The variability of the incubation period of the beet mosaic virus [Beta virus 2(Lind) Smith] was investigated in a three year experiment. The virus was transmitted by the black bean aphid (Aphis fabaeScop.) or by a mechanical inoculation onAmaranthus caudatus L. Variability characterized by the standard deviation indicates a closer distribution of measurements when the virus was transmitted by mechanical inoculation. The differences in variability of the incubation period between the two methods of virus tramission are statistically significant; dispersion and standard deviation are lower after mechanical inoculation. The average length of the incubation period after virus transmission by aphids and by mechanical inoculation was 10.8 and 7.7 days, respectively. The difference was found statistically significant and may be explained by the higher number of viral particles transmitted by mechanical inoculation which may accelerate the process of infection. A significant correlation between the temperature of the environment and the length of the incubation period was also found in some experiments.

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.

Changes in the variability of quantitative characters (number of fertile stems, length of the stem and of the spike, number of spikelets in the spike, number of seeds in the spike and in the spikelet) in M₂ induced with 0.1 mM, 0.2 mM and 0.3 mM N-nitroso-N-methylurea (MNH) and with 5000r and 10 000 r of X-rays inTriticum monococcum L. var.sofianumKörn. were evaluated. The mean of the populations remained practically unchanged by the mutagens whereas the variability increased considerably with increasing concentration or dose. Changes in the variability were more pronounced in the values for the first stem than in the values for the first three stems. When changes in the population mean were found (with some of the most elevated concentrations and doses), these changes were shown to be mostly due to a repetition of the cultivation, whereas the changes in the variability were mostly due to the action of the mutagens. In all experimental populations, mutations in quantitative characters were successfully induced.

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.

The stem pith discs of kale and tobacco were cultured on simple sugar-mineral media. The dry weight of the expiants rose almost linearly for 20 days and was doubled in 10 to 12 days. Neither protein accumulation nor the increase in cell number are responsible for this relatively high increase in dry weight of discs. The accumulation of sugars or polysaccharides is thought to be the cause of this increase.

Growth correlations among lateral shoots of one-year-old apple treesMalusMill., were described. The existence of a mechanism was postulated through which small original differences between buds or young shoots are quickly augmented, thus leading to differentiation of long shoots and short shoots. Existing hypotheses do not seem sufficient for explaining correlative phenomena of this type; a cybernetic approach was therefore applied. Studying growth correlations in terms of cybernetic revealed that previous hypotheses concerning correlations do not contradict each other as often thought, but depict different links in a more general chain of events. A cybernetic model points out the importance of root influences in interaction among shoots. It also shows that synergism between auxin, gibberellin and cytokinin in xylem and phloem differentiation and in starch metabolism is very important for understanding correlations in apple trees.

The presence of native cytokinins was studied in growing apices of apple-tree annual shoots. During June the presence of two compounds showing cytokinin activity in biotest was observed and their R_F value was determined in three chromatographic systems.

Germination ofPinus banksiana seeds is controlled by the photoreversible phytochrome reaction. The seeds, even unimbibed, are sensitive to red light. At 660 nm, the energy required to promote germination to the same order of magnitude is much higher for unimbibed seeds than for the imbibed ones. In both cases it is possible to reverse the effect of a single red light irradiation by applying far red light (730 nm).

The interaction of GA and IAA in apical dominance was investigated in an experiment in which first of all an IAA paste was applied to the cut areas formed by the decapitation of epicotyl apices of pea seedlings, followed after one week by the application of a 0.25 % GA paste. The latter treatment was able to overcome the growth inhibition of cotylary buds induced by a 0.03 % IAA paste, but not that caused by 0.06 and 0.12 % IAA pastes.
The correlative function of a root in the renewal of the apical dominance can, to some extent, be directly simulated by exogenous gibberellin, as has been demonstrated in the experiment with decapitated pea seedlings deprived of one cotyledon, on which the growing axillary of the amputated cotyledon was decapitated. In this case the axillary of the remaining cotyledon grows in the plants where the root has been left, but in those deprived of the root, there appears a serial of the amputated cotyledon (Dostál, Biol. Plant. 9 : 330, 1967). When GA was supplied to the plants treated in this way, the coty lary of the remaining cotyledon grew even in the plants deprived of the root.

Phosphorus oxytriamide PO(NH₂)₃ was proved chromatographically in the exudate of decapitatedPhaseolus vulgaris plants. This fact verified the presumption that covalent compounds of phosphorus and nitrogen enter roots without previous hydrolysis.

The effect of nutrient solutions with certain essential elements lacking, on oxidation reduction potential (RP) of the first leaf was examined in two cultivars of barley seedlings NO₃^- and K⁺ decreasedRP considerably, PO₄^3- did not. The effect of NO₃^- and K⁺ was dependent. on the illuminance. Under glasshouse conditions, the increased level of NO₃^- and K⁺ did not cause any change ofRP. In field conditions, the increased supply of nitrogen fertilizers resulted in a lowerRP in leaves at ear emergence and a higher yield. The use ofRP measurement in leaves for the estimation of the effect of mineral nutrition on plants is discussed.

Using regression analysis a proof of the relation between the electric capacitance and the root surface in maize, sunflower, oats and onion plants was given. This dependence is possible to exploit in the selection of plants (of the same population grown under the same conditions) for a well-developed root system.

Changes in the percentage of seed germination, the growth and respiration rate of the seedlings were observed at 15-day intervals from the stage of the full germination capacity of rice (Oryza saliva L.) seeds till they became non-viable. At the beginning, the respiration rate changed but little, but afterwards, with the approach of non-viability, the rate declined sharply. A positive correlation of respiration with a decrease in the germination percentage and the length of seedlings and a negative correlation with days of storage were also established. A strong correlation existed between catalase and peroxidase activity with respiration, indicating that the activity of these enzymes can be used as an indicator of metabolism, and therefore can be considered as part of the respiratory mechanism of rice seedlings.

The production of ethylene in the leaves ofSalix viminalis L. increased gradually from May till October. The emanation from the leaves, the main constituent of which was ethylene, inhibited the extension growth and the formation of the dry matter of rye seedlings more or less equally during the whole growing season. This indicates that the effect of ethylene on the growth is not, to any great extent, dependent on its concentration.

Ethylene production and respiration rate of an early cultivar of apples, Letní průsvitné žluté, is significantly increased after the application of the lowest tested concentration of CCC (0.1% in lanolin). These effects, calculated from the amount of released ethylene and carbon dioxide, were observed during the whole period of ripening. The production of ethylene is slightly inhibited by the higher concentrations of CCC while the respiration rate is not significantly affected.
The rate of the ethylene production of the early cultivar of apples is decreased 4.4 to 9.7 fold by 0.1% CCC as compared with the winter cultivar Jonathan. Although these ratios rise gradually during the ripening of fruits treated with other higher concentrations of CCC, the total amount of ethylene produced by the winter cultivar Jonathan is 1.5 fold higher than that of the early one.

Structural proteins of both chlorophyll - deficient mutants, extracted with a phosphate buffer solution pH 8,3, using Triton X-100 as detergent, exhibit, in comparison with normal plants, a faint cathodic fraction giving positive staining for lipoproteins and containing chlorophyll. No differences in soluble proteins were found between the mutants and control plants. The pattern of the individual protein fractions differs according to the method employed.

Using immunochemical methods the authors investigated the evolutionary taxonomic distribution of the reserve seed protein "phaseolin" in cultivars ofPhaseolus vulgaris, in a series of species ofPhaseolus, and in representatives of some additional genera ofViciaceae.
"Phaseolin" is typical of the seed ofPhaseolus vulgaris L.: it was detected in all 658 investigated cultivars - and also in species related toPhaseolus vulgaris L.(Ph. vulgaris L. ssp.aborigineus Burk.,Ph. polyanthus Green,Ph. dumosus Macf.,Ph. coccineus L., and in an undescribed species from the group ofPh. vulgaris L. -Ph. coccineus L.). A protein immunochemically somewhat similar to "phaseolin" occurs inPh. acufifolius A. Gray. In all other taxa"phaseolin" is absent.

The meioses of four sterile species in the genusAllium which develop bulblets in the inflorescences instead of seeds were compared, namelyAllium sativum, A. cepa var.viviparum, A. carinatum, andA. oleraceum. The most important of them,A. sativum, is an ancient cultivated plant and its vegetative reproduction prevents it from more rapid evolution such as is known in generatively propagated cultivated plants.A. sativum shows fully normal meiosis. After the disintegration of the tetrads, however, the blockade of 1. pm takes place. The cause of the blockade has not yet been cleared up. Removing of bulblets appeared as having no influence on the development of microgones. It is assumed that there may be a viral phenomenon causing a disease of the tapetum without disturbing other functions. InA. cepa var.viviparum there was observed a heavy aberration disturbance in the meiosis, which had already been signalled by the mitosis. On this ground 1. pm does not occur and sterility is fully justified. The aberration disturbance does not seem to spoil the vegetative development but on the contrary to give it a vigorous character.A. carinatum andA. oleraceum are triploid and tetraploid forms; in the meiosis they form various configurations-univalents, bivalents, trivalents, and quadrivalents. The following irregular chromosome distribution results in the coming into existence of variously valuable gametes. 1. pm takes place. There is a theoretical possibility of generative reproduction (after the extirpation of bulblets).

A phosphatase enzyme hydrolysing NADP⁺ and NADPH to NAD⁺ and NADH was found to be present in extracts ofChlorella pyrenoidosa

The present paper incorporates a detailed study on the distribution of 5-nucleotidase in the germinating pollen grains ofEschscholtzia califomica. The intense activity of this enzyme has been found in the wall of pollen grains and pollen tubes and small positive granules in the lumen of both in the pollen grains and pollen tubes. The presence of this enzyme in the wall is presumably connected with the permeability and transport process and growth regulation of the pollen tubes.

The nucleic acid fractions in cotyledons of young Chenopodium rubrum plants exposed to continuous light, continuous darkness and short (8 h) day, respectively and labelled with³²P 24 h prior to harvesting were studied by means of chromatography on MAK columns. Some parameters of cotyledon growth (dry weight, cotyledon area, occurrence of mitoses) were also investigated.
The changes in the nucleic acid fractions agreed with the dynamics of cotyledon growth. In continuous light the content of all fractions increased. The radioactivity of DNA and s-RNA did not undergo any great changes and only r-RNA increased. The specific activity of r-RNA increased slightly, that of soluble RNA and DNA was reduced. In continuous darkness the content of all the fractions did not undergo any great changes. The radioactivity as well as the specific activity of all fractions decreased. In short day the content of the nucleic acid fractions did not change conspicuously. Only the specific activity of s-RNA increased in a noticeable way while the radioactivity of r-RNA and the specific activity of DNA decreased and this of r-RNA did not change. The changes in nucleic acid metabolism were partially connected with changes in³²P uptake which depended upon light conditions but they were not merely a consequence of this fact. Obviously, there also exists a more direct relationship between nucleic acid synthesis and growth.

The analysis of diurnal oscillatory movements of tobacco leaves was used in the diagnosis of viral infection of plants. The oscillatory helices circumscribed by a growing leaf of a healthy plant were regular, but some deviations, particularly in the transition points, were recorded.
In order to make clear the cause of these irregularities of trajectory, the course of elongation of leaf petiole and blade in relation to localization and shift of zones of elongation during ontogenesis was analysed. The present analysis is similar to that described by the author's earlier experiments with pea roots. Oscillatory curves circumscribed by petiole, projected on a horizontal plane, were compared with curves circumscribed by the blade tip. The analysis of the leaves of different ages enabled us to study this process in dependence on growth rate. It was confirmed that oscillations are a result of elongation; the extent of oscillations is quantitatively dependent on the growth rate. An analysis of the zones of growth showed that in petiole the active meristems are localized near to its base while in the leaf lamina they move gradually during the ontogenesis from the apical to the basal part of the leaf blade. Active meristems of young rapidly growing leaves are localized approximately in the middle of the blade while those of old leaves were found in close proximity to the base of the lamina. The growth rate of petiole can be expressed in hundreds of mm per hour (4.8×10^-2 mm h^-1); half of this value was recorded for its apical part. The growth rate of leaf blade was found approximately ten times higher (3.2×10^-1 mm h^-1).
The oscillatory movements of growing leaf consists of two integrate components: of oscillations originating in the base of the petiole and of oscillations of leaf blade the centrum of which is localized in the basal third of the blade.
The arrangement of the experiments did not enable us to determine to what extent the phototropic response of leaf blade participates in leaf movements. The movements of leaves of an intact plant are evidently affected by rhythmic stem oscillations. Stem is an integral part of a system which participates in the transfer of information in plants.

Studying relationships between tobacco mosaic virus reproduction, anthocyanin biosynthesis and phosphorus content in cultivation medium, it was found thatMartin's (1958) finding of an indirect proportion between anthocyanin and virus synthesis is valid even under the complicated conditions of pathological anthocyanin formation induced by phosphorus deficiency. A decrease of anthocyanin biosynthesis with simultaneous stimulation of virus reproduction takes place at temperatures below 20°C. Increased anthocyanin biosynthesis accompanied with the inhibition of virus reproduction occurs at temperatures above 20°C. The obtained results suggest that enzyme systems and substrates participating in considerably increased anthocyanin biosynthesis induced by phosphorus deficiency, differ from those taking part in anthocyanin synthesis induced by virus infection.
The enhanced phosphorus content in the cultivation medium does not influence anthocyanin biosynthesis significantly. Nevertheless, a highly significant inhibition of tobacco mosaic virus reproduction takes place at temperatures above 20°C. This inhibition may be in correlation with some other metabolic systems affected probably by the enhanced phosphorus concentration in the nutrient medium.

The photosynthetic production of dry matter of discs cut out from leaves of cucumber plants severely infected withCorynespora melonis was significantly lower than that of discs from healthy plants. The decrease was found in discs from leaves both infected and symptomless. Expected inhibition agent has not been isolated up to now.

Anthers ofLycium halimifolium were grownin vitro at the following stages of development: tetrads, microspores and binucleate pollen grains. Pollen plantlets were obtained only from anthers inoculated at the stage of microspores. The growth of androgenic embryos was very slow. Mature embryos were formed in about 3% of the inoculated anthers. The largest number of embryos obtained from one anther was 4.