Changes in cytokinin concentration during early development of American sycamore leaves

Abstract

Concentrations of cytokinin-like substances (CKs) change rapidly during early leaf expansion of American sycamore (Platanus occidentalis L.). Endogenous CKs, measured by bioassay, are highest in the smallest leaves and decline several hundredfold as leaves rapidly enlarge. These rapid phytohormone changes during development demonstrate the need to carefully standardize sample collection. For some developmental or comparative studies leaf size may be a suitable criterion.