Sugar availability is involved in rose bud outgrowth stimulation following a temporary light intensity restriction during the vegetative development of the main stem
Branching is a major agronomic variable determining yield and quality, and is very sensitive to environmental conditions. Previous studies on rose showed that a continuous high light intensity perceived during the bud outgrowth period stimulated bud outgrowth compared to a continuous low light intensity. This effect was related to higher cytokinin contents in the nodes. Interestingly, a temporary light intensity restriction applied before the bud outgrowth period over-stimulated bud outgrowth, but the mechanisms involved remain unknown. In this case, we assume a non-limitation in cytokinins because of the current high light intensity during the bud outgrowth period, but an increase in sugars that would explain bud outgrowth stimulation. To test sugar involvement, we quantified bud outgrowth, sugar contents, and the balance between sources and sinks for sugars in the bud outgrowth period of plants grown under either continuous high light intensity or under a temporary light restriction followed by a high light intensity. In addition, we quantified the effect of exogenous sugar supply on bud outgrowth for plants under continuous high light intensity, and the effect of leaf masking under the non-continuous treatment. Our results showed that after a temporary light intensity restriction and return to high light intensity, sugars accumulated compared to a continuous high light intensity. Furthermore, the growth of apical organs was reduced indicating that sugar accumulation might be due to a higher balance between sources and sinks for sugars. Exogenous sucrose supply through the petiole of intact plants grown under high light intensity stimulated bud outgrowth. Conversely, leaf masking after a temporary light intensity restriction inhibited bud outgrowth. This supports that sugar accumulation is an important trigger of bud outgrowth after a temporary light intensity restriction. Together these results indicate that an anterior low light intensity applied during the main stem development reduces growth of apical organs while higher sugar availability afterward favours lateral bud outgrowth.
Schneider, A., Boudon, F., Demotes-Mainard, S., Ledroit, L., Perez-Garcia, M.D., Brouard, N., Godin, C., Sakr, S. and Bertheloot, J. (2020). Sugar availability is involved in rose bud outgrowth stimulation following a temporary light intensity restriction during the vegetative development of the main stem. Acta Hortic. 1296, 395-400
bud outgrowth, light intensity, branching, sugar, source-sink