A Novel Framework to Consider Endogenous Hormonal Control of Apple Tree Flowering

Abstract

<jats:p>Inhibition of flower initiation by nearby developing fruits is one of the main causes of biennial bearing in apple trees. This localized inhibition may depend on a critical ratio of inhibitor and promoter hormones that inhibits flowering of apical meristems. A model is proposed to explain this phenomenon. In the model, it is assumed that seeds and leaves act as point sources and export inhibiting and promoting hormones to apical meristems. The model assumes critical ratios of promoting and inhibiting hormones determine whether an apical meristem flowers or not and this may be a cause of biennial bearing. Thus, the spatial arrangement of shoot apical meristems on a limb is perhaps critical in determining whether meristems initiate flower clusters. This article presents a novel framework to view the hormone hypotheses of biennial bearing in apple trees and how management strategies such as flower removal could be used to achieve regular numbers of flower clusters over consecutive years.</jats:p>

Reducing the incidence of calyx cracking in ‘Pink Lady’ apple using a combination of cytokinin 6-benzyladenine and gibberellins (GA4+7)

“…Thus, contrary to previous reports showing that application of GA 3 , GA 4 , or GA 7 during flowering could affect the following year's bloom (Westwood, 1993;Tromp and Wertheim, 2005;Pellerin et al, 2012), no such phenomenon was observed in the present research (data not shown).…”

Crop Load Influences Fruit Quality, Nutritional Balance, and Return Bloom in ‘Honeycrisp’ Apple

“…Crop load management is particularly important for 'Honeycrisp' because it can limit inconsistent annual flowering and fruit set (Embree et al, 2007), improve fruit quality (Baugher and Schupp, 2010), and decrease susceptibility to storage disorders (Robinson and Watkins, 2009). 'Honeycrisp' has exhibited an extreme predisposition to overcropping, therefore, is susceptible to biennial bearing (Crassweller et al, 2005;Embree and Nichols, 2005;Robinson and Watkins, 2003;Wright et al, 2006), especially when thinning is completed too late (Pellerin et al, 2011(Pellerin et al, , 2012. Thinning is a common agronomical practice to optimize crop load to improve fruit size and quality as well as reducing biennial bearing (Dennis, 2000;Link, 2000;Wertheim, 2000).…”

Effect of Fruiting and Biennial Bearing Potential on Spur Quality and Leaf Gas Exchange in Apple

“…Theories to explain the effect of fruiting on flower formation generally fall into three categories: 1) plant growth regulators (Guitton et al, 2012;Krasniqi et al, 2013;Pellerin et al, 2012), 2) source-sink competition (Bruchou and G enard, 1999;Palmer et al, 1991;Saa and Brown, 2014), and 3) the interaction between plant growth regulators and sink-source competition (Smith and Samach, 2013;Untiedt and Blanke, 2001).…”