The effect of summer shading on flower bud morphogenesis in apricot (Prunus armeniaca L.)

Abstract

AbstractThe aim of this investigation was to assess whether imposed summer shading treatments in apricot (Prunus armeniaca L.) can affect the main phenological phases related to the floral morphogenesis (floral differentiation, xylogenesis), flower bud growth and quality in terms of bud capacity to set fruit. Experimental trials were carried out on fully-grown trees of ‘San Castrese’ and ‘Stark Early Orange’ cultivars characterized by different biological and agronomical traits to which shadings were imposed in July and August. Histological analysis was carried out from summer onwards in order to determine the evolution of floral bud differentiation, and the acropetal progression of primary xylem differentiation along the flower bud axis. Periodical recordings to evaluate the bud drop, blooming time, flowering and fruit set rates were performed also. These shade treatments determined a temporary shutdown of floral differentiation, slowed xylem progression up to the resumption of flower bud growth and a reduced entity of flowering and fruit set. These events were particularly marked in ‘San Castrese’ cultivar, which is well known for its adaptability to different climatic conditions. These findings suggest that adequate light penetration within the canopy during the summer season could be the determining factor when defining the qualitative traits of flower buds and their regular growth, and ultimately to obtain good and constant crops.