Fractions of acid phosphate (orthophosphoric monoester phosphohydrolase, EC 3.1.3.2) were studied in extracts of segments from three growth zones of broad bean roots by means of electrophoresis in acrylamide gel. The azocoupling reaction with α-naphtyl phosphate was used for detection. The phosphatase activity was investigated in the range of pH 3.6-7.2. Altogether nine fractions moving towards the anode were revealed. Some fractions differed slightly in their pH optimum. The presence of Mg⁺⁺ in the incubation medium resulted in the activation of two fractions, Mn⁺⁺ showed activation of three fractions and inhibition of the rest of the fractions; the presence of Zn⁺⁺ resulted in a slight inhibition of all fractions. Between electrophoreograms of extracts of segments from the division zone and electrophoreograms of extracts of segments from the enlargement zone and from the maturation zone considerable quantitative differences were found with one fraction; proportions of the other fractions were approximately identical in electrophoreograms of all three growth zones. The response to the presence of Mg⁺⁺, Mn⁺⁺ and Zn⁺⁺ in the incubation medium as well as the pH optima of the individual fractions were identical for all three growth zones.

Fractions of non-specific esterase were studied in homogenates ofVicia faba L. root tips using disc electrophoresis in acrylamide gel. With α-naphthyl acetate, 7 bands were revealed in electrophoreograms, whereas only 5 bands appeared with naphthol AS acetate; the position of bands detected with naphthol AS acetate corresponds to 5 of 7 bands which appear when using α-naphthyl acetate. If incubated with α-naphthyl acetate, 1 band is totally blocked by the inhibitor E 600, whereas the other bands are weakened slightly and-more or less- proportionally, similarly, as if incubated with naphthol AS acetate. No bands appear after detection with α-naphthyl caprylate and with α-naphthyl myristate. Electrophoreograms developed with α-naphthyl propionate differ both from those treated with α-naphthyl acetate and from those treated with α-naphthyl butyrate. Remarkable, but only quantitative differences were revealed when comparing electrophoreograms from division, enlargement and maturation zones, detected with either α-naphthyl acetate, or α-naphthyl propionate. The non-specific esterase fractions revealed by disc electrophoresis are correlated with protein fractions distinguished in the same material by the same technique using xylene brilliant cyanine G staining and with fractions of the same enzyme found in sections of the same object treated histochemically.

A simple modification of a laboratory gravimetric technique for the study of transpiration of intact plants is described, by which the process can be followed continually. The plants are grown in light vessels on a light "keramzite" or other suitable medium, either alone or in combination with agar gel. The mineral component provides for the necessary cultivation properties of the medium, whereas agar gel ensures steady and undisturbed water relations in longer experiments.
The calculation of the transpiration intensity per unite of time is described. For reliable results the number of samples must be lange chough, so that the coefficient of variation does exceed 10 per cent. The determination of the transpiration is sufficiently exact even without a correction for changes in dry solids, the absolute increments in dry solids during the time interval studied being of a smaller order of magnitude than the values of transpiration. The results are expressed per fresh weight of the transpiring unite, by which an undisturbed transpiration study of a longer duration is rendered possible and the effects on the plant are excluded.

A now mathematical model, representing the transpiration process during ontogenesis and a circadian transpiration cycle, analysed in detail statistically, was designed using data obtained by the new modification of the gravimetric determination of the transpiration of intact plants. Regression analysis applied to the circadian cycle makes it possible to characterize basis parameters of the intensity and of the extent of this process and may serve a s a starting point when studying transpiration methodologically in greater detail.

The following work deals with the role of auxin in growth and differentiation processes of isolated shoot tips ofZea mays L. It seems that an optimal auxin concentration is apparently a function of a photoperiod duration. In case of a short day the optimal concentration is approximately 5 mg/l and in case of a long day it represents 1 mg/l. The duration of photoperiod influences even the level of exogenous auxins in explants. The plants exposed to the short photoperiod contain more substances of stimulative character while the ones exposed to the long day possess inhibitive substances. Externally applied auxin takes part in differentiation processes, especially in the formation of female elements in tassel spikelets and in transformation of the tassel primordium in pistillate ear.

The present paper deals with the epidermal structure and ontogeny of stomata in vegetative and floral organs ofHybanthus enneaspermus. The epidermal cells are either polygonal or elongated with straight, sinuous or arched thick anticlinal walls. The surface of the cuticle shows parallel striations radiating from the guard cells or hair bases. Unicellular and uniseriate bicellular trichomes with verrucose margins have been observed on all organs. The mature stomata are anisocytic, paracytic, anomocytic and transitional between anisocytic and paracytic. The ontogeny of anisocytic and paracytic stomata is syndetocheilic or mesogenous, anomocytic is haplocheilic or perigenous, while that of the transitional type is mesoperigenous. Four types of stomata have been observed on all the vegetative and floral organs and their ontogeny from organ to organ of this plant is constant. Stoma with a single guard cell is the result of disintegration of one of the guard cells before or after pore formation. Contiguous stomata are also occasionally noticed.

An expressive effect of temperature on water saturation deficit determined by "leaf-disc extrapolation method" was found. This error may reach about 15 to 40% of measured value with the temperature gradient of 10° between tissuein situ and under conditions of W.S.D. determination.

In these experiments the inhibitory ability of 12 varieties ofNicotiana tabacum L. to potato virus Y was studied by means of drop serological precipitation method. In 11 varieties under study a correlation was found between field resistance and the inhibitory ability of sap. Varieties S 390/1, line 40, fixed A 1 exhibited low inhibitory ability of sap, lines Bel 61-10, R 3, Criolo and Burley N-15 were of medium inhibitory ability and high inhibitory ability was found in varieities Viržinský zlatý, line 37, A 5205 and R 1. The variety Viržinský zlatý, which is believed to be susceptible to potato virus Y was found to have high inhibitory ability. This was confirmed by inoculation of leavesChenopodium giganteum Don., determination of the number of lesions by the half leaf test, and determination of relative concentration of potato virus Y by means of serological drop method. None of the varieties under study showed extremely high inhibitory ability against potato virus Y.
We believe that laboratory methods of determining the inhibitory ability of sap of tobacco leaves can be used to produce hybrids with high inhibitory ability on potato virus Y. The field resistance of those hybrids should, however, be checked by provocative field experiments.

The following paper deals with the character of endogenous auxins and gibberellinlike substances in the maize tassel and ear primordia during differentiation. Using bioassay the character of substances extracted from tassel primordia, internodes below the tassel, ear primordia and stem base was determined and correlated with the course of morphogenesis and differentiation. A low level of auxins and a high content of gibberellin-like substances accompanies the differentiation of terminal tassel. The differentiation of an ear is associated with an increment in auxin content while the level of gibberellin-like substances decreases. The character of growth substances in primordia remains practically unchanged in the course of further differentiation. The inhibitions appear in the plant and probably start numerous morphological reductions in the pistillate inflorescence structure or inhibit the growth of lateral primordia on the stemetc. The treatment of plants with maleic hydrazide at the beginning of tassel differentiation shifts the normal levels of endogenous regulators and brings about the transformation of tassel primordia into an ear. This transformation is accompanied by a marked rise in gibberellin-like substances, by an increment in auxins and the appearance of inhibitors.

The dependence of the frequency of recessive lethal (two groups), chlorophyll and morphological mutations on the mutagen concentration was determined in M₂ after subjection to N-nitroso-N-methylurea applied to seeds ofArabidopsis in three concentrations (0.05, 0.10 and 0.20mm). The observed frequencies were compared with the theoretically expected ones for the linear and for two exponential types of dependence, by using the t-test, according to the formulas m=k. C, m=k. C^3/2, m=k. C². No satisfactory agreement with any expected type of dependence was found when directly observed frequencies were used. Since a considerable deficit of mutation frequency was observed in high concentrations, the correction of frequency values was done with respect to the probability of occurence of double mutations. After such a correction, a clear exponential relation was found in both types of lethals and a linear one in chlorophyll and morphological mutations. The probable occurence of multiple mutations should be, therefore, taken into account if the dependence of mutation frequency on the concentration of mutagen is discussed.

As part of our studies on respiration systems in root zones of the horse bean (Vicia faba L., cv. Chlumecký) the influence of quininehydrochloride and potassium cyanide on respiration was followed. The inhibition of the oxygen uptake by quininehydrochloride was highest in the elongation zone and lowest in the meristematic zone. Thes shows that the flavine enzyme content is lowest in the meristem, highest in the elongation zone. The inhibition of Fe- and Cu-enzymes by KCN increases from the root tip towards the older parts of the root, but is lower than the inhibition by quininehydrochloride. The difference between the intensity of action of both, applied separately, and of the combined effect of both if compared with the action of cyanide alone, is highest in the elongation zone; this shows that relatively higher amounts of non-metallic flavine enzymes participate in this zone. Their relation to the pentose phosphate cycle is discussed.

In lupin (Lupinus albus L.) and pea (Pisum sativum L., cv. Raman) it was shown that the uptake of⁸⁹Sr from Knop's nutrient solution is significantly increased from a solution with decreased calcium content (one tenth of the normal content) and is slightly decreased from a solution with higher calcium content (150% of the normal content). The calciphile pea absorbs approximately 50% more calcium than the calciphobe lupin, and accordingly 50% radiostrontium less. The pea plant more strongly blocks the translocation of radiostrontium from roots to overground parts, as is proved by the higher discrimination factor of pea (i.e. by the ratio of specific activities of mCi⁸⁹ Sr/g Ca of roots to overground parts). The presence of chlorine in the nutrient solution decreases the content of radiostrontium per gram of dry matter, both in pea and lupin. Radiostrontium is absorbed quickly by both species of plants and is autoradiographically detectable as early as 2 hours after the introduction of radiostrontium to the nutrient solution. *** DIRECT SUPPORT *** A01GP049 00004

Floral buds ofBrowallia demissa, at three stages of development, were cultured on Nitsch and Nitsch basal medium. The supplements used include IAA; several cytokinins- benzyladenine, kinetin and 6-benzyl-9 tetrahydropyran-adenine (SD 8339); gibberellic acid (GA₃); 2, 3, 5-triiodobenzoic acid (TIBA); arginine and cysteine. All three stages of floral buds failed to complete development. In some treatments stages II and III produced callus and/or roots from the morphological basal end. Cytokinins promoted bud formation whereas both IAA and GA₃ depressed bud formation The shoots differentiatedin vitro were capable of setting flowers, fruits and seeds in all the treatments. The seeds were viable. Comparative studies of development of flowersin vivo andin vitro were made. In some treatments the flowers exhibited abnormal corolla, and roecium and gynoecium. Factors affecting normal bud initiation, organization and development are discussed.

The investigation concerns to what extent the phenotypic variability of some characters connected with the developmental rate inArabidopsis thaliana (L.)Heynh. is of genetic nature. For this reason, in a variable natural populationStř the values of coefficients of heritability were estimated by means of offspring-parent regression coefficients and of intraclass correlation coefficients for the three following characters: "number of days to appearance of the flower primordia", "number of rosette leaves" and "number of rosette leaves per day". The regression coefficients were calculated (1) by using simple progeny means, (2) the maternal data were repeated with each individual offspring value, and (3) the weighted regression coefficients were used.
It has been found that about a half of phenotypic differences in developmental characters studied is determined genetically. The question is discussed whether such heritability estimates can be influenced by dominance or interactions, as it results from considerations about the population structure inArabidopsis. There are no substantial differences between the methods used, and in the given case, the estimation of heritability with the aid of the intraclass correlation coefficient appears to be very advantageous.

Grains ofTriticum monococcum L. var.sofianum Körn. were treated with O.1 mM, 0.2 mM and 0.3 mM solutions of N-nitroso-N-methylurea (MNtt), with 0.03 M solution of buthylmethane sulphonate (BMS) and with X-rays in doses of 5 000r and 10 000r. The germination and development of individual colors of chlorophyl mutants were observed by the system developed byLamprecht (1960). All the mutants induced were classified according to their color changes into three main categories-homogenous unicolor, homogenous multieolor and heterogenous multieolor. In the last type the colors of individual leaves of the same plant varied. Anthocyanin mutations "albina" and "albino-transvirgata" sometimes coincided with the chlorophyll mutations. Some chlorophyll mutations showing complicated groups of colors appeared which were beyond the scale of classification by ordinary systems. The largest proportion in the spectrum of chlorophyll mutations, induced by MNH and X-rays was occupied by mutations of thealbina type. The broadest mutation spectrum in our experiments was induced by the application of 0.3 mM MNH. The doses of X-rays used induced relatively higher numbers of albina-type chlorophyll mutations than MNH and BMS. In our experiments we succeeded in inducing on medium size samples ofTriticum monococcum L. var.sofianum Körn not only almost all types of chlorophyll mutations, induced byFuji (1960, 1962) andMatsumura (1960), but in addition also a great number of other even more complicated chlorophyll mutations, which have never been previously described inTriticum monococcum. L.

Samples of the leaf tissue (14cm²) were placed in a plexiglass chamber which consisted of three parts. Water absorbed by the leaf tissue on one side of the sample was transported through the middle part of the sample to the opposite side and was transpirated there. The intensity of transpiration the intensity of water absorption and water saturation deficit (w.s.d.) were determined simultaneously in this tissue by gravimetry. Water balance was studied either in saturated samples of leaf tissue or in tissue where w.s.d. (10%, 20%, 30%, 40%) was established in advance. Although conditions for water absorption in leaf segments were optimal, w.s.d. originated in the saturated leaf tissue under all given external conditions (evaporation from 41.7 to 17.8 mg cm^-2 h^-1). W.s.d. which was established in advance for the most part increased during the experiment and reached even high values (more than 60%). the equilibration was reached only under conditions of low evaporation and initial w.s.d. higher than 20% in young leaves and higher than 30% in adult leaves. A positive correlation between the ratio of the intensity of water absorption to the intensity of transpiration and w.s.d. was found only under conditions of lower evaporation (17.8 and 23.2mg cm^-2h^-1). The maximal values of w.s.d. were limited in this way.
Water balance was studied: 1. in leaf tissue of upper, middle and lower leaves of fodder cabbage, 2. in leaf tissue of middle leaves of young and adult plants of fodder cabbage, 3. in leaf tissue of dicots (fodder cabbage) with different vessel orientation in respect to water transport, 4. in leaf tissue of monocots (banana-tree) with water transport upright to the vessel orientation.
Considerable change of water balance was observed when the water transport was prolonged by two incisions in the middle part of the sample.
Results of all these experiments revealed the possibility of water stress origin even in leaf tissue sufficiently supplied with water.

Genotypic, phenotypic and environmental correlations were ascertained in a set of 18 winter wheat varieties from experiments conducted for two years on two levels of mineral nutrients. Analysis of genotypic relationships found between yield components, area and length of the last leaf, angle of the second leaf and length of the plant at heading time was made using Wright's path coefficients.
In some instances the analysis showed, in comparison with simple genotypic correlation in reality, a different direct association of the pair of characters, the causal basis of which consisted in a relatively high indirect effect of other variables used in the experimental model.
From results cited it may be judged that the effect of the last leaf area was at least under our experimental conditions closely associated with both factors of ear productivity,i.e. with number of grains and average weight of one grain. The influence of the angle of the second leaf (next to the last at the top) was associated first with the number of productive stems, thus rather with a factor of productivity of plant stand and only in a wider action with the average weight of one grain.
In the future it will be useful to confirm the effect of subcharacters as additional criteria in the selection of plant types with higher prospective yield. From preliminary, as yet unpublished results, the use of selection indices in winter wheat may be considered an available method for estimating the expected genetic advance from the selections.

The inhibitors present in the extracts ofCinchoma ledgeriana, Emblica officinalis, Chrysobalanus C. icaco andTerminalia chebula were heat-stable, resistant to autoclaving, aging and desiccation for a week. However, they did not withstand dialysis for 48 hrs (exceptT. chebula extract.) These four extracts markedly inhibited the virus even on dilution in the ratio of 1ů1 but viral infectivity was sharply reduced at higher dilutions in each case. Moreover, the inhibitors in the stem bark extract ofC. ledgeriana, fruit pericarp extract ofE. officinalis andT. chebula were highly inhibitory even at pH 10.0, whereas inhibition of the virus by leaf extract ofC. icaco was reduced to 24 per cent only at the same pH. The inhibitors in these four extracts were found to be probably not proteinaceous in nature, when precipitated with ammonium sulphate and ethanol.

Changes in the protein constituents in pea stem sections during root formation and its inhibition by kinetin and ethionine were studied. Only quantitative differences in the protein fractions separated on DEAE-cellulose column were noted.
The formation of foci of meristematic cells in pericycle was accompanied by an increase in the amount of fraction "l". This fraction disappeared rapidly in sections where root formation either did not occur (internodial sections without nodes) or was inhibited by ethionine (stem sections with basal and apical nodes). Incubation of stem sections in a kinetin solution for 16 hours after cutting of stems partially preserved fraction "l". The increase in the amount of fraction "l" was one of the first metabolic changes in root-forming pea stem sections after cutting of stems.

This paper is a study of the effect of exogenous DNA of different genetic origins on the repair of meristematic cells of primary roots ofVicia faba, damaged by 24 hour treatment with 0.01mm solution of Ypenyl. Both kinds of DNA,i.e. isologous and heterologous, stimulated cell proliferation which was decreased by the action of the radiomimetic and influenced both dynamics of production of chromosome aberrations and the interchromosomal distribution of induced damage. While heterologous DNA increased the frequency of aberrations after all recovery periods studied, isologous DNA significantly decreased the number of chromosomal aberrations. Heterologous DNA increased at the same time the relative number of breaks in the group of small chromosomes, while by the action of isologous DNA the number of aberrations related to this group of chromosomes was relatively decreased.

The interactions between cereals-wheat, barley, rye and oats-in combined cultivation in mixtures of always two species in relation 1:1 in the initial phase of growth were studied. During thirty days' cultivation in pots the growth of the experimental plants in pure cultures and in mixtures and the changes of the nitrate nitrogen content of the soil in the experimental vessels were followed.
The experiments showed that all tested species of cereals interacted with each other during the growth in mixture. The growth changes began soon after sowing, were of a stimulating and inhibiting character and increased during the growth. An exception was the small reaction of oats to rye.
Decrease of the nitrate nitrogen content was determined in the soil of the experimental vessels during the cultivation of the plants. The changes of the nitrate nitrogen in the soil corresponded on the whole with the exception of the last phases of the experiments to the growth intensity of the experimental plants. No essential differences, either in the content or in the rate of the decrease of nitrate nitrogen, were found in the soil of control plants and in the soil of plant mixtures. Small differences which were manifested cannot be considered the primary cause of the mutual relations of cereals. The cause of the mutual relations may be attributed to allelopathic factors.

The peroxidase activity both of intact strawberry receptacles and of freshly bissected receptacles was determined by a chemiluminescence method. It was found that the chemiluminescence effect, when calculated per unit cut-surface area of receptacle, was correlated with the stage of development but, when calculated per whole cut-surface of receptacle, there was no clear correlation with the developmental stage.
With intact tissue, chemiluminescence did not occur in all cases.
IAA in the presence of peroxidase and hydrogen peroxide gave some low luminescence.

Bratislava mosaic virus was transmitted mechanically toChenopodium quinoa. The virus was isolated by means of gradient ultracentrifugation and the, proteins were distributed on an automatic recording photometer. Single fractions were taken with a fraction collector and used as antigen.
At the same time, antigen from leaves of the variety Sylván zelený infected with the Bratislava mosaic virus was prepared by means of the gradient ultracentrifugation.
The antisera were obtained from rabbits immunized with individual antigens. The antisera were tested with the saps ofC. quinoa infected with the Bratislava mosaic virus, by the method of double diffusion into agar according to Ouchterlony, and with adjusted saps from suckers infected with the Bratislava mosaic virus, by the method of double diffusion into agar according to Oudin. A specific reaction can be obtained in both cases only under the assumption that all conditions mentioned in the study are strictly kept.

The translocation of¹⁴C-labelled assimilates from a single leaf in bent and intact apple shoots was studied in varying stages of shoot development. In actively growing shoots¹⁴C-labelled assimilates translocated from the treated leaf and accumulated mainly in the shoot apex. In moderately growing apple shoots radioactive assimilates were translocated from the treated leaf in both directions towards and down the shoot. In apple shoots showing only slight growth activity the¹⁴C-labelled assimilates were transported from the treated leaf mainly to the base of the shoot, stem and roots. Bending shoots changed the pattern of distribution of radioactive assimilates. Bending actively and moderately growing shoots resulted in higher concentration of 14-carbon in the shoot apex than in controls. In slowly growing and non-growing apple shoots bending caused a higher accumulation of radioactive assimilates in the bent section than in an equal section of control shoots.

Pea enation mosaic virus (PEMV) was isolated from disea sed field pea (Pisum sativum L.ssp. arvense A.Gr.) and broad bean (Faba vulgaris Moench) plants grown as filed crops at Bohumilice in Bohemia. The virus proved to be pathogenic for the following plant species:Pisum sativum L. cv. Raman,Faba vulgaris Moench,Lens culinaris Med.,Vicia sativa L.,Lathyrus odoratus L.,Glycine soja L.,Phaseolus vulgaris L.,Chenopodium amaranticolor Coste andReyn,Nicotiana clevelandi Gray,Trifolium incarnatum L. The dilution end point of the isolate was higher in pea plants (10^-4) than in broad bean plants (10^-2). The thermal inactivation point was 65-68° and the longevityin vitro between 10 and 14 days. According to the host range, symptoms on pea plants and physical properties the virus isolate studied resembles some isolates described in the U.S.A. and represents a PEMV strain different from those reported so far in Czechoslovakia.

1) At a so-called natural anaerobiosis during the first 48 hours of germination the concentration of ethanol in pea tissues increases (according to the cultivation conditions) up to 40 μmol per gram fresh weight.
2) In a nitrogen atmosphere the content of ethanol in pea seedlings increases as well, and after a 90 hour incubation in N₂ it can reach even 100 μmol ethanol per gram fresh weight. In older plants the content increases the most markedly in cotyledons, but considerable amounts were revealed also in stems and roots. Its increase in vegetative organs of plants cultivated both in light and darkness is more or less identical. Ethylalcohol can be formed by the vegetative organs themselves, as proved by the increase of this metabolite in plants deprived of reserve organs; in addition, however, it is evidently transported into them from reserve parts. Ethanol formed under anaerobiosis is catabolyzed after transferring plants to the air.

Labelled carbon dioxide was supplied for 22 hrs to a leaf of the leader or to the lateral shoot in two-year-old apple seedlings. The distribution of radioactive assimilates within the plant following this treatment was investigated by using radioautography.
The transport of labelled assimilates from the young leaf of the leader was very meagre and affected only parts of the stem and the leaves situated in the close vicinity of the treated leaf.
The¹⁴C-labelled assimilates from the mature leaf of the leader were transported in a considerable amount to the apex and to the other leaves of the leader. They were also found in an appreciable amount in the stem and the roots, as well as in some lateral shoots.
After supplying¹⁴CO₂ to the lateral shoot remarkable transport of labelled assimilates was observed. Radioactivity was detected in the tip and in the youngest leaves of the leader, as well as in the roots. Their path in the stem was studied by dissecting the plant and examining the cross section from each internode. This method revealed that the assimilates from the treated leaf or shoot were transported downward only on one side of the stem in a helical pattern. The lateral shoots situated on the radioactive side of the stem were also labelled, whereas those situated on the opposite (non-radioactive) side were not labelled.

1. Kinetin at a supra-optimal dose of 1.0 mg/l reduces the growth inhibitory effect of CCC at 5 × 10^-2 M on tobacco callus and increases it on tobacco crown-gall.
2. CCC increases the content of total, acid soluble, protein anti nucleic acid nitrogm in both tissues. Kinetin partially reduces the effects of CCC on nitrogem metabolism in callus tissue, and increases it in crown-gall.
3. It is suggested that (1) CCC affects the synthesis of RNA directing the synthesis of protein, and (2) interaction of kinetin with CCC realizes via the genetic apparatus of the cell.

In this paper we compare the influence of heterologous and isologous DNA on the radiation damage repair of primary root meristematic cells ofVicia faba. Roots, irradiated by exposure of 150 r were cultivated at different time intervals either in tap water, or in a solution of heterologous or isologous DNA. In comparing mitotic activity of meristematic cells it was found that both types of DNA studied enhance the recovery of irradiated cells. The frequency of postmetaphase chromosomal aberrations of irradiated cells was influenced also by post-irradiation action of exogenous DNA. While heterologous DNA exhibited synergical effect with radiation in the sense that it increased the post-irradiation incidence of aberrations in all time intervals studied, isologous DNA had a strong repair effect-the application caused a significant decrease of the percentage of post-metaphase aberrations. Both kinds of DNA caused changes in the relation of chromosome to chromatid aberrations; a higher percentage of chromatid aberrations was registered. The study of the distribution of aberrations between large and small chromosomes ofVicia faba showed that the post-irradiation application of heterologous DNA increases damage of small chromosomes while isologous DNA caused an increased repair ability in this chromosomal group.

Floral differentiation ofChenopodium rubrum is more AD-sensitive than growth of the vegetative organs. With a suitable combination of the manner of application and the concentration of AD used, selective inhibition of flowering can be attained without any effect on growth. The inhibition of flowering was greatest if AD acted during the first two days of photoperiodic induction. With later application its effect on flowering was weaker. RNA synthesized in the first days of photoperiodic induction to a considerable extent ensured its further course.