3.1.1 Constitutive release of infochemicals as information
sources
Plants continuously release a profile of volatile organic compounds
(VOCs) and non-VOCs to the root and atmosphere. These chemical profiles,
concentrations, and release time courses function as signals of plant
presence and health status. Constitutive release of specific chemical
signatures can be exploited by neighbor organisms to determine the
presence and identity of neighboring plants. Receiver plants recognize
the degree of phylogenetical relationship of neighbor plants to
discriminate kin and non-kin plants (Biedrzycki, Jilany, Dudley & Bais,
2010, Yang, Li, Xu & Kong, 2018). In most cases, signals from healthy
plants can affect neighboring plants by modifying biomass allocation,
lateral root formation, and chlorophyll and phenolic compound
biosynthesis, or directly inhibiting seed germination (Delory,
Delaplace, Fauconnier & du Jardin, 2016, Takigahira & Yamawo, 2019).
The sagebrush volatile compounds methyl jasmonate, camphor, 1,8-cineol,
α-thujone, and nerol inhibit the germination of Nicotiana
attenuate seeds (Jassbi, Zamanizadehnajari & Baldwin, 2010). Exposing
potato to healthy onion changes potato volatiles, which are repellent to
an aphid pest and attractive to the aphid predator ladybird beetle
(Ninkovic, Dahlin, Vucetic, Petrovic-Obradovic, Glinwood & Webster,
2013, Vucetic, Dahlin, Petrovic-Obradovic, Glinwood, Webster &
Ninkovic, 2014). (E )-nerolidol and
(3E ,7E )-4,8,12-trimethyl-1,3,7,11-tridecatetraene were the
primary effective volatiles released by exposed potato plants (Vuceticet al. , 2014). (Jassbi et al. , 2010)
Some plant infochemicals are released primarily by healthy plants and
can be considered as a marker of plant health status. Isoprene emission
levels are linked to plant health and photosynthetic efficiency. The
reduction of isoprene emission after pest and disease attacks is
considered as a marker for plant stress (Copolovici, Kannaste, Pazouki
& Niinemets, 2012, Jiang, Ye, Veromann & Niinemets, 2016, Toome,
Randjärv, Copolovici, Niinemets, Heinsoo & Luik, 2010). Isoprene
alleviates plant oxidative stress (van Doorn, Merl-Pham, Ghirardo, Fink,
Polle, Schnitzler & Rosenkranz, 2020).