1. The volatiles from damaged plants induce defense in neighboring
plants. The phenomenon is called plant-plant communication, plant talk
or plant eavesdropping. Plant-plant communication has been reported to
be stronger between kin plants than genetically far plants in sagebrush.
2. Why do plants distinguish volatiles from kin or genetically far
plants? We hypothesize that plants respond only to important conditions;
the induced defense is not free of cost for the plant. To clarify the
hypothesis, we conducted experiments and investigations using goldenrod
of 4 different genotypes. 3. The arthropods community on tall goldenrods
were different among 4 genotypes. The response to volatiles was stronger
from genetically close plants to the emitter than from genetically
distant plants from the emitter. The volatiles from each genotype of
goldenrods were different; and they were categorized accordingly.
Moreover, the arthropod community on each genotype of goldenrods were
different. 4. Synthesis: Our results support the hypothesis: goldenrods
respond to volatiles from genetically close plants because they would
have similar arthropod species. These results are important clues
elucidating adaptive significance of plant-plant communication.