Chromosomal variability in callus culture ofAsparagus racemosus was comparatively higher in the presence of 2,4-D than of NAA. The frequency of polyploid cells was enhanced with the increase in the concentration of 2,4-D or with the addition of coconut water. Gradual polyploidization with increasing age of the callus has been recorded.

Embryogenic callus which has maintained its embryogenic ability on media without growth regulators for three years has been induced at the base of shoots of a genotype with CMS propagated for a long timein vitro by transferring the shoots onto media richer in inorganic and organic components. The effect of two basal media (MS and PG₀) on the intensity and completeness of the proliferation of somatic embryos was examined with different combinations of growth regulators. Pollen fertility was evaluated in 87 plants regenerated from somatic embryos. Cytoplasmic male sterility was conserved in all of them.

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.

On the basis of earlier data it was suggested that the induction of cytokinin autonomy might be accompanied by disorders in plastid function and a decrease in cytokinin utilization. In the work presented below the formation of chlorophyll and the isozyme patterns of nine enzymes, some of which are known to be localized in plastids, were compared in tobacco callus tissues differing in their hormonal requirements. Tissues either not requiring cytokinin or both auxin and cytokinin for their growth, contained a lower amount of chlorophyll than the cytokinin-and auxin-dependent strain. The number of isozymes of glucose-6-phosphate and NADP-malate dehydrogenase (i.e. enzymes which are known to be located in plastids) was reduced from four in the cytokinin-and auxin-dependent strain to two and one in the two cytokinin-autonomous strains, respectively. The fully habituated tissue contained an additional isozyme of NADP-malate dehydrogenase. The total number of isozymes of the remaining enzymes (NAD-malate dehydrogenase, peroxidase, esterase and a-and β-galactosidase) either was decreased or not changed in the cytokinin autonomous strains. The exception was an additional anodic peroxidase in one strain. The number of these isozymes in tissue habituated with respect to both auxin and cytokinin either remained the same or increased. Tobacco callus strains with altered requirements for growth regulators contained some new isozymes which were not present in any other strain and some isozymes present in other strains were absent. These differences are discussed in relation to the possible role of plastid function disorder associated with habituation.

Flow cytometry was used to analyse the DNA content of nuclei isolated from intact plant tissues and from callus and cell suspension cultures invitro. Cell nuclei were isolated either mechanically (chopping, syringing) or by a hypotonic lysis of isolated protoplasts. Although both methods gave similar results, a slight shift to lower ploidy levels was observed after protoplast isolation from intact tissues and calli. No differences were observed if the two methods were compared using cell suspension cultures. The results showed that flow cytometry is a rapid method of nuclear DNA content analysis in intact plant tissues and variousin vitro cultures.

Axillary meristems of short day plantChenopodium rubrum are localized as caulinar, foliar or axillar. The localization of axillary meristems and axillary buds of 14 day old plants varied in similar pattern as in other plant species so far investigated: after several nodes with foliar axillary meristems the caulinar ones were produced. However, unlike in other species, in C.rubrum a very high percentage of caulinar meristem is produced also on the first node. In this case, like in the case of its later differentiation at higher nodes, the formation of caulinar meristem is confined also to the vegetative state. It was found that the caulinary position coincides with higher responsiveness to photoperiodic induction. The developmental significance of such behaviour is discussed.

Five days of suitable continuous light induced flowering in the majority ofChenopodium murale L. ecotype 197 plants as early as at the phase of the first pair of leaves. At the time of initiation of the 2nd to 4th pairs of leaves the capacity of plants to flower was reduced, the number of flowering plants being significantly lower under the same inductive light treatment. The capacity to flower increased again at the phase of the 5th and the 6th pairs of leaves. Inductive light treatment brought about a marked growth activation of organs present before induction, shoot apex elongation, precocious formation of new leaves and activation of axillary meristems. The course of these changes in plants of different age is demonstrated. The terminal flower developed during 5 short days following inductive light treatment. The paper shows similarities and differences between long-daymutale L. ecotype 197 and short-day C.rubrum L. ecotype 374 grown under practically uniform conditions.

Six thousand anthers ofSecale cereale cv. Dańkowskie Zlote and inbred lines L214 L215 and L258c/5, in the uninuclear microspore were cultured over a period of three months on Murashige and Skoog nutrient medium supplemented with IAA (1-2μg1^-1), kinetin (0.2 to (1.0μg1^-1) and 2,4-D (0.5-2.0μg1^-1). First divisions of microspore were observed after 7 days. In the course of 10 weeks, 4 albino tic embryos at the cotyledon stage were observed that died away in the course of further culture. The course of androgenesis was regular in inbred lines and irregular in rye cv. Dańkowskie Ziote. The efficiency of androgenesis and the amount of observed globular structures in anthers were also dependent on the genetic potency of the material. Inbred lines did not show any greater viability of embryos.

Buckwheat cotyledons were induced to form callus tissuein vitro, in which shoots or roots could be regenerated, by changing the hormonal composition of the medium. The effect of gibberellic acid (GA₃) was studied in these processes. Addition of GA₃ to cell division medium during the first 5 days after inoculation did not interfere either with the induction of cell division, or with the subsequent organogenesis. However, GA₃ had a very pronounced effect on organogenesis when added immediately upon the transfer of expiants to organ induction medium. While root initiation was accelerated and root number increased, bud induction was inhibited. An initial GA₃ treatment had a long-lasting effect on bud induction and the tissue recovered from inhibition only in the fifth subculture.

Alterations in protein pattern were observed in the callus tissues ofVigna unguiculata (L) Walp. up to tenth passage from its initiation. A gradual increase in quantity of protein was found up to sixth passage of culture. Decrease in the quantity of protein after eight months of culture might be correlated with the cytodifferentiation of the tissues. It has been recorded that with the initiation of morphogenesis there is an increase in the number and intensity of protein bands at the anionic end of the polyacrylamide gel.

High rates of oak shoot multiplication were achieved on low salt nutrient media (BTM, WPM) supplemented with adenine type cytokinin or BAP. Low concentration of (0.2-0.6 mg 1^-1) stimulated formation of a large number of axillary shoots and their elongation. Thidiazuron in very low concentration (0.001 - 0.002 mg 1^-1) promoted shoot proliferation, in high concentration stimulated formation of large callus. More than twelve thousand micropropagated shoots were rooted in low salt agar media supplemented with low concentration of auxin (IBA or NAA 0.2 - 0.5 mg 1^-1). High rooting percentages (81 %) were obtained. Survival of the mieropropagated plantlets transplanted into soil was high (78 %). Micropropagated trees planted in the field withstood severe winter frosts without significant losses. At the end of the fifth growing season trees attained considerable size.

All the concentrations (25-150 mgl-¹) of the phytohormones kinetin, IAA (indol-3-ylacetic acid) and GA₃ (gibberellic acid) increased the activity of DCPIP (2,6 dichlorophenolindophenol)-Hill reaction, chlorophyll and protein contents over the control data in leaves ofSechium edule Sw. on Darjeeling hill of the Eastern Himalayas; while ethrel (2-chloroethylphosphonic acid) treatments decreased these parameters in the hilly species. The most effective concentrations in increasing these parameters were 50 mg 1-¹ of kinetin, 50 mg 1-¹ of IAA and 100 mg 1-¹ of GA₃; whereas 50 mg 1-¹ of ethrel was most effective in decreasing these parameters during the induction of senescence in the hilly vegetable crop. The increase in these parameters was greatest with kinetin, followed by IAA and least with GA₃ in the hilly plant species studied.

Pollen embryogenesis occurred in anther cultures of two genotypes ofBrassica carinata A. Braun. Pretreatment of anthers at 35°C for 3 or 6 days was essential for the induction of androgenesis on growth regulator-free culture medium. A combination of sucrose and glucose was better than sucrose alone. None of the pollen embryos germinated normally. Full plants were raised through adventitious bud differentiation from their hypocotyl.

Ethylene formation by loaves of the central stem zone of the short-day tobacco cv. Maryland Mammoth and long-davNicntiana sylvestris was followed for 40 days during in duction and transition to flowering. In SD tobacco Mammoth, ethylene formation rose between days 0-10, remained unchanged for the next 10 davs, rose slightly between days 20 - 30 and sharply within the last 10 days. The time-course of ethylene formation by the leaves of LD tobacco N.silvestris resembled that of Mammoth, but tho changes were less pronounced, especially at the beginning of the period. Generally, ethylene formation is much higher in SD tobacco Mammoth than in LDN. silvestris.
Ethephon (0.02 %) application during flower induction significantly reduced flowering in SD tobacco Mammoth (by 47.5 %) and also reduced apical meristem length. In N.silvestris ethephon application did not reduce flowering, but most of the treated plants (62.5 %) did not attain the stage of inflorescence. Apical meristem (or inflorescence) and stem length were also reduced. The possible role of ethylene in regulation of transition to flowering is discussed.

On rooting the poplar stem cutting, the growth processes are coordinated so as to ensure optimum development of the new, vegetatively acquired individual. At first, adventitious roots develop on the cutting from latent root primordia. A part of them is short-lived, but in the meantime other, the so-called wound adventitious roots initiate from the callus on the lower cut surface of the cutting, which complement the permanent root system. In this way, conditions are prepared for a rapid growth and development of the stem, which forms from the upper bud on the cutting. The action of apical meristems providing the elongation of the stem and root, is followed by the action of vascular cambium. By the radial growth of organs controlled by cambium, the capacity of substance transport increases relatively to progressing development of the new plant. In the buried stem cutting cambium is the first to start functioning. Its reactivation is slow, discontinuous, and at the beginning it depends on local stimulating sources of the cutting itself. It was observed for the first time that, in addition to expanding buds, activated root primordia are also such sources of stimuli. The overall induction of cambial activity in the cutting occurs only in the period of rapid growth and development of the new stem, which thus becomes the main source of factors controlling the cambial activity of the cutting. In comparison with the growth of stem and cutting, the radial growth of adventitious roots is limited and there are considerable differences in the thickness of radial increments between individual roots.

The protoplasts of the moss Anoectangium thomsonii, isolated from protonemal cells underwent divisions in 48-72 hours on modified MS medium enriched with growth regulators, 2,4-D and kinetin, 10 % sucrose and coconut water (5 %). Subculture of protoplast derived cells in a medium of relatively low osmotic potential (5 % sucrose) produced dark green calli which could be maintained completely undifferentiated.

With the aim to increase citrus fllowering under tropical conditions, two formulations of 2-chloroethyl phosphonic acid (Ethrel and Flordimex), Alar (succinic acid-2, 2-dimethyl hydrazide) and Cycocel (2-chloroethyl-trimethyl ammonium chloride) were applied during the flower induction period (December) to young "Valencia" orange trees at concentrations of 1000, 2500 and 5000 mg l^-1. These treatments effectively increased flowering, mainly at lower concentrations. Treatment using Flordimex at 500 and 1000 mg l^-1 concentrations resulted in flowering increase which is analyzed in this paper.

Individual specimen trees (or replicated clonal material) of 33 species and hybrids in theCupressaceae andTaxodiaceae were injected with gibberellic acid (GA₃) solutions, to test the general applicability of cone induction techniques developed forThuja plicata. Reproductive material for taxonomic study was subsequently available in 82% of treated taxa, compared with 39% of untreated. The latter generally produced small numbers of male or female cones, but both were formed in abundance in half the hormone-treated taxa. Eleven species and hybrids are reported for the first time as responding to GA₃.

Habituated sugarbeet callus examined by means of a light-microscope is characterized by absence of differentiated tracheary elements and of the reaction with syringaldazine. Habituated tissues also were found to exhibit low guaiacol- and syringaldazine-peroxidase activities, a deficiency of lignin as well as lower cellulose, dry mass and chlorophyll contents as compared to the normal auxin-requiring callus. These histological and cytological features led to consider this habituated callus as a vitrified tissue under stress. The question of a relationship between vitrification and habituation is posed.

Phenolic compounds l,2,3-trihydroxy-5-methoxyxanthone, l-hydroxy-3,5,6,7, 8-pentamethoxyxanthone, and l,8-dihydroxy-2,3,4,6-tetramethoxyxanthone predominate in the callus tissue ofCentaurium erythraea, their content increasing with culture age. By contrast, the contents of the derivatives of cinnamic, chlorogenic, and ferulic acids decrease or do not change. In the cell suspension culture ofC. erythraea a larger amount of xanthones is synthesized than in the callus from which the suspension culture was derived. The content of phenolic acids is lower in the suspension culture than in the callus, but a larger number of low-molecular-mass phenolic substances occurs in the suspension culture than in the callus tissue.

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.

Inhibition of root growth was observed inChenopodium rubrum under photoperiodic conditions inducing flowering. That this inhibition is mediated by the cotyledons was shown directly by the effect of their excision, which changes the responsiveness of the roots to photoperiodic treatment. On the other hand, decapitation did not lead to such an effect. Some evidence is put forward suggesting that changes in IAA may be involved in these correlations. The existence of two different mechanisms of photoperiodic action in flowering and in root growth is proposed to explain these differences.

Sucrose synthetase was purified about 130-fold from morning-glory (Pharbitis nil Choisy cv. Murasaki) callus cells, and the properties of sucrose synthesis and cleavage activities of the enzyme were compared.
The enzyme preparation gave a single band by disc electrophoresis. The molecular mass of the enzyme was estimated to be 4.2 × 10⁵ by gel filtration. The enzyme preparation gave two bands by SDS disc electrophoresis, suggesting the molecular mass of about 3.8 ×10⁴ and 7.0 × 10⁴.
The pH optima of sucrose synthesis and cleavage activities of the enzyme were different from each other, giving pH 9.0 and pH 6.5 respectively. MgCl², MnCl² and CaCl² activated the sucrose synthesis activity about two times the normal rate and conversely inhibited the sucrose cleavage activity.
F-6-P was not replaced by fructose. UDP was the only valuable substrate as a nucleotide diphosphate.
The enzyme showed the negative ecoperativity effect of UDPG suggesting to be an allosteric enzyme. The Km values of sucrose and fructose were calculated to be 167 mM and 5 mM, respectively. UDP suggested substrate inhibition. The apparent equilibrium constant varied between 1 to 3.
Based on these results, the role of the enzyme in the sucrose metabolism of morning-glory callus cells will be discussed.

The salt tolerance was studied according to both fresh and dry matter increases of callus cultivated on the media supplemented with various sodium chloride concentrations as well as a high amount of K⁺, Na⁺, Ca²⁺, and Mg²⁺ ions as found in the East Slovakia salt soil lowland. The cells tolerate salinity at least up to 85 mM. According to statistical evaluation the salt concentrations used did not inhibit growth rate and development of tissue cultures.

The induction of gametogenesis in the studied homothallic alga by the transfer to a nitrogen-Less medium leads to an adaptation of the cell population until a dynamic equilibrium is attained. Throughout the adaptation, the homeostatic forces regulating the number of the cells in the population assert themselves on the basis of internal nitrogen circulation. Part of the induced cells which perform no conjugation is probably destroyed by lysing, whereas the cells being just in the pre-Induction phase as well as those having passed the phase without being induced to gametes, continue their cycles by means of the released nitrogenous substances. The conditions which in some cells cause the induction of gametogenesis, produce a partial spontaneous synchronisation in other cells. The course of the cell cycles in parts of the culture may be determined according to the pulses of the increasing number of the zygotes within the whole cell population, if the cell cycles have run at a certain degree of synchrony. The culture conditions which induce gametogenesis cause a quick decrease of the biosyntheses of the RNAs while the biosyntheses of the DNAs are almost maintained at the original level. During the dynamic equilibrium of the population, the average content of the RNAs per cell remains very low, whereas the average content of the DNAs per cell virtually does not change (compared with the original state).

The induction of gametogenesis has its beginning in the most diluted cell suspension after the transfer of the cells to a nitrogen-less medium. Here, the highest percentage frequencies of zygotes are formed within the same period of time in comparison with the less diluted cell suspensions. The zygotes formed in the mostly diluted cell suspensions mature relatively very slowly and germinate very irregularly. The induction of gametogenesis retards in the denser cultures probably due to the strongest homeostatic forces trying to return the cell population to its initial stage. In our experiments up to now, the effects of the changing irradiance of the cells inside the suspension were not separated from the effects of the changing number of the cells in the given volume of the culture. Neither were the ratios of distilled water to the amount of the zygotes, nor to the vegetative cells constant. Thus, it is necessary to consider the mentioned effects as the result of an interaction of both factors under consideration. Each of the cell populations behaved as an autonomous whole. Also the populations, starting after the transfer to a nitrogen-less medium of the same culture density, may sometimes differ significantly in the observed characteristic features at various phases of their growth. The discontinued supply of nitrogen obviously causes a change of the cell metabolism in favour of the nitrogen-less substances, especially in the more diluted cell suspension. This work completes and explains some earlier results obtained from the study of the life cycle inChlamydomonas geitleri.

Influence of high intensive flashes on the yield of free radicals in intact seeds and excised embryonic axis, endosperm, and seed coat, and its resulting effect on seedling growth, total biomass production and phosphorus metabolism in wheat (Triticum aeativum), vetch (Vicia sativa L.) and onion (Allium cepa L.) was studied. Free radicals (f.r.) were formed mainly in seed coat and not in the endosperm. Vetch seeds after irradiation had 20.76 X 10¹³ f.r. g^-1 dry intact seed and 17.30 X 10¹³ f.r. g^-1 dry seed coat. Excised seed coats exposed to irradiation also yielded 17.28 × 10¹³ f.r. g^-1 dry matter. High irradiance "white light" flashes induced more f.r. than a monochromatic one of the same photon content. Red (650 nm), farred (750 nm) and even infra-red (1100 nm) radiation did not initiated f.r. formation but resulted in their decay in samples irradiated earlier by "white", blue and green parts of the spectrum. Blue irradiation of seeds led to the decrease in the length of shoots and roots in comparison to "white", green and red irradiation but their biomass increased faster than in the seedlings obtained from non-irradiated or irradiated with "white" and green radiation. The quantity of total acid soluble phosphorus followed a sequence with respect to wavelength of radiation: 436 nm > 650 nm> > 540 nm > non-irradiated > 300-800 nm. Quantity of inorganic phosphorus remained unaffected by different spectral character of radiation. The quantity of organic acid soluble nucleic phosphorus and acid insoluble polyphosphates was higher in samples irradiated with red beams (650 ± 6 nm).

The current status of our knowledge of auxin effects on floral induction is summarized. The most general effect is inhibition, although the concentration of synthetic auxins added to. plants tends to be too high for us to be certain that the inhibitory effects are truly physiological. Studies of endogenous levels of auxin have focused almost entirely on IAA-like bioassay activity. Chemical identifications of endogenous IAA are needed and feasible. In addition, a search for-other auxins involved in vegetative to floral transitions, their chemical identification, and measurement of their changing levels in the plant are urgently needed.

Callus culture was derived from haploid barley embryos after crossing withHordeum bulbosum. The callus tissue is cytologically heterogeneous, containing haploid, diploid and polyploid cells. Aneuploidy and karyokinetic irregularities were also observed. Some problems of chromosomal instabilities in plant tissue cultures are discussed.

The fluctuation of free IAA under 16 h dark period in shoots (receptor organs of photoperiodic induction) and roots of the short-day plant (SDP)Chenopodium rubrum and in shoots of the long-day plant (LDP)Chenopodium murale is very similar. The data reflect the general adjustment of auxin level to day-length rather than changes due to floral induction. However, the shift in phasing of the circadian rhythm of flowering was accompanied by a change in the position of the' troughs' of free IAA levels indicating a possible relationship between the two processes. Periods of higher sensitivity to application of IAA (3. 10^-4M) inhibitory to flowering have been observed both during the endogenous rhythm of flowering in the SDPC. rubrum and during induction by days of continuous illumination in the LDPC. murale. There exist common traits in the response of LDP and of SDPChenopodium to auxin treatment. Aminoethoxyvinylglycine (AVG), an inhibitor of ethylene biosynthesis, counteracted some flowering inhibitory effects of IAA when applied simultaneously with it. This suggests that auxin effects in modifying flowering might in fact be due to ethylene.