Retention of Stored Water Enables Tropical Tree Saplings to Survive Extreme Drought Conditions
To test the ability of tropical tree saplings to avoid dehydration during severe droughts, as well as the mechanisms and traits associated with dehydration avoidance, potted saplings were subjected to three months without water and their water relations were compared to well-watered control plants.
Some tree species remained well hydrated even after three months without water. These species had reduced root surface area in the drought treatment, suggesting a role for root abscission in preventing water loss from roots to soil during severe drought.
Tree species vary greatly in their ability to extract water from drying soil, yet it is unclear how much they vary in their ability to remain hydrated when soil water is unavailable. To explore variation in the ability to regulate plant water status, this study subjected potted saplings of tropical trees to extreme drought and compared their responses to well-watered plants. After three months, soil in the drought treatment was extremely dry, yet some species had 100% survival and maintained water status similar to well-watered plants (i.e., dehydration-avoiding species). Other species had low survival and reached low water status. The dehydration-avoiding species had traits that favor water storage (e.g., low tissue density), which could provide a reservoir that buffers water status despite water loss, yet they maintained most of their stored water during the drought. The dehydration-avoiding species also had low lateral root area, which was further reduced in the drought treatment. This may slow water loss into dry soil. Together, these results suggest that the ability to avoid dehydration during extreme drought varies greatly among species and is dependent on retaining stored water within the plant.
Smithsonian Tropical Research Institute
Research was funded with a Garden Club of America award in tropical botany and a Smithsonian Tropical Research Institute short-term fellowship. During manuscript preparation, BT Wolfe was supported in part by the Next-Generation Ecosystem Experiments (NGEE)–Tropics, funded by the Office of Biological and Environmental Research within the U.S. Department of Energy Office of Science.
Wolfe, B. T. “Retention of stored water enables tropical tree saplings to survive extreme drought conditions.” Tree Physiology 37(4), 469–480 (2017). [DOI:10.1093/treephys/tpx001].