Effects of various concentrations of streptomycin sulphate either alone or in combination with different cations and hormones on mungbean (Phaseolus aureus L.) seedling growth were studied. The relative inhibition of root growth was stronger than that of hypocotyl growth. Root growth inhibition was completely overcome by calcium, while other cations were ineffective. Inhibition of hypocotyl elongation could not be prevented by cations. IAA and GA₃ were capable of relieving streptomycin inhibition but kinetin was ineffective.
In the coleoptiles of streptomycin-treated rice (Oryza sativa L.) seedlings, there were accumulation of nucleic acids and decline in protein content resulting in increased RNA/protein and DNA/protein ratios. High nucleic acid content induced by streptomycin could be correlated with reduced activity of the nucleases.

The content of substances showing the cytokinin activity was estimated on decapitated and one-cotyledon-deprived pea plants during that period when the promoting effect of the cotyledon excision had not yet been manifested. Results of the bioassay showed that after the excision an increase in the level of substances with cytokinin activity occurred only in cotylars growing in axillas of these excised cotyledons. These results coincide with earlier data about the content of gibberellins and auxins in the same object.

The manner of regeneration phenomena of carpophores ofCoprinus congregatus planted on the fresh nutritional substrate was studied. In the cultures taken from the carpophores that had completed their development the first viable regenerated primordiums appear mainly on the mycelium developed from the carpophore-implant (indirect regeneration). On the contrary, in the cultures taken from the carpophores in which the final morphogenesis was checked by unfavourable conditions, temperature or light, the first regenerated structure developed essentially on carpophore-implants (direct regeneration). It appears that a relation exists between the regeneration potential an development of the phenomena of maturation in carpophore-implants.

An installation is described enabling measurements of photosynthesis, transpiration and dark respiration, and estimation of photorespiration rates at different carbon dioxide and oxygen concentrations, at different irradiances and leaf temperatures.

Humic acids can inhibit the activity of wheat phytase in model experiments, because they are able to form complexes with hexainositol phosphates and have considerable adsorption properties. Decarboxylated humic acids do not show any inhibitory effects.

Respiration of protoplasts isolated from the leaf mesophyll ofPetunia hybrida was estimated by the Warburg method. The time course of respiration rate shows an initial decrease followed by a prominent increase which is caused by shaking of the protoplast suspension. The absolute respiration rates are low and show an unusual spread, but the temporal form of the curve is always similar to that one shown in Fig. 1.
The RQ-values shift from below 1 during the initial phase to far above 1 during the increase of the respiration. For isolated protoplasts from petals the same is true. Feeding the protoplasts with DNA does not influence the respiration rate significantly. The physiological quality of protoplasts seems to suffer in a high degree from the isolation process.

A non-specific effect of antiviral factor (AVF) was proved by interference of five different viruses (CMV, PVX, PVY, TMVe, TMV vulgare) with CBRV.
The non-specific AVF originates in non-infected tissues around TMV lesions. Transmitted mechanically to other plants this AVF exhibits the same suppressive effect on multiplication of TMV and CBRV.
The AVF is formed in the non-infected apical part of the leaf which was infected in its basal region. The susceptibility of leaves is decreased even when AVF is added to virus inoculum and applied mechanically on the leaf. The apical part of the leaf the base of which is met with necrotic reaction to TMV, is considerably less susceptible and TMV multiplication in this region is decreased. The necrosis on the leaf base induced by mechanical injury or by cysteine hydrochloride may decrease the susceptibility of the leaf to some extent, but has no effect on multiplication of the virus.
The activity of AVF in healthy apical region of the leaf increases till the fifth to the eighth day after its basal part was infected. The apical region then exhibits lower susceptibility (decrease in number of lesions) and the growth of lesions is decreased. This indicates the virus multiplication being suppressed.

In comparison with controls, the respiratory activity in locally infected leaves was lower until the 8th day after inoculation, whereas it was higher with the leaves in which systemic infection was expected. In the course of the remaining period of investigation, the respiratory activity was almost identical in both cases, showing a rising tendency. Ascorbic acid oxidase whose activity curves correspond to those of respiration, represents the main terminal oxidase. Its activity is probably coupled to the respiratory chain in which glutathione, reduced by NADPH, is capable of reducing reversely dehydroascorbic acid originating from the action of ascorbic acid oxidase. Virus Y-infected plants containing excess NADPH, as found out in our previous paper, the respiratory chain mentioned is likely to be utilized preferentially.

Free nucleotides of the primary root of maize were extracted with 5% HClO₄ and separated on a column of Dowex 1×8 ion exchanger in HCOO^- cycle. A two-step elution gradient (HCOOH, HCOOHNH₄) was used for the elution of the nucleotides. The incorporation of³²P into the nucleotides was followed at different time intervals and also in young and more mature root tissues. The nucleotides AMP, GMP, ADP, GDP, and ATP were identified. Labelled phosphorus was found in ATP after 30 s, in ADP after 3 min, and in AMP after 5 min incubation of the roots. More mature roots (18 days) contained higher amounts of AMP than the young ones (3 days).

Experiments with the growth regulator ethephon (2-chloroethylphosphonic acid) were made to stimulate the flower differentiation in the 'Carola' and 'Golden Delicious' apple cultivars in Pillnitz (GDR) and 'Jonathan' and 'Golden Delicious' in Ujfehértó (Hungaria). A twofold application of 150 ppm ethephon in June proved most effective. Our results indicate that it is possible to promote flower differentiation in apple trees without growth retardation and fruit thinning.

Wheat embryos floated off from organic solvents have been compared with mechanically isolated embryos. The results of comparative investigations, including germination,in vivo formation of polysomes and efficiency of cell free preparations forin vitro protein synthesis, favour the use of floated embryos for studies of biochemical processes during germination.

The application of 10^-3 g 1^-1 of 2,4 dichlorophenoxyacetic acid, 2-methyl-4-chlorophenoxyacetic acid, 3-amino-1,2,4-triazole and 6-chloro-2-ethylamino-4-isopropyl-amino-1,3,5-triazine toNicotiana tabacum cv. 'Samsun' plants inoculated with tobacco mosaic virus results in an increase in the content of this virus in the tissues. When whole plants are used, TMV content increases by 20% after herbicide application; when leaf dises are used, the amount of the virus can be doubled by the herbicide in comparison with control untreated inoculated discs. The results clearly show that the used non-selective herbicides act as stimulators of virus biosynthesis, probably via enhanced pentose phosphate cycle activity which enables an enhanced formation of viral RNA.

If one cotyledon is removed from decapitated pea seedlings and the remaining one is treated with the cytokinin BA, then a complete correlation reversal occurs in numerous cases: instead of the bud belonging to the removed cotyledon, the bud belonging to the remaining cotyledon starts to grow. However, if GA is applied to the remaining cotyledon together with BA, then the number of these correlation reversals sharply drops. This in respect to cytokinin morphogenetically (correlatively) contradictory effect could play a significant role in apical dominance in plants.

The enzyme xylonase was used to isolate the protoplasts from the leaves ofCalendula officinalis L.,Gazania splendensMoore,Tithonia rotundifoliaBlake,Zinnia elegansJacq- and from the petals ofDahlia variabilis(Willd.) Desf. The recovery of spherical undamaged protoplasts differed. The same method did not lead to the isolation of the protoplasts from callus cultures derived fromCalendula, Gazania andTithonia leaves respectively.

The exposure of maize plants to drought led in most cases to a decrease in both the total and free water percentages, but to an increase in cell sap concentration, bound water percentage and bound water/free water ratio, comparing with the case of normal water supply. The employment of any of the studied treatments at either the normal or low soil moisture levels led throughout the period of time preceding the milky stage to a decrease in the free water percentage in maize leaves, but to the reverse effect with respect to both the bound water percentage and the bound water/free water ratio. The determinations of water fractions in leaves (free, bound water % and the ratio between them) before or at the tasseling stage appeared to be more reliable, compared with osmotic pressure determinations, as indication for the effective use of a given treatment in increasing the drought resistance of maize plants.

A technique is described for the establishment of infectious axenic callus cultures originated from stems of tobacco plants suffering from a mycoplasma disease, potato witches' broom. When stem pieces from a diseased tobacco plant (Nicotiana glaucaGrah.) are culture on a modified nutrient medium according toMurashige andSkoog (1962) with added kinetin (0.64 mg or 2.56 mg 1 000 ml^-1) and IAA (2 mg or 4 mg 1 000 ml^-1), the pathogen persists and spreads in the newly formed callus tissue. The presence of the pathogen was proved by implantation of callus slices into stems of tomato plants which indicate the disease very reliably. Reconstituted tobacco plants too recovered the infectious agent of potato witches' broom; 27 plants from the 35 reconstituted plants were diseased. Similar results were obtained with Crimean yellows. Calli were cultured and subcultured from 1 to 18 monthsin vitro and some infectious cultures are maintained and their investigation goes on. We suppose that kinetin plays a very important role for infectivity preservation in callus cultures.

The differences between leaves of different age according to their descending insertion level (starting from the youngest, 18th leaf) were compared with the changes occurring during the corresponding period of ontogenesis of the 18th unshaded leaf using the gas exchange [net photosynthetic CO₂ uptake (P _N ), water vapour efflux (E)] of the adaxial and abaxial surfaces of tobacco leaves as an example. Experimental elimination of the influence of shading during the involved period of ontogenesis of the 18th leaf manifested itself by a relatively slower decrease inP _N and by fluctuation of theE values at approximately the same level. Thus the differences between leaves of different insertion levels cannot be exclusively ascribed to the effect of their ontogenetic age.

Humate (10 mg l^-1) supplemented to streptomycin solutions (0.1 and 1 mM) stimulates growth of germinating wheat and barley grains and of apical cuttings ofCrassula portulacea after 24 h treatment. It does not, however, prevent formation of albinic leaves. Albinism induced by the streptomycin alone and by streptomycin in presence of humate is irreversible and can be removed neither by an iron salt nor by a chelate added to the nutrition solution or applied on the leaves. Cells of plants treated with streptomycin and humate are larger than those of plants treated with the streptomycin alone. The same is true for plastids which in both cases are colourless and much smaller than chloroplasts of control plants. These plastids in a living or a fixed state have reduced ability to uptake stains. The albinic leaves are anatomically similar to chlorotic leaves of virus infected plants.

Initially closed stomata in isolated leaf epidermal peelings ofCalotropis procera, Prosopis cineraria andTephrosia purpurea, opened when incubated in distilled water in light or in darkness. Water-induced open stomata closed down on incubation in abscisic acid (0.01 ppm) solution within half an hour. Sodium chloride induced the opening of stomatal aperture. NaCl-induced open stomata also completely closed down when incubated in abscisic acid solution, but open again when transferred to NaCl.

The effect of gametocides FW-450, maleic hydrazide and Dalapone on the course of microsporogenesis, gametogenesis and starch synthesis in pollen grains of winter rye ev. 'Esto' was investigated. Solutions containing various concentrations of tested substances were applied on leaves in amount of 2.5 ml and 5.0 ml per plant at the beginning, at the full and at the end of shooting. The effect of gametocides was detectable already in the phase of microspore formation when a decrease of anther weight, pollen grain size and starch content in grains and an increase of the number of microspores with nonfinished development were observed. The manner and the extent of injuries were dependent on the applied substance, its concentration and on period of its application.

Vicia faba plants cv. 'Erfordia' were treated with single application of CCC at 250 mg l^-1, 7 days before extraction. Such a concentration resulted in a 10.4, 14, 5 and 3.3 fold, respectively, increase in the levels of endogenous IAA, ABA, gibberellins and cytokinins relative to the controls. The results obtained indicate that a single application of CCC at a low concentration was sufficient to enhance the endogenous growth hormones in the treated plants. The results were obtained using GLC analyses for IAA, ABA and cytokinins, and the lettuce hypocotyl and soybean callus bioassay for gibberellins and cytokinins, respectively.

The cytokinin-autonomous strain (A_s) of tobacco callus differs from the original cytokinin-dependent strain (D) and from the cytokinin- and auxin-autonomous strain (A₄) by a significantly lower activity of glucose-6-phosphate dehydrogenase (G-6-PDH). Changes in the total G-6-PDH activity were associated with differences in the number of G-6-PDH isozymes. The A_s strain contained only one isozyme, four isozymes were found in D and A₄ strains.

In Jerusalem artichoke tuber,in situ RNA synthesis along vegetative cycle shows two maximums. The first one appears during tuberization and installation of dormancy and a growth inhibition is sufficient to bring it about. The second reveals breaking of dormancy and precedes germination.