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.

Several improvements of the method of sap flow rate determination in full-grown trees elaborated by the authors are described. The method is based on heat balance with direct electrical heating of the xylem. The accuracy of the relationship for the calculation of flow rate was improved, the influence of unevennesses of flow in different annual rings was reduced. A method of extrapolation of the results obtained by measuring an individual xylem segment against the whole tree and of interpolation to a unit segment was elaborated, a simplified method of connecting the electrodes supplying the thermal input to the segment is described and an indicator of the relative water content of the xylem was derived.

The cells of some pea, tobacco and haplopappus callus strains reveal considerable variability in nuclear morphology (polymorphous nuclei, differences in nucleolar size and number, enlarged chromocentres) and chromosome counts. The specific features in the nuclear morphology of callus cells are related with some pecularities in the reproduction activity of these cells (amplification, amitosis, fragmentation, various deviations from normal mitosis) under cultural conditions including both the definite action of the culture system and the absence of the regulatory control by the intact organism.

Hormone-directed transport is shown in a detached adult leaf ofPelargonium zonale, after a local application of solution (0.1 ml) of various groups of phytohormones (GA3 -BAP-AIA-ANA-2,4-D). Importance of isolated leaf as a simplified experimental system is underlined by the positive results obtained with³⁵S (or³²P).
The idea of competition between two attractive foliar centers, induced by hormones is illustrated:
i) with regard to the concentration of the same hormone (higher effect at 25 mg than at 2.5 mg.l-1 with GA₃ for example);
ii) when two different hormones are competitive on the same leaf. In this respect, GA3 appears to be the most effective hormone tested on this material.
Finally, the idea of a hormone-directed transport, independent of the antisenescence effect is supported by the fact that an orientated translocation remains induced after general pretreatment with an alternative hormone (BAP and GA₃, for instance).

The germination of the pollen from11 individuals of six wildRosa species was studied. The presence of calcium resulted in increased pollen germination, longer pollen tubes, and in a decrease of the requirement of sucrose concentration in cultivation media. Pollen germination in the medium with Ca reached the values of pollen viability estimated by tetrazolium test in all cases except with roses with balanced heterogamy, of the sectionCaninae. The stimulating effect of calcium was generally most pronounced in the pollen from roses of hybrid nature, such asR. jundzillii, R. canina, and especially in the case of the calciphilous speciesR. eglanteria.

The ultrastructure of differentiating epidermal cells of maize root (within the distance of 1 and 2 mm from the root body apex) were studied under conditions of non-lethal and lethal osmotic stresses of nutrient medium containing polyethylene glycol 4000, as well as regeneration of their ultrastructure following rehydration. The structural response to water deficit of the cells investigated was dependent on both the stress duration and the stage of their ontogenic development. Following non-lethal stress, in younger cells investigated (1 mm), condensation of nuclear chromatin, decrease of polyribosomes and increased density of free ribosomes in cytoplasm, reduction of mitochondrial cristae and occurrence of intramitochondrial inclusions, less compact dictyosomes were observed. Pastid structure remained unchanged. Microtubules were lacking in treated cells. In the more differentiated cells (2 mm) protoplast retreat from cell walls was also observed as well as a general decrease of ribosomes and ER elements in parietal cytoplasm, an increased number of intramitochondrial inclusions and mitochondrial membrane fragmentation. In these cells, Golgi apparatus was also lacking. The ultrastructure regeneration of the more differentiated cells was less pronounced. Lethal osmotic stress would cause more severe structural damage in all the cell components investigated.

The study deals with the absorption and translocation of Ca²⁺ by án intact plant of pumpkinCucurbita pepo L. and with the effect of various concentrations of 2,4-dinitrophenol (DNP) on these processes. The absorption of Ca²⁺ was reduced by the application of this inhibitor, but not completely stopped. The translocation of Ca²⁺ into shoots was affected more expressively: it was almost completely inhibited by higher DNP concentrations. The uptake of Rb⁺ is aubstantially more influeneed than that of Ca²⁺: higher inhibitor concentrations caused its complete cessation.

Crystal-containing organelles in cells of virus infected plants lying at chloroplasts and mitochondria are identical with single membrane-bound microbodies containing crystals of catalase described in healthy plants. Massive complex inclusions caused by turnip mosaic virus very frequently contain the same microbodies with crystal inclusions; that phenomenon may be related to some pathophysiological changes of virus infected plants. Comparable proteinaceous crystals, but not lying within microbodies limited by a membrane, may also be found in cytoplasm of infected cells. These crystals are sometimes surrounded by a substance resembling the microbody matrix. Disintegrated cytoplasm of virus infected cells may also contain the same crystals lying free in "empty spaces". Cytopathological effects responsible for this phenomenon and possible artifacts as well are discussed.