Formation and fate of kino veins in eucalyptus l'hérit

Abstract

Kino veins, generally referred to as gum veins, are formed in Eucalyptus spp. in response to injury. Although they are retained as defects in the wood of many species, in some they become included in the phloem, then the rhytidome and are eventually shed. Ninety-three Eucalyptus spp. were sampled to determine whether they had xylem or phloem (bark) veins. The species which exhibited kino veins in the phloem were all members of three sections of the subgenus Symphyomyrtus. All species examined of the subgenera Monocalyptus and Corymbia had xylem veins. Kino veins are formed by the lysigenous breakdown of parenchyma bands produced by the cambium. The difference which results in the veins either being shed in the bark or included in the xylem is determined at the time of their initiation. The parenchyma bands may be produced on either the xylem or on the phloem side of the cambium. The fate of the veins becomes apparent once normal cambial divisions resume the production of xylem and phloem.