Four Hypotheses to Explain Axillary Budbreak after Removal of Flower Shoots in a Cut-rose Crop

Abstract

<jats:p>When flower-bearing shoots in cut-rose (<jats:italic>Rosa</jats:italic> ×<jats:italic>hybrida</jats:italic>) are harvested (removed), a varying number of repressed axillary buds on the shoot remainder start to grow into new shoots (budbreak). Besides removing within-shoot correlative inhibition, it is hypothesized that shoot removal leads to 1) increased light intensity lower in the crop canopy; 2) changes in the light spectrum (particularly red:far-red ratio); and 3) changed source:sink ratio (i.e., the ratio between supply and demand of assimilates). As a fourth hypothesis it is proposed that the degree of budbreak on a shoot remainder is also influenced by the correlative inhibition exerted by other shoots on the plant. It is the goal of this work to determine which of these four hypotheses is most important for budbreak in a cut-rose crop. Four experiments were conducted, in which these factors were varied by leaf removal, removal of mature shoots, varying the number of young shoots, shading of the crop, and application of direct light on the buds. Increase in source:sink ratio was not consistently associated with higher budbreak. If source:sink ratio was decreased by removal of leaves or a mature shoot, budbreak showed even a tendency to increase. Budbreak was subject to correlative inhibition exerted by other shoots on the plant. Treatments where more light reached the bud (as a result of less shoots, no shading of the crop, application of local light) increased budbreak. Increased red:far-red ratio had the same result as more light reaching the bud but was often interrelated with light intensity. It was concluded that after removal of the flower-bearing shoot, among the factors tested, light intensity on the buds was an important and consistent factor explaining budbreak on the shoot remainder, whereas the effect of light spectrum should be further investigated.</jats:p>

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

“…On the basal part of the shoot that is left (the shoot remainder), axillary buds break and develop into the next harvestable flower shoots. A previous study (Wubs et al, 2013) indicated that the degree of budbreak on shoot remainders positively responded to more light in combination with higher red:far-red ratio received by the buds, but effects of light intensity and light spectrum could not be separated. The experiments in this study were set up to disentangle the effects of light intensity and red:far-red ratio reaching the axillary buds in a rose crop, trying to determine whether one or the other is more important for triggering axillary budbreak of a crop or that both are equally important.…”

“…However, the number of broken buds is variable: a plant has several axillary buds, which potentially form a shoot, but not all of them do. As discussed by Wubs et al (2013), shoot removal (harvest) not only removes apical dominance and correlative inhibition, but also leads to 1) increased light intensity reaching the axillary bud; and 2) changed spectrum of light reaching the bud (particularly a higher red:far-red ratio); and 3) changed source:sink ratio (i.e., the ratio between supply and demand of assimilates). Furthermore, the degree of budbreak on a shoot remainder is also influenced by the correlative inhibition exerted by other shoots on the plant (Wubs et al, 2013;Zieslin and Halevy, 1976).…”

“…As discussed by Wubs et al (2013), shoot removal (harvest) not only removes apical dominance and correlative inhibition, but also leads to 1) increased light intensity reaching the axillary bud; and 2) changed spectrum of light reaching the bud (particularly a higher red:far-red ratio); and 3) changed source:sink ratio (i.e., the ratio between supply and demand of assimilates). Furthermore, the degree of budbreak on a shoot remainder is also influenced by the correlative inhibition exerted by other shoots on the plant (Wubs et al, 2013;Zieslin and Halevy, 1976). Wubs et al (2013) concluded that after removal of a mature shoot, light reaching the axillary buds is an important factor explaining budbreak on the shoot remainder.…”

“…Furthermore, the degree of budbreak on a shoot remainder is also influenced by the correlative inhibition exerted by other shoots on the plant (Wubs et al, 2013;Zieslin and Halevy, 1976). Wubs et al (2013) concluded that after removal of a mature shoot, light reaching the axillary buds is an important factor explaining budbreak on the shoot remainder. However, those experiments could not completely discriminate between the effect of light intensity and light spectrum.…”

From leaf to crop : quantifying photosynthesis responses of two flower crops

“…This may affect compensatory responses such as leaf area production due to changes in source-sink relations, as stem can be a storage organ for assimilates. Branch pruning also stimulates axillary bud break because of the removal of correlative inhibition and the increase of light intensity at the positions of axillary buds due to branch removal (Wubs et al, 2013). Shoot bending is normally applied in some woody species crops (e.g., rose) and fruit trees (e.g., apple and pear) (Ito et al, 1999;Han et al, 2007;Liu & Chang, 2011;Lopez et al, 2014).…”