Axillary Budbreak in a Cut Rose Crop as Influenced by Light Intensity and Red:far-red Ratio at Bud Level

Abstract

<jats:p>When flower-bearing shoots in cut rose (<jats:italic>Rosa</jats:italic> ×<jats:italic>hybrida</jats:italic>) are harvested, a varying number of repressed axillary buds on the shoot remainder start to grow into new shoots (budbreak). Earlier experiments indicated that light reaching the bud affected the number of budbreaks. In all these studies, whole plants were illuminated with different light intensities or light spectra. The aim of this article is to disentangle the effects of light intensity and light spectrum, in this case red:far-red ratio, at the level of the buds on budbreak in a rose crop. Three experiments were conducted in which light intensity and red:far-red ratio at the level of the buds were independently varied, whereas intensity and red:far-red ratio of incident light on the crop were not changed. Light intensity and red:far-red ratio at the position of the buds were quantified and related to budbreak on the shoot remainders. Removal of vertical shoots increased light intensity and red:far-red ratio as well as budbreak (1.9 budbreaks per shoot remainder compared with 0.4 budbreaks when five vertical shoots were present). No vertical shoots and red light-absorbing shading paper over the plant base mimicked the effect of vertical shoots with respect to light intensity and red:far-red ratio, but budbreak (1.0 budbreaks) was intermediate compared with treatments with and without shoots. This suggested that the presence of shoots exerts an inhibiting effect on budbreak through both effects on light at the bud and correlative inhibition. When plants had no vertical shoots and light intensity and red:far-red ratio at bud level were changed by neutral and red light-absorbing shading paper, there was a positive effect of light intensity on budbreak (0.3 more budbreaks per shoot remainder) and no effect of red:far-red ratio. Combinations of high and low light intensity with high and low red:far-red ratio on axillary buds showed that there was a positive effect of light intensity on budbreak (0.5 more budbreaks per shoot remainder) and no effect of red:far-red ratio. Our study reveals that when light intensity and red:far-red ratio received by the plant are similar but differ at bud level, budbreak was affected by light intensity and not by red:far-red ratio.</jats:p>

Cytokinins and Abscisic Acid Act Antagonistically in the Regulation of the Bud Outgrowth Pattern by Light Intensity

“…The reduced PPFD applied from the FBV stage onward reduced the number of outgrowing buds, consistently with previous results in rose ( Bredmose, 1995 ; Furet et al, 2014 ; Wubs et al, 2014 ). To address the question of how the CK, ABA, and sugar regulation pathways take part in the control of the branching pattern by light intensity, we focused on bud 4 that displayed the most contrasted fate with 100% or 0% outgrowth under high or low PPFD, respectively.…”

Sugar as a key component of the shoot branching regulation network

“…; Wubs et al . ). Even though artificial selection for a stable, predictable branching behaviour in crops may have removed some of the plasticity in shoot branching, many crops still display a great sensitivity to environmental and management factors in terms of the number of branches they produce and maintain (e.g.…”

“…The number of branches formed in cereals, as well as broadleaf crops such as rapeseed and cotton, is an important determinant of crop biomass production and ultimately crop yield, and is heavily affected by population density of the crop (for a classic example see Darwinkel 1978). For horticultural crops, such as glasshouse cut rose, shoot branching is also a crucial trait: the shoot harvesting strategy determines abundance and quality of newly formed shoots in strong association with environmental signals such as light (Girault et al 2010;Wubs et al 2014). Even though artificial selection for a stable, predictable branching behaviour in crops may have removed some of the plasticity in shoot branching, many crops still display a great sensitivity to environmental and management factors in terms of the number of branches they produce and maintain (e.g.…”

Multiple pathways regulate shoot branching

“…Shade is also characterized by decreased incident light intensity. Whether low light intensity contributes to SAS or whether SAS is primarily a response to the changes in light quality associated to shade has long been debated ( Bartlett and Remphrey, 1988 ; Ballaré and Casal, 2000 ; Evers et al, 2006 ; Wubs et al, 2013 , 2014 ). In fact, results in Arabidopsis suggest a fine tuning of shoot branching by these two parameters whereby reduced branching will only occur when R/FR and light intensity are both low (as under established shade), while branching will still be promoted when R/FR alone is low (as in the neighborhood of a not yet shading plant; Su et al, 2011 ).…”