Endogenous auxin and cytokinin contents associated with shoot formation in leaves of pineapple cultured in vitro

Abstract

The in vitro culture of pineapple leaves on a shoot induction medium (SIM) results in the formation of protuberances and further development in shoots, and plantlets. The contents of endogenous indoleacetic acid (IAA) and five cytokinins (Cks), N6(2-isopentenyl)adenine (iP), N6(2-isopentenyl)adenosine (iPR), zeatin (Z), zeatin riboside (ZR) and N6-benzyladenine (BA), present in the basal portion of those leaves, were correlated to the organogenic response that occurs over 15 days of culture. The endogenous auxin/cytokinins ratio was lowest on the 3rd day, mainly due to a strong increase in the iP level. It seems that endogenous iP concentration triggered the induction signal for an organogenic response in pineapple leaf bases. The rise in iP content required the presence of BA and a-naphthaleneacetic acid (NAA) in the medium, suggesting that endogenous iP production is regulated in response to these growth regulator uptakes.

Osmotic stress stimulates shoot organogenesis in callus of rice (Oryza sativa L.) via auxin signaling and carbohydrate metabolism regulation

“…The initiation of regeneration from callus may be related to the balance between auxin and cytokinin. Although the exact nature of these hormonal signals may vary between species, the balance in auxin to cytokinin has a consistent effect on the type of regenerated organs (Charriére et al 1999;Sugiyama 1999;Fernando and Gamage 2000;Mercier et al 2003;Jiménez 2005;Zhang et al 2008). In addition, the effect of added auxins and cytokinins has been related to an interaction with other endogenous hormones such as ABA, thus leading to conspicuous changes in development (Lakshmanan and Taji 2000).…”

Micropropagation of Alibertia edulis Rich

“…The importance of auxin and cytokinin balance has been reported in regulating the apical dominance as well as in a number of morphogenetic events such as shoot formation and branching (Li and Bangerth, 2003;Werner et al, 2003;Nakagawa et al, 2005). Another factor that may influence the morphogenetic events during in vitro culture is a possible interaction between the endogenous concentrations of plant growth regulators and those present in the culture medium (Pinto et al, 1994;Mercier et al, 2003). As concentrations around 0.1 mg.L -1 BA favored the sprouting in all three subcultures, this could be the optimum BA concentration for a cytokinin and endogenous auxin balance that resulted in release of the apical dominance in the culture conditions.…”

Residual effect of growth regulators in etiolation and regeneration of in vitro pineapple plants

“…The use of nodal segments as explants for micropropagation and conservation of genetic stability has been shown in pineapple (KISS et al, 1995;BARBOZA ;CALDAS, 2001;MOREIRA et al, 2003). In pineapple, this type of explant is obtained through etiolation of in vitro plants with the advantage of avoiding injuries in the regeneration region and avoiding callus formation and consequently genetic variation.…”

“…Additionally, the use of nodal segments can be an interesting strategy to increase multiplication rates. Moreira et al (2003), evaluating multiplication rates of the Pérola cultivar through shoot etiolation, found the best results for length of etiolated shoots as well as for number of buds, using the MS medium supplemented with NAA at 1.8 mg L -1 + BAP at 2.0 mg L -1 . Similar results were encountered by Barboza e Caldas (2001) with the PE x SC-52 hybrid; both works showing the viability of multiplying pineapple in vitro using nodal segments as the initial explant.…”

“…Gibberellins have been considered as a plant growth regulator acting at the endogenous level controlling many plant growth and development aspects such as stem elongation, root and fruit development. Although these regulators have being used for etiolation of pineapple stems, the residual effect in the multiplication rates are still unknown (BARBOZA;CALDAS, 2001;MOREIRA et al, 2003).…”