Fig. 7.

Schematic representation of the secondary growth of two different types of Malus peduncle construction. The increase in peduncle girth of type 1 due to cambial phloem formation entails cell elongations and division of cortical parenchyma by pushing outer tissues to the periphery. The fibre ring is displaced to the centre. The differentiation of cortical parenchyma cells outside the fibre ring into brachysclereids stiffens the structure most effectively against bending. Scale bar = 500 µm. Abbreviations: c, collenchyma; cp, cortical parenchyma; e, epidermis; fb, fibres; p, phloem; pp, pith parenchyma; scl, sclereids; vc, vascular cambium; x, xylem.