Stomatal closure prevents xylem transport of green leaf volatiles and
impairs their systemic function in plants
Abstract
Plants perceive environmental stresses as whole organisms via distant
signals conveying danger messages through their vasculature. In parallel
to vascular transport, airborne plant volatile compounds, including
green leaf volatiles (GLVs), can bypass the lack of vascular connection.
However, some small volatile compounds move through the vasculature;
such vascular transport is little known about GLVs. Here we illustrate
GLV alcohols as solutes move within xylem vessels in Zea mays. We
describe GLV alcohols, including Z-3-hexenol and its isomer
E-3-hexenol, which is not synthesized in maize, is mobilized
through the transpiration stream via xylem vessels. Since transpiration
is mediated by stomatal aperture, closing stomata by two independent
methods diminishes the transport of GLV alcohol and its isomer. In
addition, lower transport of GLV alcohols impairs their function in
inducing terpenoid biosynthesis suggesting xylem transport of GLV
alcohols plays a significant role in their systemic function. Our study
not only shows that GLV alcohols can be transported in the xylem but
points to stomatal regulation as a mechanism that climatic factors such
as drought, heat, flooding, and high CO 2 levels affect
systemic signaling functions of GLVs.