Showing papers on "Kinetin published in 1969"

The caryological analysis of plants regenerated from tumorous and other callus cultures of tobacco

Abstract: 1. Large numbers of tumorous (auxin-autotrophic) and non-tumorous (auxin-heterotrophic) tobacco callus cultures were transferred from their culture media in darkness to media with high kinetin content in light for regeneration. There were two lines of tumorous cultures, Tc and Ta; they were started in 1946 from the tobacco variety “White Burley”. Tc had been transformed by infection with Agrobacterium tumefaciens, Ta spontaneously by “habituation”. Non-tumorous cultures (Tn1 and Tn2) were started in 1961 from an unknown variety of tobacco. All the four types of cultures we received from the laboratory of Prof. R. Gautheret in Paris, in 1965. 2. Regeneration from tumorous cultures to fully developed plants was largely successful. These plants, however, were always sterile and none represents a genuine specimen of “White Burley”. Regeneration from non-tumorous, so-called “normal”, cultures was on the contrary very poor. The number of plants regenerated from Tn2 was very small. The plants were more or less uniform, growing well only as scions on other tobacco plants. Only a few “teratomata” from Tn1 developed and, in one case only, a plantlet with roots, shoots and leaves. In grafting experiments with Tn1 teratoma as scion on “Xanthi” tobacco stock, all regenerating plants originated from material with the gene N, probably from the “Xanthi” stock. 3. A comparison of the chromosome numbers of the callus cultures with those of the plants regenerated from them shows that selection plays an important part in the process of regeneration. Plants regenerated from tumorous cultures had extreme aneuploid chromosome numbers and this fact supports the assumption that abnormal chromosome numbers of tumorous cells (in the original callus cultures) are not the cause of tumor growth. On the other hand, the high aneuploidy of the regenerated plants suffices to explain their abnormal morphology and sterility. These abnormal features should not be regarded as a consequence of the tumor condition of the original cultures. The poorly regenerating non-tumorous Tn1 and Tn2 plants, which were always abnormal and aneuploid, underline this viewpoint as do our own observations (Melchers, 1965). 4. TMV in the callus cultures (Tc and Tn2) does not influence the chromosome numbers or the ability to regenerate normal plants. In Tc nearly all regenerated plants are free of TMV, whereas all Tn2-regenerates contain TMV. This interesting difference remains unexplained. 5. “Secondary” callus cultures started from regenerated plants of Tc and Ta behave as control material of “White Burley”: on a medium with auxin, this material grows as callus, without auxin it regenerates to plantlets. 6. The experiments of Braun (1959) and his arguments against the interpretation of “recovery” (from Agrobacterium transformed cells to completely normal plants) excluding the possibility of a selection process, are discussed. His work is compared with our own and that of Lutz (1966) who described the isolation of two single cell clones, one with high, the other with low tumorous activity, from habituated material.

The Hypersensitivity Reaction of Tomatoes Resistant to Meloidogyne incognita: Reversal by Cytokinins

Abstract: Initiation of larval growth, induction of cell necrosis, and gall formation in the host were measured as criteria of resistance or susceptibility of tomato seedlings to the root-knot nematode, Meloidogyne incognita (Kofoid &White) Chitwood. Seedlings grown at 27 C on water agar containing additions were scored 3 or 4 days after infection.In the absence of exogenous plant growth regulatory substances, approximately 73% of larvae that entered roots of susceptible plants showed growth, none induced necrosis and nearly all induced gall formation. In roots of a resistant variety, only 4% of the larvae grew, 88% induced necrosis of host cells, and only 29% induced galls. Exogenously supplied cytokinins shifted the response of the resistant plants toward the susceptible reaction. Exogenous kinetin at 0.4 and 0.8 micromolar allowed 55 and 57% of the nematodes to grow, reduced the incidence of necrosis to 32 and 31%, and increased gall formation to 73 and 65%. Three additional cytokinins, Zeatin, 6-(gamma,gamma-dimethylallylamino)purine, and 6-benzylaminopurine produced effects similar to kinetin. Exogenous indoleacetic acid, gibberellic acid, adenine, guanine, uracil, thymine, cytidine, and 6-methylaminopurine neither increased the percentage of larvae which grew nor decreased the extent of host cell necrosis.

Hormonal Control of Cell Proliferation and Xylem Differentiation in Cultured Tissues of Glycine max var. Biloxi

Abstract: The relationship between tracheary element differentiation, cell proliferation and growth hormones was examined in agar-grown soybean callus. The time course of cell division and tracheary element formation in tissues grown on a medium containing 5 × 10−7m kinetin and 10−5m NAA was determined by means of maceration technique. After a slight lag period, a logarithmic increase in cell number was observed through the twelfth day of the culture period. Cell numbers increased at a considerably slower rate after the twelfth day. The rate of tracheary element formation varied with the rate of cell proliferation. Tracheary elements increased logarithmically during the log phase of growth. As the rate of cell division decreased after the twelfth day of culture, the rate of tracheary element formation also decreased. In the presence of 10−5m NAA, cell number increased as the kinetin concentration was increased between 10−9 and 10−6m. However, tracheary element formation was not initiated unless the kinetin concentration was 5 × 10−8m or above. When the Biloxi callus was subcultured repeatedly on media containing 10−8m kinetin, a tracheary element-free population of cells was obtained. This undifferentiated tissue produced tracheary elements upon transfer to a medium containing 5 × 10−7m kinetin. In the presence of 5 × 10−7m kinetin, NAA stimulated cell proliferation between 10−7 and 10−5m, but no tracheary elements were formed without auxin, or with 10−7m NAA. Neither NAA nor kinetin at any concentration tested stimulated tracheary element formation in the absence of an effective level of the other hormone. However, 2,4-D at 10−7 or 10−6m promoted both cell proliferation and tracheary element differentiation in the absence of an exogenous cytokinin.

In vitro culture of wheat tissues. i. callus formation, organ redifferentiation and single cell culture

Abstract: Callus induction, organ formation from callus and single callus cell culture have been tried in wheat. Though kinetin showed no effects, supplements of 2,4-D (1~10mg/1) or IAA (50mg/1) to the basal media induced calluses from seedling roots of einkorn, emmer and common wheats, and from stem pieces of common wheat. The best callus growth was obtained when casein hydrolysate (1g/1) or coconut milk (1%) was added to the basal media. Callus growth was also vigorous when 2,4-D (0.5~2.0mg/1) was added. Root formation from callus took place in all kinds of tested media, except those containing no growth factors or supplemented with 2,4-D at high concentrations (1~5mg/1). Shoot formation occurred in six cases and no growth factors were found to be specifically effective on shoot differentiation. Two plants were restored and reached maturity. Calluses of common wheat consisted of eudiploid and aneuploid cells at almost the same frequencies. The great majority of aneuploid cells had 42 ± 3 chromosomes. The restored...

Flower Formation in Excised Tobacco Stem Segments; I. Methodology and Effects of Plant Hormones

Abstract: The formation of flowers has been studied in stem tissue excised from flowering plants of Nicotiana tabacum variety Wisconsin No 38, and cultured in vitro on Murashige and Skoog nutrient medium A procedure for quantitative evaluation of factors influencing floral expression has been developed and effects of the growth substances, indole-3-acetic acid (IAA), kinetin and gibberellic acid (GA(3)), on the process are reportedAlthough a low (1 mum) level of IAA was required for the development of normal flowers on stem segments, higher concentrations tended to inhibit flowering The decrease in floral buds was rapid in the 3 to 15 mum range IAA concentrations up to 75 mum increased vegetative bud formation so as to effect a transition from floral to vegetative buds rather than merely an inhibition of bud formation Higher IAA concentrations inhibited both vegetative and floral bud formationKinetin in high concentrations greatly increased the number of vegetative buds but had no significant effect on the number of floral buds per segment High kinetin concentrations also permitted branching of floral shoots so that flower clusters were formedGA(3) applied in the medium from the start, strongly inhibited bud formation on the stem segments, but when applied to young floral buds after they had formed, it promoted their further development ("bolting")Flower formation occurred in complete darkness, but light of moderate intensity was required for the development of normal flowers

Abscisic-acid-stimulated rooting of stem cuttings.

Abstract: Abscisic acid (ABA) has been found to stimulate rooting of stem cuttings of mung beans and English ivy. ABA partially overcame the inhibitory effect of gibberellic acid on root formation of mung bean cuttings but at the concentrations used did not overcome the inhibitory effect of kinetin on root formation.

Changes in phenylalanine ammonia-lyase activity during xylem differentiation in Coleus and soybean

Abstract: Xylem differentiation was induced in cultured Coleus internode slices when grown in the light on a simple agar/sucrose/IAA medium and in darkgrown soybean callus tissue when cultured on a complex defined medium containing 5×10-7 M kinetin. In the Coleus system, the activity of phenylalanine ammonialyase followed the same time course as the formation of lignified wound vessel members. The specific activity of PAL was higher in the soybean callus tissues grown on 5×10-7 M kinetin, which produced tracheary elements, than in the soybean tissue grown on 10-8 M kinetin, which did not produce tracheids. These observations suggest that PAL is a “marker enzyme” for xylogenesis and that PAL activity may be a rate limiting step in lignification.

Induced differentiation of geranium plants from undifferentiated callus in vitro

Abstract: A B S T R A C T Geranium callus produced from explants of stem tip, internode pith with vascular tissute on synthetic media with or without coconut milk and 2,4-dichlorophenoxyacetic acid grew well for many generations, but only tracheids were induced in them. If callus produced on these media was subcultured immediately on Murashige and Skoog medium with 0.1 mg/liter/a-naphthalene acetic acid (NAA) and 10.0 mg/liter kinetin (K) and incubated at 16/8-hr light/dark cycle, shoots were induced in 8-10 weeks and roots in another 8-10 weeks. Callus produced on the MS medium with the same supplements of NAA and K, subcultured on the same medium and incubated in 16/8-hr light/dark cycle, produced shoots in 6-8 weeks. However, on callus subcultured more than three times, shoots differentiated with greater difficulty and none differentiated after six subeultures. Some abnormal shoot-like structures were also produced, the cells of which showed virus-like inclusion bodies. Requirements of the different varieties for differentiating organs differed. Among 12/12-, 1a/9-, 16/8-, and 20/4-hr light/dark photoperiods that induced differentiation, 15/9- and 16/8-hr were more effective than the others. Continuous illumination did not induce differentiation. Differentiated shoots formed roots more readily on a medium with reversed proportions of auxin and kinetin. On agar roots were devoid of root hairs. Root hairs were formed when the shoots and plantlets were cultured on filter-paper bridges. Many "mother" stock plants were produced. These are being studied for their growth qualities and for possible viruses and other pathogens.

Auxin, ethylene and kinetin in a carrier‐protein model system for the polar transport of auxins in petiole segments of phaseolus vulgaris

Abstract: Summary The capacity of bean petiole segments to transport 14C-indole-3-acetic acid decreases to approximately half within 5 hours of excision and to less than one-tenth after 10 hours. Exposure of the segments to ethylene enhances this loss in capacity, but pretreatment with an auxin completely protects the transport system from both the natural and ethylene-induced fall. A decrease in synthesis of protein accompanies the natural loss of transport capacity, and treatments with auxin or kinetin which retain synthesis also retain transport. Only auxin treatments protect against the effects of ethylene. To correlate these results, a theoretical model for polar transport is developed in which it is proposed that auxin molecules are bound to a specific carrier protein sited at the plasmalemma. Transport capacity could be regulated by the rate of synthesis of the carrier protein, with a secondary regulation of the activity of the carrier by the binding of either auxin or ethylene molecules to specific sites on the protein.

Sodium and Potassium Absorption by Bean Stem Tissue

Abstract: The effect of various periods of pretreatment in CaSO(4) solutions (aging) on the absorption of Na and K by bean stem slices was investigated. Freshly sliced tissue absorbed Na over the entire range of concentrations studied (0.02-50 mm). Potassium absorption by fresh tissue was nil at concentrations below 0.5 mm but at higher concentrations was similar to that of Na. When tissue was aged by aerating slices for 20 hr in 0.5 mm CaSO(4), K absorption was substantial over the entire range (0.01-50 mm), with evidence of a dual mechanism of absorption, whereas Na absorption was nil at concentrations below 0.2 mm. The formation of K-absorbing capacity with aging, and the loss of Na-absorbing capacity at low concentrations, were temperature-dependent and did not result from significant changes in rates of efflux of either ion. The absorption of Na by fresh tissue and K by aged tissue was sensitive to antimetabolites, with K uptake the more sensitive. Benzyladenine, an analog of kinetin, suppressed the formation of K-absorbing capability in aged tissue but did not prevent the loss of Naabsorbing capacity. Possible mechanisms for this alteration in ion-specificity of transport mechanisms are discussed.

Cytokinin‐Inhibitor Antagonism in the Hormonal Control of α‐Amylase Synthesis and Growth in Barley Seed

Abstract: The effect of cytokinins and gibberellic acid on the inhibition of growth and α-amylase synthesis by germination inhibitors was investigated in intact and embryoless seed halves. The cytokinins, kinetin and benzyladenine, effectively reversed the inhibition of coleoptile growth and α-amylase synthesis by abscisic acid and courmarin in barley seed. An antagonism between cytokinins, kinetin and benzyladenine, effectively reversed the inhibition of coleoptile growth and α-amylase synthesis by abscisic acid and coumarins in barley seed. An antagonism between cytokinins and germination inhibitors was also shown in root growth. Abscisic acid inhibited coleoptile growth to a greater extent than the root growth while the opposite held true in the case of coumarin. The apparent increase in coleoptile growth and α-amylase synthesis by gibberellic acid plus abscisic acid (or coumarins) over abscisic acid (or coumarin) appears to be a result of the overall stimulation of growth and metabolism by exogenous gibberellic acid and probably does not involve an interaction of gibberellic acid with the inhibitors. Gibberellic acid reversed root inhibition to some extent. Abscisic acid inhibition of gibberellic acid induced α-amylase synthesis in the embryoless endosperm was not reversed by excess gibberellic acid or kinetin Cytokinin reversal of inhibition of growth and enzyme synthesis probably depends on some factor(s) in the embryo. Cytokinin reversal of inhibitor action leading to enzymen synthesis and growth may be at the level of genome or at the site protein assembly.

Interaction between Gibberellic Acid and Kinetin in Overcoming Apical Dominance, Natural and Induced by IAA, in Tomato (Lycopersicum esculenturn Mill. Cultivar Potentate)

Abstract: Interaction between Gibberellic Acid and Kinetin in Overcoming Apical Dominance, Natural and Induced by IAA, in Tomato (Lycopersicum esculenturn Mill. Cultivar Potentate)

Growth of Plasmodiophora brassicae in host callus.

Abstract: SUMMARY: Explants of young tumour tissue from several Brassica species infected with Plasmodiophora brassicae plasmodia gave rapid callus growth on medium containing 2,4-dichlorophenoxyacetic acid and coconut milk. Degeneration of the callus followed as resting spores were formed. The resting spores germinated in situ and primary plasmodia and zoosporangia developed in some cells, then secondary plasmodia reappeared and normal callus growth was resumed; thereafter all stages of the parasite life-cycle were present in active cells. This situation has been maintaned for over 18 months by 8-weekly transfer of calluses to new medium. Callus clones containing only vegetative plasmodia were established on a coconut-milk + 2, 4-dichloro-phenoxyacetic acid medium. Sporogenesis did not occur readily in these clones unless callus was transferred to a kinetin + α-naphthylacetic acid medium or to other media which did not contain 2,4-dichlorophenoxyacetic acid. Stages of the P. brassicae life-cycle found in callus appeared similar to those in intact hosts, while zoosporangia were formed in the root hairs of Sinapis alba organ cultures infected with callus-produced resting spores. It was concluded that on suitable media P. brassicae may be maintained in complete balance with host callus.

Non-photosynthetic effects of red and far-red light on root-nodule formation by leguminous plants

Abstract: Nodulation of pea and broad bean plants grown in the light was found to be reduced when the roots were exposed to far-red light for 5–15 minutes daily during 5 consecutive days following inoculation with nodule bacteria. Similar results were obtained following a single exposure to far-red light during a period of 15 minutes at the 3rd or 4th day after inoculation. When the roots were exposed to far-red light either before inoculation or during the first two days afterwards there were either no effects or only slight effects on nodulation The inhibitory effect of far-red light on nodulation was partly reduced by subsequent exposure to red light, provided that the same part of the plant was exposed to both red and far-red light,viz either the root or the shoot. When different parts of the plant were exposed to red and far-red light respectively, there was no interaction between the two kinds of light on nodulation. Plants whose roots were exposed to far-red light did not subsequently show stem elongation. Nodules were found to develop on the roots of pea plants grown in the dark, provided that the plants were kept at or below 22°C. At 25°C nodulation was almost absent. Nodulation was decreased by addition of kinetin and IAA. In contrast to plants grown in the light pea plants grown in the dark, inoculated with either an effective or ineffective strain of Rhizobium, developed equal numbers of nodules. Exposure to red light slightly increased the percentage of nodulated plants but decreased the number of nodules per plant. Exposure to far-red light slightly decreased both the percentage of nodulated plants and the number of nodules per plant. The effect of far-red light was counteracted by red light andvice versa.

The Effect of Environmental and Nutritional Factors on the Development of Flower Apices Cultured in vitro

Abstract: Flower buds of Visearia candida, excised at 1-2 mm in length, have been grown to maturity in sterile culture, often producing normal flower parts. The calyx and the corolla developed under a wide range of conditions provided gibberellic acid was present. The development of the ovary and of the ovules tended to be irre gular and no consistent effects of treatment could be obtained. Pollen production was promoted by a temperature of 15 °C as opposed to one of 25 °C, and by the addition of gibberellic acid to the medium; it was inhibited by the addition of kinetin or hydrolysed casein to the medium, and by growth in continuous dark ness as compared with that in 8 or 16 h of light daily.

Selective effect of hormones on nucleic acid metabolism during germination of pear embryos.

Abstract: 1. The effect of hormones on 32P incorporation into various RNA fractions in germinating pear embryos was studied by fractionation on methylated albumin–kieselguhr columns. Abscisic acid inhibited labelling of soluble RNA, DNA–RNA hybrid and light-ribosomal RNA fractions with 32P and this effect was reversed by both kinetin and gibberellic acid. 2. Kinetin reversed the inhibition by abscisic acid of 32P incorporation into total ribosomal RNA and appeared to promote labelling of heavy-ribosomal RNA. Gibberellic acid was more active than kinetin in reversing the inhibition by abscisic acid of labelling of the DNA–RNA hybrid fraction with 32P, but in contrast with kinetin appeared to increase further the inhibition by abscisic acid of labelling of total ribosomal RNA. 3. The percentage of radioactivity in various RNA fractions showed marked variation in response to hormones. 4. The pattern of labelling of RNA in pear embryos during reversal of inhibition by abscisic acid with a combination of kinetin and gibberellic acid was similar to that after cold-treatment of dormant pear embryos. This is suggestive of hormonal interplay in dormancy release by cold-treatment in pear embryos.

Cytokinins as Endogenous Growth Regulators in the Algae Ecklonia (Phaeophyta) and Hypnea (Rhodophyta)

Abstract: Cytokinin activity was detected in extracts prepared from Ecklonia radiata (Phaeophyta) and Hypnea musciformis (Rhodophyta), and was associated with chromatogram bands which appeared to contain purine. Kinetin, a cytokinin with a purine ring system, stimulated growth in cultured plants of the same species. It is concluded that cytokinins are normally involved in regulating growth in these algae. On the basis of this and other evidence, it is suggested that plant growth regulators of the auxin, gibberellin, and cytokinin type may have arisen early in plant evolution.

Light and hormones: interchangeability in the induction of nitrate reductase.

Abstract: Suitable concentrations of kinetin and gibberellic acid permit induction of nitrate reductase in leaves of tobacco in the dark Hormone sprays eliminate the need for light induction of the enzyme The concentration of gibberellic acid required for optimal induction varies according to the concentration of kinetin supplied

The Changes in Soluble Protein of Excised Barley Leaves during Senescence and Kinetin Treatment

Abstract: Sterile detached barley leaves were floated on water or kinetin (10 mg/1)and supernatant extracts (30,000 x g for 30 min) were prepared from these leaves over an 8 day incubation period. Changes in selected total enzyme levels and in individual soluble protein components wore compared. Ribonuclease, deoxyribonuclease and peptidase activities rose in senescing leaves, even as total protein levels fell. Kinetin to some extent depressed these activities. Evidence of considerable loss of ribonuclease and to a lesser extent of deoxyribonuclease into the surrounding medium was obtained. Soluble supernatant ant extracts were resolved on DEAE-Sephadex (A-50) columns into about 15 components. While most components were degraded during senescence they did so at different rates. Kinetin lowered the rate of degradation of all components. Since no conclusive evidence of a new protein(s) was obtained in water and kinetin treated leaves, it was considered that any protein changes may have been of a quantitative rather than qualitative nature.

Effect of Kinetin on Organ Formation in Callus Tissue Derived from Rice Embryos

Abstract: Effect of kinetin on organ formation in rice callus tissue was studied using Maede's medium containing yeast extract, vitamines and 2, 4-D. The following results were obtained. (1) When kinetin was added in to the medium containing 2, 4-D at 10-7M, shoot formation in callus was promoted as concentration of kinetin increased. Root formation was not influenced by addition of kinetin. (2) Shoot-like protuberances appeared in callus tissues at 10 to 14 days after transfer of callus in to the test medium. Numerous protuberances did not make any growth, and they turned to be necrosis for 30 days after the transfer. Few protuberances developed to normal shoots, while a half of the shoots were albino. (3) Varietal difference was not observed in the effect of kinetin on shoot formation in the callus tissues of various varieties, which are Te-Tep, Norin-8, Norin-29, Kyoto-asahi and Tan-ginbozu. (4) It is necessary for acceleration of kinetin action to contain yeast extract and/or casein hydrolysate in the medium. Adenine failed to exert any effect on shoot regeneration in callus tissues.

Sclerospora graminicola Axenic Culture

Abstract: Sclerospora graminicola (Sacc.) Schroet., the obligate pathlogen causing downy mildew (green-ear) of pearl millet (Pennisetum typhoides Stapf. and Hubb.) has been successfully cultured for the first time on a known semisynthetic mediumn with no evident loss of fructifications. Sclerospora graminicola was first grown on host callus tissue and subsequently on a modification of White's basal medium that contained casein hydrolyzate (Oxoid). 2,4-dichlorophenoxyacetic acid, and kinetin.

The interchange of (14)C-kinetin and (14)C-gibberellic acid between the bark and xylem of willow.

Abstract: Considerable two-way interchange of label derived from 14C-GA3 and 14C-kinetin has been shown to occur between the xylem and extra-cambial tissue of Salix viminalis L Radial translocation of both growth substances from the transpiration stream to the sieve-tube sap has been demonstrated by the use of an aphid technique This is the first record of the bark-xylem interchange of these two growth hormones

An Interaction between the Effects of Kinetin and Gibberellin in Retarding Leaf Senescence.

Abstract: The relation hetween the effects of kinetin and gibberellin on retardation of leaf senescence was studied. Leaf discs were incubated for five days in several hormone concentrations, the chlorophyll was extracted and its amount estimated spectrophotometrically. Investigation of leaves from actively growing plants of Taraxacum megalorrhizon and Tropaeolum majus showed that an interaction existed between the effect of both hormones. Leaf age, light intensity and day length had a marked effect on the degree of response to the hormonal treatments, hut the change in response effected by these conditions remained similar for both hormones. Possible interpretations of the interaction observed between the effects of kinetin and gibberellin are discussed.

Control of Logarithmic Growth Rates of Tobacco Callus Tissue by Cytokinins

Abstract: The growth rates of tobacco callus tissues on media containing 10(-6) to 10 mum 6-(gamma,gamma-dimethylallylamino)purine (2iP) were measured. At concentrations of 10(-4) mum and above growth rates were exponential and dependent on cytokinin concentration. At 2iP concentrations of 10(-4) to 0.33 mum, the exponential rate was maintained for 4 to 5 doublings of fresh and dry weight. After this period a linear phase, resulting in approximately 1 doubling of weight, occurred. The growth of tissues on media containing higher than 0.33 mum 2iP was exponential for only about 15 days. At the end of this time, and well before they achieved half their final weight, they exhibited growth which was less rapid than logarithmic but more rapid than linear. Comparisons with zeatin, 6-benzylaminopurine and kinetin indicated that, although the maximum growth rates obtained with relatively high concentrations (0.1-1 mum) were similar, the naturally occurring cytokinins, 2iP and zeatin, promoted faster rates at lower concentrations (10(-3)-10(-2) mum) than did 6-benzylaminopurine and kinetin.

Combined effect of 6‐benzylaminopurine, gibberellic acid, and 3‐indoleacetic acid on the expansion of isolated pumpkin cotyledons

Abstract: A B S T R A C T The effect of 6-benzylaminopurine, gibberellin, and 3-indoleacetic acid, used separately or in combinations, on the expansion of isolated pumpkin cotyledons has been studied. All three types of phytohormones can promote the expansion of isolated cotyledons. The resulting effect depends on the concentration of the particular phytohormone and on its quantitative ratio with the other phytohormones. The optimum combinations of phytohormones introduced externally varied according to the seed. The stimulating effect on the expansion of cotyledons is evidently exerted by those phytohormones which are present in the seeds in minimum amounts. An analysis of the concentration curves of the phytohormone effect indicates that they are not interchangeable as regards their influence on the expansion of isolated pumpkin cotyledons. THE STIMULATION of the growth of isolated leaves is one of the typical manifestations of the physiological activity of cytokinins. This effect is most prominent in segments of nonexpanded leaves (Kuraishi and Okumura, 1956; Miller, 1956; Scott and Liverman, 1956) and in isolated cotyledons (Banerji and Laloraya, 1965). The stimulation of the expansion of discs from etiolated leaves of bean plants (Miller, 1956, 1963; Scott and Livermann, 1956) in darkness and from leaves of Raphanus sativus (Kuraishi, 1959) in the light serves as the basis for quantitative assays to determine cytokinins. Their effect on the growth of leaves is studied in the greatest detail in the work of Kuraishi (Kuraishi, 1959). He showed that in discs from leaves of Raphanus sativus seedlings cytokinin promotes growth by stimulation of cells expansion, rather than by intensification of their division. Cytokinin-induced growth increases the surface of leaf discs and their fresh weight. At the same time it has little effect on their dry weight. In Kuraishi's experiments it was demonstrated that gibberellin also promoted the expansion of discs from leaves of radish and pea plants (Kuraishi and Hashimoto, 1957). The combined action of gibberellin and kinetin is synergistic. 3-Indoleacetic acid did not promote the expansion of leaf discs, but it somewhat enhanced kinetin-induced growth (Kuraishi, 1959). Expansion of isolated pumpkin cotyledons could be stimulated not only by kinetin but by gibberellin as well, while it was not affected by 3-indoleacetic acid (Banerji and Laloraya, 1967). These data indicate that the growth of leaves and cotyledons may be sensitive to two phytohormones used simultaneously in one combination or another.

Movement and Metabolism of Kinetin-14C and of Adenine-14C in Coleus Petiole Segments of Increasing Age

Abstract: To see if polar movement was typical of growth-regulators other than auxins, the movement of adenine-8-(14)C and of kinetin-8-(14)C was studied in segments cut from petioles of increasing age. No polarity was found. In time-course experiments lasting 24 hr, kinetin showed a progressive increase of radioactivity in receiver blocks, while adenine showed a maximum at 8 hr with a decline thereafter. More kinetin moved through older segments than through younger ones. There was no difference in net loss as far as the position of the donor block is concerned. However, the loss of radioactivity from adenine donor blocks was much higher than the loss of radioactivity from kinetin donor blocks.The radioactivity in receiver blocks after 24 hr treatment with kinetin-(14)C was still with kinetin, judging by location on chromatograms. By the same criterion, adenine and a smaller amount of some other compound were in receiver blocks after a 6 hr transport with adenine-(14)C in the donors. By contrast, more zones of radioactivity were extracted from petiole segments to which kinetin or adenine had been added. For both purine derivatives the original compound represented no more than 20% of the total radioactivity extracted from the tissue after a transport period of 24 hr.

Responses of tobacco pith nucleic to growth substances.

Abstract: A cytological study was made of excised segments of pith of tobacco (ev. Wisconsin 38) grown in vitro on media containing various growth substances. Explants were cultured on a basal medium and on media containing kinetin, indoleacetic acid, gibberellic acid, and combinations of these three growth substances. Controls consisted of pith segments chemically fixed immediately after excision. The nuclei of explants on the basal medium and those on media containing the growth substances showed a response as early as 1 day after the beginning of the experiment. Nucleoli were indicators of initial stimulation in that they became swollen and displayed internal “vacuolation”, a known characteristic of active cells. These fatures were more pronounced by the second day for cultures grown on media containing growth regulators. Nucleoli were centers of nucleohistone staining as shown by the ammoniacal silver method. Continued and sustained growth of explants was possible only on media containing combinations of IAA and kinetin, or a combination of kinetin, IAA and GA. The greatest initial nucleolar stimulation occurred with IAA alone, even though subsequent growth did not take place. There was no nucleolar response of explants grown on abscisic acid alone.