Comparison of Ontogeny of Three Types of Leaf Architecture in Sorbus L. (Rosaceae)

Abstract

Ontogeny of leaf architecture was studied in Sorbus decora with compound leaves, S. alnifolia with simple leaves, and S. hybrida with half-compound leaves. Development of the three leaf forms differs in the relative timing and extent of fractionation of marginal growth. Leaflets are formed by early discontinuities of marginal growth. Simple laminas are unfractionated until teeth are formed. Primary and secondary veins of leaflets and simple leaves form progressively. Percurrent tertiary veins in leaflets and simple leaves form simultaneously. Tertiary veins which taper and branch, similar to secondary veins, in S. hybrida form progressively. Vein endings in the margins or in areoles form progressively.