Temporal Competence of Embryonic Pinus Ponderosa Cotyledons to Form Multiple Buds in Vitro

Abstract

To investigate temporal changes occurring during tissue maturation and loss of organogenic competence, embryos of Pinus ponderosa Laws, were excised from seed and placed horizontally on medium in sterile culture. On a hormone‐free basal medium, cotyledons differentiated and failed to form multiple buds. When placed on a benzyladenine (BA)‐containing medium, the lower cotyledons in contact with the medium formed multiple buds while those elevated above the medium did not. Cotyledons became incompetent to form buds when embryos were initially placed on basal medium for 2 days before being transferred to the BA‐supplemented medium. In order to initiate buds, cotyledons of newly excised embryos had to be exposed to BA for at least 3 days. Exposure to BA for longer than 7 days did not significantly increase the number of cotyledonary buds. Cotyledons elevated above the BA‐supplemented medium retained organogenic competence to form buds for up to 14 days but did not form buds unless the cotyledons were placed in contact with the medium. The presence of BA is required to retard cotyledon maturation and sustain tissue competence to initiate buds.

In vitro regeneration of plantlets from immature zygotic embryos of Picea chihuahuana Martínez, an endemic mexican endangered species

“…Generally, they developed from the cotyledon portion of the explants, only a few developed from the hypocotyl portion. Similar results with mature zygotic embryos have been reported for Pinus contorta (von Arnold and Eriksson, 1981;Patel and Thorpe, 1984) and P. ponderosa (Ellis and Bilderback, 1989). As for other conifers, development of adventitious buds has been stimulated by the dilution of the culture medium (von Arnold and Eriksson, 1981;Thorpe and Harry, 1991;Harry et al, 1995).…”

“…A lesser production of buds was reported on MS medium (Garcõ Âa-Ferrõ Âz et al, 1994), considered as a high salts concentration medium. Many of the published reports on morphogenesis in vitro for gymnosperms point out that the combination of high BA concentrations and low or null auxin concentrations have been the most effective treatments to promote the development of adventitious buds in zygotic embryo cultures (von Arnold and Eriksson, 1981;Villalobos et al, 1985;Ellis and Bilderback, 1989;Harry et al, 1995;Capuana and Giannini, 1997). Even though BA is generally the most effective cytokinin for adventitious shoot production (Thorpe and Harry, 1991), in the present study it was not most effective.…”

Optimization of bud induction in cotyledonary explants of Pinus canariensis

“…Buds were present along the length of the whole Day 0 explant after 30 min induction, but only at the tips of Day 3 explants pulsed for the same time period (Figs 2, 3). A similar pattern of differentiation in vitro has been reported for Pseudotsuga menziesii (Winton & Verhagen 1977), Picea abies (Janson & Bornman 1980), Pinus radiata (Biondi & Thorpe 1982) and Pinus ponderosa (Ellis & Bilderback 1989).…”

“…It has been established that BA inhibits elongation and maturation, and induces bud formation (Ellis & Bilderback 1989;Villalobos et al 1984). However, the mechanisms involved are still unknown, and a series of factors like cytokinin concentration, time of exposure, degree of explant maturation, and other environmental factors like pH, temperature, light etc., which could influence cytokinin uptake, have to be combined to re-direct competent tissue into meristematic nodule formation, and eventually into de novo bud development.…”

Adventitious Bud Formation from Mature Embryos of Picea chihuahuana Martínez, an Endangered Mexican Spruce Tree

“…Competence has been de®ned as the ability of tissue to respond to morphogenetic induction (organogenic or embryogenic). This response may be obtained in cells that develop autonomously or that receive a chemical or environmental signal (Flinn et al, 1988;Ellis and Bilderback, 1989;Lyndon, 1990). To understand the processes of adventitious bud dierentiation, it is essential to investigate the stages prior to their expression (von Arnold and Eriksson, 1985), as in the studies on Pinus coulteri (Patel and Berlyn, 1983), Pinus radiata (Villalobos, 1983;Villalobos et al, 1985) and Pinus strobus (Flinn et al, 1988) in which it was possible to determine induction periods and events prior to in vitro formation of adventitious buds.…”