PERIDERM AND XYLEM FORMATION IN ANNUAL RASPBERRY TILLERS OF TYPICALAND EVERBEARING TYPES

Abstract

Multiyear histological study was conducted in the processes of periderm and xylem formation in the tillers of raspberry varieties of different bearing types. Versus everbearing varieties, the variety of the typical bearing type is established to have a relative 31-46% increase for the thickness of periderm. The typical bearing type variety has the number of periderm cell layers and suberinized layers by 54-55 and 52-85 higher, respectively. As for xylem thickness and lignificated part, they are 1.3-1.5 and 1.6-2.0 times as much, respectively, as those in the everbearing. The everbearing varieties had a 2-3 week delay in the dates of periderm and xylem maturation start and rates as compared to analogous processes in the typical fruit-bearing type variety. The increased sum of effective temperatures for the vegetation period considerably intensified periderm maturation in the tillers of all the varieties, subernized layers forming 1.6 times as much in number. Everbearing varieties were revealed to have smaller thickness, weaker degree of ripening and delayed periderm and xylem maturation dates result in possibly increased susceptibility of tillers to infections and lesions. All these require additional measures in plantations protection.