The interaction of nutation oscillation and phototropic curvature mechanisms of growing pine hypocotyl(Pinus silvestris L.) was investigated. Nutation parameters of growing hypocotyl are not affected by continuous lateral illumination. Frequency and nutation amplitudes undergo changes which are dependent on plant development and are nearly the same when plants are illuminated from one side or from above. Lateral illumination, however, induces a phase shift. This deviation from a normal nutation rhythm usually disappears after a period of time equal to three nutation revolutions,i.e. after 12 h.
The positive phototropio response of nutating hypocotyl is dependent on the phase in which the hypocotyl is exposed to the lateral illumination:(a) nutation perihelium,(b) ahelium and(c) nutation interphase. These response-variants are compared with the expected gradients of plant hormones at the opposite sites of the hypocotyle. Analysis of location of the individual movement reactions(i.e. oscillations as a component of the geocontrol system and phototropic curvature) together with the determination of the zone of maximum elongation indicates the existence of different receptory centres of these two movement systems. In the case of the phototropic response reaction it is possible to consider the presence of different photo- and biochemical mechanisms at least for a part of this system.

0.25 % ammonium oxalate in a mixture of ethyl alcohol, chloroform, formaldehyde, acetic acid and hydrochloric acid works as a very fast and efficient macerating fixative for the root meristems ofAllium cepa, Allium sativum, Ornithogalum thyrsoides, Pisum sativum andVicia faba. Slicing the tip region of excised meristems hastens spindle poison pretreatment, fixation and staining. Owing to the dissolution of the middle lamella and eliminating a physical barrier to permeability an extremely rapid fixation and staining schedule involving several stains has thus been developed.

1. Ethyl methanesulphonate (BMS)-treated barley seeds stored at 30 % water content for 1 - 4 weeks are capable of recovering from the mutagen induced injury. The level and speed of the recovery depends on the EMS dose and storage period. Seeds treated with extremely severe EMS doses reducing the% of germination to 5 - 10 % cannot recover from the induced injury. 2. Due to a 1 to 6 weeks storage of EMS-treated seeds with 20 % water content the amount of induced injury increases in dependence on the applied EMS dose and storage period. Doses of EMS, reducing the seedling height in the M₁ generation to 90 - 95 % of the control reveal no storage after-effects. 3. Storage of X-ray exposed seeds at 20 % or 30 % water content did not result in any significant changes in the yield of induced genetic damage.

The seeds ofFraxinus excelsior L. were stratified at 17-20 °C (warm stratification), at 4-6 °C (cold stratification) and at alternating temperature (warm - cold stratification). The seeds subjected to warm stratification only, remained dormant. The seeds stratified only at 4-6 °C germinated gradually during a long period of time. The seeds subjected to warm - cold stratification, however, germinated with great intensity within a relatively short period of time.
GA₃ was shown to stimulate the growth of embryos markedly, and its effect on the germination of seeds depended on the temperature of stratification. GA₃ applied during the cold stratification accelerated the removal of dormancy by shortening the period of stratification and by influencing the germination of seeds. The results obtained indicate a similarity between the effect of temperature 17-20 °C during the warm stratification and that of gibberellic acid. Both those factors applied separately affect favourably after-ripening of the embryos and accelerate the germination of seeds.

The volumes of tissues in leaves of two species ofTypha with different habitus were measured. It was found that air cavities occupy more than 50%, parenchyma about 20% and photosynthetic tissue about 10% of the total volume of the leaf. If the cavities are omitted, parenehyma amounts to approximately 50% and photosynthetic tissue to little more than 20% of the total volume of tissues. The relative volumes of tissues vary continuously from the base to the tip of the leaf. The differences between the two species studied were not large. Besides the relative volumes, the real ones of leaves and tissues were calculated.

Trypsin and chymotrypsin inhibiting activities were detected in a "crude inhibitor" fraction of a lipid free cashew nut (Anacardium occidentale L.) meal. Both activities were shown to be heat resistant and not affected by pepsin at pH 3.0. Molecular weight distribution of tho trypsin inhibiting activity is similar to the known range of molecular weights for trypsin inhibitors of plant origin.
A "crude extract" of the cashew nut meal was shown to contain strong L-leucine-p-nitro-anilide and moderately strong α-N-benzoyl-DL-arginine-p-nitroanilide hydrolyzing activities. This last activity was strongly inhibited by the "crude inhibitor" fraction shown to contain trypsin and chymotrypsin inhibiting activities. The presence of this endogenous inhibitor-endo-peptidase system seems to indicate that the protein proteinase inhibitors of plant origin could be involved in the control of protein mobilization in the seed.

In the course of cold stratification ofAcer pseudoplatanus L. fruits a statistically significant alternation occurs in their seeds of a rise and fall in the level of endogenous growth regulators. In the initial weeks the inhibitory effect slightly declines, or, on the contrary, the stimulatory effect slightly increases; in the middle phase of stratification a marked increase in inhibitions and reduction of stimulations appears, and towards the end of stratification the stimulatory effect of isolated substances in the individual biotests rises again, or their inhibition effect is decreased. No direct dependence was found between the decrease of the degree of dormancy and the drop of inhibitor, or increase of promotor levels. However, a certain analogy was observed between the time course of fluctuations in the level of growth regulators and the germination energy of the seeds investigated. An enhancement of the growth activity of the substances isolated (e.g. those of a gibberellin-like nature) in the last weeks of stratification can already be considered as the result of the release of fruits from dormancy.

The blue-green algaeChroococcus, Oscillatoria and Nostoc, excrete vitamin B₁₂ and pantothenic acid in the culture filtrates during the phase of active growth. The excretion has an ecological significance.

Total activities of nitrate and nitrite reductases were higher in 4 to 20 day old maize plants in the leaves than in the roots. The ratio of activities found in the leaves and in the roots respectively was much higher in the case of nitrate reductase than in the case of nitrite reductase. On the other hand higher glutamate dehydrogenase activity in the roots than in the leaves clearly indicates that the roots play a more important role in the assimilation of ammonium than in the assimilation of nitrate. When comparing the distribution of seminal and nodal adventitious roots of maize seedlings with the assimilation of inorganic nitrogen on the basis of enzyme levels, it could be deduced that during the first 20 days of seedling growth seminal roots were more involved in the assimilation of nitrate whereas nodal adventitious roots were more active in ammonium assimilation.

Two soluble protein fractions were found to increase under cold treatment in winter rape plants. They were the proteins of low molecular weight, impoverished in proline and methionine residues and localized in the citosol subcellular fractions. They seem to be linked in "situ" with the hydrophobic compounds of cytoplasm. Owing to those properties, they seem to be more resistant against salt-induced aggregation which may occur at freezing or at A01GP096.

Papaverine hydrochloride, which is an alkaloid found in opium, inducedc-metaphase,c-anaphase, non-congression, diagonal anaphase, chromosome and chromatid bridges, lagging of chromosomes, micronuclei and multinucleated cells in root tips ofAllium cepa. It is the only one amongst the alkaloids of opium which caused a high increase in MI after a long period of treatment with some low concentrations.

Funaria spores must structure their photosynthetic apparatus before germination. A lack of manganese in the culture media affects neither the final structure of chloroplast nor the chlorophyll synthesis. Fixation of CO₂, reducing power of chloroplasts (DPIP) and RPE photo-induced signal S II are modified by this lack of manganese. The study of Mn/Chl and CO₂ fixed/Mn ratios shows that Mn is a limiting factor for CO₂ fixation and that in the spores depleted of Mn the residual Mn is "structural" Mn.

Effects of exogenous application of auxin, GA3, abscisic acid, ethrel, methionine and α-alanine to the cut ends of the pedicels of flower buds, flowers and fruits on their abscission behaviour were studied. Fruit pedicels required more time for abscission compared with flower and flower bud pedicels. NAA inhibited abscission of all types of pedicels and the inhibition was maximum in matured fruit pedicels and minimum in flower bud pedicels. Flower pedicels were more sensitive towards the abscission promotive effects of GA3, abscisic acid and ±-alanine and the flower bud pedicels towards ethrel and methionine. The duration of Stage-I of abscission was maximum in cut pedicels of fruit and minimum in those of flower buds. Biochemical analyses revealed greater quantities of endogenous amino acids in the epicalyx of flowers with the exception of methionine and aspartic acid which were found to be present in higher quantities in the epicalyx of flower buds. Levels of IAA-like compounds were maximum in the epioalyx of flower buds and minimum in the epicalyx of flowers. Higher levels of abscisic acid were found in the epicalyx of matured fruits and the epicalyx of flower buds showed a minimum amount of abscisic acid-like compound.

A number of phenolic compounds have been tested for ability to inhibit the cytokinin-induced synthesis of betacyanin inAmaranthus caudatus cotyledons. Under the conditions employed, the compounds responded thus: (1) no inhibition with up to 1 mg ml^-1 (quercetin 3-rhamnosylglucoside and chlorogenic acid), (2) partial or no inhibition up to 0.1 mg ml^-1 with greater inhibition at 1 mg ml^-1 (phloridzin, arbutin, caffeic acid, p-hydroxybenzoic acid and 3,4-dihydroxyphenylalanine) and (3) partial or no inhibition up to 0.1 mg ml^-1 with complete, inhibition at 1 mg ml^-1 (o-coumaric,m-coumaric,p-coumaric, protocatechuic and ferulic acids and phenylalanine). The results show that if theAmaranthus betacyanin bioassay for cytokinins is to give reliable results, then certain contaminating phenolics must be removed beforehand; some difficulties involved in this are briefly discussed.

The cytogenetic effect of two radiolytic cytosine products, i.e. of isobarbituric acid and of dialuric acid has been studied on a system of resting meristem ofVicia faba L. on chromosomal level. Both compounds produced in a concentration 10^-3 and 10^-4 M chromosomal aberrations with a relatively low frequency, about 4 aberrations per 100 anaphases after 12 h of treatment. Among the aberration types chromosomal and chromatid breaks and minutes pre-dominated.

The paper deals with the effect of some factors on the set of mature seeds in artificially pollinated excised placentae cultivatedin vitro.
It was revealed that both the degree and the variability of the seed set depend on the age of the experimental flowers. The best results were achieved using placentae excised from the flowers collected 1 to 3 days after anthesis.
The technique of pollination which consists in applying pollen onto a certain site of the placenta was substantially more successful than dusting pollen over the entire placenta surface or sowing pollen on the nutrient medium in close proximity to placentae.
It was confirmed that casein hydrolysate at a concentration of 500 μg ml^-1 nutrient medium favourably affected the seed formationin vitro.
The seed set resulting fromin vitro fertilization does not depend upon whether, during, a fourweek cultivation, the cultures are kept in the dark or in diffused daylight.

In 7 species (Eleocharis palustrisR. Br.,Juncus bufonius L.,Gypsophila muralis L.,Trifolium repens L.,Agrostis stolonifera L.,Potentilla anserina L. andAchillea millefolium L.) growing in a gradient of habitats from aquatic to terrestrial, on a sandy fishpond shore in Southern Bohemia, Czechoslovakia, the daily course of transpiration rate and water content was assessed gravimetrically in their cut-off transpiring parts on two typical summer days. Transpiration rate was largely controlled by microclimate but depressions occurred inJuncus and in some species growing in the drier habitats. The highest instantaneous transpiration rate and total daily transpiration per unit dry weight, about 100 mg g^-1 min^-1 and 50 g g^-1 d^-1, respectively, were recorded inAchillea andTrifolium. The water turnover rate ranged from 16.1 g g^-1 (H₂O) d^-1 inJuncus to 10.7 inGypsophila. The estimated daily maximum water saturation deficit was highest inEleocharis (45.7%) and lowest inAchillea (15.0%). The adaptational significance of the observed phenomena is discussed.