Showing papers on "Kinetin published in 1981"
TL;DR: Rapid clonal propagation via somatic embryogenesis in Pennisetum americanum (L.) K. Schum is reported and the regenerated plants showed normal chromosome numbers.
Abstract: Immature embryos as well as explants obtained from young inflorescences of Pennisetum atnericanum (pearl millet) give rise to callus tissues on nutrient media containing 2,4-dichlorophenoxyacetic acid (2,4-D). A compact and pale-yellow callus that arises from the peripheral cells of the scutellum, and from the young inflorescences, undergoes further organized growth. When transferred to a 2,4-D-free medium, supplemented with indole-acetic acid or kinetin, or both, embryoids are formed in the organized areas of the callus. Embryoids show a bipolar organization with a shoot-coleorhiza (root) axis and have a coleoptile-like structure surrounded at the base by a cup-shaped structure that resembles the scutellum in texture and morphology. Embryoids show bilateral or radial symmetry and "germinate" in vitro to form plants that have been grown to maturity in soil. Similar embryogenic callus cultures have been produced from young inflorescence tissues of hybrid Pennisetum, a triploid sexually sterile hybrid of P. americanum x P. purpureum. Plants derived from these have also been transferred to soil. The regenerated plants showed normal chromosome numbers. REGENERATION of plants from cultured immature embryos and inflorescence tissues of several species of cereals and grasses has been described (Thomas and Wernicke, 1978; Thomas, King and Potrykus 1979; I. K. Vasil, Ahuja and Vasil, 1979). In cereals it is the scutellar tissue of the immature embryo which proliferates in vitro (LaRue, 1952; Narayanaswamy, 1959; Norstog, 1970), and has the maximum potential for organogenesis and plant regeneration (Green and Phillips, 1975; Cummings, Green and Stuthman, 1976; Gamborg et al., 1977; Thomas, King and Potrykus, 1977; Gosch-Wackerle, Avivi and Galun, 1979; Rybczynski, 1979). Plant regeneration from hypocotyledonary explants of Pennisetum typhoideum has been reported by Rangan (1976). The differentiation of shoots in tissue cultures of cereals and grasses is not too frequent, and is often sporadic and short-lived. Plants are formed from shoot primordia that arise in centers of meristematic activity located in the surface layers of callus tissue cultures (Rangan, 1974; Dunstan et al., 1979; Nakano and Maeda, 1979; Shimada and Yamada, 1979; Springer, ' Received for publication 2 June 1980; revision accepted 11 October 1980. Florida Agriculture Experiment Station Journal Series No. 2462. This research was supported by the Florida Agriculture Experiment Station, and by the Science and Education Administration of the U.S. Department of Agriculture under Grant No. 5901-0510-8-0141-0 from the Competitive Research Grants Office. Green and Kohn, 1979). The phenomenon of somatic embryogenesis in cereals and grasses is even rarer (Gamborg, Constabel and Miller, 1970; Norstog, 1970; V. Vasil and Vasil, 1980, 1981). The formation of shoots and embryoids cannot be ascribed to any known plant growth substances, although it is generally known that shoot differentiation follows the transfer of callus tissues from a medium containing 2,4dichlorophenoxyacetic acid (2,4-D) to media devoid of this synthetic auxin, or containing very low concentrations. We report rapid clonal propagation via somatic embryogenesis in Pennisetum americanum (L.) K. Schum. = P. typhoides (Burm.) Stapf & C. E. Hubb. (pearl or Indian millet), and hybrid Pennisetum (P. americanum x P. purpureum Schumach, Napier or elephant grass; Muldoon and Pearson, 1979). Both plants belong to the tribe Paniceae of the Gramineae, and are widely grown in the arid tropical and subtropical parts of Asia and Africa. Pearl millet is an important human food, and along with hybrid Pennisetum is also used extensively as a fodder crop. Our interest in the clonal propagation of these plants in vitro is related to our attempts to develop the necessary technology for the somatic hybridization and genetic manipulation of cereal crops through unconventional means. The regeneration of plants from cultured protoplasts, single cells, and callus tissue is a basic prerequisite that must be satisfied before any of these potentially useful techniques can be adopted for cereals (I. K. Vasil and Vasil, 1980). Pearl
191 citations
TL;DR: While almost half as effective as kinetin in promoting expansion of cucumber cotyledons, BR was ineffective in cytokinin bioassays involving expansion of dwarf pea epicotyl hooks, dark synthesis of betacyanin in Amaranthus and retardation of Xanthium leaf disc senescence.
Abstract: Brassinolide (BR), a naturally-occurring steroidal lactone was compared with GA3 and kinetin for activity in a number of bioassays. BR was highly active in elongation bioassays employing the dwarf pea epicotyl and etiolated bean hypocotyl that are responsive to GA3 but not IAA (at 0.01 to 10 μM). The elongation of the cucumber hypocotyl elicited by BR and GA3 was reduced far more than that elicited by IAA, following removal of the cotyledons. BR, like GA3 also inhibited betacyanin accumulation in Amaranthus seedlings and prevented adventitious root initiation in hypocotyls of mung bean, dwarf bean and cucumber. Application of BR promoted rather than retarded senescence of Rumex leaves.
While almost half as effective as kinetin in promoting expansion of cucumber cotyledons, BR was ineffective in cytokinin bioassays involving expansion of dwarf pea epicotyl hooks, dark synthesis of betacyanin in Amaranthus and retardation of Xanthium leaf disc senescence. Unlike the case with IAA, BR does not interact synergistically with GA3. BR has proven active in promoting stem elongation in plant bioassays responsive to either IAA or GA3, or to both phytohormones. This effect, coupled to its effect on adventitious root formation, qualifies BR as a unique plant growth substance.
169 citations
TL;DR: Multiple shoots were obtained from terminal buds of 20-year-old trees of Eucalyptus citriodora Hook on Murashige and Skoog's medium supplemented with calcium pantothenate, biotin, benzylaminopurine and kinetin.
111 citations
TL;DR: Although regeneration of soybean plants was not achieved, these observations suggest that it may be achievable, and Concentrations and chemical forms of the growth regulators in liquid and solidified media were altered in an attempt to achieve in vitro plant regeneration.
Abstract: Glycine max (L.) Merr. (soybean) andGlycine soja Sieb. and Zucc. cell suspension cultures were grown and used as inoculum sources for growing callus on agar-solidified nutrient media. Concentrations and chemical forms of the growth regulators in liquid and solidified media were altered in an attempt to achieve in vitro plant regeneration. Numerous embryoids, particularly ofG. soja, were produced on basal nutrient media supplemented with 100 ppm casein hydrolysate, 0.1 μM abscisic acid, 2.25 μM 2,4-dichlorophenoxyacetic acid, and 15 μM adenine or 0.46 μM kinetin. Often the roots of the embryoids elongated. This was enhanced in the presence of an inhibitor of gibberellin synthesis (1 to 20 μM Amo 1618). Callus recovered from aG. soja suspension culture produced one shoot structure when grown on a solid medium containing 0.2 μM Amo 1618 and 80 μM glutathione. The shoot structure consisted of two distinct buds, one producing two leaves. The shoot did not develop into a plant. Although regeneration of soybean plants was not achieved, these observations suggest that it may be achievable.
69 citations
TL;DR: Seeds from plants regenerated from cells in culture had higher lysine than the original field controls and had increased levels of free alanine, arginine, and asparagine.
Abstract: Rice cells derived from PI 353705 (similar to Assam 5) were isolated from anthers cultured on Blaydes medium containing IAA, 2,4-D, kinetin, yeast extract, and coconut milk. Isolated aggregates of cells were plated on a modified Blaydes medium containing 10−3
M S-aminoethyl-l-cysteine (S-AEC). This level ofS-AEC inhibits nonselected wild type cells. Cells or aggregates of cells resistant to this analog of lysine were subcultured three times in the presence of 2×10−3
M S-AEC. The selected cells were then placed on a Murashige-Skoog (MS) regenerating medium containing 1 mg/l each of IAA and kinetin. Ten plants were recovered from 34 selected cell lines, three plants grew to maturity, and two produced seeds. Seeds from plants regenerated from cells in culture had higher lysine than the original field controls and had increased levels of free alanine, arginine, and asparagine. The in vitro selection produced plants with higher protein than the field controls. Plant breeders have begun to evaluate the genotype recovered from in vitro selection.
62 citations
TL;DR: The concentrations of cucumber mosaic (CMV) and alfalfa mosaic viruses, present in various types of cultured plant tissues, were significantly less when ribavirin (syn. Virazole) at 50 or 100 mg/litre was present in the culture medium.
Abstract: SUMMARY
The concentrations of cucumber mosaic (CMV) and alfalfa mosaic viruses, present in various types of cultured plant tissues, were significantly less when ribavirin (syn. Virazole) at 50 or 100 mg/litre was present in the culture medium. CMV concentrations decreased within 24 days in infected cultures treated with ribabirin, but incubation periods of up to 127 days were required before the virus was undetectable. However, virus-free cultures were obtained from CMV-infected meristem-tips irrespective of the presence or absence of ribavirin. Kinetin at concentrations up to 25.6 mg/litre had no persistent antiviral effect.
55 citations
TL;DR: In vitro regeneration of plants from immature leaflets of 3 day-old pea seedlings was studied under defined nutritional, hormonal and environmental conditions and shoot regeneration from the primary callus occurred within 45 to 90 days of culture in most of the hormone combinations.
Abstract: In vitro regeneration of plants from immature leaflets of 3 day-old pea (Pisum sativum L. cv. Century) seedlings was studied under defined nutritional, hormonal and environmental conditions. Immature leaflets isolated from the second and third apical leaves of aseptically germinated seeds were cultured on MS medium containing vitamins as in B5 medium, 3% sucrose, 0.8% agar and supplemented with 0.1, 1, and 10 μM concentrations of naphthaleneacetic acid (NAA) and 1 and 10 μM levels of benzyladenine (BA) in various combinations. Shoot regeneration from the primary callus occurred within 45 to 90 days of culture in most of the hormone combinations. Although the number of calli producing shoots was maximal at 10 μM levels of NAA and BA, multiple shoot regeneration was predominant at a combination of 0.1 μM NAA and 10 μM BA. Indoleacetic acid (IAA) and kinetin (K), both at 10 μM, also induced shoot regeneration. No shoots were regenerated when 10 day-old leaflets were used as explants. Root production generally occurred on non-shoot regenerating calli. Roots were induced to differentiate by transferring the regenerated shoots onto half-strength B5 medium supplemented with 1 μM NAA.
55 citations
TL;DR: Cytological analyses performed on root tips of 20 randomly chosen plantlets showed that all the analysed plants contained the diploid number of chromosomes and the method described seems to be suitable for rapid propagation of globe artichoke.
55 citations
TL;DR: The results indicate that kinetin is capable of breaking dormancy in these species and there is a significant interaction with salinity in tomato and cotton.
48 citations
TL;DR: One to five percent of Lycopersicon peruvianum (L.) Mill undergo cell division and concomitant organization to form embryogenic-like structures when cultured in Murashige and Skoog medium (1962).
Abstract: One to five percent of Lycopersicon peruvianum (L.) Mill. leaf mesophyll protoplasts undergo cell division and concomitant organization to form embryogenic-like structures when cultured in Murashige and Skoog medium (1962) containing 3% sucrose, 9% mannitol, 1.0 mg/l kinetin (K) and 1.0 mg/l naphthalene acetic acid (NAA) at pH 5.6–5.8 (medium A). These embryogenic structures, after passing through developmental stages similar to those observed in zygotic embryogeny, are capable of forming shoots on hormone-free medium A. In medium B, wherein 0.5 mg/l of 2,4-dichlorophenoxyacetic (2,4-D) replaced the hormones (K and NAA), embryogenic structures did not develop. However, callus originating in medium B retained morphogenetic capacity as was evidenced by subsequent shoot regeneration when they were transferred to medium A with K and NAA replaced by 1.0 mg/l zeatin (Z). The potential value of incorporating this regeneration trait into Lycopersicon species and cultivated lines for use in tissue culture programs is discussed.
38 citations
TL;DR: Experiments are described which improve the protocols for initiating in vitro cultures of sugarcane and allowing efficient regeneration of plants even after 30 months of callus proliferation, but no plants have yet been regenerated derived from isolated protoplasts.
Abstract: Experiments are described which improve the protocols for initiating in vitro cultures of sugarcane and allowing efficient regeneration of plants even after 30 months of callus proliferation. Procedures adopted included use of leaf base explants, CS medium with 3 mg/l 2, 4-D and 0.25 mg/l kinetin for callus initiation and growth, MS medium with 0.5 mg/l IAA and 1 mg/l BAP for shoots, MS medium with 5 mg/l NAA and 7% (wt/vol) sucrose for rooting of shoots. Casein hydrolysate (N-Z amine) significantly shortened the lag period in the growth of sugarcane suspension cultures, but did not increase the rate of growth following the lag phase. Protoplasts isolated from two types of cultures could be grown to re-establish cell cultures but no plants have yet been regenerated derived from isolated protoplasts.
TL;DR: A brief irradiation with red light was as effective as continuous white light and kinetin in arresting the losses of chlorophyll and protein in detached whole leaves and leaf discs of cucumber and tomato plants, suggesting the involvement of the phytochrome system.
TL;DR: Nodal stem segments of Dioscorea bulbifera were induced to form plantlets in vitro and Rooted plantlets could be successfully transferred to in vivo conditions.
Abstract: Nodal stem segments ofDioscorea bulbifera were induced to form plantlets in vitro. Rooted plantlets were obtained on Murashige-Skoog [14] revised medium supplemented initially with 5 mg 1−1 kinetin and subsequently with 5 mg l−1 indole-butyric acid. By increasing the kinetin concentration from 5 mg l−1 to 10 mg l−1, the number of shoots forming per node was increased from five to eight. When kinetin was substituted with 6-benzylaminopurine at only 1 mg l−1, nine shoots formed on each node. Each shoot could be excised from the node and induced to form a new crop of multiple shoots. Rooted plantlets could be successfully transferred to in vivo conditions.
TL;DR: The most successful combination of phytohormones for the induction of shoot development in undifferentiated callus, was 2.0 mg/1 benzyladenine and 1.0mg/1 naphthaleneacetic acid, which resulted in regeneration of whole plants from these calli at high frequencies.
Abstract: Callus cultures were established on Murashige and Skoog medium from seedling hypocotyls and roots of Slylosanlhes guyanensis (Aubl.) Sw. cv. Cook and from leaves of 6-month-old) plants. Shoots developed in primary calli derived from seedling tissue with a number of benzyladenine or kinetin and naphthaleneacetic acid combinations. Shoot formation on primary leaf callus, occurred with 2.0 mg/1 benzyladenine and 2.0 or 1.0 mg/l naphthaieneacetic acid. Undifferentiated callus from all three sources was induced and maintained on medium with 2.0 mg/1 kinetin and 2.0 mg/1 2, 4-dichlorophenoxyacede acid in the dark. Shoot formation and regeneration of whole plants from these calli were achieved at high frequencies. The most successful combination of phytohormones for the induction of shoot development in undifferentiated callus, was 2.0 mg/1 benzyladenine and 1.0 mg/1 naphthaleneacetic acid. The regenerated plants showed no phenotypic abnormalities.
TL;DR: Early stages in embryogeny and induction of complete plantlets from catkin tissue cultures of birch is described, and the callus is maintained since the last 10 months.
TL;DR: In this article, the anthers of three genotypes of Lycopersicon esculentum, viz. cv. HS-101, HS-102 and an F1 hybrid (Montfavet 63-4xHS-101), were cultured in various defined nutritive media.
Abstract: The anthers of three genotypes ofLycopersicon esculentum, viz. cv. HS-101, cv. HS-102 and an F1 hybrid (Montfavet 63-4xHS-101) in different stages of development were cultured in various defined nutritive media. Only anthers containing microspores in the early uninucleate stage were found to respond with the culture medium in the formation of androgenic callus. The DGII medium with 2 mg l−1 NAA and 1 mg 1−1 kinetin was found to be best for callus induction but MS medium supplemented with 2 mg l−1 2,4-D and 0.1 mg 1−1 BAP favoured proliferation and growth of the callus. The androgenic microspores followed the ‘B’ type pathway of androgenesis in the formation of callus.
TL;DR: It has been concluded that the regeneration of whole buckwheat plants is feasible from differentiated cotyledon cells, provided three different media were subsequently used, each one suitable for a specific phase of development.
TL;DR: No new morphological structures were observed in these soybean cultures, indicating that other factors are related to the failure of soybean cells to regenerate in culture.
Abstract: Kinetin, and all other cytokinins tested, inhibited the conjugation of [14C]2,4-dichlorophenoxyacetic acid (2, 4-D) to amino acids when supplied simultaneously with the 2,4-D to cultured soybean cells. Upon transfer to hormone-free medium, the cytokinin-treated cells released more of their [14C]2,4-D than did the control cells. Initial exposure to low 2,4-D and high kinetin levels resulted in the greatest release of 2,4-D upon subsequent transfer. The observed alteration in 2,4-D metabolism did not seem to be correlated with growth rate. Appropriate treatment of soybean cells with kinetin resulted in 2,4-D metabolism that resembled the 2,4-D metabolism of embryogenic carrot cells. However, no new morphological structures were observed in these soybean cultures, indicating that other factors are related to the failure of soybean cells to regenerate in culture.
TL;DR: It is concluded that DCA has properties distinct from those of purine cytokinins, and acted synergistically with kinetin to promote soybean callus growth.
Abstract: A compound that stimulated growth of soybean callus was isolated from spring sap of sycamore (Acer pseudoplatanus L.). Insufficient compound was isolated to permit it to be characterised. A compound with identical properties was isolated from commercial maple syrup, the concentrated spring sap of Acer saccharum L. The compound was identified as 3-(3-methoxy-4-hydroxyphenyl)-propan-1-ol (dihydroconiferyl alcohol, DCA). DCA was also active in the tobacco callus and radish leaf senescence assays, but was inactive in four other tests for cytokinin activity. DCA acted synergistically with kinetin to promote soybean callus growth. It is concluded that DCA has properties distinct from those of purine cytokinins.
TL;DR: Observations were made on the effects of indoleacetic acid (IAA), kinetin (K), benzyladenine (BA), and triiodobenzoic acid (TIBA) on the lateral buds of decapitated and intact gametophores of Plagi...
Abstract: Observations were made on the effects of indoleacetic acid (IAA), kinetin (K), benzyladenine (BA), and triiodobenzoic acid (TIBA) on the lateral buds of decapitated and intact gametophores of Plagiomnium cuspidatum (Hedw.) Kop. Gametophores were cultured in both solid and liquid Parker's nutrient medium and treated with hormones either in solution or in lanolin paste. Based on numbers of activated buds counted from day 16 to 24, it appeared that IAA, K, and BA, when supplied to the decapitated stump, can to varying degrees replace the inhibitory influence of the apical bud. Closer study, however, of activated and inhibited lateral buds suggests that only IAA in the presence of a cytokinin can maintain inhibition in a morphological and anatomical state which is similar to that of intact control plants. Treatment of intact gametophores with TIBA increased bud activation below the treatment ring. Based on bud morphology and anatomical observations in conjunction with records of bud activation response, endog...
TL;DR: Anthers of 2 tetraploid Rosa species were plated on selected basis media, supplemented with various amounts of auxins and kinetin, at different bud stages and using various light conditions, and cytological examination showed that most cells of both species had 2 n =14 chromosomes and thus were of pollen origin.
TL;DR: Application of abscisic acid (ABA) induced pithiness in non-stressed plants and also enhanced the effect of a short period of dehydration, while kinetin, although causing severe wilting, did not induce pithness.
Abstract: The pith parenchyma in tomato (Lycopersicum esculentum) stems was found to be disrupted in response to water stress (stem pithiness). The process of the degradation starts at the upper part of the stem and proceeds downwards as the stress is prolonged. The damage to the stem tissue was found to be irreversible upon rehydration of the stressed plants. Scanning electron microscopy revealed that the protoplast of the affected cells is disrupted first, followed by degradation of the cell wall.
Application of abscisic acid (ABA) induced pithiness in non-stressed plants and also enhanced the effect of a short period of dehydration. Kinetin, although causing severe wilting, did not induce pithiness. However, when given after a short period of water stress or within the period of stress, kinetin enhanced pithiness development.
In the course of the stress, ABA levels in the upper part of the stem and in the young leaves were higher than the levels found in the lower parts of the plant shoot. The increase in ABA levels was detected before any sign of pithiness.
It is suggested that ABA might be the triggering agent of the cellular degradation process initiated by water stress.
TL;DR: It is concluded that light influences the action which auxin exerts on glycoside formation in newly emerged roots of leaf explants of Digitalis purpurea.
TL;DR: Phytphormones such as auxins, cytokinins, gibberellins, and abscisic acid differentially affect gametangial induction in male and female clones of Bryum argenteum.
Abstract: Phytphormones such as auxins, cytokinins, gibberellins, and abscisic acid differentially affect gametangial induction in male and female clones of Bryum argenteum. Both IAA and GA3 increased the percentage of fertile gametophores in the male clone, and inhibited the response in the female clone. GA3 was more effective than IAA in eliciting the response in the male clone. Cytokinins, on the other hand, increased the production of fertile gametophores in the female clone, and inhibited it slightly in the male clone. The two cytokinins tested (kinetin and DMAAP) were almost equally effective for the female clone. An interaction of IAA and kinetin nullified their individual inhibitory effects on the female and male clones, respectively. Cyclic AMP prevented the inhibitory effect of kinetin in the male clone; whereas, in the female clone, it stimulated the response elicited by kinetin. Abscisic acid (ABA) acted as a general inhibitor of vegetative growth and gametangial induction in this moss. However, the inhibition of gametangial induction was greater in the female clone which is also more sensitive to ABA than the male clone.
TL;DR: Haploid calluses obtained from the pollen of Chinese Spring, Orofen, Dansheng 15 and (Orofen×Hsiaoyen)F1 remained capability of differentiation to plantlets for about a year, and normal plants were restored from them.
Abstract: Anthers of Triticum aestivum L, cv Chinese Spring and of some Japanese and Chinese wheat cultivars were cultured on the N6 basal medium supplemented with inositol, glutamine, serine and 2, 4-D after the treatment with low temperature (5°C) for 7 days Haploid calluses were obtained from the pollen of Chinese Spring, Orofen, Dansheng 15 and (Orofen×Hsiaoyen)F1, and were maintained by continuous subcultures, in which calluses were transferred once for every 30 to 40 days on the PM-64 basal medium supplemented with 2mg/l of 2, 4-D Many regenerated plantlets were obtained on the RM-64 basal medium supplemented with 1mg/l of IAA and kinetin The regenerated plants were mostly haploid and green A few plants from Orofen and Dansheng 15 were diploid The haploid calluses remained capability of differentiation to plantlets for about a year, and normal plants were restored from them These haploid calluses from wheat pollen may be useful in mutant selection studies
TL;DR: A culture medium and culture conditions are described that enable generative cell division and sperm formation to occur in a large proportion (greater than 70%) of the pollen tubes of Tradescantia paludosa within six to eight hours of culture of pollen.
Abstract: A culture medium and culture conditions are described that enable generative cell division and sperm formation to occur in a large proportion (greater than 70%) of the pollen tubes of Tradescantia paludosa within six to eight hours of culture of pollen. The nature of the nitrogen source, speed of shaking, and ratio of pollen to medium are important parameters in determining the extent of sperm formation. Addition of the plant hormones indole acetic acid, gibberellic acid, and kinetin to the growth medium does not influence generative cell division.
TL;DR: For three components (apical meristem, subapical internodes, and foliar apparatus) of Pisum sativum cotyledonary buds, DNA microdensitometry, mitotic indices, and release of growth have been used to detect changes produced by kinetin applications.
Abstract: For three components (apical meristem, subapical internodes, and foliar apparatus) of Pisum sativum (cv. nain hâtif d'Annonay) cotyledonary buds, DNA microdensitometry, mitotic indices, and release of growth have been used to detect changes produced by kinetin applications (50 μg/mL). One kinetin treatment is sufficient to release the cell cycle, but continuous kinetin supply is necessary to maintain bud elongation. At the apical, subapical, and foliar levels, inhibited cotyledonary buds contain a majority of nuclei with 2C DNA content, in the G1 phase of the cell cycle. Following hormonal treatment, the prereplicative phase of the noncycling cells is at least 6 h in the whole bud. The lag period for the release of bud growth is between 15 and 23 h in subapical regions (first and second internodes) and between 23 and 38 h at the foliar level. At subapical and foliar levels, a few mitoses precede and then follow the elongation process. The first mitoses are from G2 nuclei of the inhibited bud. The followin...
01 Jan 1981
TL;DR: In this paper, the cytokinin activity of 1,3-diphenylurea (DPU) was investigated in the tobacco bioassay and it was concluded that DPU has a definite cytokinIN activity, giving ca 4 g of callus at 10 ppm.
Abstract: About 17 years ago, when Okamoto et al. had been studying azaindene compounds [1] (e.g., 8-benzylamino-2-methyl-s-triazolo[l,5-a]pyridine, 4(7)-benzylaminobenzimidazole, etc.) which have no purine ring yet have apparently analogous chemical structure to N6-benzyladenine (BA) or kinetin (K), it was suspected that they might have antagonistic effect on BA or K in the tobacco bioassay. But the result was that they showed cytokinin activity and gave ca 4 g of fr. wt of callus at 10 ppm, while BA and K gave similar callus yield at 0.01 ppm in the same bioassay. We were also interested in 1,3-diphenylurea (DPU). Because there were many papers reporting the cytokinin activity of DPU [1, 2], but perhaps owing to the difference of bioassay methods and also possibly its low solubility in H2O, the results differed one from the other and it was generally concluded that its cytokinin activity is low and sporadic. We intended to clarify this confusion, and tested DPU in the tobacco bioassay many times carefully and concluded that DPU has a definite cytokinin activity, giving ca 4 g of callus at 10 ppm [1].