Confronting sea level rise: combined effects of salinity and inundation on C4 metabolism of cordgrasses and their hybrids

Authors: CASTILLO, JESUS - University Of Sevilla; PEINADO-TORRUBIA, PROCOPIO - Instituto De Recursos Naturales Y Agrobiologia De Sevilla (IRNAS-CSIC); ALVAREZ-MORALES, MARIA ROSARIO - University Of Sevilla; Grewell, Brenda; DRENOVSKY, REBECCA - John Carroll University; GALLEGO-TEVAR, BLANCA - University Of Sevilla

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/3/2019
Publication Date: 7/2/2019
Citation: Castillo, J.M., Peinado-Torrubia, P., Alvarez-Morales, M., Grewell, B.J., Drenovsky, R.E., Gallego-Tevar, B. 2019. Confronting sea level rise: combined effects of salinity and inundation on C4 metabolism of cordgrasses and their hybrids. Meeting Abstract. Abstract.

Interpretive Summary: The field of conservation physiology has grown exponentially over the last decade as conservation biologists and physiological ecologists are finding novel ways to apply physiological concepts and tools to characterize biodiversity and predict multi-scale responses to environmental change. Research results by an international team will be presented by invitation in a special sesson on Threatened plants and animals – can understanding physiology inform conservation strategies? at the 2019 meeting of the Society for Experiment Botany. The presentation entitled “Confronting sea level rise: combined effects of salinity and inundation on C4 metabolism of cordgrasses and their hybrids”reports results of experimental research conducted in aquatic mesocosms at the ARS lab in Davis, California. The session not only serves as a platform to present the most cutting-edge tools in conservation physiology, but it serves to identify convergent themes in plant and animal conservation physiological studies. In the context of sea level rise, our physiological findings are useful to implement conservation strategies for native Spartina foliosa in tidal wetlands of the Pacific Coast of California, and to support eradication of invasive S. densiflora and its hybrid, which has developed transgressive traits in its enzymatic activities. These traits provide a mechanism to increase invasiveness of the hybrid taxa.

Technical Abstract: Salt marshes are subjected to biological invasions that threaten native species. Both native and invasive species must confront salinity and flooding fluctuations, especially in a content of climate change and sea level rise. Moreover, invasive and native species may hybridize and these hybrids may be more agrresive than the parental species. In this context, numerous studies attributed to several Spartina species (cordgrasses) the ability to invade and hybridise with native species. We studied the combined effect of salinity (0.5, 10, 20 and 40 ppt) and inundation depth (4.5, 35.5, and 55.0 cm deep) on the phosphoenolpyruvate carboxylase (PEPC) activity (amount of enzima and activation level, IC50) of invasive Spartina densiflora, native Spartina foliosa and their hybrid S. densiflora x foliosa from San Francisco Bay (California) in controlled conditions in a greenhouse experiment. PEPC is a ubiquitous enzyme involved in CO2 assimilation, whose role is crucial in C4 metabolism. We also recorded the effects of stress by assessing malondialdehyde (MDA) and proline concentration in flag leaves. Spartina foliosa tended to have lower levels of MDA at 10 and 40 ppt salinity. In contrast, S. densiflora showed similar MDA levels at every salinity. The hybrid increased its MDA concentration with increasing salinity, showing lower levels than its parental species between 0.5 and 20 ppt salinity. Comparing different inundation treatments at 10 ppt salinity, S. foliosa did not alter its MDA levels with inundation; S. densiflora increased its MDA concentration only at intermediate inundation; and the accumulation of MDA in the hybrid did not change with inundation. Overall, S. foliosa was the taxon that accumulated more MDA, except at hypersalinity. In shallow inundation, each taxon exhibited low proline concentration from fresh water to 20 ppt salinity. At hypersalinity, there was a high accumulation of proline for every taxa, with S. densiflora showing the hihest values. S. foliosa had a slight tendency to increase its accumulation of proline as inundation was deeper. S. densiflora maintained its proline levels until 20 ppt and inundation did not alter its accumulation, except for 40 ppt. Inundation depth did not affect proline accumulation for the hybrid. Under shallow inundation, S. foliosa and the hybrid showed an abrupt decrease in PEPC specific activity at salinities equal and higher than 10 ppt, whereas S. densiflora presented this decrease at 20 ppt. Both abiotic stresses combined provoked different responses in each taxon. There was a tendency either to maintain or decrease its specific activity in S. foliosa when salinity was combined with inundation, whereas an improvement of PEPC activity was recorded for S. densiflora except at 40 ppt. The hybrid showed a remarkable increase in PEPC specific activity at fresh water at intermediate inundation. PEPC in vitro phosphorylation (IC50) showed a general increase at higher salinities and shallow inundation for both parental taxa, whereas the hybrid kept constant IC50 values. S. densiflora exhibited the highest levels of IC50 in comparison with the other taxa. On the other hand, S. foliosa tended keep stable IC50 levels with inundation and S. densiflora exhibited a two-fold dephosphorylation with increasing inundation depth. The highest IC50 values were recorded for each taxon under hypersalinity and medium to high inundation depth. In the context of sea level rise, our physiological findings are useful to implement conservation strategies for native S. foliosa in tidal wetlands of the Pacific Coast of California, and to support eradication of invasive S. densiflora and its hybrid, which was able to develop transgresive traits in its enzymatic activities.