A decreased germination capacity of the seeds ofChenopodium bonus- henricut collected at high altitude is not due to an embryo dormancy. It is caused by a seed coat inhibition. The seed coats contain large amount of strongly oxidisable phenolic compounds which deprive the embryo of oxygen.

In agreement with the results of biological tests with transmission to herbaoeous indicators and on orientation electron microscopic investigation, alfalfa mosaic virus (AMV) and tomato bushy stunt virus (TBSV) were serologically identified in the leaves of some of 8 samples of hop plants and of 17 bushes of grapevine, showing a complex of symptoms described in this paper. The latter reacted in double gel diffusion tests toPetunia strain but not to artichoke strain. The identification of these two viruses in grapevine is the first finding in Czechoslovakia, whereas in hop it is probably the first finding anywhere.

The role of a globule-like structure in the leaf epidermal cells ofC. auriculata has been studied in relation to stomatal regulation. Water stress and direct sunlight promote the appearance of globules at the same time as the stomata close. Ample water supply and shade inhibit the appearance of globules and the stomata open. The number of stomata is the same on either leaf surface, but their behaviour is different because of different exposure to light.

Indole-³H or tryptophan-³H are applied to tips of sterile grown oat or maize coleoptiles. The produced amounts of IAA and Try are extracted, purified by paper ohromatography, and quantitatively determined by liquid scintillation spectrometry. Admixtures of serine or inhibitors of monoamine oxidase are without effect on the IAA production from indole. The yield of IAA from indole equals the IAA yield from Try. If the amount of free Try-³H in the tissue is used as a reference quantity, indole-³H application yields higher³H-activity in the protein and in the IAA fraction than does Try-³H application, probably as a result of compartmentation effects. There are no results indicating a pathway of IAA biosynthesis from indole without Try as an intermediate.

The effect of short and long term auxin treatments on the elongation of axillary buds and³²P accumulation were studied in 2-leaf decapitated Alaska pea sailings. It was found that (1) auxin delayed the elongation of the lateral buds, (2) none of the auxin concentration applied completely inhibited the elongation of axillary buds, (3) auxin had no retarding effect on the growing buds, (4) strong polarization of 32P occurred in the parts above the treated leaf, when auxin was applied for a short period just after decapitation, (5) long term auxin treatments did not induce any such polarization of 32P to the parts above the treated leaf, (6) the root acted as an alternate accumulating organ for 32P when the apex was removed and the buds were inhibited, and (7) in decapitated plants the growing buds polarized 32P.

Most of the peroxidase activity of strawberry petiole is obtained from ionic treatment and pectinase-cullulase digestion of the cell-walls: two ionically-and three covalently- bound isoperoxidases were separated by starch gel electrophoresis. A technique is described for preparing an active IAA-oxidase extract. Final oxidation products of indoleacetic and indoleacrylic aeids appear to be the most effective IAA-oxidase promoters.

The virus replication capacity (determined by density gradient centrifugation and spectrophotometric virus assay) and severity of symptoms were compared in ten cucumber(Cucumis sativus L.) cultivars infected by cucumber virus 4. Except the expected resistant susceptible and symptomless virus carrier plants a new paradoxial group of cultivars was found. This group is characterized by low virus reproduction rate but simultaneously associated with severe symptoms and is responsible for difficulties in the virus transmission and purification. It is concluded that the critical evaluation of the resistance against viruses of TMV-group must include symptomatic and quantitative virus assays, as there need not be a direct relationship between virus symptoms and the virus increase.

During their short preparasitic stage, dodder seedlings are able to absorb phosphates, by means of their rudimentary root. The absorbed phosphorus is translocated into the stem of the young parasite and metabolized.

The endodermal cells of the maize roots are linked to each other via plasmodesmata mainly localized at the proximity of the Casparian band on the anticlinal walls. In this part of the walls was noticed the absence of the suberin lamella in the thickening endodermal cells.

Pollination induced dissolution of nucellar cells at the micropylar end forming a passage for pollen tube entry even when the pollen tubes are in the stylar region.

Virus origin of lilac ringspot and chlorotic ringspot of lilac was identified serologically by means of double gel diffusion method. The former of these diseases is due to Arabis mosaic virus, the latter to a mixture of Arabis mosaic virus and cherry leaf roll virus. The occurrence of these viruses has been detected for the first time in Czechoslovakia.

Anomocytic stomata and stomata with single subsidiary cells are commonly observed Sometimes a stoma appears anisocytic. Double cytoplasmic connections between nearby stomata and division of guard cells with persistent or degenerating nuclei are seen in GA. One or more divisions of guard cells, displaced guard cells and single guard cells with or without pore are noticed in SUC. Formation of single guard cells is a common feature in TIBA. Paracytic stomata, one and a half stomata and persistent stomatal initials are seen in SUL. COUM seems to be not inhibitory inCucumis sativus. In COL stomata with unequal guard cells, unequal stomatal cells with thickening in between but without intervening pore, stoma with double pores, persistent stomatal initials which may be solitary or in groups with varying shapes and with one or two nuclei of different shapes are noticed. The growth regulators affect the frequency of stomata, epidermal cells; stomatal index; size of guard and epidermal cells.

The uptake and translocation of³²P applied to nutrient solutions, as influenced by (2-chloroethyl) trimethylammonium chloride (CCC) and 2, 4-dichlorobenzyltributylphosphonium chloride (Phosfon), were investigated in growth chambers. Specific effects depended on the "Retardin", the method of application, and the concentration.
Foliar applications of CCC had no significant effect on³²P uptake 5 h after feeding. At 20 and 80h after feeding, CCC at 100 and at 1 000 mg l^-1 decreased P uptake. With root applications of CCC the same concentrations decreased P uptake as early as 5h after feeding, while the 1 mg l^-1 concentration enhanced P uptake by 40% after 20h. Both the foliar and the root applications of Phosfon influenced P uptake 5h after feeding. With foliar applications the low Phosfon concentration of 0.01 mg l^-1 increased P uptake throughout the experimental period of 80h, but the magnitudes of enhancement declined from 109% at 5h to 63% at 80h. Similarly, the enhancement of P uptake due to the 0.1 mg l^-1 foliar treatment declined from 132% at 5h to 80% at 80h.
100 mg l^-1 CCC enhanced P translocation to the shoot in 5h, with magnitudes of 29% (foliar application) and 64% (root application). At 20 and 80h the stimulations were nullified. The highest concentrations (100 mg l^-1 CCC; 10 mg l^-1 Phosfon) enhanced P translocation 80h after feeding. There were thus general enhancements of P uptake at low concentrations and suppressions at high concentrations, but these effects diminished with time, indicating transitory influences.

Populations ofScenedesmus quadricauda grown in a continuous chemostatic regime and synchronized by light and dark intervals were exposed to continuous illumination. The effect of light on synthetic and reproduction processes during the time of the omitted dark period and in the subsequent cell cycle was studied. In general, the sequence of cellular processes and their mutual coupling remain the same as in the darkened population. Synthetic processes and photosynthetic activity are depressed during the period of protoplast fission also in the light. The synchronizing effect of the dark period in chlorococcal algae consists in reducing the developmental variability in the population. The developmental state of daughter cells at the end of the dark interval varies in the span of two (as a rule) or four (at maximum) genomic cycles, while at the end of the light period this variability comprises up to eight genomic states. The more advanced autospores start the next cycle with a greater lag.

The preparation of antisera against S alleles of homozygous incompatible lines of the marrow-stem kale (Brassica oleracea var.acephala DC.) is described. The antisera obtained reacted specifically with homologous antigens on using the serological method of double diffusion into agar. The results confirmed the specificity of S alleles of incompatible lines of the marrow-stem kale.

A method of enzymatic separation of protoplasts from long-term tissue culture ofNicotiana tabacum L. is described. The efficiency of this method is dependent on conditions of separation and on the portion of meristematic cells in the tissue culture. This portion can be increased by pre-cultivations of the tissue on medium containing suitable concentration of hormones. The knowledge of the micromorphology of the filamentous culture enables us to investigate the course of release of protoplasts from various cell types. A preferential lysis of cell walls was observed between neighbouring cells in filaments and the fusion of their protoplasts was recorded. The preservation of cell walls which are not in a contact with other cells may be a result of the cell wall heterogeneity.

The relationships between protein- and RNA synthesis and the germination behaviour of lettuce seeds were studied. Protein synthesis starts right at the beginning of imbibition and increases until the radicle protrudes. According to our results the causes for a blocked development of scotodormant lettuce seeds cannot be seen in a generally reduced protein or RNA synthesis.

Growth of primary (cv. Wisconsin 38) and long-term (cv. Virginia Bright Italia) tissue cultures obtained fromNicotiana tabacum L. pith was affected by exposure to a single dose of gamma-radiation ranging from 1 to 150 krad. The inhibitory effect was proportional to the applied dose. Changes in the degree of inhibition during the subculture interval were ascertained by quantitative evaluation of the growth response. Primary cultures proved to be several times more radiosensitive than long-term cultures, the capacity to recover from radiation damage of the cultures participating in the resulting manifestation of the effect. The possible reasons for these differences are discussed.

Metabolic changes in tomato plants infected with potato leafroll virus were followed. The virus was transferred by grafts taken from diseased tomato plants. Sharp changes in the respiration rate and in the activities of the investigated enzymes observed before the concrescence of the graft with the stock are obviously connected with the defence reactions of the plant. In the roots of the experimental plants a nearly complete correspondence of the course ofo-diphenol oxidase and ascorbic acid oxidase activities with the respiration rate occurs. In the shoots the respiratory chain with ascorbic acid oxidase as terminal oxidase is involved, whereas both chains probably take part in the respiration in the roots by which a link with sugar degradation is achieved. The rate of glycolysis and that of pentose phosphate cycle in the roots of experimental plants are nearly identical. The comparison of glucose-6-phosphate dehydrogenase activity with ascorbic acid oxidase activity reveals that both curves show the same course, which indicates the presence and action of a respiratory thain with ascorbic acid oxidase functioning as terminal oxidase.

A new method enabling to localize recessive alleles controling lethal embryonal or chlorophyll mutations in linkage groups has been devised and verified. The information on the linkage was obtained in B₁ in repulsion after the crosses with recessive visible markers representing the individual linkage groups. The distinction of four B₁ genotypes was achieved by means of Müller's embryotest. Altogether eight mutant alleles were localized. The allelesch 2411, ch 4062 andX 3 are carried by the first linkage group, the allelesM 33 andM 25 by the third and the allelech 1378 by the fourth linkage group. The mutant allelesch 42 andM 4-6-18 showed the linkage with the markers of the fifth and the sixth linkage groups simultaneously. The possibilities of further development and use of this method are discussed.