Heteroblastic seedlings of green ash. II. Early development of simple and compound leaves

摘要

Simple and compound leaf primordia of green ash seedlings differ in shape from initiation. Simple leaf primordia are flattened until their lamina margins grow out at a primordial length of 150ensp;mu;m. Compound leaf primordia are rounded and peglike at initiation and lateral leaflet buttresses appear when primordia are 150ensp;mu;m long. Terminal leaflet margins appear when compound leaf primordia are 200ensp;mu;m long. At initiation both types of leaf primordia are composed of densely cytoplasmic cells. Vacuolation proceeds so that densely cytoplasmic cells remain only in areas developing blades and leaflets and in procambium. Because simple and compound leaves of green ash differ from initiation, neither leaf type can be considered to result from a change in the ontogeny of the other.