Self And The Phenomenon Of Life: A Biologist Examines Life From Molecules To Humanity

The Plant Self 97

“9x6” b2726 Self and the Phenomenon of Life: A Biologist Examines Life from Molecules to Humanity

and waxy cuticles serve as sunscreens and prevent desiccation. Rubber
and lignin provide mechanical support, wound healing, and seed protec-
tion. A huge repertoire of compounds is produced not only to cope with
changing environment, but also for interspecies interactions that affect
pollination. Genomic comparisons suggest that the expansion of plant
metabolic pathways occurred 500 million years ago, when plants started
to colonize the land, and the process continues ever since.^2

5.3 Tree Talks and Eavesdropping

Plant-plant communication can be conducted through the air by a group
of gaseous substances (Fig. 5.1). About 2,000 of these volatile organic

Fig. 5.1. Volatile signals between plants. Plants subject to biotic and/or abiotic stress
emit a bouquet of volatile organic compounds (VOC) that is carried in the air to other
parts of the same plant (remote from the site of injury) or to other plants of the same or
different species. The composition and relative intensity of each component molecule
depends on the type of stress and the emitter plant. Upon sensing the stress signal, the
receptors in the neighboring plants trigger a series of intracellular signal transduction
cascades, leading to gene activation and metabolic alterations. [See Note 6.]