Delayed Onset of Isoprene Emission in Developing Velvet Bean (Mucuna sp.) Leaves.

Isoprene (2-methyl-1,3-butadiene) is one of the major volatile hydrocarbons emitted by plants, but its biosynthetic pathway and role in plant metabolism are unknown. Mucuna sp. (velvet bean) is an isoprene emitter, and leaf isoprene emission rate increased as much as 125-fold as leaves developed, and declined in older leaves. Net CO(2) assimilation and stomatal conductance, under different growth and environmental conditions, increased 3 to 5 days prior to an increase in isoprene emission rate, indicating that photosynthetic competence develops before significant isoprene emission occurs.