The effect of methyl jasmonate (JA-Me) applied in concentration 1.0 % in lanolin paste to detached tomato fruits at the mature green, advanced mature green and light red stages on the ethylene production and l-aminocyclopropane-l-carboxylic acid (ACC) content was investigated at different times after treatment. JA-Me stimulated ethylene production in all stages of ripening, but the level of ACC increased or decreased in comparison with control depending on the stage of ripening. Higher level of ACC in JA-Me treated tissue was found in mature green stage and fully ripened tomatoes-treated at advanced green stage; lower one in light red stage - treated at advanced green stage and fully ripened stage - treated at light red stage.

Green islands were observed around infection spots ofAlternaria brassicicola on mustard leaves in nature. These green islands had higher cytokinin-like substances as compared to surrounding yellowed tissue and healthy tissue. Presence of starch in green islands has been correlated with formation of metabolic sinks in green islands, because of higher cvtokinin-like substances in them.

This article reports the effect of cold storage at 4 °C from December to April on chestnut cuttings. Rooting was found to increase after four months preceded by treatment with 4000 mg l^-1 IBA.
ThePhaseolus test of the biological activity of extracts of the cuttings showed the inhibition exerted by the acid fraction of the fresh (December) cuttings to have been replaced by a rootpromoting effect in cuttings stored for 4 months at low temperature. Cold storage thus seems to favour rooting.

The content of phenolic substances in the cell suspension culture ofCentaurium erythraea fluctuated during a 21-day-long subcultivation period in dependence on the growth phase. The total relative content of the phenolics reached its maximum at the time of transition to the exponential growth phase, similarly as the fraction of free phenolic acids, glycosides, and the fraction of phenolic acids released from the cells after alcaline hydrolysis. On the other hand, the content of phenolic acid esters decreased at this growth phase of the culture. Changes in the level of phenolic substances in the culture medium corresponded in their character to changes in the relative content of the phenolics in the cells.

Regenerants from tobacco(Nicotiana tabacum L. cv. White Burley) leaf segments cultivatedin vitro in vessels with solid agar medium under usual conditions (plantlets) grew under very low irradiance (I = 40 μxmol m-2 s-1), very high relative humidity (more than 90%) and decreased CO₂ concentration (c_a) during light period. In comparison with seedlings of a similar number of leaves and similar total leaf area grown in sand and nutrient solution, the plantlets had lower dry mass of shoots and roots per plant and thinner leaves almost without trichomes and epicuticular waxes. Due to a low transpiration rate under high relative humidity the water potential of plantlet leaves was higher than that of seedling leaves and the difference in water potential between leaves and medium was lowei. The rate of water loss from leaves detached from plantlets was considerably faster than that from seedlings under the same conditions (I = 110 μrnol m^-2; s^-1, temperature 30 °C, relative humidity 50 %). Net photosynthetie rates (P_n) of leaves of plantlets and seedlings measured under saturating I, natural ca and the leaf temperature 20 °C were similar, nevertheless the shape of curves relating Pn to c>> indicated some differences in photosynthetie parameters(e.g. saturation of Pn under lower ca> higher CO2 compensation concentration in plantlets than in seedlings). Similarly compensation and saturating I were lower in plantlets than in seedlings. The shape of transpiration curves as well as the expressive linear phases of P_N(ca) and P_N(I) curves of plantlet leaves indicated ineffective stomatal control of gas exchance. These results were confirmed by microscopic observations of stomatal movementsin situ

The level of endogenous gibberellin-like and cytokinin-like substances was estimated in the plumule and the root of 2-to 3-day-old intact pea seedlings, in the plumule of seedlings from which the radicle was cut off, and in the root of seedlings from which the plumule was removed.
An increase in the level of gibberellin-like substances and a decrease in the level of cytokininlike substances in the plumule as a consequence of radicle amputation were observed within 48 h. Plumule amputation resulted in a decreased level of both gibberellin-like and cytokinin-like substances in the root in the same period.

Ethylene induces the flower formation and stimulates the flower-bud development of some bulbous plants exposed to the gas when the apex is in the vegetative state. For iris bulbs cv. Ideal maximum responses have been found after exposure to 5 ppm for 8 h; lower concentrations, shorter exposure periods and, depending on seasonal conditions, low temperatures during gas treatment, gave intermediate responses. The effects are opposite to the ethylene induced flower-bud blasting which occurs when bulbous plants are exposed to the gas after completion of the flower formation.
Dry storage of the bulbs in atmospheres containing 5% CO₂ reduces the temperature-enhanced flower formation, suggesting a possible effect of endogenous ethylene.

Exogenous³H-thymidine is absorbed by the primary root of young plants ofDatura stramonium L. and gradually translocated into shoots: following a 3 to 72-h application of³H-thymidine the radioactivity was revealed, using the autoradiographic technique, especially in the region of primary and secondary meristems and in proximity to vascular bundles of the primary root, stem, hypocotyl and leaves. These regions may be considered as the sites of active DNA synthesis. The intensity of incorporation was dependent on the time of plant incubation in labelled thymidine.

Flours prepared from seeds of two non-agglutinating and one agglutinating cultivar ofPhaseolus vulgaris ssp.vulgaris (tested against human A, B, O, and rabbit erythrocytes) were stored in a refrigerator for eight months. Extracts from aliquot portions of these flours were prepared in one-month intervals, their agglutinating activity was tested against rabbit erythrocytes, and their immunoelectrophoretic patterns and protein contents were determined. Agglutinating activity occurred during storage in ageing flours of originally non-agglutinating cultivars and a typical lectin zone which was absent in extracts of freshly prepared flours appeared in their immunoelectrophoretic patterns. This newly formed agglutinating activity in some cases again disappeared during further storage.

The influence of IAA in two concentrations (10^-8M and 10^-5M) on relations between growth, water absorption and cation uptake and accumulation was tested.IAA in a higher concentration retarded growth remarkably. First of all, potassium uptake and water absorption were significantly decreased while the uptake of divalent cations was affected later and less remarkably. 10^-8 M IAA accelerated the growth rate slightly together with acceleration of water absorption and cation uptake.

Under strictly non-inductive photoperiods (24-h photoperiods) floral buds were initiated on plants receiving 25 treatments with Reso (resorcinol) or 8 treatments with GA₃ (gibberellic acid) or GA₃ + Reso, while water treated control plants did not flower at all. Although a single treatment of plants with GA₃ or GA₃ + Reso is not adequate to cause induction under LD conditions, its effect is added to the sub-threshold induction caused by one SD (short day: 8-h photoperiod) cycle. The initiation of floral buds was hastened with an increasing number of SD cycles accompanying respective number of treatments, the effect of GA₃ alone or together with Reso being more pronounced than that of Reso alone. GA₃ increased the number of floral buds more than Reso, the number being the highest in plants receiving the respective number of treatments with the combination GA₃ + Reso under both inductive as well as non-inductive photoperiods.

The effects of salicylate on stomatal resistance (a measure of stomatal opening) were compared with those produced by 2,4-dinitrophenol and abscisic acid. Salicylate and dinitrophenol had the same minimum effective concentration and comparable kinetics, and induced stomatal closure persisting for a long time in the absence of further supply. However, a K and Ca solution prevented the salicylate-induced, but not dinitrophenol-induced, stomatal closure. The effects of salicylate and abscisic acid had very different characteristics. Cytokinins had no relevant effects on the stomatal closure induced by the three compounds. A close correlation was found between stomatal closure and K⁺ leakage from the treated leaves, suggesting that damage to the cell membrane may be involved.

A rapid method is presented for the determination of ribonuclease activity in coloured extracts from citrus leaves. At the same time, the influence exercised by several precipitating reagents and the storage time at 4 °c on the activity of the enzymatic system are studied. In addition the enzyme stability against heat is studied.

As the dynamics of changes in phytohormones may be involved in photoperiodic regulation of the rates of growth and flowering, fluctuation of cytokinins was followed in long-day and short-day tobacco. Zeatin (Z) and zeatin riboside (ZR) were identified in leaves and roots using a GC-MSC system. In plants of the long-day tobaccoNicotiana silvestris increasing the number of long-day inductive for flowering (10, 20, 30, 40 LD) resulted in a rise in ZR activity. Half the plants reached a reproductive stage on the 40th day of induction. In short-day Mam moth tobacco plants, short-day floral induction (10, 20, 30, 40 SD) caused similar but less marked changes in ZR.

The clone SJ ofSpirodela polyrhiza (L.) Schleiden forms turions under various nutritive conditions. As compared to 1500 μmol 1^-1 phosphate (P+), growth and frond yield of mixotropic cultures decreased, when 60 μol 1^-1 phosphate (P-) were available. By contrast, P-conditions increased the number, individual size, dry matter content, and total turion yield (mg turions per ml of the nutrient medium) of P-turions as compared to P+ ones. Germination behaviour of P-turions is characterized by fairly low zero levels in the controls, and by low heterogeneity in individual size as well as in the response patterns concerning the influence of light and/or phytoactive substances. P-turions from youngSpirodela cultures are extremely dormant. However, they undergo an after-ripening process if kept inside ageing cultures.

The objective of this study was to determine if the two surfaces of a leaf had different, or the same, water potentials. Maize (Zea mays L. cv. Cargill 805) was the test plant. During an 11 day period, the water potentials of the upper and lower surfaces of the maize leaves were measured daily with anin situ thermocouple psychrometer under growth-room conditions. Plants were grown in pots with a well-watered, commercial greenhouse soil. Stomatal resistance also was measured. The water potential of the upper surface was less negative (more wet) than that of the lower surface. The overall average of the water potential of the upper and lower surfaces was -1.48 and -2.07 MPa, respectively. The stomatal resistance of the upper surface was greater than that of the lower surface. The average stomatal resistance during the experiment was 780 and 600 s m^-1 for the upper and lower surfaces, respectively. Since the upper and lower surfaces were not at the same water potential, the results indicated that the parallel-resistance equation, used to combine resistances on the two surfaces of a leaf, was not strictly valid when applied to the maize leaves, as the law assumes equal potentials on the two surfaces.

A low frequency androgenesis was inducedin vitro in all experimental variants ofCapsicum anthers cultured in standard and minimalized media. The embryogenic frequency was stimulated by the presence of activated charcoal which also prolonged the vitality of the culture. The percentage of embryoids growing to complete plants increased, if the embryoids were removed from the anthers and cultured separately. The morphogenic initiation of globular embryoids was conditioned by the presence of FeEDTA in the culture medium. The stimulation of androgenesis initiation can be explained by the same change in the decisive factor caused by various effects. In long-term embryoid cultures, which stagnated in growing and seemingly necrotized, a second somatic embryogenesis occurred. About 10% of obtained androgenic plants were fertile and even gave progenies. The process can be recommended for breeding.

Some general data on the genetic control and the possibilities of regulation of developmental paths inDrosophila are furnished. The insights to be gained from this insect will surely have implications that extend far beyond the fruit-fly. For example, in plants, developmental programs for floral organs, implying specific proteins are known. Developmental mutants in which mutate alleles control developmental programs for flowering were also selected in several species (Zea, Pisum, Sorghum, Cucumis, Mercurialis). Chemicals, especially phytohormones interfering with these programs are discussed. The case of sexual differentiation ofMercurialis is discussed in more detail. In this species, sex organs are controlled by sex determination genes and by auxins (male) and cytokinins (female). Flowers of each sex can be characterized by specific mRNA populations. They were evidenced by translationin vitro in a cell-free system of the various kinds of mRNAs [poly(A), non poly(A), polysomes]. The feminisation of genetic males by cytokinins induces the mRNA population of female type. Evidence concerning the implications of cytokinins in protein synthesis before translation level is presented. This is also probably true for auxins, although direct evidence is lacking.

The phenotype appearance ofArabidopsis thaliana hairy roots and crown galls their teratomas and regenerated plants were compared. Several differences were found, which correlate with T-DNA differences between Ti and Ri plasmids.

CAM-like photosynthesis was found in the isoetid aquatic plantsLittorella uniflora andIsoetes lacustris, but not in the isoetid speciesLobelia dortmanna or in the elodeidElodea canadensis. Of the taxa studied, the first three are known to utilize sediment-borne CO₂, whereasElodea is dependent on bicarbonate.

The analysis of the kinetic behaviour of pea L-tryptophan aminotransferase isolated from mitochondrial and cytosolic fraction unambiguously showed the preference of some of its keto acid substrates demonstrated by statistical criteria (R2, SSQ, AIC). An attempt is made to evaluate this result in connection with the availability of the keto acid substrates in different cell compartments.

Acid phosphatase isolated from low altitude grown plants of two high altitude plant species,Selinum vaginatum Clarke andAcer caesium Wall, displayed higher thermostability than that from plants of the same species grown at high altitude. The isozyme composition, however, remained unchanged inSelinum vaginatum. InA. caesium, one of four isozymes, was thermolabile in the samples from high altitude and was lost after 10 min heating of the extracts at 60 °c. In the samples from low altitude, this isozyme was not detected and a band with slightly lower Rf value was present which was thermostable. The described changes in the thermal properties of acid phosphatase reflect an adaptive step towards high temperature acclimation at low altitude.