It is well knownthat monoterpenes s

It is well known
that monoterpenes stored in reservoirs serve as constitutive
or inducible defenses (Gershenzon and Croteau, 1993). The
monoterpenes respond differently to temperature. The emission
of cyclic monoterpenes such as
-pinene, sabinene,
-pinene, and limonene increases exponentially at temperatures
from 5 to 35 ◦C but becomes reduced at temperatures
higher than 35 ◦C, while acyclic monoterpenes such as (Z)--
ocimene and (E)--ocimene are not or barely detected below
35 ◦C as they exhibit a sharp increase at temperatures from
35 to 45 ◦C (Loreto et al., 1998; Staudt and Bertin, 1998).
One intriguing hypothesis concerning the isoprenes and
monoterpenes is that they are intended to protect the plant
leaves against thermal stresses (Delfine et al., 2000) including
bursts of heat (Delfine et al., 2000; Singsaas et al., 1997;
Loreto et al., 1998) and increase the thermotolerance of intact
leaves of isoprene emitting species (Sharkey and Singsaas,