the explants from flower head receptacles cultured on BDS medium with BAP and/or NAA. The shoots produced could be regenerated to form the whole plants and transplanted into soil. No morphological or cytological variations were observed in mature plants. The histological analysis of adventive bud formation is presented. The importance of this method for clonal propagation ofAllium porrum plants is discussed.

The β-Amylase activity was high in seeds of pre-Milk and milk stages but low in seeds of half seed and dough stages and very low at fully ripe stage of seed development. Zymogen (latent β-Amylase) was absent in half seed stage but appeared at pre-Milk stage. The content of zymogen increased progressively with advance in ripening time. No α-Amylase activity was detected at any stages of seed development in wheat.

Similarity of seed protein spectra of 13 representatives of the genusAllium, subgenusRhizirideum, was estimated by means of immunochemical analysis; the species investigated were divided into four groups more or less corresponding to the contemporary systematic division of species into sections.