Endogenous hormonal status of embryogenic callus in cocos (Cocos nucifera L.) explants

Trabajo presentado en un evento que no se pudo identificar.The application of optimum concentrations of hormones according to specific culture stages plays an important role, especially in plants which are concerned lo be recalcitrant for propagation in vitro, like Cocos nucifera L. The teasibility of the clonal propagation of coconut via somatic embryogenesis using inmature inflorescences as source of explants has been demostrated by Branton and Blake (1984). But yet there is no advanced technique for the mass producction of clonal palms available. One reason among others might be the inconsistent in vitro responses of coconut cultures observed In various clonal propagation experiments (Ebert. 1993). The present study was done to elucidate the endogenous hormonal changes In coconut explants, focusing on the 4-months period of embryogenic callus formation in rachilla explant cultures.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Centro para Investigaciones en Granos y Semillas (CIGRAS

Hormonal status of maize initial explants and of the embryogenic and non-embryogenic callus cultures derived from them as related to morphogenesis in vitro

Endogenous hormone levels (indole-3-acetic acid [IAA], abscisic acid [ABA], gibberellins 1, 3 and 20 [GAs], zeatin/zeatin riboside [Z/ZR] and N6[Δ2-isopentenyl] adenine/N6[Δ2-isopentenyl] adenosine; [iP/iPA]) were analysed in immature maize zygotic embryos of two maize (Zea mays L.) genotypes, known for their distinct ability to generate embryogenic (E) callus. No differences were found among genotypes in the hormone contents of the embryos. These embryos were also used as initial explants to establish callus cultures. E and non-embryogenic (NE) calli were obtained from the competent genotype (A188), while only NE callus was produced by the incompetent one (B73). The morphogenetic competence of each callus type was evaluated by transferring some segments to regeneration conditions. When analysing the endogenous hormone levels in the various callus types generated in each genotype, it was found that only differences in the IAA levels accounted for variations in the morphogenic properties of the calli. Higher levels of endogenous IAA were typical of embryogenic callus cultures. It was also observed, that a loss in the embryogenic competence of the calli, due to a prolonged time of culture, occurred concomitantly with a reduction in the IAA levels, practically to the levels found in the non-embryogenic calli.German Academic Exchange Service//DAAD/AlemaniaUniversidad de Costa Rica//UCR/Costa RIcaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Centro para Investigaciones en Granos y Semillas (CIGRAS

Relationship between endogenous hormone levels of grapevine callus cultures and their morphogenetic behaviour

Dark callus cultures from leaves and anthers of three grapevine genotypes (Seyval blanc, Riesling and Trollinger) were propagated in vitro for almost two years on medium deprived of growth regulators. Three different callus lines originated from these initial callus cultures: A dark non-embryogenic one, another composed by clusters of somatic embryos and a friable, whitish callus line that can produce somatic embryos under appropriate circumstances, Endogenous hormone levels viz, indole-3-acetic acid (IAA), abscisic acid (ABA), gibberellins A1, A3 and A20, zeatin/zeatin riboside and N6(∆2-isopentenyl) adenine/ N6(∆2-isopentenyl) adenosine, were analysed in the different callus types. Only higher ABA levels correlated with the morphogenetic capacity of the cultures. When endogenous hormone levels were analysed in the line constituted by conglomerates of somatic embryos at different dates during the whole culture period, higher levels of IAA and ABA were found during the winter months even if the cultures were maintained permanently under constant temperature and photoperiod conditions. A 4-week chilling period led to a reduction of the endogenous ABA level.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Centro para Investigaciones en Granos y Semillas (CIGRAS

Endogenous hormone concentrations and embryogenic callus development in wheat

Immature zygotic embryos of two wheat (Triticum aestivum L.) genotypes, known for their different ability to generate embryogenic callus, were used as initial explants to establish callus cultures. Embryogenic and non-embryogenic calluses were obtained from the competent genotype (`Combi'), while only non-embryogenic callus was produced by the incompetent one (`Devon'). The morphogenetic competence of each callus type was evaluated by transferring some segments to regeneration conditions. The endogenous hormone concentrations (free indole-3-acetic acid [IAA], abscisic acid [ABA], gibberellins 1, 3 and 20 [GAs], zeatin/zeatin riboside [Z/ZR] and N6[Δ2-isopentenyl] adenine/ N6[Δ2-isopentenyl] adenosine; [iP/iPA]) of the initial explants were determined by means of radio-immunoassay and showed that the only difference was the higher concentration of ABA found in the embryos of the most competent genotype; whose embryos showed a reduced rate of precocious germination. When analysing the endogenous hormone concentrations in the various callus types generated in each genotype, it was found that only differences in the free IAA concentrations were associated with variations in the morphogenic properties of the calluses. Higher concentrations of endogenous free IAA were typical of embryogenic callus cultures. It was also observed that a loss in the embryogenic competence of the calluses, due to a prolonged time of culture, occurred concomitantly with a reduction in free IAA concentrations, practically to the concentrations found in the non-embryogenic calluses.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Centro para Investigaciones en Granos y Semillas (CIGRAS

In vitro culture and endogenous hormone levels in immature zygotic embryos, endosperm and callus cultures of normal and high-lysine barley genotypes

Endogenous hormone levels viz. indole-3-acetic acid (IAA), abscisic acid, gibberellins 1, 3 and 20 (GAs), zcatin/zeatin riboside and N6(Δ2-isopentenyl) adenine/ N6(Δ2-i sopentenyl) adenosine were determined in immature zygotic embryos and endosperm of the barley (Hordeum vulgare L.) cultivar `Bomi' and its high-lysine mutant `Risø 1508', 15 days post-anthesis by means of radio immunoassay. Higher levels of IAA and lower levels of GAs were found in embryo and endosperm of `Bomi', when compared to the corresponding values in `Ricø 1508'. The same immature zygotic embryos were used as initial explants to establish callus cultures. Non-embryogenic (NE) friable callus cultures were obtained in both genotypes; additionally, in cultivar `Bomi', a NE 'compact' callus was also produced, but in lower amounts. No differences in the levels of any of the endogenous hormones analysed could be detected between NE friable callus cultures of both genotypes, while the cytokinin levels varied when compared to the 'compact' cultures. The results obtained point to a lack of correlation between the endogenous hormone levels in the initial explants and the morphogenetic properties of the cultures derived from them, at least in this particular case.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Centro para Investigaciones en Granos y Semillas (CIGRAS

Evolution of endogenous hormone concentration in embryogenic cultures of carrot during early expression of somatic embryogenesis

Embryogenic callus and suspension cultures of carrot (Daucus carota L., cv. Nantaise), growing on/in medium including 1 mg/l 2,4-dichlorophenoxy acetic acid (2,4-D), were transferred to medium with or without this plant growth regulator, to impair or induce, respectively, further development of somatic embryos. The endogenous hormone levels of the cultures were determined over 7 days by means of radio-immunoassay, to characterize their evolution in the initial stages of embryo development. In general, levels of indoleacetic acid (IAA) and abscisic acid (ABA) showed only short-lived differences among treatments during this time in both types of tissue analyzed (i.e., a peak of IAA in callus cultures in the absence of 2,4-D, 48 h after medium change, and higher ABA contents 144 h after subculture of suspension cultures in the presence of 2,4-D). Gibberellins (1, 3 and 20) were detected only in suspension cultures devoid of 2,4-D, starting 24 h after subculture. Concerning the evaluated cytokinins—zeatin/zeatin riboside and N6(Δ2-isopentenyl) adenine/N6(Δ2-isopentenyl) adenosine—the most remarkable observation is that high levels of the former generally coincided with low concentrations of the latter, indicating a shift from precursor to the active form, and vice versa.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Centro para Investigaciones en Granos y Semillas (CIGRAS

Endogenous hormone levels in habituated nucellar Citrus callus during the initial stages of regeneration

Embryogenic nucellar callus cultures of different Citrus species and cultivars growing in hormone-free medium were transferred to medium containing either sucrose or glycerol as the only carbohydrate source. Glycerol has been reported to induce further development of Citrus somatic embryos, while in the presence of sucrose they continue to proliferate in an 'undifferentiated' manner. The endogenous hormone levels of the cultures were evaluated after 2 and 5  days to characterise the initial steps of embryo development. In most cases, differences among treatments were observed only after 5 days of culture. Higher cytokinin levels were found in most of the cultures transferred to the glycerol-containing medium. The effect of ageing sweet orange cultures on their endogenous hormone levels was determined by leaving them in the original culture medium without subculturing for 60 days. While no changes were observed in the free indoleacetic acid and gibberellin contents, lower levels of abscisic acid and cytokinins were found in the aged cultures than in those transferred at the normal interval, every 30 days. The endogenous hormone contents of Citrus callus of different genotypes were compared. Significant differences were observed in the levels of all hormones evaluated, even when the in vitro ontogeny of the different genotypes was very similar.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Centro para Investigaciones en Granos y Semillas (CIGRAS

Efeito da cianamida hidrogenada sobre o conteúdo de hormônios endógenos em plântulas de ervilha (Pisum sativum L.)

Hydrogen cyanamide (HC) has been used to break bud and seed dormancy and to improve rooting in several species, responses usually associated with the action of plant hormones. However, very few studies have measured endogenous hormones after HC treatment. Therefore, pea (Pisum sativum L.) seedlings with two fully developed internodes above the first leaf were sprayed with 0, 0.1 and 0.3% (v/v) HC. Endogenous concentration of indole-3-acetic acid (IAA), abscisic acid (ABA), zeatin/zeatin riboside and N6(Δ2-isopentenyl) adenine/ N6(Δ2-isopentenyl) adenosine were measured by radioimmunoassay 31 and 80 h after HC treatment. A significant increase in ABA and cytokinin (CK) levels was observed 31 h after treating the plants with 0.3% HC. Small necrotic spots were also noticed in this treatment, thus revealing a toxic effect of this treatment. Additionally, at 80 h, a significant increase in IAA was found for both HC concentrations applied. The action of HC upon ABA, CKs and IAA endogenous levels is discussed.A cianamida hidrogenada (CH) tem sido usada para quebrar a dormência de sementes e estimular o enraizamento em várias espécies, respostas estas usualmente associadas com a ação de hormônios de plantas. Todavia, em muito poucos estudos se tem avaliado os níveis endógenos de hormônios após a aplicação de CH. Portanto, plântulas de ervilha (Pisum sativum L.), com dois internódios completamente desenvolvidos acima da primeira folha, foram pulverizadas com soluções de CH a 0; 0,1; e 0,3% (v/v). Concentrações endógenas de ácido indol-3-acético (AIA), ácido abscísico (AAB), zeatina/ribosídeo de zeatina e N6(Δ2-isopentenil) adenina/ N6(Δ2-isopentenil) adenosina foram medidas por radioimunoensaio após 31 e 80 h da aplicação de CH. Observaram-se aumentos significativos nas concentrações de AAB e citocininas 31 h após o tratamento das plantas com 0,3% de CH. Verificaram-se pequenas manchas necróticas nas plantas desse tratamento, que se revelou, pois, tóxico. Adicionalmente, observou-se um incremento na concentração de AIA após 80 h da aplicação de CH, tanto a 0,1 como a 0,3%. Discute-se a ação da CH sobre as concentrações endógenas de AAB, AIA e citocininas.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Centro para Investigaciones en Granos y Semillas (CIGRAS

Changes in hormone concentrations during dormancy release of oil palm (Elaeis guineensis) seeds

Oil palm (Elaeis guineensis) seeds are highly dormant immediately after harvest. In practical horticulture this dormancy has been traditionally overcome by a dry-heat treatment and, more recently, through the application of hydrogen cyanamide (HC). Initiation and release of dormancy have been related in other plant species to changes in endogenous hormone concentrations. Therefore, the effect of the aforementioned dormancy release treatments on germination and on endogenous concentration of indole-3-acetic acid (IAA), abscisic acid (ABA), gibberellins GA1, GA3 and GA20 (GAs), zeatin/zeatin riboside and N6(Δ2-isopentenyl) adenine/N6(Δ2-isopentenyl) adenosine was evaluated in oil palm seeds. Heat- and HC-treated seeds germinated above 90% after 37 d, while germination of control seeds was below 4% at the same time. A sharp reduction in ABA concentration in embryos and endosperm was the most notable outcome during the dry-heat and HC treatments, the latter one in a lesser degree. HC treatment additionally caused an increase in IAA levels in embryos and endosperm during the imbibition phase. Changes in concentration of other hormones (e.g., GAs and cytokinins) could not be directly related to dormancy release in this species. Participation of additional factors, such as changes in sensitivity to plant hormones, cannot be ruled out.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Centro para Investigaciones en Granos y Semillas (CIGRAS

Response of Endogenous Hormone Concentrations to Two Floral Inductive Treatments, viz. KNO3 and PBZ, in Mango cv. ‘Tommy Atkins’ Growing Under Tropical Conditions

Floral induction (FI) has been intensively studied in mango, more under sub-tropical than under tropical environments. Decreases in temperature below 20 °C, which is common in sub-tropical regions but seldom occurs in many tropical ones, has been considered a critical factor for FI in this species. Trying to understand the way by which two FI treatments, potassium nitrate (KNO3) and paclobutrazol (PBZ), can regulate flowering by modulating the endogenous concentrations of plant hormones, the following compounds were analyzed in terminal buds, wood and bark sections of lateral branches from treated and untreated ‘Tommy Atkins’ mango trees growing under tropical conditions: indole-acetic acid (IAA), gibberellins (GAs), zeatin/zeatin riboside (Z/ZR) and N 6 (Δ2-isopentenyl) adenine/N 6 (Δ2-isopentenyl) adenosine. Behavior in the contents of these endogenous hormones was often irregular but their course was in general similar for all three treatments. However, levels of GAs were consistently lower in most evaluations of wood and bark sections of PBZ-treated trees compared to KNO3-treated and control plants. In contrast, the endogenous levels of the presumably FI promoting Z/ZR raised considerably at the time close to FI in buds of KNO3-treated trees. These KNO3-treated trees flowered earlier and more profusely than those from other treatments. Although PBZ could be related in this work to a reduction in GA contents, no direct influence of this compound over FI could be established. KNO3 might partially exert its promoting effect on mango FI by increasing Z/ZR contents.Universidad de Costa Rica/[734-A5-180]/UCR/Costa RicaGerman Academic Exchange Service/[]/DAAD/AlemaniaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Centro para Investigaciones en Granos y Semillas (CIGRAS