Effect Of Cytokinins Research Articles

The Plant Hormone Cytokinin Confers Protection against Oxidative Stress in Mammalian Cells

Modulating key dynamics of plant growth and development, the effects of the plant hormone cytokinin on animal cells gained much attention recently. Most previous studies on cytokinin effects on mammalian cells have been conducted with elevated cytokinin concentration (in the μM range). However, to examine physiologically relevant dose effects of cytokinins on animal cells, we systematically analyzed the impact of kinetin in cultured cells at low and high concentrations (1nM-10μM) and examined cytotoxic and genotoxic conditions. We furthermore measured the intrinsic antioxidant activity of kinetin in a cell-free system using the Ferric Reducing Antioxidant Power assay and in cells using the dihydroethidium staining method. Monitoring viability, we looked at kinetin effects in mammalian cells such as HL60 cells, HaCaT human keratinocyte cells, NRK rat epithelial kidney cells and human peripheral lymphocytes. Kinetin manifests no antioxidant activity in the cell free system and high doses of kinetin (500 nM and higher) reduce cell viability and mediate DNA damage in vitro. In contrast, low doses (concentrations up to 100 nM) of kinetin confer protection in cells against oxidative stress. Moreover, our results show that pretreatment of the cells with kinetin significantly reduces 4-nitroquinoline 1-oxide mediated reactive oxygen species production. Also, pretreatment with kinetin retains cellular GSH levels when they are also treated with the GSH-depleting agent patulin. Our results explicitly show that low kinetin doses reduce apoptosis and protect cells from oxidative stress mediated cell death. Future studies on the interaction between cytokinins and human cellular pathway targets will be intriguing.

Production of cytotoxic compounds in dedifferentiated cells of Jatropha curcas L. (Euphorbiaceae).

This study addresses the in vitro culture as an alternative to obtain compounds with cytotoxic activity from the medicinal plant Jatropha curcas (Euphorbiaceae). We determined the presence of cytotoxic compounds in both whole plants and dedifferentiated cells. We evaluated the effect of auxin, cytokinins and light on callus induction in cotyledon explants. We found that the most effective combination to induce callus was the auxin 2,4-D (5 mM) with the cytokinin 6-BAP (2.5 mM), on Murashige-Skoog medium in darkness. We compared the callogenic potential among accessions from different geographic origins, finding that ARR-251107-MFG7 is most prone to form callus. The roots of J. curcas grown in field produced a compound chromatographically similar to the cytotoxic diterpene jatrophone. The profile of compounds extracted from the dedifferentiated cells was similar to that of the whole plant, including a relatively abundant stilbene-like compound. This study contributes to the future establishment of protocols to produce anti-cancer compounds from J. curcas cultivated in vitro.

Multiple phytohormones promote root hair elongation by regulating a similar set of genes in the root epidermis in Arabidopsis.

Multiple phytohormones, including auxin, ethylene, and cytokinin, play vital roles in regulating cell development in the root epidermis. However, their interactions in specific root hair cell developmental stages are largely unexplored. To bridge this gap, we employed genetic and pharmacological approaches as well as transcriptional analysis in order to dissect their distinct and overlapping roles in root hair initiation and elongation in Arabidopsis thaliana Our results show that among auxin, ethylene, and cytokinin, only ethylene induces ectopic root hair cells in wild-type plants, implying a special role of ethylene in the hair initiation stage. In the subsequent elongation stage, however, auxin, ethylene, and cytokinin enhance root hair tip growth equally. Our data also suggest that the effect of cytokinin is independent from auxin and ethylene in this process. Exogenous cytokinin restores root hair elongation when the auxin and ethylene signal is defective, whereas auxin and ethylene also sustain elongation in the absence of the cytokinin signal. Notably, transcriptional analyses demonstrated that auxin, ethylene, and cytokinin regulate a similar set of root hair-specific genes. Together these analyses provide important clues regarding the mechanism of hormonal interactions and regulation in the formation of single-cell structures.

Influence of Plant Growth Regulators and Medium Strength on Micropropagation of the Biodiesel Plant, Jatropha curcus

Leaf explants were cultured to evaluate the effect of different auxins and cytokinins and its concentrations; MS salts on micropropagation of the promising biodiesel Jatropha curcas plant under Egyptian conditions. Results showed that shoot initiated on 0.5 mg/l BA + 0.25 mg/l IBA. Multiplication and elongation were found to be the best using 0.5 mg/l BA in combination with 0.05 mg/l IBA. The multiple shoots were cultured on MS or half strength of MS supplemented with different concentrations of IAA and IBA for rooting phase. Half strength of MS containing 1.0 mg/l IAA was the best for rooting of micropropagated shoots. The rooted plantlets were acclimated in sand : peat?moss mixture (1 : 1) successfully.Plant Tissue Cult. & Biotech. 26(1): 85-96, 2016 (June)

High-frequency Direct Somatic Embryogenesis and Plantlet Regeneration from Leaves Derived from In Vitro-Germinated Seedlings of a Coffea arabica Hybrid Cultivar

Breeding work carried out during the period 1971–85 by the Coffee Research Institute, Ruiru, Kenya resulted in the release of a new improved hybrid Coffea arabica named Ruiru 11. The cultivar combines resistance to coffee berry disease (CBD) and leaf rust, with high yield and good cup quality attributes. The propagation by F1 hybrid seeds production, cuttings, and tip grafting do not produce enough planting materials. There was a need to explore alternative methods and tissue culture offers potential options. The objective of the study was to evaluate the effect of explant sources and cytokinins on induction and regeneration of somatic embryos. Eight different explants were cultured on half-strength Murashige and Skoog (MS) medium supplemented with 10 µm benzylaminopurine (BAP). The effect of kinetin, N6-(2-isopentyl) adenine (2iP) evaluated at (0, 0.5, 5, or 25 µm) or thidiazuron (TDZ) (0, 0.5, 1.0, or 5 µm) added in separate experiments was also evaluated. The percentage of embryogenic cultures and the numbers of embryos per explant were determined after 3 months’ culture. The explant type had a significant effect (P > 0.05) on the induction of somatic embryos. Explants from in vitro-germinated seedlings produced the highest embryogenic cultures (90%) and the highest mean number of embryos (19.36) per explant. Cytokinins strongly enhanced induction and regeneration of somatic embryos. TDZ at 1 µm produced the highest embryogenic cultures (100%) and the highest mean number of embryos (24.2). The embryos were germinated on half-strength MS medium without any hormones. A high (98%) survival rate of the regenerated plantlets was recorded over all the treatments in the greenhouse. This is the first report on induction of high-frequency direct somatic embryos from coffee juvenile tissues. This is of great significance in tissue culture and indeed molecular biology manipulations because it allows regeneration of coffee from several explants.

Induksi Tunas pada Kotiledon dan Hipokotil Tanaman Jarak Pagar (Jatropha curcas L.) melalui Organogenesis Tak Langsung

<p>Propagation through tissue culture of plant<br />species with rich secondary metabolites such as Jatropha<br />curcas L. is difficult to obtain. However, once established, it<br />can be used as one of the alternatives to supply uniform<br />propagules. The effects of auxin and cytokinin on the<br />regulation of de novo woody plants shoot development have<br />been studied through shoot induction, differentiation and<br />development. The objective of this research was to identify<br />explant and suitable culture media for in vitro shoot induction<br />through indirect organogenesis. Factorial experiment<br />was arranged in a completely randomized design, replicated<br />20 times. The first factor was explants, i.e. cotyledons and<br />hypocotyls. The second factor was MS media containing<br />combination of plant growth regulator IAA (0, 0.05, and 0.1<br />mg/l) and BAP (0, 1.0, 2.0, 3.0 mg/l). The results of the<br />experiment showed that the fastest callus initiation was<br />achieved by MS + IAA 0.1 mg/l, i.e. 9.5 days after explants<br />were cultured. Shoots with leaves can be induced from both<br />cotyledons and hypocotyls. However, hypocotyls gave more<br />shoots and leaves than cotyledons when cultured in MS +<br />IAA 0.1 mg/l + BAP 3.0 mg/l. Shoots obtain from hypocotyls<br />and cotyledons were successfully rooted in MS medium<br />without any growth regulator.</p>

Pengaruh Sitokinin, Jenis Eksplan, dan Genotipe terhadap Embriogenesis Somatik Kakao

<p><em>Information on the effect of cytokinins on cacao (</em>Theobroma cacao<em> L.) primary somatic embryogenesis and its interaction with explant types and genotypes is not yet known. This study aimed to evaluate the effect of cytokinins and its interaction with explant types and genotypes on cacao somatic embryogenesis. The study was conducted at tissue culture laboratory of IAARD, Bogor from April until December 2012 and October 2014 until February 2016. Three types of cytokinins i.e. kinetin (0.58, 1.16, and 2.32 </em><em>μ</em><em>M), thidiazuron (0.01, 0.02, and 0.04 </em><em>μ</em><em>M) and benzylaminopurine (0.55, 1.11, and 2.22 </em><em>μ</em><em>M) in combination with 9 </em><em>μ</em><em>M 2,4-D were tested for their effectiveness in inducing somatic embryogenesis from petals and staminoid explants of Cimanggu 1 genotype. Furthermore, three levels of kinetin (0.58, 1.16, and 2.32 </em><em>μ</em><em>M</em><em>) also in combination with 9 </em><em>μ</em><em>M 2,4-D were evaluated for their influences on the somatic embryogenesis from petals and staminoid explants of three cacao genotypes i.e. Sulawesi 02, ICCRI 04 and Cimanggu 3. The result demonstrated that 2.32 </em><em>μ</em><em>M kinetin and staminoids explant were more effective to induce cacao somatic embryogenesis of Cimanggu 1 genotype (7%, 0.23 embryos/explant). Additionally, there were interaction effects between the level of kinetin with explant types and genotype on the percentage of explants forming embryo at 12 weeks after culture. The highest percentage of somatic embryo formation was shown by ICCRI 04 genotype with the use of petals explant and a kinetin level of 1.16 </em><em>μ</em><em>M (31.85%), but not significantly different from the level of kinetin 2.23 </em><em>μ</em><em>M (25.55%). The formation of primary somatic embryos of cacao is largely determined by the type and level of cytokinins, type of explant, and genotype.</em></p>

Effects of cytokinins on physiological and biochemical responses of the agar-producing red alga Gracilaria caudata (Gracilariales, Rhodophyta)

The red alga Gracilaria caudata J. Agardh (Gracilariales) is commercially exploited in Brazil as a source of raw material for agar production, and its cultivation is needed for sustainable biomass production to avoid overexploitation of natural populations. The objective of the present study was to evaluate the effects of aromatic and isoprenoid-derived cytokinins under two photon flux densities (PFDs) on growth rates, formation of lateral branches, pigment content (chlorophyll a and phycobiliproteins), and total soluble proteins in G. caudata. Aromatic cytokinins (benzylaminopurine, BA, and kinetin, K) and isoprenoid cytokinins (2-isopentenyladenine, 2iP, cis-zeatin, and trans-zeatin) were tested at 50 and 100 μmol photons m−2 s−1, temperature of 23 ± 1 °C, and light:dark cycle of 14:10 h. Cytokinins were added to the ASP 12-NTA synthetic medium (salinity 30 PSU, pH 8.0) in concentrations ranging from 0.0 to 50.0 μM. Growth rates of G. caudata were not affected by addition of isoprenoid and aromatic cytokinins. Zeatins (cis and trans forms) and BA at the concentrations of 0.5 and/or 5.0 μM stimulated the branch formation at 100 μmol photons m−2 s−1. In general, concentrations of isoprenoid cytokinins showed negative correlation with total soluble proteins and pigment contents at both PFDs. On the other hand, aromatic cytokinins did not affect protein contents, and K inhibited the pigment contents in both PFD levels. In conclusion, our results indicate that the isoprenoid and aromatic cytokinins and PFD levels did not affect the growth rates of G. caudata, but influence the branching and contents of pigments and total soluble proteins. Moreover, aromatic cytokinins and zeatins stimulated branch formation, which is a morphogenetic process useful for micropropagation of G. caudata, and could improve its cultivation in the Brazilian coast.

Cytokinin Regulates the Etioplast-Chloroplast Transition through the Two-Component Signaling System and Activation of Chloroplast-Related Genes.

One of the classical functions of the plant hormone cytokinin is the regulation of plastid development, but the underlying molecular mechanisms remain elusive. In this study, we employed a genetic approach to evaluate the role of cytokinin and its signaling pathway in the light-induced development of chloroplasts from etioplasts in Arabidopsis (Arabidopsis thaliana). Cytokinin increases the rate of greening and stimulates ultrastructural changes characteristic for the etioplast-to-chloroplast transition. The steady-state levels of metabolites of the tetrapyrrole biosynthesis pathway leading to the production of chlorophyll are enhanced by cytokinin. This effect of cytokinin on metabolite levels arises due to the modulation of expression for chlorophyll biosynthesis genes such as HEMA1, GUN4, GUN5, and CHLM Increased expression of HEMA1 is reflected in an enhanced level of the encoded glutamyl-tRNA reductase, which catalyzes one of the rate-limiting steps of chlorophyll biosynthesis. Mutant analysis indicates that the cytokinin receptors ARABIDOPSIS HIS KINASE2 (AHK2) and AHK3 play a central role in this process. Furthermore, the B-type ARABIDOPSIS RESPONSE REGULATOR1 (ARR1), ARR10, and ARR12 play an important role in mediating the transcriptional output during etioplast-chloroplast transition. B-type ARRs bind to the promotors of HEMA1 and LHCB6 genes, indicating that cytokinin-dependent transcription factors directly regulate genes of chlorophyll biosynthesis and the light harvesting complex. Together, these results demonstrate an important role for the cytokinin signaling pathway in chloroplast development, with the direct transcriptional regulation of chlorophyll biosynthesis genes as a key aspect for this hormonal control.

Pineapple harvest index and fruit quality improvement by application of gibberellin and cytokinin

Introduction. Gibberellin application alone in Lampung, Indonesia, has not been successful in overcoming the low harvest index of pineapple. Cytokinin is known to promote the allocation of assimilates to sink organs. The effect of gibberellin and cytokinin on the harvest index and fruit quality of pineapple was evaluated in this study. Materials and methods. Three levels of gibberellin (0, 100 and 200 ppm) combined with three levels of cytokinin (0, 24 and 48 ppm) were applied in the 12th and 14th weeks after flowering induction treatment. The experiment was conducted with the pineapple cv. Smooth Cayenne in a randomized complete block design with three replications. Harvest index and fruit quality analyses were carried out in fruits harvested during the 23rd week after flowering induction treatment. Results and discussion. Gibberellin alone (100 or 200 ppm) or combined with cytokinin (24 or 48 ppm) increased the fruit weight, harvest index and fruit crown length – a positive effect on the quality of this planting material – and delayed fruit maturity (5 days) of ‘Smooth Cayenne’ pineapple. Conclusion. Gibberellin and/or cytokinin improved some properties of the pineapple fruit quality. Treatment with 100 ppm of gibberellin combined with 24 ppm of cytokinin was the best treatment for improvement of the pineapple harvest index and fruit quality.

Exogenous Cytokinins Increase Grain Yield of Winter Wheat Cultivars by Improving Stay-Green Characteristics under Heat Stress.

Stay-green, a key trait of wheat, can not only increase the yield of wheat but also its resistance to heat stress during active photosynthesis. Cytokinins are the most potent general coordinator between the stay-green trait and senescence. The objectives of the present study were to identify and assess the effects of cytokinins on the photosynthetic organ and heat resistance in wheat. Two winter wheat cultivars, Wennong 6 (a stay-green cultivar) and Jimai 20 (a control cultivar), were subjected to heat stress treatment from 1 to 5 days after anthesis (DAA). The two cultivars were sprayed daily with 10 mg L-1 of 6-benzylaminopurine (6-BA) between 1 and 3 DAA under ambient and elevated temperature conditions. We found that the heat stress significantly decreased the number of kernels per spike and the grain yield (P < 0.05). Heat stress also decreased the zeatin riboside (ZR) content, but increased the gibberellin (GA3), indole-3-acetic acid (IAA), and abscisic acid (ABA) contents at 3 to 15 DAA. Application of 6-BA significantly (P < 0.05) increased the grain-filling rate, endosperm cell division rate, endosperm cell number, and 1,000-grain weight under heated condition. 6-BA application increased ZR and IAA contents at 3 to 28 DAA, but decreased GA3 and ABA contents. The contents of ZR, ABA, and IAA in kernels were positively and significantly correlated with the grain-filling rate (P < 0.05), whereas GA3 was counter-productive at 3 to 15 DAA. These results suggest that the decrease in grain yield under heat stress was due to a lower ZR content and a higher GA3 content compared to that at elevated temperature during the early development of the kernels, which resulted in less kernel number and lower grain-filling rate. The results also provide essential information for further utilization of the cytokinin substances in the cultivation of heat-resistant wheat.

Cost Effective Techniques for In Vitro Propagation of Two Varieties of Sugarcane

The present study was carried out to optimize cost effective in vitro protocol for mass propagation of two commercial sugarcane varieties grown in Maharashtra, India. The effect of different cytokinins and auxins on in vitro initiation, multiplication and rooting was investigated in sugarcane (Saccharum spp.) varieties; Co86032 and CoC671. Shoot tip explants comprising of apical meristems and 1-2 leaf primordia were carefully excised from the apical region and inoculated on MS basal liquid medium supplemented with different concentrations and combinations of Kinetin and BAP. Only initiation medium was sterilized by autoclaving and further shoot multiplication, rooting was done on medium sterilized with sodium hypochlorite (4% w/v available chlorine) at the concentrations 0.05% corresponding to total active chlorine concentration 0.002% in the medium. With regard to shoot initiation, variety Co86032 showed maximum shoot formation (96.67%) on MS medium supplemented with BAP (0.2mg/L) and Kinetin (0.1mg/L) with 3% sucrose and 10% CW on the other hand variety CoC671 showed maximum shoot formation (93.33%) on MS medium supplemented with only Kinetin( 0.5mg/L), 3% sucrose, 10% CW. The best response in terms of shoot multiplication for variety Co86032 was observed on MS medium with BAP (0.2mg/L) and Kinetin (0.1mg/L)with 3% commercial sugar while for variety CoC671 it was observed on MS medium with Kinetin and BAP (0.2mg/L each) and 3.0% commercial sugar. Variety Co86032 produced multiple shoots with an average number of 31.25±0.99 shoots per bottle while variety CoC671 produced 27.72±0.66 shoots per bottle. For rooting, the multiplying shoots were separated in smaller groups and transferred on half strength MS liquid medium containing different concentrations of NAA or IBA with different concentrations of commercial sugar. Half strength MS basal medium with NAA (5.0 mg/L) and 5.0% commercial sugar induced highest rooting (84.44%) with average root number per shoot of 8.49 ±0.25 in Co86032. In variety CoC671, half strength MS basal medium with IBA (5.0 mg/L) and 5.0% commercial sugar induced highest rooting (82.22%) with average root number per shoot of 6.72 ±0.48. The use of commercial sugar can effectively replace the use of expensive sucrose in in vitro multiplication of sugarcane varieties. All culture media were used in liquid state instead of semisolid agar media. Rooted shoots were transplanted in green house for hardening. Use of liquid media, chemical sterilant Sodium hypochlorite (NaOCl) and commercial sugar helped in reducing the cost per plantlet to a considerable extent.

Effects of Cytokinin and Nitrogen on Drought Tolerance of Creeping Bentgrass.

Cytokinin (CK) is a vital plant hormone that controls many aspects of growth and development in plants. Nitrogen (N) is the indispensable macronutrient needed in plants and also one of the most important limiting factors for plant growth. This study was designed to investigate the simultaneous effects of CK and N on the visual turf quality and antioxidant metabolism of drought-stressed creeping bentgrass (Agrostis stolonifera L.). ‘PennA-4’ creeping bentgrass treated with trans-zeatin riboside at three rates of CK concentrations of 0, 10 and 100 μM (designated by CK0, 10, and 100) and two nitrogen rates with 2.5 and 7.5 kg N·ha-1 every 15 days (designated by low and high N) in a complete factorial arrangement was grown under two soil moisture regimes: well-watered and drought stress. Exogenous CK improved turf quality and delayed leaf wilting under drought stress, especially under high N. The grasses treated with CK10 and CK100 had lower O2- production and H2O2 concentration than those without CK treatment. The CK100 treatment enhanced the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), and guaiacol peroxidase (POD) by 25%, 22%, 17% and 24%, respectively, relative to CK0. Moreover, the activity changes of the antioxidant enzyme isoforms were more significant under high N condition relative to low N condition. Our results demonstrated the beneficial impacts of CK and N on physiological reactions, especially antioxidant metabolism, and foliar application of CK at 10 or 100 μM plus 7.5 kg ha-1 N biweekly may improve drought stress resistance of creeping bentgrass.

Do cytokinins, volatile isoprenoids and carotenoids synergically delay leaf senescence?

Do cytokinins, volatile isoprenoids and carotenoids synergically delay leaf senescence?

Comparative Organogenic Response of Six Clonal Apple Rootstock Cultivars

The organogenesis potential is different among cultivars and must be optimized for individual genotype. Shoot organogenesis capacity from in vitro leaves and root organogenesis capacity of in vitro shoots in six clonal apple rootstock cultivars were compared. The shoot organogenesis capacity was highly genotype dependent. ‘GM256’ was found to be the most responsive genotype for shoot regeneration from leaf explants among the cultivars, showing high regeneration percentage on all tested media. The effects of basal medium composition and cytokinins on shoot regeneration were different depending on rootstock genotype. Optimum regeneration occurred on Murashige and Skoog (MS) basal medium for ‘71-3-150’, and optimum regeneration occurred on Quoirin and Lepoivre (QL) basal medium for ‘60-160’ and ‘ПБ’. Thidiazuron (TDZ) was more effective than 6-benzylaminopurine (BA) for Malus prunifolia (Y), whereas TDZ and BA were not significantly different for the other cultivars. All rootstock cultivars showed high root organogenic capacity. The percentage of rooting reached more than 90% and the mean root number per plantlet ranged from three to five. The optimum rooting medium was different for different rootstock cultivars. Optimum root organogenesis occurred on half-strength QL medium for ‘GM256’ and ‘Y’, and for ‘ПБ’ and ‘JM7’ on one-quarter-strength MS medium.

Effect of various cytokinins and auxins on in vitro regeneration of plantlets from isolated bud clumps of Silk Banana var. Nanjanagud Rasabale (Musa AAB)

Separated bud clumps of Silk Banana containing single and double buds were transferred on media containing six different cytokinins at three different levels and the proliferation capacity was determined. Proliferation, though occurred in single bud explants, the rate of multiplication was lower when compared with double bud explants, irrespective of the type of cytokinin used. Maximum shoot proliferation was observed in explants cultured on media supplemented with thidiazuron and 2-isopentenyl adenine (2-iP), and was significantly superior when combined with kinetin and BAP. Meta-topolin though reported to be highly efficient in improving multiplication in other banana varieties, no appreciable response was observed during present investigation. Use of NAA (2 mg l−1) was found to promote rooting process with superior root induction parameters and survival.

Callus Induction and Adventitious Shoot Regeneration of Centaurea zeybekii Wagenitz: Endangered Endemic Plant

In this paper we reported the effect of different cytokinins on callus induction and adventitious shoot regeneration from leaf segments of in vitro grown Centaurea zeybekii Wagenitz seedlings. Callus was not induced when the explants were cultured on MS medium devoid of any growth regulators. Callus formation was observed in MS media containing TDZ, BA and KIN. The highest callusing response was observed in the media containing 0.005 mg/Land 0.01 mg/LTDZ (100%). In adventitious shoot induction experiments, well developed shoots were observed only MS media supplemented with KIN at the end of sixth week. The highest number of shoot per explant was obtained from the MS medium containing 1 mg/LKIN (6.2 shoots/explant). The highest average of maximum shoot length was also observed in this medium (4.17 cm). There was no difference between MS and ½ MS media in rooting but it was very low and only 15 % of total shoots could rooted in medium containing 0.5 mg/LIBA.

Tehlike Altındaki Endemik Bitki Centaurea zeybekii Wagenitz ‘nin Kallus İndüksiyonu

In this paper we reported the effect of different cytokinins on callus induction and adventitious shoot regeneration from leaf segments of in vitro grown Centaurea zeybekii Wagenitz seedlings. Callus was not induced when the explants were cultured on MS medium devoid of any growth regulators. Callus formation was observed in MS media containing TDZ, BA and KIN. The highest callusing response was observed in the media containing 0.005 mg/Land 0.01 mg/LTDZ (100%). In adventitious shoot induction experiments, well developed shoots were observed only MS media supplemented with KIN at the end of sixth week. The highest number of shoot per explant was obtained from the MS medium containing 1 mg/LKIN (6.2 shoots/explant). The highest average of maximum shoot length was also observed in this medium (4.17 cm). There was no difference between MS and ½ MS media in rooting but it was very low and only 15 % of total shoots could rooted in medium containing 0.5 mg/LIBA.

CHANGES IN THE CHARACTERISTICS OF ‘PRATA’ BANANA TREATED WITH CYTOKININ AND GIBBERELLIN

ABSTRACT Plant growth regulators can influence fruit yield and quality. This study aimed to evaluate the effect of cytokinin and gibberelin on the agronomic and physicochemical characteristics of banana fruits cv. ‘Prata’ (Musa spp. AAB), according to the formation period and position in the bunch. The experiment was conducted in a completely randomized 2 x 5 factorial design, two periods of bunch development (summer and winter), five treatments and ten replicates. To study the effect of position in the bunch, split plot was adopted, considering in the plot, 2 x 5 factorial and in subplots, hand 1, hand 4 and last hand. Treatments consisted of 2 pulverizations with water, 150 mg L-1 cytokinin, 200 mg L-1 of gibberellic acid, 100 mg L-1 of cytokinin plus 200 mg L-1 of gibberellic acid and 200 mg L-1 of cytokinin plus 200 mg L-1 of gibberellic acid, applied from the fourth to the last hand of the bunch. Cytokinin and gibberellin, alone or associated, regardless of formation period and position, did not affect the size and physicochemical characteristics of fruits, only delayed the bunch harvest.

Effects of variations in culture media and hormonal treatments upon callus induction potential in endosperm explant of Barringtonia racemosa L.

ObjectiveTo induce callus from the medicinally valuable species, Barringtonia racemosa L. (B. racemosa) whereby the formation of callus is essential for micropropagation studies and in vitro plant secondary metabolites production. MethodsThe callus induction potential in B. racemosa was assessed from endosperm explant cultured on different culture media and plant hormonal treatments. Lloyd and McCown's woody plant medium and Murashige and Skoog's medium were used in the study as culture media. On the other hand, various concentrations and combinations of 2,4-dichlorophenoxyacetic acid (1.0–2.0 mg/L) and kinetin (0.5–2.5 mg/L) had been incorporated in the culture media to exert the effects of auxin and cytokinin on callus induction. ResultsFrom the present study, it was found that the profuse [(1.681 ± 0.770) g fresh weight, (0.239 ± 0.239) g dry weight] and friable callus formation was optimally produced with desirable morphology and considerable percentage of callus induction (56.70%) in endosperm explants cultured on 1.0 mg/L 2,4-dichlorophenoxyacetic acid and 1.5 mg/L kinetin in Murashige and Skoog's medium. ConclusionsA reliable protocol for inducing callus formation of profuse and friable morphology in endosperm explant of B. racemosa had therefore been successfully established.