The level of gibberellin-like substances was determined in the cotyledons and axis of developing seedlings of dwarf (Little Marvel) and normal (Tall Telephone) cultivars of pea (Pisum sativum L.). The effect of cotyledon removal with GA₃ application on growth was also examined. Greater levels of gibberellin-like substances were observed in the cotyledons of the normal cultivar than the dwarf. This was particularly evident in the cotyledons during the early stages of seedling growth. Subsequently there was a decline in GA levels in the cotyledons. This was coincidental with a rise in GA content in the axis with markedly greater levels in the normal than the dwarf cultivar.
Decotyledonated dwarf and normal plants supplied with GA were much taller than the decotyledonated controls. This observation along with those of the gibberellin levels in the cotyledons and axis, provided circumstantial evidence that there may be translocation of gibberellins from the cotyledons to the axis.

Gladiolus "grassy top" disease was recorded in Czechoslovakia. Electron micrographs of ultrathin sections prepared from dwarfed leaves sprouting in spring from corms of affected gladiolus plant showed a very high accumulation of mycoplasma-like organisms (MLO) in sieve tubes. These corms were stored during the winter period in a cold glasshouse and their overground plant parts were removed only before planting in spring.
In autumn, when the corms were dug up in the field, those of affected plants were mostly infected withFusarium sp. while those of apparently healthy ones were intact. This observation may indicate a conspicuously increased susceptibility of affected corms to the fungus.

Virus particles of isometric shape with a diameter of 26 nm were found in the sieve tubes and accompanying phloem cells in ultrathin sections prepared from the nerves of white mustard (Sinapis alba L.) leaves and roots infected with the beet mild yellowing virus (BMYV). BMYV particles were much more frequent in the roots ofSinapis alba plants. Isometric particles were not found in the leaves and roots of healthy mustard plants.

Alfalfa (Medicago sativa; L.) plants susceptible (S) and resistant (R) to the bacterial wilt were fedvia roots with a nutrient solution labelled with⁸⁶Rb⁺, at different times after inoculating them withCorynebacterium insidiosum (McCull.) H. L. Jens. The infection did not influence⁸⁶Rb⁺ uptake per plant in the course of a 14-day-period following inoculation, however it did affect its distribution differentially in the S- and the R-plants.⁸⁶Rb⁺ uptake was significantly decreased due to the infection in the S-plants on the day 49 after the inoculation (a 4-h-exposure to⁸⁶Rb⁺), with the iona also being more slowly translocated to the shoots in diseased S-plants than in diseased R-plants. Likely factors causing these effects and their relationship to alfalfa resistance to the bacterial wilt are discussed.

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.

With the aim to reduce the period of flowering and of fruit maturation, we investigated the effect of auxins on flower formation. For these experiments we used young decapitated plants with two plagiotropic branches. Both the auxins, indol-3-ylacetic acid (IAA) and 2,4-dichlorophenoxyacetic acid (2,4-D), retarded flower formation in coffee, the latter one being more effective. The effects of 2,4-D if applied on only one of the two plagiotropic branches can be observed only in this treated one. Furthermore, the auxins seem to act in coffee plant directly by affecting flower formation and not indirectly by inducing endogenous ethylene production.

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.

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.

An analysis of axillary meristem (axillary bud) localization of radish (Raphanus sativus L. cv. Tetra-Iłówiecka) was undertaken on vernalized (flowering) and unvernalized (vegetative) plants. It has been shown that the localization of these meristems can be different on successive nodes of the same plant and is connected with the development stages of the plants. The axillary meristems can arise on the stem as well as in the leaf axil or on the base of the subtending leaf. The localization of axillary meristems has been discussed in relation to growth directions and growth correlations inside the meristematic region of the shoot apex.

N-malonyl-D-tryptophan (MT) and D-tryptophan added to the medium instead of auxin stimulated growth of soybean and tomato cell and tissue cultures. Effects of 50-100 μmol 1^-1 MT and 100 -300 μmol 1^-1 D-tryptophan were equal to the effect of 3-10 μmol 1^-1 IAA. Soybean cells grown in the presence of 100 μmol 1^-1 MT contained 125-170 ng IAA per 1 g fresh mass (as determined by spectrofluorimetric indole-α-pyrone method), whereas the cells grown in the presence of NAA 10. 7 μmol 1^-1 contained 50 -60 ng IAA and the cells grown in the absence of auxin failed to show endogenous IAA. MT as proposed can be hydrolyzed by plant cells with liberation of D-tryptophan, which in turn can be used in IAA synthesis. It is proposed that MT is a possible source of endogenous auxin in plants.

The effect of phosphorus deficiency on the activity of acid phosphatase of the first, second and third leaves of maize plants was followed. The supernatant obtained by centrifuging the homogenate of plant tissue at 1500 ×g was further centrifuged at 18 000 ×g, the sediment marked as fraction II and the supernatant as fraction III. Acid phosphatase activity of fraction II of the first to third leaves was for the whole period of culture higher in plants grown in the nutrient solution without phosphate. In fraction III this relation was established in the first leaf, after 3 days of culture in the second leaf and after 5 days in the third leaf. In all leaves higher enzyme activity was unambiguously determined in fraction III when compared with fraction II. Higher acid phosphatase activity was established in those leaves which were younger in their development, particularly in the first days of culture. With the ageing of leaves the enzyme activity decreased.

An improved system of plant cultivation at stable and specific levels of polyethyleneglycol (PEG, mol. mass 1400-1600) - induced water stress has been described. To set up this system a perforated tubular glass vessel containing soil to support seedling growth was wrapped externally first with a layer of macroporous silica gel-G and then with three layers of a dialysis membrane of a lower exclusion limit (2000 mol. mass). Effects of 8 days of PEG - induced stress have been studied on uptake and translocation of N and P and growth of barley (Hordeum vulgare L. cv. KN 16) seedlings. Some of the noteworthy improvements of the system were exelusion of PEG from the plant consequent upon use of silica gel-membrane combination, shorter time (2 days) for the soil-plant-air continuum to attain steady state, and stability of the plant water potential over a period of a few days.

The rates of maintenance and growth components of leaf dark respiration of a C₃ plant (Phaseolus vulgaris L.) and C₄ plant (Zea mays L.) as affected by temperature were studied using the McCree concept. Respiration rates were measured by means of infrared gas analysis in a closed gas exchange system. In both C₃ and C₄ species R_D and R_m increased with temperature in the temperature range (15-62 °C) studied. R_G depended on temperature with an optimum near the temperature optimum of gross photosynthetic rate, P_g. Significant correlation between R_D and R_M and between R_G and P_G was found.

Leaf expiants from vegetative plants of the short-day plantStreptocarpus nobilis (C. B. Clarke) developed flower budsin vitro when cultured in 8 h photoperiods. Tn non-inductive photoperiods only vegetative buds were formed.In vitro photoinduction was demonstrated by giving the expiants short-day (SD) cycles and then transferring them to non-inductive photoperiods for expression of flowering. On medium containing 6-benzylaminopurine (BAP) organogenesis was initiated during the photoinductive treatments. Photoinduction of leaf tissue without adventitious bud development was obtained on medium without BAP. The photoinductive state of the leaf tissue was fairly stable, being expressed after 2-3 weeks in non-inductive photoperiods when adventitious buds were formed. The quantitativein vitro flowering response to the endogenous floral stimuli, resulting from photoinduction, could provide the basis of a bioassay for presumptive flower inducing chemicals.

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.

Bacteria of the speciesPseudomonas putida andPseudomonas fluorescens isolated from the rhizosphere of maize and bean plants produce indol-3-ylacetic acid and some other auxins when grown in suspension cultures. IAM and ILA were also found besides IAA and its degradation product IAH by means of HPLC and MS methods. This finding indicates the involvement of two different metabolic pathways in IAA synthesis in bacteria. The amounts found varied between 1.6 and 3.3 μg IAA per ml of media which corresponded to 100-200 μg per gram of bacterial dry mass. The effect of IAA production by rhizosphere bacteria on IAA level in the plant is discussed.

Using water culture technique, some experiments have been performed to investigate the effect of 60 days salinization treatments (0.0-100 meq 1^-1 NaCl) on dry weight and on the content of some nutrient elements (Na, K, Ca, Mg, P, N) in castor bean, sunflower and flax plants. In general the content of sodium increased progressively with the rise of salinity level. The relatively low and moderate salinization levels (20 and 40 meq I^-1 NaCl) resulted in a promotion rather than inhibition of the dry weight and in the content of most of the investigated elements in the different organs of the test plants. However with the rise of salinization level from 60 to 100 meq l^-1, the dry weight and the content of these nutrient elements were mostly reduced.

Flower initiation takes place during a rise of peroxidase activity following a peak of minimum activity which marked the completion of the flowering inductive phase. Since basic isoperoxidases underwent an inverse variation of activity in the course of successive inductive and initiative phases, it was hypothesized that the induction of flowering led to a temporary peak of maximum auxin level in the leaves. Our analyses and available literature data support the view. They also show the different capacity of non-induced and induced material to respond to external auxin application. Since some aspects of the physiological state characterizing induced plants can be simultaneously obtained in all plant parts as a result of rapid interorgan communication, the classical florigen theory is seriously challenged.

Chlorides, nitrates, and sulfates of alkali metals, ammonium, calcium, and magnesium inhibit P_i uptake into maize root cortex segments. The concentration 100 mM brought about 50-100% inhibition, whereas 10 mM concentration (with the exception of salts of NH₄+, Ca²⁺, Mg²⁺) about 15-55%. Also potassium benzenesulfonate (100 mM) dramatically decreases P_i uptake.
Osmotic shock also inhibits P_i uptake. Marked decrease of P_i uptake ability proceeds in concentration range 0.12-0.13 M NaCl. Concomitantly, proteins are released into rehydration medium and their amount is proportional to the degree of P_i uptake inhibition.
The effect of 0.13 M NaCl on P_i uptake and protein release is about the same in roots of intact plants, excised roots, root segments and segments of isolated cortex and stele. Roots of intact plants and excised roots are more responsive to osmotic shock than studied segments.
The degree of salt tolerance of glycophytes is in correlation with NaCl concentration, which brings about 50% inhibition of P_i uptake.

³H-labelled zeatin riboside (ZR) was applied to pod walls of intactLupinus luteus L. plants. Metabolites present in mature, dry seeds were zeatin nucleotide (ZNT), zeatin riboside (ZR) and zeatin (Z), zeatin O-glucosides and lupinic acid (LA), and the corresponding dihydro-derivatives of the cytokinins listed. Endogenous cytokinins were rapidly metabolised in germinating seeds. In seeds labelled with [³H]ZR for 90 min following a 2 h period of imbibition in water, ZR was actively converted to ZNT and dihydro-ZNT but the prevailing CTK was Z in cotyledons and ZR in embryo axes (EA); later LA and dihydro-LA, and O-glucoside metabolites accumulated. When [³H] zeatin was introduced into imbibing seeds, it was converted to dihydro-ZNT, ZNT, dihydro-ZR, ZR and dihydro-Z; in EA of the Z-labelled seeds, dihydro-ZR and ZR were the main cytokinins. After incubation of the Z-labelled seeds for 6 h in water, the ratios of dihydro-ZNT: ZNT and dihydro-ZR: ZR were, respectively, 20: 1 and 3.4: 1 in EA, and 3.5: 1 and 1.4: 1 in cotyledons.

During high altitude acclimatization both the number of stomata and their pore width decreased. The number of open stomata per unit leaf area in the morning and evening hours was higher as compared to that in plants grown at a lower altitude. Thickness of leaves also decreased at high altitudes but the effect on the size of epidermal, mesophyll and spongy parenchymatous cells varied from species to species. Adaptational significance of these changes are discussed.

The decrease of peroxidase (PO) and IAA-oxidase (IAAO) activities in stem bark of intact photoperiodically neutral tobacco plants was shown both in the course of development and in an acropetal direction along the stem as related to flowering regulation. In stem expiantsin vitro, the realisation stage of floral morphogenesis is related to an increase in PO and IAAO. This correlates with low auxin concentrations in the medium as required for floral morphogenesis. The changes in both PO and IAAO are suggested to be in the opposite directions during floral induction and floral morphogenesis.

Experiments were conducted (a) to identify optimum media pH for nitrate uptake by intact corn (Zed ways L. cv. XL-81) plants grown under solution culture conditions, (b) to understand the effect of media pH on growth, nitrate uptake, water use and nitrogen accumulation. pH was maintained using carboxy cation exchange resin IRC-50. Plantswere grown in 15mM NO₃-N per litre and nitrate depleted from nutrient solution over a period of time was measured. Dry matter accumulation by the plants decreased progressively with increased pH. However, the decrease was significant only at pH 7.0 and 8.0. Data on water use showed results similar to dry matter accumulation. Correlation coefficients (r values) among nitrate uptake, dry matter production, water use, nitrate -N accumulation and reduced -N accumulation was observed to be high (above 0.99). All effects of media pH are significant only at pH range 7.0 to 8.0. Despite adequate supply of iron, the plants at pH 7.0 and 8.0 showed symptoms of iron deficiency. Thus, iron and possibly micro-nutrient deficiency could have resulted in poor plant growth. These experimental results indicate optimum pH range for nitrate uptake is 4.0-6.0. Plant growth and dry matter accumulation were directly affected by media pH. The differences in nitrate uptake, water use and total nitrogen accumulation appeared to have resulted as a consequence of differential dry matter production. Whether these differences are due to altered metabolic uptake characteristics of the loots is not known.

The mechanisms by which exogenously applied plant growth regulators act to express those genes that are selectively involved in cell and tissue differentiation are not at all well comprehended. However, the ontogenetic sequences of events that enable receptor or target cells to be activated and to undergo dedifferentiation and redifferentiation, can often be followed experimentally and can lead to a better understanding of the causal relations and control mechanisms in coordinated cell growth and development.
Cytokinins, applied either in an agar medium or as high-concentration, short-duration pulses to expiants or as high-concentration, intermittent sprays to intact plants, induce switches in the normal developmental pattern of cells of certain explanted tissues. Examples of cells that are particularly receptive are the subsidiary cells of stomatal complexes and the differentiating cells of very young presumptive leaf primordia, that is before the latter have become irreversibly determined as leaves.

Anatomical-histological investigations of slide series revealed that the secondary vascular formations appearing scattered in callus tissue culture derived from a stem piece containing mycoplasma-like organisms (MLO) (potato witches' broom agent) have no connection with the vascular tissues of the original stem piece. 77% of reconstituted tobacco plants (Nicotiana glauca Grah.) from these callus cultures were infected with MLO. When diseasedNicotiana glauca scions are grafted on healthy tomato plants as stocks, MLO transmigration into the stocks is realized in all cases ten days after grafting; at that time, the scions and stocks are united only by a zone of a few layers of parenchymatous cells without any indication of vascular tissue union between the two components. In both cases, the MLO transmigration could not be realized by passage through sieve pores in sieve tubes. Our results bring indirect evidence of MLO transmigration through parenchymatous cells and thus support the hypothesis of MLO passage through the plasmodesmata.

The influence of different organs on flowering of photoperiod- or temperature-dependent plants and of neutral plants is described. Special attention is given to the influence of roots which generally inhibit flowering. High or low temperatures applied to the roots ofChenopodium polyspermum, a quantitative short day plant, induce flowering. Vernalizing treatment of roots ofCichorium intybus suppresses the inhibition of flowering arising from the tissues immediately underlying the terminal bud. Other plants such as coniferous trees can flower more intensively if the growth of their roots is reduced. After a short presentation of the very complex situation concerning the regulation of floweringvia the presently known hormones, the methodological limitations of our understanding of the precise hormone mechanism of flowering will be discussed. One example of an immunologica 1 approach to localize endogenous hormones inside tissues is given, using abscisic acid.

Black currant reversion disease causes serious problems in some cultivars of black and red currant. Investigating ultrathin sections prepared from overground parts of diseased red currant plants cv. Heinemann's rote spätlesse, we observed consistently local cell wall disintegration of tracheids in vascular bundles. We have observed these changes in red currant plants showing reversion symptoms during the vegetation period from March to June. The observed phenomenoni.e. cell wall disintegration of tracheids might be utilized as an auxiliary diagnostic criterion m ident ification of red currant reversion disease in the cultivar Heinemann.

Exogenoualy applicated indol-3-ylaeetic acid (IAA) is metabolized mainly to IAA aspartate in intact plants and plant segments and to IAA glucose in suspension cultures fromBeta vulgaris andChenopodium album.
Main metabolic product of D-tryptophan is N-malonyltryptophan in both suspension cultures and hypocotyl segments of both species. The turnover rate of L-tryptophan to IAA is comparatively low (0.1 %); inBeta the turnover rate is higher than inChenopodium. In sugar beets phenmedipham leads to a decrease in the IAA. biosynthesis rate in suspension cultures of both plant species. There is, however, an increase in the IAA content in all intact plants. The metabolic activity is substantially higher in suspension cultures than in intact plants and plant segments.

Genetically identical mirror-imaged left and rightLemna minor plants were treated using the stereomers of arginine, asparagine and atebrine (mepacrine). In contrast with the stereomers of arginine and asparagine, those of atebrine were found to be isoeffective throughout the dosage range from the ineffective dose to the lethal one. All indices used (rate of reproduction, length of a frond and sensitivity to the treatments) pointed to the absence of any difference between left and right plants. The left or right handedness inLemna cannot be explained bv assuming the existence of any stereochemical difference between left and right plants.