Plant responses to variation in moisture availability
Water availability is the primary factor limiting the productivity of plants and ecosystems. Global climate models indicate an increase in the temporal and spatial variation of water availability in most terrestrial systems. One primary focus of my research is thus to explore adaptations in plants to water-stress.
To this end, as part of an undergraduate thesis project (with Hafiz Maherali and Chris Caruso, Guelph), I studied the evolution of physiological adaptions to water stress, namely phenotypic plasticity. In greenhouse conditions representative of Californian Mediterranean systems in the wet (El Niño) and dry (La Niña) phases of the ENSO oscillation, we tested “fine-grained” evolution (i.e., GxE interactions) by assessing genetically based differentiation in protective plastic changes to frequent drought (e.g., down-regulation of photosynthesis, reduced leaf-area, early flowering) in recombinant inbred lines of Avena barbata. While only marginal GxE interactions were detected, we found some trade-offs between physiological plasticity and biomass accumulation to frequent droughts, suggesting that the fitness of plants may be reduced by evolved plasticity to persistent drought. I furthered this work by conducting another similar experiment but with the addition of arbuscular mycorrhizal fungi (AMF) to test whether the symbiosis is maintained under extreme variation in moisture availability. We found AMF to be ‘cheaters’ in the relationship whereby plants inoculated with AMF had reduced fitness under recurring drought, likely due to carbohydrate provisioning by the host-plant to AMF.
Changes in the flowering phenology of trees are also expected to occur with increased variation in moisture availability. To explore this, during the extreme El Nino in 2016, I surveyed the effects of water stress on general flowering in lowland Dipterocarp forests of Peninsular Malaysia (Pasoh field station, Forest Research Institute of Malaysia). I found widespread early termination of flowering in drier sites, with large trees aborting flowering almost entirely. El Niño events are believed to initiate general flowering of Dipterocarps; however, these results show that termination of flowering occurs during extreme events, which has potentially catastrophic implications.
To this end, as part of an undergraduate thesis project (with Hafiz Maherali and Chris Caruso, Guelph), I studied the evolution of physiological adaptions to water stress, namely phenotypic plasticity. In greenhouse conditions representative of Californian Mediterranean systems in the wet (El Niño) and dry (La Niña) phases of the ENSO oscillation, we tested “fine-grained” evolution (i.e., GxE interactions) by assessing genetically based differentiation in protective plastic changes to frequent drought (e.g., down-regulation of photosynthesis, reduced leaf-area, early flowering) in recombinant inbred lines of Avena barbata. While only marginal GxE interactions were detected, we found some trade-offs between physiological plasticity and biomass accumulation to frequent droughts, suggesting that the fitness of plants may be reduced by evolved plasticity to persistent drought. I furthered this work by conducting another similar experiment but with the addition of arbuscular mycorrhizal fungi (AMF) to test whether the symbiosis is maintained under extreme variation in moisture availability. We found AMF to be ‘cheaters’ in the relationship whereby plants inoculated with AMF had reduced fitness under recurring drought, likely due to carbohydrate provisioning by the host-plant to AMF.
Changes in the flowering phenology of trees are also expected to occur with increased variation in moisture availability. To explore this, during the extreme El Nino in 2016, I surveyed the effects of water stress on general flowering in lowland Dipterocarp forests of Peninsular Malaysia (Pasoh field station, Forest Research Institute of Malaysia). I found widespread early termination of flowering in drier sites, with large trees aborting flowering almost entirely. El Niño events are believed to initiate general flowering of Dipterocarps; however, these results show that termination of flowering occurs during extreme events, which has potentially catastrophic implications.