Growth measurements on individual polycormones ofScirpus lacustris L. cultivated in hydroponic sand cultures from single rhizome cuttings enabled us to analyse the process of offshoot formation. The time interval in the growth of individual subsequent shoots of one polycormone (plastochron), the final length of the shoot and the number of shoots formed during the growth period are suitable parameters for describing the rhythm of offshoot formation. The interdependence of these parameters and the effect of cutting or shading of individual shoots characterize the translocation of assimilates produced by individual shoots, and their use for the growth of subsequent shoots.

The author compares the activity of ¶-fluorophenylalanine and the effect of a medium without nitrogen on the morphogenesis of hyphae of Achlya ambisexualis ♀. A hyperramification often corresponds to a mode of prelethal development and is observed in the same conditions as an asexual multiplication.

The metabolism of¹⁴C-anthranilic acid (¹⁴C-AA) in kohlrabi (Brassica oleracea L. var.gongylodes L.) and the effect of radiation gamma⁶⁰Co on this metabolism was investigated. In hypocotylar segmnents of seven days old etiolated seedlings¹⁴C-AA was metabolised par, tially to its detoxication product¹⁴C-β-glucoside of AA. Simultaneously L-tryptophan was also formed, which in these plants is a precursor of indolic glucosinolates glucobrassicin and neoglucobrassicin.
The metabolism of¹⁴C-AA was followed for 97 h. Radiation, applied both to seeds and to seven days old plants did not affect the metabolism of¹⁴C-AA substantially. The intermediary reaction AA → L-tryptophan in the biosynthesis of L-tryptophan is not a radiosensitive part of the synthesis of this amino acid. A not too high radiation sensitivity (max. 45%) was observed in the metabolic pathway leading from L-tryptophan to glucobrassicin.

The formation of the isothiocyanate group of the aglycone of glucobrassicin (Glubr) an indole glucosinolate present in relatively large quantities in plants of the familyBrassicaceae, was studied. Labelled Glubr was synthesized from L-tryptophan-3-¹⁴C-amino¹⁵N in winter rape hypocotyl segments. After extraction it was finally isolated in a crystalline state by mixed crystallization with added inactive Glubr tetramethylammonium salt. The specific activity of¹⁴C and the atoms % excess¹⁵N were determined in both the precursor and the product. The ratio¹⁴C/¹⁵N as well as the values of dilution of¹⁴C and¹⁵N were in agreement in the precursor and in the final product. This shows,inter alie, that during the biosynthesis of Glubr, L-tryptophan is not deaminated. Thus the presumed isothiocyanate group of Glubr is synthesized on the α-carbon of the L-tryptophan alanine chain, the α-carbon together with the attached nitrogen pass directly from the precursor into the Glubr aglycone. This represents a type of glucosinolate aglycone biosynthesis where the carbon chain of the initial amino acid is not elongated. This finding is supported by the fact that L-tryptophan-l-¹⁴C does not yield labelled Glubr the C₁ carbon being decarboxylated during Glubr synthesis.

A very simple and quick procedure for the visualization of local lesions caused by the common bean mosaic virus was developed. It consists in a treatment of bean leaves in 96 % èthanol 50 °C warm and in the subsequent staining of the leaves in Lugol solution and washing in 30 % ethanol.

Time doses of a single concentration of streptomycin and its concentration doses acting for the same time period in a liquid medium had different effects on three strains of chlorococcal algae. This concerned both the physiological responses and permanent changes in the characteristics of cell colonies growing from treated cells. Significant differences were recorded in: the number of autospores produced during the first division of the treated cells on the surface of a solid medium, the length of the lag phase, the growth rate of the diameter of cell colonies, and the survival of the treated cells. The permanent changes in the characteristics of the growing colonies were very different in the individual algal strains in quality and frequency. Physiological and the mutation effects were compared and discussed.

Cycloheximide, ethionine,p-fluorophenylalanine, 6-azauracil, 5-diazouracil and vanillin, applied at relatively high concentrations, retarded the yellowing of kale (Brassica oleracea L. var.acephala) leaf discs in darkness, and stimulated it in light. All the compounds inhibited protein synthesis and retarded protein breakdown. Cycloheximide,p-fluorophenylalanine, diazouracil and vanillin also inhibited the incorporation of uracil-¹⁴C into RNA of senescing discs. Abscisic acid and 2-chloroethylphosphonic acid accelerated yellowing both in darkness and in light and stimulated the protein breakdown in senescing discs.
Abscisic acid inhibited the chlorophyll, protein and RNA synthesis in detached, greening cucumber cotyledons. There was no direct correlation between the activity of a given compound as an inhibitor of yellowing in darkness, and the degree of inhibition of RNA synthesis. The arrest of yellowing in darkness is possibly a consequence of the retarded rate of protein breakdown. Yellowing in light, on the contrary, is dependent on the actual rate of protein synthesis.

Studying the spread of mycoplasma, the causal agent of potato witches' broom disease, in tomato plants after grafting with infectious grafts ofNicotiana glaucaGrah., we found that after 9 days of graft symbiosis a hundred per cent infection occurred, whereas with infectious grafts ofSolanum lycopersicum this took place after 16 days. The first symptoms of the disease were manifested on tomato plants 21 days after grafting with infectiousNicotiana glauca grafts and 28 days after grafting with infectious tomato grafts. The results obtained present evidence for the possible preference of tomato plants for mycoplasma.

The content of endogenous GA₄ and GA₇ was determined in apple embryos cultured either on water or in the presence of ABA solution. The embryos were isolated from dormant seeds and from seeds removed from stratification which was effected either in water or in the presence of ABA. The influence of ABA on the decrease of two GAs levels was proved. The relation between the effect of ABA and the stage of stratification is closer in the case of GA₄ than GA₇. It is assumed ABA to inhibit the gibberellin biosynthesis.

A mycoplasma-like microorganism was identified on electron micrographs of ultrathin sections of roots and abnormal underground sprouts growing from roots of young apple trees artificially infected with the proliferation disease. Specimens taken in November, contained mycoplasmas at various stages of reproduction in sieve tubes of the host. Mycoplasma-like bodies occurred especially in abnormal underground sprouts, and rarely also in lateral roots.

Tre potato cultivars Erika and Krasava are unable to reproduce two strains of TMV systemically except when in graft symbiosis under normal greenhouse conditions with tomato which has been infected with the virus. The escape resistance of potato to TMV infection due to slight hypersensitivity was not changed either by long-lasting non-infectious symbiosis with TMV-sensitive tomato or in a constant environment (32±2 °C, 9 700 lx) which was adequate to change the hypersensitive reaction of some other TMV-hosts. On the contrary, enhanced temperature provoked a still more severe local and necrotic response in the potato varieties. This led to systemic necrosis and the quick death of potato components systemically infected in graft symbiosis with tomato under normal greenhouse conditions when transferred into an environment of enhanced temperature.

The determination of mitotic frequency was made in two variants: one part of seeds was germinated in darkness, the other-under periodical artificial lighting. The diurnal mitotic activity varied from 6.2 to 13.5 per cent. After germination under periodical lighting two peaks of mitotic activity [at 6°c a.m. and 4°c p.m.] were found whereas after germination in darkness there was only one [at 12°c a.m. or 6°c p.m. in different repeats].

The effect of growth retarding amino acids (L-aspartic acid,L-leucine,L-methionine, andL-threonine) on nitrate reductase (NO₃R), nitrite reductase (NO₂R), and NADH₂ dependent glutamate dehydrogenase (GDH) in excised pea roots was followed,L-methionine andL-threonine slightly depressed NO₃R activity,L-aspartic acid enhanced NO₂R and GDH activities.L-methionine andL-threonine also slightly decreased nitrate uptake. The results obtained are discussed in connection with the growth effects of the amino acids investigated.

The paper deals with the effect of some factors on the set of mature seeds in artificially pollinated excised placentae cultivatedin vitro.
It was revealed that both the degree and the variability of the seed set depend on the age of the experimental flowers. The best results were achieved using placentae excised from the flowers collected 1 to 3 days after anthesis.
The technique of pollination which consists in applying pollen onto a certain site of the placenta was substantially more successful than dusting pollen over the entire placenta surface or sowing pollen on the nutrient medium in close proximity to placentae.
It was confirmed that casein hydrolysate at a concentration of 500 μg ml^-1 nutrient medium favourably affected the seed formationin vitro.
The seed set resulting fromin vitro fertilization does not depend upon whether, during, a fourweek cultivation, the cultures are kept in the dark or in diffused daylight.

Deformities of leaves induced by 2,3,5-triiodobenzoic acid (TIBA) may be helpful in elucidating certain plant growth correlations. The different behaviour of long and short shoots as regards apical dominance may be tested with this substance. Shoots growing out through ring fasciations first form leaves lacking the teeth and marginal primordia corresponding to bud scales. Are fasciations facilitate correlative studies on anisophylly. Sylleptic branching is cleared by additional fasciations provoked by the cytokinin supply. The effect of gibberellin which decreases these deformities corresponds to the correlative influence of roots. The TIBA induced modification of aerial roots on internodes treated with naphthalenacetic acid reveals the importance of polarity and periodicity in the shoot development.

Five mm sections excised from 20, 30 and 40 mm long coleoptiles were transferred into a indole-3-acetic acid (IAA) solution after an incubation in a medium containing buffer and sucrose without IAA. The ability of sections to elongate in dependence on IAA treatment was rapidly decreased at a temperature of 23 °C within a period of time depending both on the duration of incubation and on the age of coleoptiles from which sections were obtained. Under the same conditions of incubation and age the same decrease of the ability of sections to elongate at 4 °C was, however, observed only after a period fourfold longer than at 23 °C. Incubation of sections in the presence of benzimidazole did not extend their reactivity to IAA. This phenomenon may be therefore considered as a senescence reaction which is more effective at 23 °C than at 4 °C.

The employment of the classic stand density experiments in studies of the horizontal organization of plant stands is very laborious and requires a large experimental field area. The procedure based on the regular thickening of plant stands is more convenient for plants grown in a lower density. A simplified modification of this method is described which keeps a constant square nutritional area regardless of the plant densities.

Five strains of cucumber mosaic virus (CMV) were distinguished in the isolates of viruses which attack cucumber in Czechoslovakia (Havránek 1970). The strains A, B, C, D, and E of CMV were defined according to different syndromes onNicotiana tabacum L.,N. glutinosa L.,Phaseolus vulgaris L. andChenopodium polyspermum L. The Czechoslovak strains, in comparison with American ones, did not cause systemic disease inCucumis anguria L. orCucurbita moschataDuch., but strains D and E of CMV suppressed the tolerance of American cucumber cultivar Wisconsin SMR 18. The propertiesin vitro of isolated CMV strains correspond to the description of CMV, but we did not succeed in establishing their antigenic behaviour. The relation of the Czechoslovak CMV strains to those described in publications is discussed.

Both CCC and cold (5°C) treatment gave rise to an increased content of the water-soluble proteins in leaf tissue of the winter rape, irrespective of the day length. This effect was accompanied by a decrease of the insoluble nitrogen compounds content, mainly under theLD (the 16 hour day). The applied retardant also stimulated the consumption of the structural compounds induced by low temperature.
Low temperature treatment hardened plants more distinctly than the CCC application. The frost hardening effect of CCC andSD (the 8 hour day) was manifested only at 20°C and it disappeared at 5°C.
Changes in frost hardiness were not correlated with the changes in the reducing sugar content and in the reducing ability of the studied tissue. The coincident effect of CCC and cold on the reducing sugar content was observed underSD conditions.

Barley seeds were treated with ethyl methanesulphonate (EMS), washed for 24 h, redried to 15 per cent moisture and stored at 25°C. The criteria used for expressing the effect of storage were chromosomal aberrations in root tips, M₁ germination, M₁ seedling height, M₁ survival and the frequency of M₂ chlorophyll mutants. The increase of the M₁ biological injury due to storage was not influenced:
a) by applying EMS solutions at pH 2, pH 7 and pH 10,
b) by lowering the EMS concentration and increasing the treatment time,
c) by different variations of washing with water and by washings with 0.005 N NaOH, 200 mM cysteine or 200 mM thiourea. The rate of the increase of the M₁ injury due to storage depends on the EMS dose. With a decrease in the EMS dose the storage effect is more delayed.

The influence of photoperiodic induction on the incorporation of uridine-³H into the shoot apices ofChenopodium rubrum was studied using the technique of autoradiography. No increase in uridine incorporation was detected either during induction lasting three days or immediately after its termination. Pyroninophylia likewise did not rise. However, changes in uridine incorporation related to morphogenetic activity during leaf formation and later during differentiation of inflorescences were well marked. The distribution of label in the nucleus immediately after three inductive cycles shows the ratio of extranucleolar to nucleolar incorporation to be higher in non-induced control plants than in induced ones.
Data from literature pointing to an activation of RNA synthesis during transition to flowering are discussed and compared with other systems where ontogenetic changes are accompanied by marked changes in RNA synthesis. It is assumed that the activation of RNA synthesis after induction is connected mainly with the activation of growth. However, inChenopodium rubrum photoperiodic induction proceeds together with limited growth and without activation of RNA synthesis.

Nitrate reductase (NO₃R) activity, nitrite reductase (NO₂R) activity and NADH₂ dependent glutamate dehydrogenase (GDH) activity were followed in extracts from excised pea roots incubated under aseptic conditions for 9 and 24 h in nitrate containing nutrient medium to which IAA was added in concentrations promoting lateral root formation (1 × 10^-5; 3 × 10^-5; 5 × 10^-5 M) and kinetin in concentrations which reduce lateral root formation (0.1; 1; 5 mg 1^-1, that is 4.65 × 10^-7;4.65 × 10^-6 and 2.3 × 10^-5 M). NO₃R activity was not influenced by IAA, NO₂R activity was slightly depressed by IAA after 24 h incubation and GDH activity was slightly increased after 24 h incubation in the presence of IAA. Kinetin decreased NO₃R activity significantly both after 9 h and 24 h incubation, slightly increased NO₂R activity after 9 h incubation but slightly decreased it after 24 h incubation, and did not affect GDH activity after 24 h incubation. However, when applied together with IAA, kinetin abolished the promoting effect of IAA on GDH activity. IAA neither reversed nor accentuated the effect of kinetin on NO₂R activity. Nevertheless the depressing effect of kinetin on NO₃R activity was emphasized by the presence of IAA after 9 h incubation. The results obtained indicate that reduced nitrate assimilation due to the depression of nitrate reductase activity caused by kinetin probably contributes to the negative growth effect of kinetin in pea root segments grown in nitrate medium.

The root surface determined microscopically amounts only to ten per cent of the surface assayed with methylene blue. This difference is assumed to correspond to the sorption surface of cell wall interfibrillar capillaries. The volume of these capillaries amounts to 0.1 per cent of the total volume of the organ only, but their surface far exceeds the external root surface. It is suggested that the interfibrillar capillaries of the epidermis cell walls constitute the main elements of the root sorption surface.

No influence of IAA on the endogenous estrogen content in bean plants was stated. At the same time kinetin was found to increase and abscisic acid to decrease the amounts of estrogens.

To study the effect of high altitude cosmic radiation the seed material of 15 species ofAcanthaceae was subjected to 3 types of exposures in balloon flights at an altitude of 30 900 to 38 100 metres. Germination behaviour was recorded and cytological studies were made. In the material subjected to one exposure, no detectable cytological or morphological change could be recorded. Material subjected to two exposures showed a 1 1/2 to 2 fold increase in cellular dimensions. A fragmented chromosome was observed inRostellularia procumbens. Flowering inJusticia betonica was advanced by 3 weeks. Among the species subjected to 3 exposures, two species showed diminution in height, and entered into flowering earlier than the controls. A study of germination behaviour showed, in general, that the decrease in germination percentage was directly proportional to the amount of radiation. The results indicate that the treatment with cosmic radiation may be helpful in reducing the period between sowing and harvesting. Therefore, if similar experiments be conducted on crop plants, they might yiled interesting and important results from the agricultural point of view.

The transpiration rate of detached leaves exposed in the atmosphere saturated with water vapour increased after a certain time. This time as well as the shape of the transpiration curves varied according to the duration of the exposure of the leaves in the humid atmosphere.

Highly active NAD-MDH (E.C.1.1.1.37) and low activity of NADP-MDH (E.C.1.1.1.40) were found inVicia faba roots. The NAD-MDH activity is associated with 6 to 12 isoenzymes. The number of isoenzymes is dependent on the extraction (use of Triton X-100etc.) and detection procudures (presence of KCN, phenazine methosulphate). The meristematic zone does not contain one isoenzyme (X) which is present in the other two zones. The meristematic zone, elongation zone and zone with the beginning differentiation differ in their activity of individual isoenzymes.