Sammendrag
Inducible plant defense is a beneficial strategy for plants, which imply that plants
should allocate resources from growth and reproduction to defense when herbivores
attack. Plant ecologist has often studied defense responses in wild populations by biomass
clipping experiments, whereas laboratory and greenhouse experiments in addition
apply chemical elicitors to induce defense responses. To investigate whether field
ecologists could benefit from methods used in laboratory and greenhouse studies, we
established a randomized block-design
in a pine-bilberry
forest in Western Norway.
We tested whether we could activate defense responses in bilberry (Vaccinium myrtillus)
by nine different treatments using clipping (leaf tissue or branch removal) with or
without chemical treatment by methyljasmonate (MeJA). We subsequently measured
consequences of induced defenses through vegetative growth and insect herbivory
during one growing season. Our results showed that only MeJA-treated
plants showed
consistent defense responses through suppressed vegetative growth and reduced
herbivory by leaf-chewing
insects, suggesting an allocation of resources from growth
to defense. Leaf tissue removal reduced insect herbivory equal to the effect of the
MeJa treatments, but had no negative impact on growth. Branch removal did not reduce
insect herbivory or vegetative growth. MeJa treatment and clipping combined
did not give an additional defense response. In this study, we investigated how to induce
defense responses in wild plant populations under natural field conditions. Our
results show that using the chemical elicitor MeJA, with or without biomass clipping,
may be a better method to induce defense response in field experiments than clipping
of leaves or branches that often has been used in ecological field studies.
bilberry, chemical elicitor, clipping experiment, deer, field experiment, growth, herbivory, insects,
methyljasmonate, Vaccinium
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