Abscisic acid (ABA) was applied in a concentration of 1. 10^-3 M and 1. 10^-4 M to the quantitative SD plantChenopodium rubrum under various light regimes. ABA did not influence flowering in plants under continuous illumination, enhanced flowering in plants subjected to long days and inhibited it in plants induced by short days. It was concluded that ABA can not substitute for inductive treatment but its action may be additive to initial stages of reproductive morphogenesis (enhanced growth rate and branching of the apical meristem) as evoked by long days.

Biosynthesis of nucleic acids in the pea buds released from apical dominance by decapitation has been studied.
The rate of biosynthesis of all nucleic acid classes separated by means of methylated albuminkieselgur (MAK) column chromatography was found to be increased in released pea buds as judged by the extent of orotic-6-¹⁴C acid incorporation. This increase has been observed in all experimental points examined (15, 24, 36 and 48 h after decapitation), being the most pronounced 15 h after decapitation. After that a certain decrease of the specific radioactivities of nucleic acids has been registered, but even 48 h after decapitation specific activities of the main nucleic acid classes were higher in comparison with those found in dominant buds.
Variations of the free pyrimidine nucleotide pools were about 14% suggesting that this parameter did not influence the extent of the uptake of labelled orotic acid.

Four days oldAmaranthus seedlings responded to light treatment with an increase of amaranthin accumulation. With increasing irradiation time, red light caused a saturation effect. Blue light induced a high irradiation response. The blue light effect was reversible to a certain extent by far-red irradiation given at the end of the treatment with blue light. Intermittent red light (3 h red light, 3 h dark, …) caused a higher amaranthin accumulation than 24 h continuous red light. Results obtained with red and blue light are discussed on the basis of the phytochrome system.

Plant tissue connected in a d.c. circuit behaves as a capacitor, short-circuited through a resistor. Using a saw-tooth voltage (T = 2 ma, U_max = + 13 V), structural and physiological conditions in a plant tissue can be analyzed on the basis of changes in the current character.

Occurrence and distribution of trehalase were examined in cytoplasmic and cell wall fractions of cultured cells of morning-glory, soybean and persimmon. Also, some enzymatic properties and solubilization of the enzyme from cell walls were examined. Trehalase was present in both fractions of morning-glory and persimmon cells while trehalase was present only in the cytoplasmic fraction of soybean cells. Morning-glory trehalases in both fractions showed the same optimum pH at 5.5, while persimmon trehalases in both fractions showed the same optimum pH at 6.0. Soybean enzyme in the cytoplasmic fraction showed two optimum activities at 4.0 and 6.5.
Morning-glory cell wall bound trehalase was solubilized with various IM salts at about 70 to 75%. Also, the enzyme was solubilized with various buffers and the solubilization ratio increased with increasing in pH of a same series buffer. After multiple extractions with IM NaCl, about 15% of the original trehalase activity still remained in cell walls. On the other hand, Triton X-100 and the substrate, trehalose, at the various concentrations did not release trehalase from cell walls.
Invertase and cellobiase solubilized from morning-glory cell walls were re-adsorbed to the cell walls. However, readsorption of trehalase to cell walls has not yet been attained. Based on these results, physiological roles of plant cell wall-bound trehalase were discussed.

We have compared the action of light on ribosomal RNA synthesis in mustard and cabbage seedlings, two of the most frequently used systems for the studies of anthocyanin synthesis. The level of RNA (both t-RNA and r-RNA) "stored" in mustard dry seeds is much lower than in cabbage dry seeds. The kinetics of RNA synthesis in cabbage and mustard seedlings exposed to light are very different: In cabbage seedlings, light produces no apparent stimulation of cytoplasmic r-RNA synthesis, while it does increase plastid r-RNA synthesis. On the other hand, in mustard seedlings, light promotes both cytoplasmic and plastid ribosomal RNA synthesis. Streptomycin, which inhibits chlorophyll formation and chloroplast development while having no effect (mustard) or enhancing (cabbage) anthocyanin synthesis in these two systems, is in both cases an effective inhibitor of plastid r-RNA synthesis, but not of cytoplasmic r-RNA synthesis.

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.

In an embryo shoot apex more different mutations may be induced after the mutagenic treatment of seeds. These mutations may be distributed among the apical initial cells in different ways. According to the proposed mathematical model it is possible to estimate the proportion of initial cells with 0, 1, 2, …,x mutations in the apioes with a given number of initials,k, which is characteristic for each plant object, and under a certain number of induced mutations per apex,n, determined by the conditions of the mutagenio treatment. Owing to the disadvantage of multimutations in plant breeding it is possible according to the formula P(X > 1) = 1 -e^-n/k(l + n/k). to use, at a knownk, suchn's which secure minimum multimutations.

Large complex inclusions evoked by wisteria vein mosaic virus contain cylindrical inclusions, mostly pinwheels (and bundles) and rarely also scrolls and laminar inclusions. Bundles are often abutted to cell walls at plasmodesmata and show association with endoplasmic reticulum and cisternae. Virus aggregates are attached to cylindrical inclusions, various membranes and/or plasmalemma.
Cytoplasm contains more or less disintegrated chloroplasts and mitochondria, abnormal membranes, many ribosomes, bounded vesicles with fibrillar contents, numerous and large microbodies, and membranous whorls. These phenomena are not specific.

Spring barley cv. Spartan was cultivated in a complete and nitrogen lacking Richter's solution. In other experimental variants the nitrogen was omitted after six days of cultivation in the complete nutrient solution or the nitrogen lacking solution was replaced with the complete solution after the same period of time. Anatomy of the second leaf blade was quantitatively analyzed after 12 days of cultivation. Continuous nitrogen deficiency resulted in thinning of the blade, reduction of the cross-section areas of the blade, vascular bundles and sclerenchyma region. The most sensitive reaction to the nitrogen deficiency was that of assimilation parenchyma. The values of characters of the other two investigated variants were between the control and permanent nitrogen lacking variant.

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.

Upon rooting of poplar stem cuttiags the total inductive stimulation does not take place, but the individual root primordia maintain a relative independence. This becomes evident by various time parameters of their differentiation. Under experimental conditions, in dormant cuttings from one year individuals of the hybrid I 214 the activation of the first root primordia occurs after 24 h, the pre-emergent development of the roots formed was completed after 72 h.
The activated root primordium is divided into two regions. In the distal region with the predominating cell division the root apex with histogens is formed by the action of initials. From peripheral cell layers of the distal region the so-called "Wurzeltasche" develops which covers the root cap. Due to cell elongation in the proximal region the root apex is pushed up towards the stem surface. The beginning differentiation of the connective vascular tissue is a preparative step for the connection of the vascular system of the developing root with the secondary vascular system of the maternal stem. Following the penetration of the root through the peripheral stem tissues this connection is realized with progressing development. In the developed root the protoxylem elements differentiate continuously and acropetally in direct continuity with tracheids of the basal connective region.

Shoot t ps, young internodal segments and young developing leaves ofBetula ver rucosa Ehrh. in contact with agar nutrient medium formed tissue with numerous buds if medium contained a low concentration of cytokinin (BAP) and auxin (IBA or NAA). Tissue with induced buds transferred on a fresh nutrient medium continued in a formation of new buds which developed into shoots. Excised shoots were rooted on agar medium with a low concentration of auxin. Regenerated trees showed a genetic uniformity.

The influence of growth regulators (GA and IAA) on the genetic effects of sodium azide was studied. Treatments with growth regulators were administered either prior to or after the mutagen. Post-treatments were found to be more effective against mutagen-induced plant growth injury and gave a slightly higher frequency of mutations. M₁ spike sterility however showed a rise following treatments with growth regulators.

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 substituted 5-chlorodiphenylamine-2-carboxylic acid hydrazides and their N-benzylidene derivatives were tested for their antiviral activity against gomphrena mosaic virus in a hypersensitive hostin vitro as well asin vivo. Most of the compounds exhibited potential antiviral activity. These compounds may be useful in controlling viral infections in garden as well as in field crops.

SixteenPisum sativum cultivars were mechanically inoculated with two isolates of PVX. Distinct necrotic local lesions on the inoculated leaves were found in six cultivars 5 to 6 days after inoculation. The best results were obtained with the Meteor and Raman cultivars, 17 to 23 days old.

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.

Sucrose was markedly superior to fructose and glucose in promoting growth of plantlets from immature maize embryos. The elongation of roots is shown to be more sucrose dependent than that of shoots. On the other hand, the exogenous sucrose was less effective than fructose as substrate for carbohydrate catabolism and for the synthesis of alcohol-insoluble compounds at the beginning of embryo cultivation. The absorbed fructose was found to be rapidly converted to sucrose and the level of endogenous sucrose derived from sugar supplied to the medium was higher in fructosethan in sucrose-fed embryos. The preferential utilization of fructose over sucrose, however, declined with the progress of germination which may be related to the decrease in proportion of scutellum in total mass and physiological activity of the embryo.

Two barley chloroplast nuclease fractions were separated by the affinity chromatography and gel electrophoresis. Both were about 2 times more active to RNA than to native DNA and about half as active to denaturated DNA as to native DNA. Both fractions were as active to UV-irradiated (270 J m^-2) native DNA as to intact DNA but their action was inhibited by apurinic sites. The enzyme activities were inhibited by high concentrations of EDTA, NaCl, Mn²⁺, Ca²⁺, Zn²⁺ ions and by N-ethylmaleimide. They do not require Mg²⁺ ions but are stimulated or at higher concentration inhibited by their presence. Both RNase and DNase were active over a wide pH range (5.5-9), the optimum for DNase action in the presence of Mg²⁺ being 6.5, for RNA decomposing activity at pH 8.0. As no mononucleotides were detected in acid soluble form, it seems likely that DNase acts in the endonucleolytic way.

A previously undescribed disease onLupinus hybrids manifesting typical witches broom symptoms occurred spontaneously in a locality in North Bohemia. Broomed shoots appeared only in late summer and resulted from the abnormal proliferation of dormant axillary buds in leaf and fruit axils. The shoots were bushy and their leaves were dark green and not reduced in size. Electron micrographs of ultrathin sections showed the presence of numerous mycoplasma-like organisms (MLO) in diseased but not healthy phloem tissues.

Changes in glutamine synthetase activity located in the cytosol of root nodules were followed in pea (Pisum sativum L.) plants in relation to their nitrogenase activity. The highest glutamine synthetase activity was found in young nodules (15 days after inoculation) and its changes in 17-to 45-day-old plants showed a positive correlation with nitrogenase activity. In contrast to nitrogenase activity, changes in glutamine synthetase activity during the day and night period could not be unequivocally interpreted in terms of diurnal fluctuation.

Using immunochemical methods a comparison was made of a complex of water soluble (albumins) and salt soluble (globulins) seed proteins, especially vicilin and legumin, in selected species of the genusPisum, to determine the degree of their taxonomic relationship.
Within the genusPisum the interspecific differences betweenP. abyssinicum, P. cinereum,P. elatius, P. fulvum, P. sativum, andP. syriacum are much smaller, and thus the taxonomic distances are shorter than is the casee.g. in the genusPhaseolus. In spite of this fact one may state thatPisum sativum, P. elatius andP. syriacum constitute a definite group, whereasP. abys-sinicum, P. cinereum and P.fulvum have longer taxonomic distances.

The contribution deals with the distribution of β-glucuronidase in the germinating pollen grains ofPortulaca grandiflora. In non-germinating pollen grains the enzyme is localized in the pollen wall; the cytoplasmic activity is subdued. With the initiation of germination, the activity of enzyme increases and the positive granules are richly packed in the pollen grains and pollen tubes. The stigma hairs also have such an activity. The functions of the enzyme in the metabolism of germinating pollen grains are discussed.