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.

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.

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.

The screening of enzyme patterns in seeds ofAllium cepa cv. Všetatská revealed the presence of the following enzymes: alcohol dehydrogenase, lactate dehyd ogenase, NAD+- and NADP+-glyceraldehyde-3-phosphate dehydrogenase, glucose-6-phosphate dehydrogenase NAD+- and NADP+-malate dehydrogenase, NADH₂- and NADPH₂-tetrazolium reductase catalase, Superoxide dismutase, acid and alkaline phosphatase, L-leucine aminopeptidase, glutamate dehydrogenase, non-specific esterase, and cholinesterase. Altogether 17 enzymes were detected in onion seeds, nine of which had more than three isoenzymes, NAD+-malate dehydrogenase had 8, and non-specific esterase 9 isoenzymes. The demonstration of cholinesterase and Superoxide dismutase activities is remarkable.

Using the enzyme-linked immunosorbent assay (ELISA) beet yellows virus (BYV) could be detected reliably in the leaves of sugar beet andTetragonia expansa Pall. and in the roots of sugar beet. Specifio γ-globulin of BYV antiserum was coupled to horse radish peroxidase by periodate oxidation. Optimum dilutions of antigen (extract from infected leaves) were1: 50 to 1: 200 for BYV detection in sugar beet andT. expansa leaves and1: 2 to 1: 5 for detection in sugar beet roots. Extracts from beet roots are not to be purified by ultracentrifugation, however, by the described method virus can be demonstrated only in 80-90% of naturally infected sugar beet roots. The method is specific, no increase of extinction values was found in healthy or beet western yellows virus infected plants. Presence of virus can be demonstrated by visual as well as photometric evaluation. Results confirmed the suitability of peroxidase application for detection of plant viruses by ELISA.

Cell division contributing to longitudinal growth of the shoot apex was investigated inChenopodium rubrum in segments marked by the axils of leaf primordia. Plants treated with two short days (16h of darkness and 8h of light) were compared with two non-induced controls (cultivated in continuous light or treated by alternations of 8 h of darkness and 4 h of light for two days). During the short-day treatments the rate of cell division contributing to the longitudinal growth decreases in all segments of the shoot apex irrespective of whether the darkness was given in inductive or non-inductive photoperiods. The rate of cell division contributing to longitudinal growth increases in the upper internodes of the shoot apex after the termination of the photoperiodic treatment and transfer of the plants to continuous light. However, cell division remains inhibited in the lowest segment of the shoot apex. This inhibition in the differentiating parts of the shoot apical meristem is a direct consequence of photoperiodic induction. It is supposed that this inhibition is related to evocation similarly as the well-known phenomenon of stimulation of cell division in the apical dome.

The absorption of³²P-phosphate (KH₂PO₄-0.1 mM) was studied with discs ofPelargonium zonale leaves, in relation to the age of the leaf, to the ageing process and in relation to the influence of GA3 and BAP. The results show that: i) the speed of absorption reaches a maximum which is characteristic of the adult phase (stage); ii) the "ageing" (washing during 24 h) induces a general increase in the absorption velocity which is dependent on the temperature of the ageing medium (optimum at 26 °C). On the other hand, ageing appears to be a process able to increase the physiological differences which are present before "ageing". This phenomenon also appears in the case of the influence of phytohormones; iii) if BAP exercises a dose-dependent inhibitory action, in contrast, GA₃ acts by increasing the velocity of the absorption which appears to be a process independent of the hormone concentration.
These results underline a phytohormonal specificity.
All these results are discussed in relation to hormone-directed transport, cell permeability and leaf senescence.

Cotyledons of gourd (Cucurbita maxima Duchesne) and bean (Phaseolus vulgaris L.) were used to study the changes in the activities of catalase, peroxidase, acid inorganic pyrophosphatase and alkaline inorganic pyrophosphatase during ageing and the diversion in such changes that occur when cotyledon senescence was retarded by detopping the seedlings above the cotyledons. Catalase, acid inorganic pyrophosphatase and alkaline inorganic pyrophosphatase activities declined during the senescence of the cotyledons. When cotyledon senescence was retarded by detopping as marked by the increase in the levels of chlorophyll and protein, there was also an increase in the activities of these enzymes. Peroxidase activity, on the other hand, increased during the senescence of the cotyledons and detopping the seedlings resulted in a further increase in the peroxidase activity. It can be suggested that some root factor(s) probably cytokinin(s) is (are) mobilised into the cotyledons of the detopped seedlings which otherwise would have been mobilised into the shoot apices, and help retard or even reverse the senescence of the cotyledons.

Protoplasts isolated from cell suspension cultures of potato were cultured as far as the level of regeneration of substrains. The influence of various factors (age of the cell culture, mode of precultivation, composition of the enzymatic mixture, incubation period) on the efficiency of isolation as well as the viability of protoplasts, has been studied. Various cultivation procedures have been screened and the effect of especially the hormonal composition of the medium on different phases of the regeneration of cell colonies (regeneration of the cell wall, growth and elongation, cell division) evaluated.

The reaction: Chlorophyll + Enzyme → Chlorophyllide + Phytol follows a first order kinetics with regard to the quantity of enzyme, when it is saturated by substrate. K_m and V_m were determined from the average reaction rates for the substrates: Chlorophylla andb, pheophytina andb, methylchlorophyllidea and methylpheophorbide a: The lowest K_m corresponded to chlorophylla and the highest V_m to methylpheophorbidea. For a substrate of chlorophyll (a + b), K_m and V_m were determined also using the initial reaction rates. "Enzyme efficiency" was calculated using both methods of determination. The reaction products partially inhibit the hydrolytic process.

The investigation of the substrate specificity of the anionic peroxidase isoenzymes, isolated from the zone of differentiation of the primary roots ofZea mays, for some representatives of phenolic compounds and aromatic amines, as hydrogen donors, is reported. The investigation was carried out electrophoretically with peroxidase isoenzymes partially purified by a combination of gel filtration by Sephadex G-25 and Sephadex G-100. A difference in the substrate specificity of the individual isoenzymes is observed. It was established that the anionic peroxidase isoenzymes showed a similarity in total number and relative activity on staining with bivalent phenols and difference on staining with trivalent phenols, as hydrogen donors. A greater number of isoenzymes was stained with benzidine ando-dianisidine and a lesser number witho- andp-phenylendiamine. The substrate specificity of the peroxidase isoenzymes was compared for guaiacol and benzidine. The substrate specificity of peroxidase soenzymes was discussed as regards their diverse role in the plant metabolism.

Growth behaviour, proline changes and water saturation deficit (WSD) changes were studied in two maize cultivars, Agati-76, a drought resistant oultivar, and cv. Vijay, a susceptible one after stress conditions were removed. Plants of both the cultivars showed a tendency to recover during rehydration. Phenotypically the plants appeared just normal on 7th day of rehydration, although recovery was never complete. Significant positive correlation existed between free proline content and concomitant change in water saturation deficit. Significantly higher proline content in cv. Agati-76 was reoorded in cv. Vijay, immediately after the stress was released, thereafter continuous decline was observed up to 7th day of rehydration in both the cultivars. Proline changes in relation to recovery of plants from stress conditions are discussed.