Showing papers on "Kinetin published in 1982"

Inhibition of cytokinin-induced plant growth by jasmonic acid and its methyl ester

Abstract: Effects of jasmonic acid, methyl jasmonate and ABA on cytokinin-induced soybean (Glycine max Merrill cv. Kingen No. 1) callus growth and radish (Raphanus sativus L. cv. Comet) cotyledon growth were studied. Jasmonic acid and methyl jasmonate were powerful inhibitors of kinetin- or N-phenyl-N′-(2-chloro-4-pyridyl)urea-induced soybean callus growth, the former being more effective than the latter, especially at low concentrations (0.45 to 4.5 μM). These compounds could completely eliminate kinetin- or N-phenyl-N′-(2-chloro-4-pyridyl)urea-induced soybean callus growth at 45 μM. At low concentrations ABA had no effect but at 450 μM it completely eliminated callus growth induced by kinetin. Of the compounds tested ABA was the most powerful inhibitor of radish cotyledon growth in the presence or absence of kinetin. Jasmonic acid and methyl jasmonate were much less effective than ABA in this assay system.

Plant Regeneration from Callus Culture in Wheat 1

Abstract: Plant regeneration was investigated from embryo-callus culture in bread wheat, Triticum aestivurn L. Immature embryos of cultivar ‘Maris Huntsman’ were cultured on half-strength Murashlge and Skoog's medium (half-MS) supplemented with 0.5 mg 2,4-D[(2,4-dichlorophenoxy) acetic acid], 3.2 mg IAA (indole-3-acetic acid) and 1.0 mg kinetin [6-(furfurylamino) purlne]/liter or without kinetin. On medium with 2,4-D, IAA and kinetin, 77% of the embryos produced a visible callus within 2 weeks. On medium without kinetin, all embryos produced a callus. Calll were cloned and maintained for over 900 days by subculturing at 50 to 60 days interval on half-MS medium with 0.5 mg 2,4-D/llter but regeneration ceased after 680 days. Calli showed organogenesis within 120 days of subculture on half-MS medium with 0.5 mg 2,4-D and 1.0 mg zeatin [6-(4-hydroxy-3-methyl but-2 enylamlno) amino purine]/liter. Plantlets originated from callus by differentiation into shoot-primordia and bipolar structures. Plantlets produced roots on half-MS medium without growth regulators; however, 1.0 mg naphthalene acetic acld/llter in the medium promoted rooting. Regenerated plants included variants for plant height, stem thickness, leaf size, spike shape, pollen fertility and seed set.

Cytokinins as inhibitors of root growth

Abstract: The elongation of roots of wheat (Triticum aestivum L. cv. Diamant II), flax (Linum usitatissimum L. cv. Concurrent) and cucumber (Cucumis sativus L. cv. Favor) seedlings in the dark was strongly inhibited by various native and synthetic cytokinins (kinetin, benzyladenine, isopentenyladenine, zeatin and their corresponding 9-ribosides). An inhibition of 50% was obtained for wheat roots with 3 · 10−9M zeatin and for flax roots with 6 · 10−9M isopentenyladenine. The ribosides were in all cases less inhibitory. The inhibition was reversed by various types of ‘antiauxins’ and ‘antiethylenes’ (such as structural auxin analogues, uncouplers, specific inhibitors of ethylene synthesis, free radical scavengers, inhibitors of ethylene action). These substances as a rule counteract also inhibitions caused by auxins. Auxins and cytokinins stimulate ethylene production synergistically, and the similar inhibitory effects of these two types of hormone can be understood if it is assumed that their effect is at least partly mediated through ethylene. The cytokinins must be considered as possible natural inhibitors and regulators of root growth.

An Improved Bioassay for Cytokinins Using Cucumber Cotyledons

Abstract: The cucumber cotyledon greening bioassay is frequently used for detecting cytokinins. Beneficial modifications of the original technique included using 5-day-old cucumber (Cucumus sativus L., cv. National Pickling) cotyledons treated with combinations of 40 millimolar KCl and various concentrations of cytokinins. A dark incubation period of 20 hours was followed by an exposure to light for 3.5 hours. Under these conditions, extremely low (0.0001 milligram per liter) concentrations of N6-benzyladenine, zeatin, kinetin, or zeatin riboside can be detected. Of the four cytokinins tested, kinetin appeared to be the least active. With these improvements, the assay is 10 times more sensitive than is the previously described cucumber cotyledon greening bioassay for cytokinins.

Regeneration of plants

Abstract: Not available – first paragraph follows: Reporting his pioneering experiments on plant cell culture to the German Academy of Science in 1902, G. Haberlandt predicted that someday “in this way one could successfully cultivate embryos from vegetative cells.” Had IAA and kinetin been at his disposal, Haberlandt might have realized his prediction, and there is no telling how much further plant cell culture might be today.

Kinetin application to roots and its effect on uptake, translocation and distribution of nitrogen in wheat (Triticum aestivum) grown with a split root system

Abstract: Simpson, R. J., Lambers, H. and Balling, M. J. 1982. Kinetin application to roots andits effect on uptake, translocation and distribution of nitrogen in wheat (Triticumaestivum) grown with a split root system. - Physiol, Plant, 56: 430-435,The root systems of wheat seedlings {Triticum aestivum L. cv. SUN 9E) were prunedto two seminal roots. One of the roots was supplied with a suboptimal level of NOj,the other was deprived of N, Different levels of kinetin were supplied to the NOj-de-prived roots. Root respiration and the iocrement of C and N in the roots weremeasured to determine the C/N ratio of the phloem sap feeding the NO^-deprivedroots. Thus, it was possible to determine retranslocation of N from the shoots to theroots, as affected by tiie rate of kinetin application. It was calculated that the C/Nratio of phloem sap feeding roots growing without kinetin was ca 61. Kinetin appiica-tion increased this ratio to ca 75, partly due to decreased translocation of N from theshoots back to the roots. Kinetin application decreased the proportion of N that wasretranslocated to the roots after translocation to the shoots. Kinetin inereased therate of NO3 uptake per root and the rate of N incorporation in both roots and shootsby ca 60%, but had no effect on shoot dry matter production. In control plants atmost 70% of the N incorporated in the NOj-fed roots could have been importedfrom the shoots, whilst kinetin application reduced this vaiue to ca 40%. Thus rootgrowth was not fully dependent on a supply of N via the phloem.It is concluded that cytoltinins affect the pattern of N-translocation in wheat plants byincreasing incorporation of N in dry matter of the shoot, thus leaving less for export.Cytokinins did not play a major role in the regulation of shoot growth and the shootto root ratio of the present plants.Additional key word — Cytokinins.R. J. Simpson (present address), Dept. of Agronomy, Univ. of Wisconsin-Madison,Madison, WI 53706, U.S.A.; H. Lambers (present address), Dept. of PlantPhysiology, Univ. of Groningen, P.O. Box 14, 9750 A A Haren (Gn), The Nether-lands; M. J. Dailing (reprint requests). Plant Sciences Section, School of Agricultureand Forestry, Univ. of Melbourne, Parkville, Victoria 3052, Australia.

Studies on the mechanisms of ozone tolerance: Cytokinin-like activity of N-[2-(2-oxo-1-imidazolidinyl)ethyl]-N'-phenylurea, a compound protecting against ozone injury

Abstract: The cytokinin-like activity of the growth regulating chemical EDU, N-[2-(2-oxo-1-imidazolidinyl)ethyl]-N′-phenylurea, was determined and compared with the actitivity of kinetin using the tobacco callus bioassay. EDU has a pronounced stimulatory effect on callus growth at concentrations of 5 × 10−4 and 1 × 10−3M but was 5 000 times less potent than the synthetic cytokinin, kinetin. Senescence regulation and oxidant resistance induced by EDU and kinetin were also studied. EDU retarded the breakdown of chlorophyll, protein and RNA in 03-sensitive tobacco leaf discs during senescence. EDU was much more effective in arresting senescence and in protecting against 03 injury than kinetin. Results indicate the EDU-induced plant tolerance to 03 phytotoxicity may be indirect through enzyme induction regulation.

Somatic embryogenesis in the opium poppy, Papaver somniferum

Abstract: A procedure is described for the induction of somatic embryos in the opium poppy. Papaver somniferum L. Callus was obtained from seedling hypocotyls on an agar solidified medium [Murashige and Skoog (1962) Physiol. Plant. 15: 473–497] containing 0.25 mg/l (1.2 μM) kinetin and 2.0 mg/l (10.7 μM) naphtalene acetic acid (NAA). Suspension cultures were initiated from callus using a liquid medium in which 2.0 mg/l (9.0 μM) 2,4-dichlorophenoxyacetic acid was substituted for NAA. Meristemoids, spheres of closely packed cells, developed in suspensions and on the surface of a few callus cultures. Differentiation of meristemoids into somatic embryos was accomplished by removing growth regulators from the liquid medium. Embryoids appeared morphologically normal and similar to torpedo stage embryos, however, they possessed mature tracheary elements and laticifers in areas that should have contained only procambium. Whole plants have been obtained by placing embryos in the light on solid medium that also lacked growth regulators.

Graft formation in cultured, explanted internodes

Abstract: Summary A novel method is described in which the two halves of an explanted internode of Lycopersicon esculentum, Datura stramonium or Nicandra physaloides may be grafted together successfully in sterile culture. An absolute requirement for the formation of a successful graft is the application of indole-3-acetic acid (IAA at 0.2 to 2.0 mg l−1) to the apical end of the internode. The addition of kinetin (0.2 mg l−1) to the culture medium stimulated graft development but gibberellic acid (GA3 at 0−5 mg l−1) was inhibitory. The development of the graft as measured by an increase in mechanical strength and the formation of vascular connections was similar to that observed in whole plant grafts; however, fewer differentiated wound vessel members (WVMs) were detected. This technique should provide a powerful tool for the further study of graft development in compatible and incompatible combinations.

Role of Cytokinin in Differentiation of Secondary Xylem Fibers

Abstract: The differentiation of secondary xylem fibers was studied in cultured hypocotyl segments of Helianthus annuus L. It is shown that cytokinin is both a limiting and controlling factor in the early stages of fiber differentiation. In the absence of kinetin or zeatin, there was no fiber differentiation. However, cytokinin could induce fiber differentiation only in the presence of indoleacetic and gibberellic acids. First fibers were observed in the tissue after 12 days in culture, and their number increased linearly during the following 2 weeks. At low cytokinin levels, there was a positive correlation between cytokinin concentration in the medium and the number of fibers formed in the explants. A similar correlation was also found at low gibberellic acid concentrations. At high concentration, zeatin was more effective than kinetin. It seems that later stages of fiber differentiation can occur in the absence of cytokinin. It is proposed that the mechanism which controls and determines the early stages of fiber differentiation is based on an interaction of three major hormonal signals: indoleacetic acid plus gibberellic acid from the leaves with zeatin from the root apices.

Does Ethylene Play a Role in the Release of Lateral Buds (Tillers) from Apical Dominance in Oats

Abstract: The growth of lateral buds (tillers), which are undergoing release from apical dominance, was measured in upright and gravistimulated intact Avena sativa L. cv. ;Victory' (oat) shoots as well as in isolated Avena stem segments treated with kinetin and sucrose. During release, the tiller bud initially shows a slow rate of elongation accompanied by swelling. It is followed by a more rapid rate of elongation. Ethylene (C(2)H(4)) production in shoot segments containing a tiller bud was found to occur at the onset of tiller swelling during gravistimulation as well as during inflorescence emergence. Exogenous application of indoleacetic acid or C(2)H(4) inhibits kinetin-induced tiller bud swelling and elongation. However, stem segments pulsed for 24 hours in C(2)H(4) or the C(2)H(4) biosynthesis precursor, 1-amino-cyclopropane-1-carboxylic acid (ACC) and then transferred to kinetin and sucrose, showed a significant increase in swelling elongation as compared with segments maintained under the same conditions but without C(2)H(4) or ACC in the pulse. Segments pulsed for 24 hours with kinetin and sucrose plus the ACC biosynthesis inhibitor, aminoethoxyvinylglycine, or the C(2)H(4) action inhibitor, CO(2), then transferred to kinetin and sucrose medium, showed inhibition of tiller swelling during the pulse and of subsequent elongation. These results indicate that C(2)H(4) plays a role in promoting tiller swelling during the onset of tiller release from apical dominance and may act as a modulator hormone in promoting tiller elongation in the presence of cytokinin.

Recent advances in anther culture of Hevea brasiliensis (Muell.-Arg.).

Abstract: The yield of pollen embryoids from cultured Hevea anthers was increased 4 fold by optimizing the proportion of ammonium nitrate to potassium nitrate in the dedifferentiation medium. For optimal differentiation of pollen embryoids, kinetin, 2,4-D and α-naphtalene acetic acid are required. Anther culture for 50 days on the dedifferentiation medium is a prerequisite for the selective development of calli and embryoids from microspores.

Plant regeneration from callus culture in potato

Abstract: A procedure for plant regeneration from callus culture of potato, Solanum tuberosum L. is described. Calli were induced from 1–2 mm long shoot apices of potato cultivars Cara and A25/19 on half-strength Murashige and Skoog's medium (half-MS) supplemented with 3.2 mg IAA (indole-3-acetic acid), 1.0 mg kinetin (6-furfurylamino)purine], and 0.5 mg 2,4-D [2,4-dichlorophenoxy)acetic acid]/1. Sixty percent explants produced nodular calli on this medium within 30 days. Calli differentiated into shoot-primordia when subcultured on half-MS medium supplemented with 0.5 mg 2,4-D and 1.0 mg zeatin [6-(4-hydroxy-3-methybut-2 enylamino)amino purine]/1. Differentiated calli on half-MS medium without growth hormones produced complete plantlets which were cloned on the same medium and transferred into soil.

The effect of abscisic acid and cytokinins on the cold hardiness of winter wheat

Abstract: The effect of abscisic acid (ABA) and the cytokinins benzyladenine (BA) and kinetin on the cold hardiness of winter wheat (Triticum aestivum L.) was investigated by controlled freeze tests. ABA or BA applied as a foliar spray to nonacclimated plants or to plants acclimated for 1 week had no measurable effect on crown cold hardiness. The crown water content of winter wheat plants grown in nutrient solution supplemented with BA or kinetin decreased by twofold but cold hardiness was not increased. Thus, a reduction in water content alone does not necessarily result in increased cold hardiness. After 7 days of hardening ABA added with BA increased cold hardiness of crowns 3 to 4 °C depending upon the treatment.

Effect of cytokinin and cultivar on shoot formation of Gerbera jamesonii in vitro

Abstract: The success of gerbera clonal propagation in vitro, using either capitulum explants or subcultured shoots in trials with up to 28 cvs, depended both on the cv. and on the cytokinin level in the medium. With capitulum explants, shoot formation was very low for some cvs regardless of the level of BA (5, 10 or 20 mg/l) whereas other cvs had individual optimum BA levels. Axillary branching of subcultured shoots differed between cvs and between levels of kinetin (1, 5 or 10 mg/l) in the medium. The optimum level for the highest quality shoots (highest leaf weight/shoot, no leaf malformation and no callus formation) was not always the same as the level producing the highest number of axillary shoots. Results are tabulated for each cv. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Stomatal responses of Argenteum - a mutant of Pisum sativum L. with readily detachable leaf epidermis.

Abstract: Epidermis is easily detached from both adaxial and abaxial surfaces of leaf four of the Argenteum mutant of Pisum sativum L. The isolated epidermis has stomata with large, easily-measured pores. Hairs and glands are absent. The density of stomata is high and contamination by mesophyll cells is low. In the light and in CO2-free air, stomata in isolated adaxial epidermis of Argenteum mutant opened maximally after 4 h incubation at 25°C. The response of stomata to light was dependent on the concentration of KCl in the incubation medium and was maximal at 50 mol m-3 KCl. Stomata did not respond to exogenous kinetin, but apertures were reduced by incubation of epidermis on solutions containing between 10-5 and 10-1 mol m-3 abscisic acid (ABA). The responses of stomata of Argenteum mutant to light, exogenous KCl, ABA and kinetin were comparable with those described previously for stomata in isolated epidermis of Commelina communis. A method for preparing viable protoplasts of guard cells from isolated epidermis of Argenteum mutant is described. The response of guard cell protoplasts to light, exogenous KCl, ABA and kinetin were similar to those of stomata in isolated epidermis except that the increase in volume of the protoplasts in response to light was maximal at a lower concentration of KCl (10 mol m-3) and that protoplasts responded more rapidly to light than stomata in isolated epidermis. The protoplasts did not respond to exogenous kinetin, but when incubated for 1 h in the light and in CO2-free air on a solution containing 10-3 mol m-3 ABA, they decreased in volume by 30%. The advantages of using epidermis from Argenteum mutant for experiments on stomatal movements are discussed.

Seed Dormancy in Red Rice (Oryza sativa). II. Response to Cytokinins

Abstract: Dormant, dehulled red rice (Oryza sativa L. 'Louisi- ana strawhulled') germinated 80 to 90% at 30 C upon exposure to 10-3 M kinetin (6-furfurylaminopurine), benzyladenine (6 - benzylaminopurine), or isopentenyladenine (6 - (3 - meth - ylbut- 2 - enylamino)purinel at pH 3.5. Zeatin (6 - (4 - hydroxy- 3 -methylbut - trans -2 - enylamino)purineI was also active, eliciting 45% germination at 10-3 M. Adenine was inactive at concentrations as high as 10-2 M. There was little influence of light and no effect of initial pH of the medium upon cytokinin- stimulated germination. At 20 C the response to cytokinins was reduced, but germination of non-dormant seeds was not prevented. At 30 C, the germination of dehulled red rice with 10-3 M kinetin occurred rapidly, with almost 70% germination after 2 days. When dehulled seeds were incubated in water and then transferred to kinetin, percent germination decreased as the duration of water incubation increased. The loss of cytokinin response did not parallel the timecourse of imbibition. Cytokinins did not break dor- mancy of intact seeds. The hull appeared to limit kinetin uptake and inhibited germination even when kinetin was forced into intact seeds by vacuum infiltration. Dry-after- ripening of intact seeds at 30 C did not increase the kinetin- sensitivity of intact red rice. Additional index words. Germination, kinetin, benzyladenine, isopentenyladenine, zeatin.

In vitro clonal multiplication of mature trees of Dalbergia sissoo Roxb.

Abstract: Multiple shoots were obtained from nodal explants of 30-year-old trees of Dalbergia sissoo Roxb. on a defined medium, MS (Murashige & Skoog medium) supplemented with auxin-cytokinin combinations. IAA (Indole accetic acid) alone promoted 15% rooted shoot buds. A combination of IAA+Kn (Kinetin) gave 100% rooted shoot buds. A combination of NAA (napthaleneacetic acid) + Kn and NAA+BAP (6-benzylaminopurine) also gave high percentages of rooted shoot buds. Ascorbic acid in the medium prevented the death of callus and plantlets, which followed darkening of the medium.

Effects of Kinetin on Formation of Scopoletin and Scopolin in Tobacco Tissue Cultures

Abstract: Kinetin increased the formation of scopoletin and scopolin in tobacco tissue cultures. The formation of scopolin was increased more in the presence of both kinetin (KIN) and l-phenylalanine (Phe) in the medium than in the case of either KIN or Phe alone. The activity of l-phenylalanine ammonia-lyase (PAL) was increased by the addition of KIN. The increase of PAL activity was inhibited by actinomycin-D and cycloheximide added at the same time as the KIN, but actinomycin-D did not inhibit the increase when added at 8 hr after the addition of KIN at which time cycloheximide inhibited it still. The incorporation of [U-14C]-Phe into scopoletin and scopolin was stimulated by KIN, but its incorporation into protein and lignin was not affected. These results suggest that KIN increased de novo synthesis of PAL through its mRNA, and the enhanced activity of PAL resulted in the increase of scopoletin and scopolin formation.