Salinity driven interactions between plant growth and a biological control agent

Drought resistance in two populations of invasive Tamarix compared using multiple methods

An on-going question in plant hydraulic research is whether there is intra-specific variability and/or plasticity in xylem traits. Plasticity could be important in taxa that colonize diverse habitats. We used Tamarix, a non-native woody plant, to investigate population differences in hydraulic conductivity (Ks), vulnerability-to-embolism curves and vessel anatomy. We also conducted a season-long drought experiment to determine water potentials associated with crown dieback of field-grown plants. We measured vessel length and diameter, and compared visual (micro-computed tomography; microCT) and hydraulic methods to quantify percentage loss in hydraulic conductivity (PLC). Among plants grown in a common environment, we did not find differences in our measured traits between two populations of Tamarix that differ in salinity at their source habitats. This taxon is relatively vulnerable to embolism. Within samples, large diameter vessels displayed increased vulnerability to embolism. We found that the microCT method overestimated theoretical conductivity and underestimated PLC compared with the hydraulic method. We found agreement for water potentials leading to crown dieback and results from the hydraulic method. Saplings, grown under common conditions in the present study, did not differ in their xylem traits, but prior research has found difference among source-site grown adults. This suggests that plasticity may be key in the success of Tamarix occurring across a range of habits in the arid southwest USA.

Soil salinization and chemically mediated plant-insect interactions in a changing climate

Increase in soil salinization due to climate change is a global phenomenon that can induce significant changes in plant growth, physiology, and chemistry, exacerbating growing threats to insect biodiversity. Insects that rely on plants are likely to be indirectly impacted by changes in soil salt content through changes in plant chemistry, yet few studies link changes in plant metabolism to impacts on higher trophic levels. Some salinity-mediated changes in specialized metabolites may be predictable due to highly conserved metabolic pathways shared between herbivore defense and stress resistance, but recent studies also suggest substantial variation across plant species and habitats. To date, most of the research on salinity and chemically mediated plant-insect interactions has focused on herbivores, particularly in agricultural systems. Published effects of salinity on pollinators and parasitoids are scarce. Future research will need to focus more on the role of plant chemistry to bridge the divide between studies of plant and insect responses to salinization.