BackgroundPlants
are exposed to various environmental challenges. Especially with
ongoing climate change, droughts and insect outbreaks are expected to
become more frequent. Plant responses to these challenges are mediated
by interacting phytohormonal pathways that influence plant growth, but
little is known how these responses to single and combined challenges
vary across different scales, within and between species. Thus, we
investigated species- and accession-specific responses to two
environmental challenges in three perennial plant species and compared
the responses between species. Clones of several accessions of the
herbaceous species Tanacetum vulgare, the woody vine Solanum dulcamara, and the tree Populus nigra
were subjected to similar control, herbivory, drought, and combined
(drought and herbivory) treatments. After the exposure, foliar
phytohormones and various morphological traits were quantified.ResultsPlants of T. vulgare
did not respond in jasmonic acid (JA) levels, but showed an increase in
abscisic acid (ABA) and a reduced aboveground biomass, particularly
under the combined challenges. Plants of S. dulcamara exhibited similar responses, but JA levels were enhanced by all treatments. In contrast, P. nigra
uniquely induced salicylic acid under the combined treatment, but
showed no impacts on growth. Phenotypic plasticity reflected these
species-specific patterns, with none of the phytohormones or
morphological traits exhibiting uniform plasticity across species, but
with substantial accession-specific pattern. Structural equation models
further revealed distinct phytohormone-mediated pathways underlying
morphological traits, potentially linking environmental challenges and
accessions to specific plant responses within each species. Besides
these species-specific differences, several traits responded
consistently in all three species to the environmental challenges.
Jasmonoyl-isoleucine was induced by herbivory and the combined
treatment, ABA by drought and the combined treatment, and indole acetic
acid by the combined treatment in all species. Root mass remained
unchanged in all species.ConclusionsOur
results indicate that plant responses to similar challenges include
both species-specific and conserved components. The combined treatment
elicited the strongest responses, suggesting that simultaneous
challenges under climate change may have complex effects on plant
performance. The intra- and interspecific differences revealed here
highlight the need to further explore the mechanisms underlying this
specificity and understand patterns of plant resilience.