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.

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.

Considerable changes in tryptophan synthase aotivity occur during the ontogenesis of pea plants (Pisum sativum L.) in their individual parts. Maximal tryptophan synthase activity is connected with the vigorous growth period of the individual organs and of the entire plant. The content of free serine which is present in excess and is one of the substrates in the reaction catalyzed by tryptophan synthase, also changes, as well as the content of free tryptophan, the product of the reaction. The changes in the contents of these amino acids do not correspond to the variation in tryptophan synthase activity and mainly follow the alterations in the total nitrogen metabolísm. The limiting factor in the biosynthesis ofL-tryptophanin vivo is probably the availability of the aromatic precursor, above all of indole-3-glycerophosphate. The content of bound tryptophan also shifts in the pea plants owing to the enrichment of proteins in older parts of pea plants with this amino acid.

Amaranthus viridis is a quantitative SD plant in which inflorescence primordia are initiated under both 24- and 8-h photoperiods after 12 and 10 days, when 8 and 7 leaves are differentiated, respectively. Photoperiod plays a non-determinate role, whereas the maturity of plants linked with the attainment of minimum leaf number is significant and of primary importance in floral induction. This is further confirmed by the more or less identical nature of changes in the total enzyme activity and isoenzyme patterns of peroxidase, esterase and alkaline and acid phosphatase under the two photoperiods. These changes occur once the minimum vegetative growth has been achieved prior to the reproductive transformation, irrespective of the photoperiod, pointing to the activation of a general common pathway of events leading to floral induction.

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.

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.

Intact maize seedlings were examined for the uptake and leakage of labelled sulphate and phosphate anions affected by temperature. Control plants, grown at 25 °C were compared from the aspects of uptake capacity and leakage with plants incubated in nutrient solutions cooled to 15 °C and 5 °C, respectively. Short time intervals as well as 1-7 d exposure to cooling were used. Already after 1 h exposure at 5 °C and 5 h cooling at 15 °C and at 5 °C, considerable changes were manifested in anion uptake and leakage.
The uptake of³²P declined more than that of³⁵S. So, after a 30 min uptake interval the uptake of³⁵S decreased at 15 °C to 49.84% and at 5 °C to 6.05% comparing with the uptake at 25 °C, while the uptake of³²P declined to 28.64% at 15 °C and to 4.45% at 5 °C. The leakage of both anions was the highest at 25 °C in absolute rates, but relatively most of the uptaken³⁵S and³²P was released at 5 °C. Longer exposure to a chilling temperature of 5 °C (1-7 days) resulted in two patterns of sulphate and phosphate uptake.

Uptake of potassium by rice plants at different stages of growth can be described by a biphasic isotherm in the range of 5 × 10^-5 M and is probably mediated bya multiphasic mechanism in the plasmalemma.

White mustard (Sinapis alba L.) plants, susceptible to 2,4-D, and scentless mayweed (Tripleurospermum maritimum L.) plants, resistant to 2,4-D, markedly differ in the distribution and metabolism of 2,4-D. When 2,4-D-¹⁴C was applied onto the leaf, radioactivity was found in mustard after 8 days in the entire plant, whereas in scentless mayweed radioactivity occurred mainly in the leaf onto which it was applied and in another one or two leaves, with the roots showing only traces of radioactivity. The two plant species differed both in the character and in the number and amount of metabolites detected in aqueous and ether fractions. The metabolite with R_f 0.63 -0.65, soluble in ethylether (39% of the total radioactivity applied), and that with R_f 0.35 -0.36 (23% of the total radioactivity) were present exclusively in the roots of scentless mayweed plants. The R_f values established indicate that the former metabolite may be a conjugate with the amino acids alanine and valine and the latter a hydroxylated derivate of 2,4-D. In the shoots of both plants, 2,4-D-¹⁴C was metabolized to identical metabolites with R_f 0.59 -0.61, which occurred in mustard plants only in trace amounts. Free 2,4-D-¹⁴C occurred in the shoots of both plants and in considerable amounts also in mustard roots; it could not be demonstrated in the roots of scentless mayweed. The two species did not differ in the uptake rate or in the amount of absorbed 2,4-D-¹⁴C.

In intact, decapitated and decapitated indole-3-acetic acid (IAA) treated pea seedlings the translocation of benzyl-8-^l4C-adenin (¹⁴C-BA) from the roots was studied with regard to the release of lateral buds from apex-induced inhibition. In intact plants (controls) a substantial part of the activity was found in the apical part of the epicotyl. Decapitation resulted in the initiation of growth of lateral buds. As early as 24 h after decapitation and application of¹⁴C-BA a significantly higher activity was found in growing lateral buds (cotylars) of decapitated plants than in inhibited ones of intact or IAA-treated decapitated plants. The accumulation of¹⁴C-activity in stump tops of decapitated plants treated with IAA was associated with the thickening growth.

The study was concerned with the effects of irradiation of the sodium humate on its biological activity, which was assessed by the elongation of the hypocotyl and root in young plants of lettuce (Lactuca sativa L. cv. Rapid and cv. Smaragd) growing in the solution of the tested preparation. It was found that its stimulative action on hypocotyl and root elongation in lettuce was changed due to irradiation. However, the degree was dependent on concentration; stimulation mostly decreased, only at some higher concentrations did it increase. Further, experiments showed that there was some interaction between the irradiation of the humate and the cultivar used for testing, but none between the irradiation and the light exposure of plants during the test. The response of the experimental plants to the concentration of the humate depends on the light exposure.

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.

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.

Changes in respiration, activity of cytochrome oxidase and ascorbic oxidase and in BSMV content were investigated on winter wheat plants cv. 'Kaštická osinatka' after application of growth stimulating and growth inhibiting concentrations of 2,4-D. It has been found that the rate of respiration is almost exclusively dependent on the activity of both these terminal oxidases. Consumption of oxygen was regularly increasing with decreasing herbicide concentration and at concentration 10^-7 M was even higher than the control value. Healthy and BSMV inoculated plants treated with 2,4-D differed in ascorbic oxidase activity while activity of cytochrome oxidase was almost the same. In contrast to healthy plants the BSMV inoculated ones were seriously damaged after 2,4-D application. Plants inoculated with BSMV and treated with 2,4-D contained in contrast to those inoculated and not treated with 2,4-D a higher content of virus (124 to 150 %) which was not proportional to herbicide concentration. These results, which were obtained from experiments with plants grown in nutrient solutions supplemented with 2,4-D, indicate that BSMV inoculation induces metabolic changes which cause a loss of selectivity of 2,4-D.

Cytochrome oxidase and ascorbic acid oxidase activities were investigated in rye, wheat, barley and oat plants. The variations in the activity of both enzymes was followed in the course of the initial 28 days of growth, as well as at the phase of milk ripeness, namely in the cytoplasmic and mitochondrial cell fractions of roots, leaves and spikes.
Both enzymes were active in all measurements. Cytochrome oxidase mostly exhibited a higher activity than ascorbio acid oxidase. The activity of the former enzyme was substantially higher in the mitochondrial fraction of leaves, roots and spikes of the four experimental plants in comparison with the cytoplasmic fraction. On the contrary, the ascorbic acid oxidase activity varied in both cell fractions according to the plant species, organ and growth phase.
The variations in the activity of both enzymes exhibited on the whole a course similar to that of the respiration rate. During the first 14 to 21 days of growth the enzyme activities increased up to the maximum. This was thon followed at first by a rapid, later on by a slow decrease. The course of variations in the enzyme activities was, with certain exceptions, alike in all the four plant species investigated.

The influence of phenolic and humic acids on the activity of glucose-6-phosphate-dehydrogenase in the roots of pea under aseptic conditions has been investigated. It seems clear that vanillic and protocatechuic acids inhibit the enzyme activity in the excised roots of pea, but their dry weight increases in relation to the control. Gallic acid stimulates the G-6-PD activity in the roots of whole plants. The humic acids influence neither the enzyme activity nor the dry weight of pea seedlings after short-term treatment.

The growth changes of cotyledons, leaves, hypocotyls and roots due to photoperiodic induction in short day plantChenopodium rubrum were investigated in relation to flowering. Six-day old plants were induced by photoperiods with a different number of dark hours. We found that the degree of inhibition which occurred during induction in the growth of leaves, cotyledons and roots similarly as the stimulation of hypocotyl is proportional to the length of dark period. The photoperiods with 12, 16 and 20 dark hours bring about marked inhibition of growth and at the same time induce flowering in terminal and axillary meristems. The inhibitory effect of critical period for flowering,i.e. 8 dark hours, is not apparent in all criteria used and even the flower differentiation is retarded. The photoperiods of 4 and 6 dark hours did not affect growth and were ineffective in inducing flowering even if their number has been increased. The experiments with inductive photoperiod interrupted by light break have clearly shown that growth pattern characteristic for induced plants can be evoked in purely vegetative ones. Such statement did not exclude the possible importance of growth inhibition as a modifying factor of flower differentiation. We demonstrated that the early events of flower bud differentiation are accompanied by stimulation of leaf growth. The evaluation of growth and development of axillary buds at different nodes of insertion enabled us to quantify the photoperiodic effect and to detect the effects due to differences in dark period length not exceeding 2 hours.

The plants of two herbaceous species, namelyPulmonaria officinalis L. andSymphytum tuberosum L., growing in two deciduous forests in SW. Slovakia, were used for analysis of anatomicphysiological gradients along the insertion level of individual leaves. The gradients were established for six leaf characteristics. Specific leaf area and development of leaf area increased, while leaf tissue hydration, degrees of succulence and consistency decreased with height of insertion of leaves upon the stems. The gradients indicate the decreasing of the leaf water content and dry mass with height of the leaf on the stem. Stomatal resistance was usually the lowest in basal leaves and the highest in apical leaves of the plant. The anatomic-physiological heterogeneity of leaves of a plant is large and cannot be neglected in any anatomical or physiological investigations.

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.

The changes in the levels of growth regulating substances using the wheat coleoptile straight growth test were determined in the leaves of vernalized (flowering) and non-vernalized (non-flowering) plants of sugar-beet, cv. Poly-AG-Poland at two stages; the end of vernalization treatment (210 days from planting) and full-flowering stage. IAA was detected only in the extracts of the leaves of non-vernalized plants after210 days from planting. No inhibitory activity was detected, except in the case of the concentrated extract of the leaves of non-vernalized plants. This growth promoting zone was found at R_f 0.5-0.8 in the leaves of flowering plants after cold treatment and at flowering time. This zone of growth promoting action was suggested to have a major role in the flowering of sugar-beet.

Humic acids in a concentration of up to 100 μg ml^-1 affect the activity of choline esterase of pea only weakly during sinapin (choline ester of sinapic acid) hydrolysis. The inhibition is stronger at higher concentrations. A similar course of inhibition with humic acids was also observed during the synthesis of sinapin catalysed with choline acyltransferase present in the same enzyme extract. The organophosphate malathion is a strong inhibitor of both the hydrolysis and the synthesis of sinapin. Thus, for example, at a 3.5 × 10^-5 M concentration it causes 85% inhibition of pea choline esterase. However, in combination with 100 μg of humic acids this inhibition decreases to about 8%. It was observed that humic acids prevent the inhibition of both the hydrolysis and the synthesis of sinapin with malathion even at low concentrations. The interaction of the organophosphate malathion with humic acids seems specific. Humic acids do not affect the inhibition of choline esterase with physostigmine or the inhibition of the hydrolysis and the synthesis of sinapin with chlorocholine chloride, alar and hexamine either. This is also true of the activation of the processes with the K⁺ ions. Humic acids represent competitive inhibitors of choline esterase. Malathion shows an acompetitive - noncompetitive character of the inhibition. The interaction of humic acids with malathion in the roots of the plants may also be assumed in the soil when malathion is applied as an insecticide.

The absorption of nitrate and the activity of nitrate reductase were much lower in Ca-deficient plants ofCururbita pepo L., cv. 'Kveta' than in normal plants grown in complete nutrient solution for a period of 8 days. After the addition of nitrate to the nutrient medium, nitrate reductase activity in the roots of NO₃-deficient plants sharply rose during the first 6 h and then remained constant during the following 6 h; the content of endogenous NO₃^- rose slowly and continuously. These processes were depressed in (Ca, NO₃)-deficient plants independently of the addition of Ca²⁺ to the medium in the variant with NO₃^-. Thus it seems that the whole nitrogen metabolism,i.e. both NO₃^- absorption and the synthesis of nitrate reductase, is impaired in Ca-deficient plants.

An isolate of wisteria vein mosaic virus (WVMV) obtained fromWisteria sinensis in Prague resembled in its properties WVMV isolates described in Italy and Holland.Nicotiana megalosiphon is reported as a new host of WVMV. Other known host plants showed reactions similar to those described formerly. The incubation period extended in some hosts up to two or four weeks. Pea plants showed symptoms within five to seven days. Species ofApium, Brassica,Datura and others were not susceptible. TIP of Prague isolate of WVMV was 61 °C, at a dilution 1: 5000 47% of plants were infected, and 48 h > LIV > 28 h. Modal particle length was 743 nm. Massive granular inclusions were seen in pea epidermal cells, usually adhering to nuclei that did not show alterations. No serological relation to turnip mosaic virus could be established.

Twenty three isolates of turnip mosaic virus (TuMV) obtained from spontaneously infected plants ofSiaymbrivm loeaelii JUSL. were serologically related, but differed in reactions of eleven host plants. Susceptibility and sensitivity of each host for each TuMV isolate were classified by one of six degrees (0 to 5) respectively. Similarities of isolates (as compared in 253 pairs) were evaluated by means of a computer; for this purpose the source program MINDIF has been elaborated using the universal program language Algol 60. A table of differences between isolates was obtained and distribution of isolate pairs dependent upon the difference values was stated. The fitness of hosts for differentiating TuMV isolates was ascertained quantitatively. No relation of isolate similarity to geographical indices could be established.

Vicia faba plants cv. 'Erfordia' were treated with single application of CCC at 250 mg l^-1, 7 days before extraction. Such a concentration resulted in a 10.4, 14, 5 and 3.3 fold, respectively, increase in the levels of endogenous IAA, ABA, gibberellins and cytokinins relative to the controls. The results obtained indicate that a single application of CCC at a low concentration was sufficient to enhance the endogenous growth hormones in the treated plants. The results were obtained using GLC analyses for IAA, ABA and cytokinins, and the lettuce hypocotyl and soybean callus bioassay for gibberellins and cytokinins, respectively.

The 2,4 dichlorophenoxyacetic acid (2,4-D) applied in solution (10μg per plant) on a leaf of lettuce plants (Lactuca sativa, cv. Grosse Blonde Paresseuse) decrease the translocation of⁴²K from the treated leaf, both in pretreatment and in simultaneous action if the interval of time is sufficiently long between the foliar applications. The metabolic action of 2,4-D seems to be located in the treated leaf. The results may be explained by a stimulation of the metabolic activity and consequently of the retention, already observed by several authors, with 2,4-D and other phytohormones. The 2,4-D had not a comparable effect on translocation of⁴²K from the leaves of maize plants (Zea mays Dekalb 202) even if the amount applied is higher and the duration of the pretreatment more important than previously. However, it must be noted for this species a light stimulation with 2,4-D on the retention of⁴²K in the sheath of the treated leaf. The results obtained with lettuce and maize might be fitted in a pattern of selectivity which appears for other aspects of the metabolism.

Decapitation induced an additional formation of secondary shoots and anomalous spikes in all the species. The moan numbers of nodes, spikelets per spike, seeds per spikelet and spike, and the mean length of the stem and spike were reduced on secondary shoots of decapitated plants, while the mean and peak numbers of flowers per spikelet and the peak number of seeds per spikelet increased. The increase in the number of flowers per spikelet was the most striking on spike base; the seeds regularly occurred even in spikelets with an expressively increased number of flowers. The post-decapitation changes of the spike could be well expressed quantitatively according to the increased mean number of the flowers per one seed. Morphological ohanges in anomalous spikes of all the wheat species resemble phylogenetic reversions described in literature. Moreover, the peak numbers of flowers and seeds per spikelet were recorded in 52 varieties belonging to 21 wheat species. As compared with the decapitation trial, the greatest variability and the greatest differences between the speoies were also reoorded in the tetraploid group, and the smallest variability and differences between the species in the diploid group. We suppose that the striking morphological differences in post-decapitation spikes take place because the apical dominance was interrupted before differentiation of the recent form had been controlled in meristems on the decapitated stem base. Ancestral forms were morphologically realized with the help of an assimilating part of the decapitated stem.

Nitrate reductase activity in the leaves of young plants of cucumber.Cucumis sativus L. cv. Bílská, as determined bothin vitro andin vivo and expressed in terms of fresh weight, gradually changes in dependence on the ontogenetic development of the plants, reaching its maximum before full expansion of the leaves.

The relationship between photoperiodically changed growth of leaves, cotyledons, hypocotyl, roots and flowering has been investigated inChenopodium rubrum. It was found that all the growth characteristics recorded in leaves and cotyledons,i.e. length, area, dry weight and chlorophyll content, were inhibited during three inductive photoperiods (16 h darkness, 8 h light-SD) as compared with control plants grown under continuous illumination. Similarly, the cessation of root elongation and a decrease in root dry weight were observed. On the contrary, the elongation and dry weight of hypocotyl are stimulated by SD. The degree of the effect exerted by SD on the growth of different organs depends both on actual growth stage and the number of SD photoperiods. Increased relative rate of growth of roots and cotyledons was recorded in plants transferred after SD treatment to continuous illumination. However, this rise possesses only transitional character and the relative growth rate of treated plants equals that of control ones afterwards. The above growth changes are discussed as a possible modifying factor of floral differentiation.