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.

In isolated leaves ofBryophylluni crenatum the intensity of marginal bud formation decreases from the apex towards the blade base, which is associated with the decreasing content of enioganous gibberallins. As proved by Dostál (1930), the formation of marginal buds on transversely divided blade of the isolated leaf increases in comparison with the non-divided control leaf. The results of our experiments have revealed that the increase in the formation of marginal buds in the blade transversely divided into the apical, middle and basal parts is connected with the increasing level of endogenous gibberellins, especially in the apical part. This rising level appears as early as 7 days following blade division,i.e. at the time preceding the formation of marginal bud bases.
InBryophyllum crenatum plants the level of endogenous cytokinins was estimated in apical, middle and basal leaves, as well as in adjacent internodia. Maximum content was found out in the leaves from the middle stem part, which is probably associated with the capacity of this part to form marginal buds spontaneously also in intact plants. However, prior to flowering the maximum of cytokinin activity is shifted to the apical stem part.

The amounts of total phytol and its chlorophyll-bound and free portions have been determined quantitatively at different developmental stages of primary leaves of wheat using thin-layer chromatography combined with a potassium permanganate reaction. During the greening of etiolated leaves a close correlation exists between chlorophyll and phytol contents. Phytol is always present in excess and only in a bound state. During induced leaf senescence phytol is essentially degraded more slowly than chlorophyll. The liberated phytol does not influence the hydrolytic activity of chlorophyllase.

Treflan has the ability to induce polyploidy inAllium cepa root tips. The frequency of polyploidy was reduced after allowing the roots to recover, which indicates that the process of polyploidy is a reversible one, if we apply Treflan for a short time (4 h). As soon as the chemioal is removed from the cells, they go on with their normal way in division. It was found that the concentration 350 × 10^-5 ml Treflan per 100 ml water is an effective concentration in producing polyploidy in the roots ofAllium cepa.
Treflan induced C-tumours in root tips ofAllium cepa. Two types of enlargement were noticed, complete swelling along the majority of root tips and complete swelling with a certain enlargement immediately after 2 mm terminal tips. The histological examination of these zones revealed that swellings were due to cell enlargement both in meristematic and in tumour zones. This conclusion was evidenced by the results obtained from the nucleoplasmic index.

The final length of the root cell is the result of a series of prooesses which represent a transition of the growing cell from its origin up to the completion of its elongation. These processes are associated on the one hand with cell proliferation, or, after the termination of proliferation, with the proceeding DNA synthesis, and with cell elongation on the other. The group of properties characterizing the growth region of the root as a cytologically heterogeneous complex, is at the same time the group of causes which affect the length of root cells. The individual cases documented in the paper point out the fact that the mechanisms regulating growth processes, have a locally limited action, often only within one single cell, and that they are simultaneously subordinated to the regulatory mechanism which controls the growth of the root as an entirety.

Calcium deficiency resulted in a 20% increase in the total content of phenolic compounds in the shoots of 10-day-old wheat plants and in a 10% decrease in the roots compared with the control. Differences in specific activities of the lyases of the shikimate pathway (L-phenylalanine ammonia-lyase, E.C.4.3.1.5, PAL; L-tyrosine ammonia-lyase, TAL) were established between control and Ca-deficient wheat and pumpkin plants. The lyase activities were higher in the shoots of Ca-deficient plants and lower in their roots, compared with the control. Thus, there is a certain correlation between PAL and TAL activities on the one hand and the content of phenolic compounds on the other. The time course of PAL activity during a few first days of growth and the dependence of TAL activity on pH were also investigated.

Excised tomato cotyledons were aseptically cultured in mannitol induced water stress solutions, and a number of changes were determined. Stressed cotyledons had less fresh weights than normal cotyledons throughout the experiment. Stressed cotyledons initially showed reduced proteins, RNA and chlorophyll contents as compared to normal cotyledons, but eventually showed increases which often surpassed values in normal cotyledons. Endogenous auxin and cytokinin activities were initially lower in stressed cotyledons than in normal cotyledons, but were later higher in stressed cotyledons than in normal cotyledons. Gibberellin changes were slight. Applications of exogenous kinetin were able to reverse the effects of stress in reducing fresh weights, proteins, RNA and chlorophyll contents. Applications of GA₃ only partially reverse stress Effects while IAA had no effects. Stressed cotyledons also senesced more slowly than normal cotyledons. The conclusion was reached that the cotyledons were initially injured by the stress but were able to adapt to the stress and that cytokinin activities were fundamental to the responses.

Following a previous biological and serological evidence of tobacco necrosis virus by means of an electron microscope, isometric virus particles of an average size of 26 ± 0.5 nm were found, in ultrathin sections prepared from the tissue of sprouting buds of underground stalks and from that of runners butts with symptoms of mosaic line pattern, as well as from the tissue of the indicator plantChenopodium quinoa.

Cucumber mosaic virus (CMV) isolates obtained from spontaneously infected (1)Chelidonium majus L. and (2)Impatiens parviflora DC. plants growing in the same part of a scree forest in central Bohemia showed differences in ten test plants, but not in further 26 plant species tested and in TIP. Slight quantitative differences between both isolates were obtained in serological tests. Properties of both isolates did not suit precisely any proposed CMV strain classification.

Paracytic, anisocytic, anomocytic, transitional forms, tetracytic, cyclocytic stomata and partly and completely amphicyclic forms are found, often on the same surface, in nine combinations. The most frequent type is paracytic. A few morphological variations in the basic types and eight types of abnormalities in stomata are recorded. The stomatal ontogeny may be mesogenous, mesoperigenous or perigenous. Trichomes are multicellular glandular club-shaped and unicellular eglandular. The taxonomic significance of stomata is indicated.

The effects of some growth regulators on the dark-germinating seeds ofCucumis anguria have been investigated. GA₃, 6-BA and ethrel strongly promoted the germination of seeds kept in white light. GA₃ had no effect in counteracting the far red effect, but did counteract partially the blue light. Ethrel partially counteracted both the far red and blue light effect. No interaction could be found between red light and GA₃ or 6-BA.

Crude extracts ofPisum sativum L. roots interfere with nitrite determination only slightly, boiled root extracts considerably, Crude leaf extracts can interfere with nitrite determination in some cases even more than boiled root extracts. The precipitate of zinc phosphate helps to remove from crude leaf extracts some but not all the interfering material. Heating does not increase the interference in adult leaf extracts but it increases it in the extracts of very youngPisutn sativum leaves.