The effect of 2,4-dinitrophenol (2,4-DNP), NaN₃, and iodoacetic acid (IDA) on glutamine synthetase (GS) and the effect of arsenate on GS, glutamate dehydrogenase (GDH) and nitrate reductase (NR) was studied in isolated pea roots. In sucrose supplied roots, GS level is depressed by higher concentrations of all the inhibitors tested and increased by lower (2 × and 3 × 10^- M) concentrations of 2,4-DNP; the decrease in GS level caused by sugar starvation is enhanced by all but IDA. GDH is enhanced by arsenate in a wider range of concentrations in sucrose-supplied roots than in roots cultivated without sucrose. NR is affected by arsenate similarly as GS.

Germination inPhaseolus trilobus is controlled by different moisture levels of seeds. The hard seed coatedness which develops secondarily can be removed by pretreatment with oonc. H₂SO₄. This also enhanced the onset of seed germination.

Carbohydrate changea in drought resistant and susceptible cultivars ofZea mays L. were studied at two different stages under imposed water stress in water culture experiments. The gradual decline in total carbohydrates with increasing stress levels was observed. At the 1st leaf stage starch content of the resistant cv. Agati-76 was lower than that of susceptible cv. Vijay but the reducing and non-reducing sugar content was much higher. At the 3rd leaf stage starch content was similar in two cultivars but sugar content was higher in the resistant cv. Agati-76. Differential changes in root and shoot carbohydrates as affected by increasing levels of stress were noticed. Carbohydrate changes have been discussed in relation to drought resistance.

Both N,N-diethyl-N-(2-hydroxyethyl)glycine (DEHEG) and N,N-diethyl-2-oxomorpholinium chloride (DEOMC) in an optimal dosage of 4 × l0 μmoles per seedling initially accelerated then retarded leaf growth in onion, and doubled the yield of bulbs in field conditions. Gibberellin and auxin nullified the latter effect. It is concluded that DEHEG represents a physiologically active form of DEOMC.

³H-thymidine incorporation and DNA-polymerase activity during early hours of wheat embryo germination at two viability levels have been studied. The patterns of two biosynthetic activities, as well as the dependence of DNA synthesis on protein synthesis, indicated the presence of a delay in the early phase of imbibition of the aged embryos with respect to viable germs.

When flax seedlings are decapitated above cotyledons and three days later one of the two cotyledons is removed then the remaining cotyledon stimulates in four to five days growth of its axillary bud. It has been found that content of endogenous cytokinins was higher in the stimulated bud as compared with the other one already 12 h after the cotyledon removal.
Flax seedlings decapitated under cotyledons regenerate adventitious buds on thy hypocotyl stump during 5-6 days. The endogenous fytohormonal preparation of this regeneration was investigated in the 20 mm apical part of the hypocotyl stump. Decrease in auxin and increase in gibberellins was already found during the first day after decapitation while the level of cytokinins increased as late as three days after the apex removal.

Ten taxa of the genusPisum were examined by disc electrophoresis in gels according to Davis and to Reisfeldet al. For evaluation of band patterns the Jaccard Index was applied.
The results in both types of gels show thatPisum abyssinicum and especiallyP. fulvum have biochemically a relatively isolated position.Pisum elatius and its subspeciescaspicum andpalestinicum form a subgroup withP. cinereum;P. sativum var.zeylanicum and cv. Jupiter form another subgroup withP. syriacum.
Our results are in good agreement with the results of Przybylskaet al. (with the exception ofP. cinereum) and also with immunoelectrophoretic analyses performed by Turkováet al. (1980), with the same exception.

Height growth ofMentha piperita L. is better at 44% than 100% daylight. At 14% daylight, growth is limited, probably by lack of photosynthate, and no flowering occurs. Specific leaf area and protein content increase significantly with the decrease of irradiance. Shade leaves contain more chlorophyll and potassium than sun leaves. Sun leaves show higher levels of calcium because of their more xeromorphic structure. Transfer experiments between light and shade indicate thatM. piperita responds very effectively to irradiance also in a late stage of the life cycle with changes of specific leaf area and chlorophyll content.

Extracts from the roots ofBoerhaavia diffusa L., stems ofCuscuta reflexa Roxb. or leaves ofEuphorbia hirta L. have shown a potential protective effect on the infection of potato virus X, in hypersensitive and systemic hosts. The inhibition by these extracts was systemic and sensitive to actinomycin D.

The xylem pressure potential (Ψ_xylem) of the leaves ofQuercus cerris, Acer campestre andCarpinus betulus was measured under anticyclonic weather types. The autocorrelation analysis revealed the daily course of the Ψ_xylem values approaching the stationary random process. A close statistical relation was found between the results obtained in three successive measurements of the Ψ_xylem (interval 2 h). A close statistical relation also between the value of the base potential (Ψ_b) measured at dawn and the actual values of the Ψ_xylem allowed the prediction of the Ψ_xylem values on the base of the known Ψ_b-values by means of a simple linear regression model.

Growth parameters and esterase isoenzyme patterns were studied in developing cotton fibre. Fibre length and dry weight when plotted against boll age showed four distinct stages; (i) initiation, (ii) elongation, (iii) secondary thickening, and (iv) maturation. Stage specificity and changing intensities of esterase isoenzyme suggested a finely modulated control of gene expression during fibre development.

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.