The effects of various cultural factors on the secretion of three pectic enzymes (PP, PG and PE) byAlternaria tenuis on synthetic media were studied. The results can be summarised as follow:
1. No definite correlation between the secretion of pectic enzymes, pH of the medium and the growth of the fungus was observed.
2. The secretion of the enzyme was dependent on the presence of pectin in the medium.
3. While various sugars were found to be equally effective, production of the enzymes was better on a medium without any sugar.
4. After varying the various concentrations and constituents of the medium, the following medium was found to be the best for the enzyme secretion: 1% pectin, 0.2% asparagine, 0.05% magnesium sulphate and 0.3% potassium dihydrogen phosphate.
5. It was established that on the above medium the fungus required four days of incubation at 25°C for the secretion of most active pectic enzymes.

Pure cultures ofChlorella pyrenoidosa (82) andScenedesmus obliquus (125) were grown in the nutrient medium according to Benson in the presence of 0.05m sugars or 0.025m sodium salts of organic acids. The density of culture was measured throughout the course of growth. Satisfactory heterotrophic sources of nutrition forChlorella pyrenoidosa appear to be galactose, glucose and acetate, whereasScenedesmus utilizes glucose, cellobiose and acetate. The growth ofChlorella in the light is enhanced by galactose, glucose, fructose, cellobiose and maltose, that ofScenedesmus by glucose, fructose, cellobiose, galactose, maltose, acetate and pyruvate. Soluble starch suppresses growth of both cultures. The role of the substrates is discussed. It follows from the results that the growth-promoting sugars and organic acids can act not only as a source of carbon during general carbon shortage but also as ergastic material. The mechanism of utilization of some organic substrates will be taken up in a subsequent paper.

The action of zinc on the growth of barley and the biosynthesis of indol compounds and gibberellin-like substances was investigated in a number of concentrations of zinc from doses stimulating growth to toxic doses. The seeds were soaked before sowing in solutions of zinc sulphate (5.10^-5 to 5.10^-1% Zn), and the plants cultivated for 7 days in water. Lower concentrations of zinc increased both plant growth and the biosynthesis of tryptophan and auxins. At the optimum concentration of 5.10^-3% Zn this increase in tryptophan amounted to 241% of the variant without zinc; in substances with an R_F corresponding to indolyacetic acid, the increase determined by the biological test, was 207% as against the variant without zinc. Higher concentrations of zinc inhibited growth, the tryptophan content was decreased to below that of the control without zinc and the auxin content also fell to below the control values. Zinc also influenced the content of gibberellin-like substances in the plants. At a concentration of 5.10^-3% Zn the increase in the growth activity in the gibberellic acid area of the chromatogram was 294% of the variant without zinc. At toxic concentrations of zinc, the content of gibberellin-like substances fell to below that of the controls. The finding that zinc acts simultaneously on the biosynthesis of auxins and gibberellins is also evidence for the common action of growth substances of various chemical types on plant growth.

The unicellular algaeScenedesmus obliquus (125),Chlorella pyrenoidosa (82) andCoccomyxa solorinae saccatae (111) were studied with respect to the form of uptake of potassium, phosphate, calcium and zinc ions and to the energy sources involved: light under autotrophic conditions, glucose under mixotrophic or heterotrophic conditions (in light and in darkness or together with yeast extract as an auxotrophic substrate). We respected the trophic conditions of algae when preparing the experimental material (precultivation). The following conditions were reached:
(1) The three algae grow faster in a glucose medium under mixotrophic conditions and are capable of growing on it also heterotrophically:Ch. pyrenoidosa andSc. obliquus grow substantially better thanC. solorinae saccatae. The first two algae grow more intensively in a glucose medium containing yeast extract whileCoccomyxa does not. After cultivation under mixotrophic conditions the first two diminish endogenous respiration, the third raises it. Glucose stimulates respiration in the first two when grown autotrophically, while after mixotrophic cultivation the effect of glucose is suppressed inCh. pyrenoidosa and in the other two only after growth on glucose with yeast extract.
(2) A relationship between sorption and metabolism was established for potassium in all the algae investigated. The effect of light is generally positive, heterotrophic components (glucose and possibly yeast extract) stimulate the uptake in the dark as long as they represent a suitable mixotrophic medium for the given alga.
(3) The uptake of K⁺ was proportional to concentration in solution and independent of Ca²⁺.
(4) The uptake of phosphate is clearly stimulated by light, while no stimulation under mixotrophix or heterotrophic conditions on glucose was observed-actually, a depression usually took place.
(5) At concentrations from 10^-6M to 10^-2M the uptake of phosphate is non-linearly but positively related to the concentration in the medium. The presence of Ca²⁺ is the cause of non-metabolic forms of phosphate sorption.
(6) Two forms of calcium uptake were found: the predominant one is adsorption which can be associated with the presence of phosphate ions; the metabolic uptake represents a considerably lower fraction which is characterized either by a light dependence or at least by a rise of calcium content between t=0.1-6 h.
(7) The absorbed Ca²⁺ can be washed out up to 75% with dilute hydrochloric acid. The total adsorption and remainder after washing depend on the pH of the solution from which the sorption took place (a considerable rise beyond pH 6.5). A substantial effect on the formation of the adsorption system was found to be due to organic nutrients. Algae after mixotrophic precultivation possess a decreased sorptive capacity.

The paper deals with the relationship between the glucose utilization and growth ofPenicillium frequentans. The vegetative growth was scanty and sporulation started at a time when glucose was abundant in the culture medium. Occurrence of autolysis in spite of the presence of glucose in the culture medium is a peculiar phenomenon reported here. The autolysing culture gives rise to conditions which favour the germination of spores and the development of vegetative growth. The citric acid is the major metabolite produced by the fungus and its biochemical origin appears to follow condensation of oxalacetate and acetate. Lastly production of citrmin as another metabolite has also been reported.

The "injection method" is recommended for maintaining a constant soil moisture at values lower than maximum capillary capacity in pot experiments. The appropriate amount of water is injected into the soil by means of a puncture needle connected with a syringe. The reliability of the above method in relation to the uniformity of the vertical and horizontal distribution of soil moisture was tested in pot experiments with maize. The fortuity of the changes in the soil moisture distribution within the scope of the given variability restricts the "growth of roots towards the water".

If the flowers for experiment were separated from the plants one day before pollination and incubated in water at a temperature of 25° C, pollen tube growth in the pistils made itself apparent during the following three days in the glucose and fructose level. On the first day after pollination the amount of these sugars in the apical style parts was higher in non-pollinated flowers, while on the other hand, in most cases it was lower in the basal sections and ovaries than in the corresponding parts of pollinated flowers. During the next two days there was a greater loss of both carbohydrates where pollination, particularly allogamy, occurred, so that after the third day the glucose and fructose level was highest in the non-pollinated pistils and lowest after compatible pollination. This decrease was most pronounced in the ovaries even though the compatible tubes had not yet penetrated into them. In experiments in which the flowers were left on plants cultivated under field conditions, a decrease in the glucose and fructose content of their pistils had not occurred even 80 hours after compatible pollination.
From these facts the following conclusions can be drawn: The growth of the tubes through the styles causes an increased inflow of carbohydrates into the whole pistils. Both compatible and incompatible tubes use sugars from the style tissue. Both these phenomena are more intense after allogamy than in the case of incompatible autogamy. In view of the fact that compatible tubes grew normally through the styles even with a lowered glucose and fructose level, an absolute rise in the content of these sugars in the pistils is not necessary for tube growth.
The proportion of glucose/fructose in pollinated styles changes in favour of glucose. The value of this quotient rises both in the apical and basal style parts mainly, however, after compatible pollination. This phenomena is in agreement with the previous hypothesis (TUPý 1959, 1960), according to which, in the respiratory process, pollen tubes consume mainly sucrose and from this, primarily its fructofuranose component.

1. Protein synthesis in pollen tubes ofNicotiana alata Link etOtto estimated by the incorporation of leucine-¹⁴C is linear over six hours of artificial cultivation after a short lag phase. 2-Thiouracil and other growth-stimulating antimetabolites of natural pyrimidines and purines, such as 6-azauracil, 5-nitrouracil, 8-azaguanine and 8-azaadenine, stimulate the incorporation of leucine-¹⁴C into protein. The intensity of stimulation of protein synthesis is associated with the intensity of growth stimulation by antimetabolite.
2. Synthesis of RNA is inhibited by 2-thiouracil (according to the incorporation of uracil-¹⁴C, orotic acid-¹⁴C and³²PO₄ ^3- ).
3. Chloramphenicol (25 and 250 ppm) decreases during a one-hour treatment of pollen tubes the incorporation of leucine-¹⁴C by 12 and 24%, respectively. The same inhibition is found in pollen tubes stimulated with 2-thiouracil.
4. Pollen tubes incorporated 2-thiouracil into RNA. Stimulation of growth by 2-thiouracil can be reversed with uracil or uridylic acid.
These findings are related to the present views on protein synthesis and the mechanism of the chloramphenicol effect especially with respect to the possible explanation of the stimulation of protein synthesis during a simultaneous inhibition of RNA formation.
Physiological resistance of pollen tubes toward RNA antimetabolites, the relatively low sensitivity toward chloramphenicol, the contradictory change in RNA and protein synthesis due to 2-thiouracil and, further, resistance toward actinomycin D (Tupý, Süss 1965) point to the stability of the complex of messenger RNA with ribosomes in pollen tubes.

Mycelium of white-rot fungi secretes laccase into the medium. It was found by cultivation on malt-agar plates that the mycelium does not produce laccase equally in all its parts. The youngest hyphae at the margins of the colony represent usually the maximum producers, whereas older hyphae produce less or none at all. An exception here isCollybia velutipes which is the weakest producer of laccase of all the fungi studied and where only the older hyphae begin to secrete it. Manometric estimation of laccase showed that maximum specific activity of laccase is achieved at the boundary between the phases of initial and linear growth and i₁₁ some cases during the first half of linear growth. Ageing of the mycelium characterized by certain changes in its metabolism is reflected in changes of enzyme production by fungal hypha of different age.

Experiments with youngHordeum sativum andHelianthus annus plants showed that in the excretion of mannitol in the guttation liquid observed byGroenewegen andMills (1960) after uptake by the root system of plants, the osmotic concentration of mannitol in the nutrient medium and the temperature are significant. The beginning of mannitol excretion during guttation is accelerated considerably by the increase of the osmotic concentration of mannitol in the nutrient medium and the rising temperature. The osmotic concentration of mannitol is also important for the duration of mannitol excretion in the guttation liquid after transfer of the plants into a nutrient medium without mannitol. In the presence of mannitol in the nutrient medium water uptake by the root system and growth are inhibited and the tissues of the organs above ground and of the root system are dehydrated. The inhibitory effect of mannitol on the water uptake by the root system is immediate.

A study was made of the action of volatile substances liberated from the rhizome of couch grass on wheat seedlings. The experiments were made in a closed atmosphere in glass vessels with continual removal of expired CO₂ and the addition of O₂.
Volatile substances liberated from couch grass produced numerous morphological and physiological changes in wheat seedlings. They caused retarding of the growth of overground parts and roots, the excessive formation of root hairs, curling of the roots and bending of the coleoptiles. The respiratory rate was higher in the leaves and roots of the experimental wheat seedlings than in the controls. The changes observed were similar to those produced by hydrocarbons of the ethylene series, which are well documented in the literature.

Many studies have been made on ribosomes both in plant and animal material, on account of their importance in the proteosynthesis of protein. In plant material, studies have been made on the pea by Ts'o andBonner (1956), Ts'o,Bonner andVinograd (1958),Setterfield et al. (1960) andSisakyan et al. (1963). Ribosome from spinach were investigated byLyttleton (1962) andMurakami (1963) and fromClivia byMikulská et al. (1962). As part of a wider study of the mechanism of biosynthesis of nucleic acids in apple trees, we isolated ribosomes from the young green fruit and studied them by means of electron microscopy. Young apples were selected because cell division is very intense at this stage of growth of the apple.

A characteristic feature of the effects of humic acids on plant growth is the stimulation of growth in length of the roots. This is sometimes explained as being due to the auxinoid nature of the acids.
The author has examined this assumption by testing segments of wheat coleoptiles and of flax hypocotyls. The growth of segments of both types remained unchanged in solutions of potassium humate in concentrations of 10^-1 to 10^-7 g./l. as compared with the controls in water.
A study was also made of the interaction of humic acids with auxins. The growth curves of segments in concentrations of auxin up to about 20 mg./l. (flax) or 50 mg./l. (wheat) were not altered by the presence of a 10^-1 g./l. concentration of humate in the test solution. With higher concentrations of auxin the growth of the segments in auxin-humate solutions was considerably greater than in solutions containing auxin alone. The effect decreased with rising concentrations of auxins (β-indoleacetic acid and α-naphthylacetic acid).
The auxinoid character of salts of humic acids in water solution was not established, nor was there any confirmation of competitive antagonism in the sense of the antiauxin conception.

After the decapitation and amputation of one cotyledon in germinating pea seedlings, the axillary bud of the amputated cotyledon always grows and the growth of the axillary bud of the remaining cotyledon is inhibited. Before morphological differences appear between the axillary bud of the amputated and preserved cotyledon, a higher endogenous gibberellin content can be demonstrated chromatographically in the axillary bud of the amputated cotyledon. This indicates that the increased growth of the axillary bud of the amputated cotyledon is in connection with an earlier increase in the activation of endogenous gibberellins.

1. The growth rate of apple pollen tubes at a temperature of 25°C in 10% sucrose solution, with or without boron (0.001% H₃BO₃), shows a practically linear relation to time for 6 hours;Nicotiana alata pollen tubes, which are slower in growth, show a decrease in growth rate after 10 to 15 hours.
2. The greater part of the sucrose in the culture solution is inverted by the pollen tubes. The rate of this reaction increases with time until the substrate is exhausted. When the sucrose concentration drops to 5%, chiefly as a result of the inversion process, the growth rate of the pollen tubes decreases.
3. The growing pollen tubes absorb sucrose from the culture solution. Exogenous utilization of sucrose was evident in the case of apple pollen after 3 hours, inNicotiana pollen after 6 to 8 hours of incubation.
4. In view of the close correspondence between the decrease in the intensity of sucrose absorption by the pollen tubes and the decrease in their growth rate, it may be concluded that the accumulation of callose in pollen tubes while their growth rate is decreasing is not due to any rise in the proportion of glucose not utilized for cell-wall formation. Further, if no change in the glucose: fructose ratio is observed in the culture solution at the time when pollen tube growth is slowed down, it follows that reduction in growth rate and increase in callose accumulation is most probably accompanied by a drop in respiration of glucopyranose component of the absorbed sucrose.
5. Boron encourages sucrose absorption proportionally to the stimulation of pollen tube growth. It is, therefore, possible that the stimulatory effect of boron on growth is connected with carbohydrate metabolism. In view of the fact that pollen tube growth is accelerated by boron at the time when the tubes are still drawing to a great extent or exclusively on the reserve substances in the pollen grain- and in view of the well-known stimulatory effect of boron in distilled water - it follows that the main factor is not necessarily the translocation of carbohydrates into the pollen tubes, but that it is rather a question of the rate of their metabolism.

It was observed that the polyploids ofTrigonella foenum-graecum produced by seed treatment with 0.2% colchicine died after two cotyledonary stage, while the ones produced by seedling treatment survived. The root and shoot of seed treated plants were found to be mixoploids. The root tips exhibited 2n to 12n chromosomes and with the passage of time there is a regular decrease in the frequency of cells with lower chromosomes. The frequency of dividing cells decreases considerably towards the end of the 6th day due to the highploidy of most of the ploid plants. In case of seedling treatment the first formed tissue was mixoploid of high level similar to that of seed treated ones but in some cases the growing tip reverted to low level of ploidy which lead to more or less normal growth.
Since the difference in the constitution of seed and seedling treated plants lies in their root system, it has been suggested that probably highploidy of root system in the former may be responsible for the 100% mortality of plants.

The effect of different exposures to RTG radiation (100 r, 250 r, 500 r, 1000 r, 2500 r, 5000 r) on the changes of the permeability of the epidermal cells ofAllium cepa L., variety Všetaty, bulbs was studied during three vegetation periods. Bulbs from growing plants (followed from the development phase of bulb growth) and bulbs immediately after harvesting were used for the experiments.
It was demonstrated in our experiments by plasmolysis that the radiation-induced changes of cell permeability were irreversible. When plasmolytic agents of non-electrolyte character (1M sucrose, 1M glycerol, 1M urea) were used, the equilibrium state (total plasmolysis) was reached more rapidly with the irradiated bulbs than with the unirradiated controls. When electrolytes were used (0.5M KNO₃, 0,5M KBr), total plasmolysis occurred less rapidly with the irradiated objects than with the controls. These relationships were manifest during the whole ontogenesis ofAllium cepa L. An exposure to 100 r was sufficient in our experiments for causing the mentioned changes, proving a considerable sensitivity of the osmotic properties of the epidermal cells ofAllium cepa L. bulbs to ionizing RTG radiation.
Plasmolytic experiments after smaller exposures than 100 r of RTG-rays are in preparation.

Decapitated seedlings ofLinum andPisum treated with TIBA paste either above or below the cotyledons, showed different morphogenetic changes especially on the epicotyl stumps, due to the differences in the correlations of their epigeous and hypogeous cotyledons respectively, these being also primarily responsible for the differing dominance of their shoot primordia.
At the earliest phases of germination, an antagonism between TIBA and IAA can be demonstrated on the first internode inLinum, which is usually very short, as well as on the petioles of thePisum cotyledons. The former could be enlarged only by treatingLinum seeds, even when ripening on the plant, with TIBA paste and the latter, if retained by soaking seeds ofPisum in a TIBA solution could be promoted by exogenous IAA. This, on the contrary, reversed the morphogenetic effects of TIBA uponLinum seeds.

Statmographs were used for determining the curves of weight decrement of severed root tips of the squash (Cucurbita maxima L.) with time and were examined under controlled conditions. The existence of two qualitatively different fractions of water could not be demonstrated by the method used, all the curves obtained displaying a completely continuous character, without any inflexion point. The basic shape of the curves remained preserved on desiccation at different temperatures (20-40° C), at different relative humidity (45-90%), with plants of different age and different composition of aqueous media (Knop's nutrient solution, calcium-free medium, distilled water). Not even a 0.01% solution of potassium humate which significantly raised the water content of root tissue affected the shape of the desiccation curves. A continuous release of water was also observed when the meristematic root zone and the zone of longitudinal growth were dried separately.

A very low, for the most part unmeasurable glutamic-aspartio transminase activity and a very high glutamic-alanine transaminase activity was found in the overground parts and roots of young wheat plants. The roots had a higher glutamic-alanine transaminase activity than the overground parts in the first and second leaf stage.
Plants cultivated in Knop's nutrient solution (variant with humate and without) showed a higher glutamic-alanine transaminase activity than poorly growing plants, cultivated in distilled water (with humate and without). In plants cultivated in nutrient solutions, transaminase activity increased with the age of the wheat plants.
As in the previous experiments, the effect of humate was only significant, in the roots of plants cultivated in distilled water with humate, where transamination activity was greater than in the control without humate. The roots of this variant with a stimulatory growth effect showed a large accumulation of free sugars in the previous experiments.
The connection between these effects of humate on the roots of young winter wheat plants is discussed.

Decreasing the illumination intensity of winter and semi-winter varieties of wheat to below a certain limit led to an accelerated development of the shoot apex of the main axis, whereas the development of spring varieties was slowed down. In plants whose development was accelerated by decreasing illumination intensity, the dry weight of the overground parts was smaller and the carbohydrate content of the shoot apex of the main axis was greater than in control plants growing under normal conditions of illumination. Plants subjected to long vernalization developed more rapidly and the weight of the overground parts was less than in plants subjected to vernalization for the normal time. The accelerating effect of decreased illumination intensity on plant development is explained by a changed manner of growth which is connected with a greater flow of assimilates to the shoot apex.

1. The influence of varying concentrations of gibberellic acid on seedlings of wheat, lettuce and oats (up 10 days old) was observed and optimal concentration of 10 to 100 μg GA/ml. was established. Biometric evaluation of the experiments showed significant stimulation of the overground parts with all concentrations used (0.1 to 100 μg. GA/ml.) and significant inhibition of bhe roots with concentrations 1 to 100 μg. GA/ml.
2. For lettuce only the concentration 10 μg. GA/ml. was used. In this case, too, increase in length of overground parts was significant and inhibition of root growth was observed. For oats the stimulating effect of GA was recorded for both overground parts and roots.
3. Fresh weight of wheat was stimulated only by concentrations of 100 μg. GA/ml. In the case of lettuce (where values of fresh and dry weight were taken for the whole plant) we found a marked stimulation of fresh weight and a somewhat smaller increase in dry weight.
4. Observation of the dynamics of growth in length of overground parts and roots and increase or fresh and dry weight in lettuce showed a mutual relation between the values recorded in control and experimental plants in the period of 4 to 10 days following germination.

An investigation was made of the anatomical structure of the shoot apex of wheat in the first four stages of organogenesis according toKuperman (1961). It was found that the shoot apex is first covered only with dermatogen (first stage). Then the hypodermis gradually differentiates (second stage) followed by differentiation of the subhypodermis (third stage). In the first stage, the central core of the apex is formed by more or less uniform isodiametric cells so that no zones are distinguishable. During the initiation of the primordia of the assimilating leaves, i.e. in the second stage, a group of larger cells was observed in the apical part of the hypodermis and can be compared with the central zone described in dicotyledons. Under it there is a characteristic group of smaller cells. In the third stage the differences between these groups of cells become less clear and in the fourth stage are no longer observable. No differences were found in the manner of initiating the leaf and bud primordia during the period of ontogenesis studied. There is, however, an alteration in the extent of growth between the bud primordium and the corresponding leaves. Short-day photoperiodic inhibition, always started on the days when the shoot apices were collected for anatomical study, showed that the determination of the primordia of the leaves and axillary buds as parts of the inflorescence is complete by the end of the third stage, at the time when the primordia in the central part of the ear are initiated

The pathophysiology of tomato plants infected with potato witches' broom was studied. Changes in dry weight, content and composition of ash and the amount of different phosphorus and nitrogen fractions were investigated. All analyses were carried out separately in leaves, stems and preliminarily also in flowers. Considerable disproportions found in the distribution of metabolites among the individual organs investigated correspond to a great extent to the morphological picture of the disease. The leaves of diseased plants are actually starving and their growth and development are greatly inhibited. On the other hand, the stems are overflowing with metabolites, in particular with nitrogenous ones. They are thickened and along their entire length rootlets and sprouts appear forming the characteristic brooms. The authors assume that the disturbances in flower formation in diseased plants are due to the lack of essential metabolites. Diseased plants contain an increased amount of alkaline metals and alkaline earths.

A study was made of the effect of substituting a short day for vernalization as a varietal characteristic of winter wheat. Varieties representing certain ecotypes were vernalized for different lengths of time and it was studied how a short day can replace or accelerate vernalization. At the same time data were obtained on the effect of a short day on individual criteria of growth. The results showed that there are ecotypes in which a short day does not replace vernalization (the varieties San Pastora and other Italian varietis). In this case growth inhibition did not occur either. Otherwise it usually accompanies the substituting affect of a short day. This finding permits the interpretation of varietal differences observed in association with short day growth inhibition and changes in carbohydrate metabolism conditioned by it. Growth inhibition produced by a short day is a general reaction which is not only associated with vernalization. The author found varieties (Chlumecká 12) in which growth was inhibited by short day without accelerated development occuring (alternative types).

The aim of this work was to establish under what conditions the water deficit values obtained byStocker's (1929) method can be considered to be those for actual water deficits. It was found that the water intake of detached leaves is not necessarily due only to incomplete saturation of the leaf tissues with water, but that in young leaves it is caused to a great extent by their extension growth. Thus, water deficit in the sense ofStocker's definition is not merely a simple physiological state of incomplete saturation of the tissues, but is expressed by the sum of the need for water to achieve the greatest possible saturation of the tissues and the need for water in the normal course of the extension growth of cells.

Results of the action of low doses of gamma irradiation, intensity 1-80 to 0-24 r/day, are recorded in this paper. Irradiation was carried out on a gamma field with a 0-50 g. equiv. Ra Co⁶⁰ source throughout the whole vegetative cycle.Trifolium pratense var. Jičínský was chosen as the experimental material. Growth and the yield of green matter was followed both on individually bedded out plants and on sown plots. Results of the measurement and weighing of the plants were statistically evaluated by means of the t-test and analysis of variation. Small, daily radiation doses (1.80-0.30 r per day) produced a significant stimulatory effect which was evidenced in the greater height of the irradiated plants as compared with the controls and a higher yield of green matter. In conclusion the paper deals with work that has already been carried out in this field. Experiments and measurements have shown that low doses of chronic gamma radiation are capable of stimulating plant growth. This work is confirmed by result obtained by Breslavets, Berezina and Shchibrya (1956) on other material.

The different components of humus-alcoholic extract, humic acids and fulvic acids-progressively isolated from compost garden soil and deprived of minerál ions by electrodialysis, were, after addition to Sachs's nutrient solution, found to have differing effects on the growth of stems and roots of tomato plants. Similarly, differences in the effect on oxygen intake of leaves and roots was confirmed and varying amounts of chlorophyll were determined in the leaves. Fulvic acids were shown to be more active components of humus than humic acids. Morphological changes in the root system were found to be more typical for an estimation of the action of the different components of humus than the changes in physiological characteristics mentioned above.

1. The relative suitability of three natural habitats ofGarex humilis was determined on the basis of dry matter production of individual plants at the end of the growing period. In the habitat which was found to be the most favourable from this point of view the lowest degree of ground cover by the plant concerned was also recorded. It is therefore possible "to assume that it is not only factors connected with the habitat that influence the occurrence ofCarex humilis under the given conditions.
2. A comparison of the course of the growth curve with changes in air temperature indicates that, for the initial growing period when soil humidity is adequate, temperature is probably the limiting factor.
3. The results of the cultivation experiments lead to the conclusion that the water factor has the strongest influence on growth in length and on increase in dry weight of the overground parts ofCarex humilis. Under the conditions obtaining in these experiments the influence of light intensity and of the chemical composition of the soil on growth were not found.

Sodium fluoride, iodoacetate and malonate inhibit or stimulate the respiration of wheat roots cultivated for 2-10 days in a solution of sodium humate (100 mg/l.) as compared with the respiration of roots cultivated in water. The influence of sodium fluoride on the respiration of leaves is similar. The ratio of the radioactivities of C¹⁴O₂ from glucose, labelled in the position 1 or 6 (C₆/C₁) is distinctly higher in roots, but not in leaves. The change in this ratio is accompanied by a decrease in the total radioactive C¹⁴O₂ from roots of plants influenced by humate, from glucose labelled specifically and totally.
Endogenous respiration (QO₂) of roots increased in humate by 5-30%, the intensity of leaf respiration remaining at the same level. The longitudinal root growth increased in humate by 20-80%, the growth of leaves by 5-15%. The above statements show that in a humate solution the glycolytic fraction of the respiratory metabolism of roots is increased.