Ascorbic acid (AA) turnover, and levels of RNA and protein were determined during germination ofCicer arietinum cv. Chafa under-(i) normal watering; (ii) water stress of six days; and (iii) revival upto next stage of seedling growth after water stress. Water stress lowered significantly AA, ascorbigen, ascorbic acid-macromolecule complex, RNA and protein content in embryo axis while a reverse trend was seen after revival. In the cotyledon, AA, RNA and protein contents were higher during water stress. However on revival only AA and protein contents decreased, whereas the RNA content showed further enhancement. It is suggested that increased synthesis of AA in the cotyledon during water stress may trigger enhanced synthesis of RNA and consequently of enzymic proteins, thus bringing about rapid mobilization of reserve materials during revival.

Under the conditions applied in our laboratory 4 1/2 days old plants ofChenopodium rubrum require 2-3 photoperiodic cycles for maximal flowering response, whereas 2 1/2 days old plants are able to flower after having obtained a single inductive cycle. The period length of the free-running rhythm of flowering observed in 2 1/2 days old plants after a single transfer from light to darkness is 30h and the first peak of flowering occurs at about hour 12 in darkness. When a cycle consisting of 16h darkness and 8h light or of 8h darkness and 8h light precedes the long dark period the rhythm is rephased. Rephasing is greater when the light commenced to act on the positive slope of the first peak of the free running rhythm than when it impinged on the negative slope. With an 8h interruption of darkness by light rhythm phase is controlled by the light-on, as well as by the light-off signal. Feeding 0.4 M glucose during the long period of darkness enhanced the amplitude of the flowering response and, moreover, substituted for one photoperiodic cycle.

Biological activity of humic acid, hymatomelanic acid, lignofulvic acid, and fulvic acids isolated from peat, from spruce wood decomposed by the fungusFomes marginatus(Fr.) Gillet, and from spruce wood decomposed by the fungusPoria cinerascensBres. was tested on cress seedlings (Lepidium sativum L.). The results evaluated by the analysis of variance indicate that humus acids show a high degree of affinity in their biological activity which is a condition for the applicability of the decomposition of wood by fungi as a model of the humus formation. Humic and hymatomelanic acids, products of an advanced step of humification, have a predominantly stimulatory effect especially on the hypocotyl. Lignofulvic acids and fulvic acids exert a rather inhibitory effect with the root being more affected.

During the 24 hours' washing of¹⁴C MNU and¹⁴C MMS-treated seeds the amount of DNA 7-methylguanine as well as the total alkylation of DNA, RNA and proteins in cells of the embryo was enhanced. The drying of shortly washed¹⁴C MNU-treated seeds to 30% and 15% water content led to, a similar increase of alkylation. In accordance with the changes in the biological damage, the amount of single strand breaks and/or alkali labile sites in DNA dropped down during a 19 h washing period of MNU-treated seeds but changed only slightly in MMS-treated and 19 hours washed seeds. The drying of 0.5 or 18 h resp. 19 h washed seeds treated either with MNU or MMS to 15 per cent water content increased the amount of single strand breaks and/or alkali labile sites in DNA.

Sixteen early, medium late, and late homozygote lines ofArabidopsis thaliana, obtained from three natural populations, were crossed with a common check variety S 96. The speed of development was expressed by the value log (x+y), wherex stands for the number of days after which flower primordia appear, andy for the number of leaves in the rosette. The experiments were caried out under conditions which emphasized the differences in the speed of development. We assessed the degree of dominancy, heritability on the basis of F₁ and F₂ variance, and analyzed F₂ distributions. It was established that some of the investigated lines differ from the variety S 96 in one pair of dominant genes or genes with incomplete dominancy for late flowering, other in two pairs of genes with complementary effects, and that the variety S 96 probably also contains other alleles causing late flowering inhibited by some type of epistasis. Even though the most important part is always played by one or two pairs of genes with high dfficiency, genes with lower efficiency often take part in the process; in some lines the genes with high efficiency could not be established.

Cells mechanically isolated from homogenized leaves ofC. sepium dividein vitro. The rate of cell division is strongly influenced by temperature with the optimum between 31 and 34 °C. The rate of cell division increases proportionally with a rise in temperature up to 31 °C and is accompanied by a reduction in the length of the preparatory phase of the division. A supraoptimal temperature (40 °C) inhibits or stops the cell division which can be restored provided that the cells are transferred to 31 °C. If the preparatory phase to the commencement of cell division is accomplished at 17 °C the cells then exposed to 31 °C divide more rapidly than if they are exposed directly to 31 °C.

Two strains of tobacco tissue cultures were investigated cytogenetically, their morphogenetic potency was revealed and the plant regenerates were analyzed. Strain I with less pronounced deficiency of nuclei was more capable to differentiation and organogenesis than the heterogenous strain II. The morphological variability of vegetative and reproductive organs of plant regenerates was described. The variations were characterized by high level of aberations during meiosis and unstable aneuploidy.

Chromatographic separation of an extract of organic acids on a Dowex-l column in the formiate cycle was used to study the content of several organic acids in pea plants, cultivated either in light or in darkness. Concentration changes of the individual acids in the course of growth indicate that the citrate cycle is blocked in the cotyledons of plants grown in light in the period around the 15th day of growth, probably at the site of succinic dehydrogenase (succinic and lactic acids accumulate and the content of citric and malic acids is exhausted). There is no inhibition in the cotyledons of etiolated plants. In vegetative organs, the concentration of the majority of the acids studied is lower than in cotyledons, probably because synthetic processes prevail over degradation processes in these organs. It seems that other processes besides the citrate cycle participate in malate synthesis in pea plants.

In the course of the study of the effect of allylisothiocyanate in a 10^-4 dilution on the mitosis ofPisum sativum root tips, some cells with typical meiotic configurations were found. After 92 h of treatment about 2% of the dividing cells were in the state resembling a so called somatic reduction.

The spread of mycoplasma causing potato witches' broom disease from infectious grafts of both tomato and tobacco plants intoNicotiana glauca Grah. plants is much slower than that into tomato plants. An earlier infection inN. glauca stock plants appears when infectiousN. glauca grafts are used. On the other hand, the process of infection proceeds very slowly when using infectious tomato grafts and in some cases the infection is not realized even after three months of graft symbiosis. The authors suppose that mycoplasma has a preference for tomato plants.

When aerated suspensions of whole yeast cells were either made anaerobic or were supplied with substrate (glucose), changes in absorption occurred which indicated cytochrome reduction. No such change was observed on addition of substrate to anaerobic suspension of yeast. These results were confirmed by obsevations of changes in absorbance at a series of fixed wavelengths corresponding to the reduced absorption peaks of cytochromesa, b andc. NAD* on the other hand was reduced on addition of substrate under both aerobic and anaerobic conditions. These results are discussed in relation to the possible role of NAD* in the Pasteur Effect.

Beginning with the second inductive cycle the rate of nucleic acid (NA) synthesis in cotyledons and apical buds ofChenopodium rubrum is higher at the end of the dark period or 4h following transfer of the plants to light in induced plants than in non-induced ones. This is due to an increase in all NA fractions. The greatest difference between NA synthesis in induced and non-induced plants was observed at the end of the second (or sometimes third) inductivecycle. In the subsequent cycles the difference decreased or disappeared eventually. During photoperiodic induction NA synthesis shows a diurnal rhythm with a peak at the end of the dark and at the beginning of the light period. Rhythmicity of NA synthesis is endogenous. The period length of the endogenous oscillation is about 18 h. Interruption of the dark period by light causea amplitude of the first oscillation to be reduced and delays the appearance of the second peak. NA synthesis did not show rhythmicity in plants grown in continuous light. The significance of the observed phenomena for photoperiodic induction is being discussed.

The influence of photoperiodic induction on the incorporation of uridine-³H into the shoot apices ofChenopodium rubrum was studied using the technique of autoradiography. No increase in uridine incorporation was detected either during induction lasting three days or immediately after its termination. Pyroninophylia likewise did not rise. However, changes in uridine incorporation related to morphogenetic activity during leaf formation and later during differentiation of inflorescences were well marked. The distribution of label in the nucleus immediately after three inductive cycles shows the ratio of extranucleolar to nucleolar incorporation to be higher in non-induced control plants than in induced ones.
Data from literature pointing to an activation of RNA synthesis during transition to flowering are discussed and compared with other systems where ontogenetic changes are accompanied by marked changes in RNA synthesis. It is assumed that the activation of RNA synthesis after induction is connected mainly with the activation of growth. However, inChenopodium rubrum photoperiodic induction proceeds together with limited growth and without activation of RNA synthesis.

Two typical dark-responses namely the excessive elongation of sprouts and the formation of sprout hook, are adversely affected by chloroflurenol. It also affects the polarity of sprouts and the formation of roots on tubers, the effect varying with the concentration and the light condition. The significance of these effects of chloroflurenol used in potato production has been discussed.

Individual leaves on apple shoots treated by pinching and/or ringing were supplied with¹⁴CC₂ and the rate of photosynthesis and the pattern of photosynthate distribution was studied. The ringing of the shoots as well as the ringing and pinching done together reduces the rate of photosynthesis almost by half. Pinching itself had no effect on the rate of photosynthesis. Removing the main sink - the growing shoot apex - by pinching leads to the accumulation of photosynthates in the shoot, mainly in the first internode below the pinching point. Accumulated assimilates were soon used up by the axillary meristems which were stimulated to grow by pinching. Very small amounts of assimilates (about 1 %) were translocated to adjacent shoots which were supplied by their own leaves. When adjacent shoots were defoliated, more assimilates were translocated there (nearly 8%), however, a strong tendency to accumulate the assimilates in the internode below the pinching point was observed. Assimilates are not located in matured leaves. The presence of an active sink located near the donor stimulates the mobilization of assimilates present in the donor leaf.

The effect of colchicine, caffeine and hydroquinone on nodal meristems ofCallisia fragrans has been studied. The polyploidy have been induced following 4 and 8 hours of treatment in 0.5% colchicine. The persistence of polyploidy in emerging roots even after 60 d. of recovery in the soil indicates that the colchicine affected not only the nodal roots but also the nodal tissue of the plant. The occurence of both diploid and polyploid roots in the same node has been attributed to the differential penetration of the compound to the different zones of tissue. The increase in the division frequency following certain period of recovery was also observed. Caffeine induced only different subnarcotic effects. The formation of the binucleate cells, (which is very common inVicia faba) has been found to be very rare in the present material. No significant results have been obtained following the hydroquinone treatment excepting some common subnarcotic effects.

The root surface determined microscopically amounts only to ten per cent of the surface assayed with methylene blue. This difference is assumed to correspond to the sorption surface of cell wall interfibrillar capillaries. The volume of these capillaries amounts to 0.1 per cent of the total volume of the organ only, but their surface far exceeds the external root surface. It is suggested that the interfibrillar capillaries of the epidermis cell walls constitute the main elements of the root sorption surface.

A comparison was made of post and simultaneous azocoupling procedures for β glucosidase localization on unfixed and fixed root tips ofZea mays. Using this object, more detailed studies of β glucosidase distribution were undertaken, concerning the time course of enzyme reaction, its pH dependence, the effect of various buffers, the comparison of several diazonium salts and the use of different naphtholic substrates. The indigogenic reaction was also applied. Attempts were made by means of azocoupling procedures to localize a and β glucosidase in root tips ofCucurbita pepo, Lupinus albus, Piswm sativum andVicia faba in comparison withZea mays. In addition to certain technical problems, the questions of constitutive and adaptive enzymes, sugar distribution and histogenesis versus function are discussed in relation to the presence and distribution of ß glucosidase in the studied objects.

Cauliflower plants in the juvenile phase treated on the leaf surface and at the apex with Morphactin solution (100 mg 1^-1) and this concentration failed to develop a curd and also to come to flowering. Instead of a curd the axis formed a conical or dome-shaped structure bearing 'nodal' rings. The number of rings increased with growth of the axis which either formed or did not form a small curd-like structure, which generally dried without flower formation.

A. latifolia grown in the Borimalan forest block in Prasad range (24°11'N and 73°42' E) exerts clear positive correlations between CBH (circumference breast height)and number of growth rings of bole and branches, tree height, total biomass and leaf area. The net above-ground biomass is 3.95 × 10⁴ kg ha^-1. The average increment in non-photosynthetic (trunk + branch) biomass shows two peaks, the lower peak at 11-16 growth ring period, and the higher one at 34-36 growth ring period. The ratio of leaf dry weight/leaf area is16.3 to 34.8 mg cm^-2, the ratios between shoot net production: leaf weight and leaf area are1.5 g per g and 212 g m^-2 respectively.

IAA, NAA and ethrel (1 × 10^-4M and 3 × 10^-4M) was applied to the plumula of Chenopodium plants at different time after the start of photoperiodic treatment and the flowering response was investigated. The inhibitory effect was found with all the applications during the first two days, whereas a stimulatory one on the third and fourth day. We assume this dual effect reflects the differences attained in developmental phase and in the degree of shoot apex differentiation.

The constant values of water potential gradient accompanying various levels of water flow rate were found in kale leaf tissue segments. This constancy might indicate the decrease of resistance to water flow as flow rate increased and this decrease of resistance was confirmed.

Using a semiconductor freezing microtome, there is no difficulty in getting an ample supply of quite suitable sections of Ca formol fixed root tips ofVicia faba, applying Holt's sirup or plain 0.88 M sucrose as media for keeping the material, getting the sections and treating them after sectioning, but the protoplasts shrink and often fall out from the cells. No improvement in this respect was revealed using - at different concentrations - sucrose and arabic gum alone. The changes in the proportions of the ingredients of the sirup were also ineffective. A series of experiments were therefore performed with plain sucrose, but none of the factors tested was efficient enough to improve the results as compared with the standard procedure, the gradual transfer being the only exception. Since this makes the procedure more laborious and time consuming, certain other media were tested, 0.88 M ethanol and 0.88 M dimethylsulf-oxide yielding the best results. Attempts are being made to understand some points of the present experience in connection with the results of other authors and on the basis of general theory respectively.

Exogenous L-aspartic and L-glutamic acids enhance glutamate dehydrogenase activity in isolated pea roots. The results obtained indicate that both ammo acids induce increased GDH synthesis.

In the present paper the oxidative and phosphorylative activity of mitochondria isolated from rye, wheat, barley and corn seedlings are compared. Mitochondria from the shoots as well as from the roots of rye, wheat and corn oxidized succinate and in the presence of ATP or ADP exhibited the respiratory control which reached the values mostly of about 2. In the presence of ATP or ADP the decrease of inorganic phosphorus was contemporarily remarcable. The P/O ratio reached the values mostly of about 0.8 up to 1.0. The presence of ATP effected in some cases more favorable the respiratory control as well as the P/O ratio in comparison with ADP. With regard to the fact that a trapping hexokinase system was not added, the presence of endogenous hexokinase in mitochondria of experimental plants is presumed. The barley mitochondria exhibited the respiratory control as well, but instead of the decrease in inorganic phosphorus content in reaction mixture, an increase took place. It was caused by the presence of active ATP-ase which was not effectively inhibited by present NaF.

Peroxidase activity and isoenzyme pattern were investigated in buds and tubers of Jerusalem artichokes in relation to induction and breaking of dormancy. Peroxidase activity per unit soluble protein is the highest in the dormant stage. Conditions leading to growth,i.e. release of dormancy by the cold, stimulation of axial growth by gibberellic acid or stimulation of radial growth (tuberization) by kinetin, cause rapid loss of total peroxidase activity together with a decrease of intensity of the most cathodic isoperoxidases. Induction of dormancy by AMO-1618 increases peroxidase activity mainly through the same cathodic isoenzymes. The role of the cathodic isoperoxidases is discussed in relation to auxin catabolism and the genesis of oxygenation products inhibitory to plant growth.

The formation of starch in excised 3-days-old pea roots was enhanced up to three fold after cultivation for five days in liquid media containing 3% glucose, microelements, and 10^-6 M kinetin or 10^-7 M naphtaleneacetic acid (NAA). A synergistic effect of kinetin and NAA on starch formation was observed when both hormones were applied simultaneously over a wide range of concentrations.