Spur survival and return bloom in almond [Prunus dulcis (Mill.) D.A.Webb] varied with spur fruit load, specific leaf weight, and leaf area

Abstract

SummaryVariation in fruit load, leaf area, and light exposure among almond spurs was used to evaluate whether or not spurs were autonomous with regard to Winter survival and return bloom. Fruiting was associated with reduced spur survival over the subsequent Winter and reduced return bloom in the subsequent year.This resulted in a tendency for individual spurs to bloom and bear fruit in alternate years. Survival was high among all non-fruiting spurs, but survival of fruiting spurs was positively related both to leaf area per spur and specific leaf weight (SLW; an indicator of light exposure). SLW was a much stronger correlate for spur survival than leaf area per spur. The likelihood of flowering varied positively with spur leaf area the previous season on both fruiting and non-fruiting spurs, but was not related to spur SLW. Localisation of leaf area and shading effects within individual spurs created spur sub-populations with differing tendencies toward alternate bearing. The likelihood of flowering on spurs was enhanced when branch-wide carbohydrate demand by fruit was eliminated by early fruit removal the previous season, suggesting that almond spurs are not entirely autonomous with regard to carbohydrate supply during floral initiation and development. Nevertheless, our data are consistent with a high degree of spur autonomy regarding Winter survival and return bloom, with each spur apparently being strongly influenced by the ability of its own leaves to meet its carbohydrate demands.