Twenty-four isolates of turnip mosaic virus (TuMV) from spontaneously infectedSisymbriutn loeselii plants were collected in Bohemian localities. Single lesions on leaves ofNicotiana tabacum cv. Samsun served for inoculating petunia plants used as infection sources for twelve host species. In no case were two identical isolates obtained. 15 isolates could be transmitted toVicia faba, a new TuMV host. Almost all isolates infectedPhaseolus vulgaris cv. Prince locally andTrifolium incarnatum systemically. Seven isolates were transmissible toPisum sativum. No substantial differences between isolates were observed with infectedAn aranthus caudatus, Chenopodium quinoa, Datura innoxia andSinapis alba plants. Several isolates could not infectNicotiana glutinosa at all, other isolates caused in it latent systemic infection and some isolates only local infection contrary to normal local and systemic infections ofN. glutinosa. Attempts to transmit one isolate to cereals failed.

Ethanol-soluble and insoluble nitrogen and protease activity in maize seeds during imbibition period of 6 to 60 h at 30 ± 2 °C were determined both in light and in the dark. In light, soluble and insoluble nitrogen in the embryo were similar to that in the dark. But the increase in soluble nitrogen in the endosperm up to 38 h was higher in light than in the dark. Decrease in insoluble nitrogen was correlated with increase in soluble nitrogen, the level always being higher in the dark. Light increased protease activity also in the endosperm. Among various light qualities, red light was most effective in inducing proteolysis, and loss of nitrogen from the endosperm. Further, the growth and organic nitrogen of primary leaves from seedlings raised from light pretreated seeds were better than those from dark pretreated ones.

A study was made of the changes in the content of essential oil and its components (farnesene, (-)-α-bisabolol, (-)-α-bisabololoxide A, (-)-α-bisabololoxide B and spathulenol, α-bisabolonoxide A, chamazulene, cis en-in-dicycloether) and of the number of secretory canals in the receptacles during the beginning of flowering, full flowering and the termination of flowering of camomile anthodia. The total content of the essential oil was highest during the beginning of flowering and lowest during its termination. The proportion of the individual sesquiterpenes in the essential oil underwent changes mostly during the beginning and termination of flowering. The number of secretory canals in the basal and middle anthodial parts increased during the beginning of flowering and the full flowering.

Three days old excised tomato cotyledons were subjected to mannitol induced water stress in the presence of actinomycin D and cycloheximide. Within a few hours, in the presence of actinomycin D but not cycloheximide, water stress induced increase in ribonuclease activities and decrease in beta-fructofuranosidase activities. The water stress action in the presence of actinomycin D was reversible by addition of kinetin. It was postulated that water stress had some immediate fundamental action on the protein synthesis sites at the ribosomes.

Genetically identical mirror-imaged left and rightLemna minor plants were treated using the stereomers of arginine, asparagine and atebrine (mepacrine). In contrast with the stereomers of arginine and asparagine, those of atebrine were found to be isoeffective throughout the dosage range from the ineffective dose to the lethal one. All indices used (rate of reproduction, length of a frond and sensitivity to the treatments) pointed to the absence of any difference between left and right plants. The left or right handedness inLemna cannot be explained bv assuming the existence of any stereochemical difference between left and right plants.

When stem cuttings were put in water the dormancy of the bud was broken. No inhibitory substances could be found in the leaves and no effect of exogenous growth substances could be detected. Dormancy of buds in the present case seems to be the result of the mechanical resistance imposed by the leaf sheath upon the bud.
Gibberellic acid was very effective in promoting root formation in the woody stem cutting ofPanicum maximum and the present results point to a direct effect on root initiation by gibberellic acid.

The effect of various sodium salts at the early developmental stages of wheat cultivars was studied. Germination was not affected by the presence of salts but cv. H-68 was more tolerant than Mexipak during later growth. The roots were more sensitive than the shoots. The salts under study could be divided into two groups. Bicarbonate, carbonate, acetate and citrate were more toxic for growth than sulphate, nitrate, phosphate and chloride of sodium. The individual members of each group did not vary much from one another.

[³H] DNA fromEscherichia coli and [³H] thymidine were applied, in sterile conditions, on isolated barley embryos and on roots excised from these embryos, both cultivated in the liquid medium and on halves of barley seeds, through the endosperm bridge. In embryos and roots, the labelled compounds were applied in 1.5% sucrose + 0.2 SSC alone, or together with either unlabelled thymidine or DEAE-dextran. Similar labelling indices were found after [³H] thymidine and [³H] DNA treatment which shows that the activity of [³H] DNA is utilized during the S phase. After application of [³H] thymidine, only cell nuclei in S phase were labelled. After the application of [³H] DNA an extranuclear label, in addition to the labelling of nuclei in the S phase, was observed in some experimental variants. The density of label above labelled nuclei after [³H] DNA treatment sharply decreased when unlabelled thymidine or DEAE-dextran was added, while the density of label above nuclei labelled by [³H] thymidine decreased when unlabelled thymidine but not DEAE-dextran was added. The labelling of nuclei with the label from [³H] DNA is the result of degradation of exogenous DNA reutilization of low molecular weight products. Extranuclear labelling is most probably due to the polymerous or partly degraded DNA.

A possible method of finding the best concentration of a chemical mutagen or a shortterm action is demonstrated by the results obtained withChlamydomonas geitleri. Mostly two cases occur. We must either use the shortest time of the mutagen action with a sufficiently high effect or utilize the whole limited time for this action using a suitable concentration with a similar effect. It is possible to choose such a structure of the doae of the chemical mutagen which in the mutation spectrum ensures either the optimal frequencies of all components or of only some of them chosen beforehand.

The effect of exogenous supply of a morphactin - chlorflurenol (IT-3456) CME 74050 p at three concentrations of 100, 500, and 1000 ppm (all applied as dispersions in lanolin paste after scraping the epidermis during December, 1976) was studied on two-year-oldMorus alba plants. Almost three months after the treatment of the regulator, along with the normal sievetube elements of the axial system, these elements were recorded in the ray system as well, arranged either vertically or horizontally. In the latter state, they appear to act as a by-pass between the normally formed sieve elements located on either side of the ray. We have termed them 'ray-sieve-tube elements' to distinguish them from the normal elements. Simultaneously, some sieve-tube elements having sieve plates on their lateral walls were also noticed in the axial system. A direct correlation was observed between the multiplicity of induction of both element types and increasing concentration of the regulator.

Cuttings of pea cv. Alaska and ov. Kelwo were both decapitated and disbudded at different time intervals after cutting. Auxin and cytokinin combined in different ratios were applied to the upper part of the decapitated and disbudded cuttings. The effects of different ratios of auxin and cytokinin were not the same when applied at different developmental stages of the root initiation phase. The results seem to demonstrate an interaction between auxin and cytokinin at different ratios throughout the root initiation phase. The effects of combined application of auxin and cytokinin suggest that different stages of the root initiation phase require different levels of auxin and cytokinin. A higher level of auxin and either lower or equal level of cytokinin may be needed only in the early stages. During the subsequent stages a lower level of auxin in combination with a higher level of cytokinin seems to be more conducive.

In the absence of cations, the release of proteins from pollen tubes ofNicotiana tabacum in culture is greatly dependent on boron concentration and inversely related to growth stimulation. The minimum of proteins in the medium occurs at 100 mg 1^- of boric acid, which is the optimum concentration for growth. The shift of boron level to this optimum further increases the proportion of proteins bound to the insoluble pollen tube fraction; on the other hand the amount of soluble proteins is not affected inside pollen tubes, but greatly decreased in the medium.
The loss of proteins into the medium is considerably reduced by oalcium and also at the optimal boron concentration and in the presence of K⁺ and Mg²⁺ ions. The rate of tube elongation, however, is slightly decreased and the duration of pollen growth activity is not extended. The release of proteins is not affected by potassium and is slightly reduced by magnesium.
The possible mechanism of calcium and boron action on protein release is discussed in relation to the exocytotic function of secretory vesicles and it is suggested that boron supports the incorporation of proteins transported to the growing tip into the pollen tube wall structures.

Twenty three isolates of turnip mosaic virus (TuMV) obtained from spontaneously infected plants ofSiaymbrivm loeaelii JUSL. were serologically related, but differed in reactions of eleven host plants. Susceptibility and sensitivity of each host for each TuMV isolate were classified by one of six degrees (0 to 5) respectively. Similarities of isolates (as compared in 253 pairs) were evaluated by means of a computer; for this purpose the source program MINDIF has been elaborated using the universal program language Algol 60. A table of differences between isolates was obtained and distribution of isolate pairs dependent upon the difference values was stated. The fitness of hosts for differentiating TuMV isolates was ascertained quantitatively. No relation of isolate similarity to geographical indices could be established.

Following moderate water stress in the cortical cells of theZea mays primary roots, the condensation of the nuclear chromatin, a higher density of free ribosomes and a reduction of polyribosomes, the reduction of mitochondrial cristae, elongation of ER elements, less compact dictyosomes and inhibited production of the Golgi vesicles were observed. Severe water stress would cause more severe structural damage in the cortical cells. The more differentiated cortical cells showed more expressive ultrastructural damage when compared with the meristematic nonvacuolated cells. Similarly, the cells of the peripheral layers of the cortex suffered more from water deficit than the cells of the layers situated closer to the central cylinder.

The effect of manganese chloride (10 mg Mn l^-1), EDTA (18 mg l^-1) and a mixture of these compounds on the nitrogen balance in maize xylem exudate was investigated. The compounds were applied as experimental solutions to the roots of 20 day old plants 24 h before excision. Application of Mn resulting in a lowered nitrogen level in the xylem exudate increased the relative content of the organic N-compounds in the exudate, particularly that of free amino acids. EDTA appreciably enhanced the content of total nitrogen in xylem exudate, however no significant changes were found in the proportion of inorganic and organic N-compounds in comparison with the water control. The significant features of the free amino acid exudate fraction of all experimental variants were, among others, the relatively high lysine content and the absence of proline arid sulphur containing amino acids. By gel filtration on Sephadex G-25 of xylem exudates UV (254 nm) absorbing fractions, four in the water control, five in Mn and six in EDTA variants were isolated. The UV absorbing fractions with the exception of one in each experimental variant (K_av 0.73 in water control, K_av 0.61 in Mn-variant, K_av 0.75 in EDTA and Mn + EDTA variant) were of peptide character, proline and sulphur-containing amino acids were missing in them. In the exceptional UV absorbing fractions (K_av 0.61-0.75) in spite of their high N-content (10.23%) after hydrolysis practically no amino acid could be detected.

Using water culture technique, some experiments have been performed to investigate the effect of 60 days salinization treatments (0.0-100 meq 1^-1 NaCl) on dry weight and on the content of some nutrient elements (Na, K, Ca, Mg, P, N) in castor bean, sunflower and flax plants. In general the content of sodium increased progressively with the rise of salinity level. The relatively low and moderate salinization levels (20 and 40 meq I^-1 NaCl) resulted in a promotion rather than inhibition of the dry weight and in the content of most of the investigated elements in the different organs of the test plants. However with the rise of salinization level from 60 to 100 meq l^-1, the dry weight and the content of these nutrient elements were mostly reduced.

The influence of light, particularly blue and red light, on the cytokinin content of seedlings ofAmaranthus caudatus was studied. Cytokinin content was determined by two different bio-assays (amaranthin accumulation byAmaranthus seedlings and mtrate-reductase activity ofAgrostemma embryos). In both bio-assays similar results were obtained. Oytokinin content is increased, especially by blue light. It is suggested that especially blue light promotes amaranthin accumulation inAmaranthus seedlingsvia the increase of cytokinin content of tissues. The results support our hypothesis on cytokinin action.

The localization was studied of α- and β-galactosidases in frozen sections of Ca-formol fixed root tips using simultaneous azocoupling reaction. In all species studied (Allium cepa,Cucurbita maxima, Lupinus albus, Pisum sativum, Vicia faba, Zea mays) positive results were obtained, the localization being ubiquitous (according to localization typology given here).
InVicia faba andZea mays the isoenzymes of α- and β-galactosidases were revealed by means of acrylamide gel electrophoresis, using authors' modification of Reisfeld method, in whole root tips, particular growth zones and separately in cortex and central cylinder. No differences were observed comparing stele and cortex. Whereas characteristic isoenzyme patterns were found in individual growth zones in maize, no differences appeared in broad bean.
A comparison was made of thein situ localization and of the isoenzyme patterns of α- and β-galactosidases with α- and β-glucosidases. In the case of galactosidases, positive results appear with both α- and β-galactoside. The rising of pH to neutrality leads to considerable decrease in the activity of both galactosidases.

A field experiment was conducted to study the effects of N doses and row-direction on LAI, light transmission, plant height and dry matter production in the pure and mixed stands of 3 wheat (Triticum aestivum L.) cultivars Moti, Sonalika, and NP 824 differing in plant height. The mixed stands gave more transmitted light and shorter plants than the pure stands but dry matter production was not much affected. Nitrogen application increased the plant height, LAI, and dry matter but decreased the transmitted light. Row direction had no influence on plant height, LAI and dry matter production.

Decapitation induced an additional formation of secondary shoots and anomalous spikes in all the species. The moan numbers of nodes, spikelets per spike, seeds per spikelet and spike, and the mean length of the stem and spike were reduced on secondary shoots of decapitated plants, while the mean and peak numbers of flowers per spikelet and the peak number of seeds per spikelet increased. The increase in the number of flowers per spikelet was the most striking on spike base; the seeds regularly occurred even in spikelets with an expressively increased number of flowers. The post-decapitation changes of the spike could be well expressed quantitatively according to the increased mean number of the flowers per one seed. Morphological ohanges in anomalous spikes of all the wheat species resemble phylogenetic reversions described in literature. Moreover, the peak numbers of flowers and seeds per spikelet were recorded in 52 varieties belonging to 21 wheat species. As compared with the decapitation trial, the greatest variability and the greatest differences between the speoies were also reoorded in the tetraploid group, and the smallest variability and differences between the species in the diploid group. We suppose that the striking morphological differences in post-decapitation spikes take place because the apical dominance was interrupted before differentiation of the recent form had been controlled in meristems on the decapitated stem base. Ancestral forms were morphologically realized with the help of an assimilating part of the decapitated stem.

Sucrose gradient analyses were made on free ribosomes extracted from Azuki bean seedling leaves subjected to mannitol induced water stress. Comparisons were made of the effect of duration of stress and the effect of urea on the free ribosomes. The capacities of the ribosomal fractions to incorporate amino-acids were also studied. Water stress reduced total free ribosomes and proportion of polysomes in the ribosomes as well as the capacity of the ribosomes to incorporate amino-acids into proteins. Polysomes which were broken down by the water stress also appeared to be more susceptible to denaturation and synthesized different proteins than polysomes which remained in the leaves after water stress.

A virus transmissible toChenopodium quinoa was isolated from leaves of sugar beet showing large chlorotic ring spots and line pattern. The virus was serologically unrelated to tobacco necrosis virus and tomato black ring virus or to its beet ringspot strain either. A positive result was obtained with antiserum against tomato bushy stunt virus. Reactions of herbaceous indicators and properties of the virus in crude sap were in accordance with the serological diagnosis. A survey of natural hosts of tomato bushy stunt virus demonstrated recently by the authors is given.

Isoperoxidase B 1 isolated from winter wheat (Triticum aestivum L., cv. Jubilar) seedlings was shown to catalyze ethylene formation from α-keto, γ-methylmercaptobutyric acid (KMBA). In the presence of Mn²⁺, indole-3-acetic acid (IAA), andp-coumaric acid, the kinetics by isoperoxidase B 1 catalyzed conversion of KMBA into ethylene and other products was similar to that of IAA oxidation. The reaction rate was therefore controlled by IAA through its electrondonating properties.
Exogenous IAA induced ethylene formation in the segments of etiolated wheat coleoptiles. IAA-induced ethylene production was enhanced by L-methionine and mitomycin C. Aminoethoxy-analogue of rhizobitoxine, ferulic acid, sodium benzoate, cycloheximide and actinomyoin D exhibited significant inhibitory effects. These data indicate that the overall reaction mechanism in coleoptile segments involves RNA and protein synthesis.
The site of IAA action is not specific; 2,4-dichlorophenoxyacetic, α-naphthylacetic and indole-3-butyric acids, respectively, possessed comparable inductive effect as IAA. Indole-3-propionic acid, indole, L-tryptophan and glucobrassicin had only low inductive efficiency, and moreover indole and L-tryptophan slowed down IAA-induced ethylene formation.