Data from: Whole-plant metabolic allocation under water stress

Trade-offs between plant growth and defense depend on environmental
resource availability. Plants are predicted to prioritize growth when
environmental resources are abundant and defense when environmental
resources are scarce. Nevertheless, such predictions lack a whole-plant
perspective-they do not account for potential differences in plant
allocation above- and belowground. Such accounting is important because
leaves and roots, though both critical to plant survival and fitness,
differ in their resource-uptake roles and, often, in their vulnerability
to herbivores. Here we aimed to determine how water availability affects
plant allocation to multiple metabolic components of growth and defense in
both leaves and roots. To do this, we conducted a meta-analysis of data
from experimental studies in the literature. We assessed plant metabolic
responses to experimentally reduced water availability, including changes
in growth, nutrients, physical defenses, primary metabolites, hormones,
and other secondary metabolites. Both above- and belowground, reduced
water availability reduced plant biomass but increased the concentrations
of primary metabolites and hormones. Importantly, however, reduced water
had opposite effects in different organs on the concentrations of other
secondary metabolites: reduced water increased carbon-based secondary
metabolites in leaves but reduced them in roots. In addition, plants
suffering from co-occurring drought and herbivory stresses exhibited
dampened metabolic responses, suggesting a metabolic cost of multiple
stresses. Our study highlights the needs for additional empirical studies
of whole-plant metabolic responses under multiple stresses and for
refinement of existing plant growth-defense theory in the context of whole
plants.