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.

Both chlorcholinchloride and ethrel are used as growth retardants in cereal cultivation. Wheat seedlings were cultivated in nutrient solutions containing 10^-3M CCC, CEPA or 5 × 10^-4M CCC and CEPA, respectively. The epidermis of full-grown primary leaves was analysed.
CCC relatively equally decreases the length of leaves and long epidermal cells, whereas CEPA mainly inhibits cell division. Leaf growth is always a little more inhibited than the number of stomata and trichomes is reduced by CCC or CEPA. This results in an increased frequency of stomata and trichomes by about 14 to 16 per cent. This means that retardants can strongly influence the length of leaves and the length or number of long epidermal cells but, due to the mechanism of programmed determination, the frequency of stomata and trichomes is kept constant within relatively narrow limits. Furthermore it can be concluded that long epidermal cells function as pace-makers in the growth of leaves of monocotyledonous plants.

Progenies were raised from seeds ofLens esculenta L., cultivar JLS-3 treated with 0.03%, 0.09%, 0.16% and 0.26% (by volume) aqueous solutions of EMS, MES and MMS. Meiotic ohromosomes were studied from anthersmears. Ring and chain configurations of chromosomes were found more abundant with higher doses of mutagens particularly those of EMS. Chromosome bridges and multinucleolate nuclei were also frequently seen.

It is wellknown that following the amputation, or darkening of one cotyledon in decapitated flax seedlings, the opposite remaining, or illuminated, cotyledon exerts a stimulatory effect on the growth of its axillary bud. For the induction of this stimulating effect a 21-72 h continuous darkening of the cotyledon is sufficient. Endogenous gibberellins take part in the stimulation effect of the illuminated cotyledon, since their level in the illuminated cotyledon increases as early as 12-48 h following the darkening of the opposite cotyledon. The apical part of the cotyledon has a higher growth stimulatory effect on the growth of the cotyledonary axillary bud than the basal half. This again is associated with endogenous gibberellins the level of which is higher in the apical half of the cotyledon than in the basal one.
Upon removal of the root and hypocotyl base in decapitated flax seedlings deprived of one cotyledon, the remaining cotyledon loses its stimulatory influence, so that the bud of the amputated cotyledon grows more vigorously (Dostál 1955). In this growth correlative phenomenon the root may be substituted by cytokinin BA applied in the form of a 0.1-1.0 per cent paste onto the remaining cotyledon, for again in this case the bud of the preserved cotyledon grows more vigorously. Following the decapitation of the axillary of the amputated cotyledon in decapitated pea seedlings with an intact root and deprived of one cotyledon, the axillary of the remaining cotyledon grows more intensively than the serial of the removed one. If the plants operated on in the same way are deprived of the root, the serial of the removed cotyledon gains a correlative growth predominance. If the plants deprived of root are cultivated at the same time in a solution of BA (10-20 mg 1^-1), the correlative predominance is acquired by the axillary of the remaining cotyledon. In growth correlations between cotyledons and their axillary buds in pea seedlings the root may thus be substituted by exogenous cytokinin, as well.

Maximum diffusive conductance of abaxial epidermis of primary bean leaves was considerably higher than that of adaxial epidermis. While conductances of both epidermes responded parallel to a decrease in leaf water potential (they increased slightly, reached maxima and decreased to very low values), differences in their response to photon flux density were found. The conductance of abaxial epidermis increased rapidly over lower photon flux densities and gradually over higher photon flux densities, on the other hand the conductance of adaxial epidermis increased only gradually over the whole range. The observed parallel or different response of adaxial and abaxial epidermes to leaf water potential or photon flux density did not change with changes in experimental conditions.

A comparison of the effects of a water extract of the fresh vegetation apex ofChelidonium majus L. var.majus, with those of berberine sulphate and of chelidonine hydrochloride is reported. The water extract of fresh stems and leaves ofChelidonium majus and the berberine sulphate solution had marked mitodepressive effects on onion root tip cells. Chelidonine hydrochloride had similar but less marked effects. On the basis of the results obtained it can be assumed that the most active group of substances with cytostatic effects, hindering the cells from entering mitosis, are protoberberine bases contained in the latex ofChelidonium majus. Within the range of the investigated concentrations the extract of fresh stems and leaves was less toxic for the cells than berberine sulphate. The data ascertained provide evidence that the mechanism of the cytostatic action of chelidonine, of berberine, as well as of the extract of fresh stems and leaves ofChelidonium, majus differs from the mechanism of the action of colchicine. Of the testedChelidonium alkaloids only chelidonine produced a partial inactivation of the mitotic spindle.