Water and sucrose regulate canola embryo development

Abstract

M. 1997. Water and sucrose regulate canola embryo development. -Physiol. Plant. 101: 361-366.The effect of water and sucrose on the growth and development of zygotic, 30-day-old canola {Brassica napus L. cv. Bounty) embryos was examined in vitro by manipulating the levels of sucrose and/or sorbitol present in the culture medium. In some experiments, the medium water potential was allowed to vary with sucrose concentration, while in other experiments, the medium water potential was held constant by adding sorbitol to varying amounts of sucrose. Our results showed that embryos cultured on sorbitol alone exhibited two developmental patterns: embryos germinated precociously on media containing up to 0.70 M sorbitol, whereas embryos became yellow and quiescent on media with higher concentrations of sorbitol. For embryos cultured on media containing sucrose alone, three distinct developmental patterns were noted: at low sucrose concentrations, embryos germinated precociously; at intermediate concentrations, embryos continued to grow in an embryonic mode; and, at high concentrations, embryos became yellow and quiescent. Continued embryonic growth was never observed in embryos cultured on media containing sorbitol alone. Embryos never germinated precociously when cultured on media maintained at a constant water potential of -1.4 MPa, rather dry weight increased in these embryos with an increase in sucrose concentration. We envision the effect of sucrose on embryo growth and development to be nested within the effect of water availability. When water availability is restricted, embryos become quiescent. When water is available, embryos have the potential to grow, but the developmental growth pattern depends on the availability of sucrose. In the absence of sucrose, embryos germinate and initiate the transition to autotrophy. If sufficient sucrose is available, embryos remain photoheterotrophic and continue to grow in an embryonic mode.

Transcriptomic comparison of seeds and silique walls from two rapeseed genotypes with contrasting seed oil content

“…In B. napus embryos, the dominant metabolic flux is the conversion of sugars into triacylglycerols (Schwender et al, 2004b), resulting in more than 60% of the carbon being stored as oil (Schwender et al, 2004a). Canola embryos cultured on sucrose develop photoheterotrophic plastids that function in storage, whereas embryos germinate and become photoautotrophic without sucrose (Johnson et al, 1997). Therefore, sucrose content may be an important factor that affects the storage level of lipids.…”