|Richards, Jennifer -|
|Bishop, Kristin -|
Submitted to: American Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 27, 2012
Publication Date: N/A
Interpretive Summary: Wetland plants like Nymphaea odorata have a pressure-driven, flow-through ventilation that aerates the submerged parts of the plant, allowing it to grow in deeper water. These ventilation systems use thermal or humidity-driven pressure gradients to establish a mass flow of air from one set of emergent leaves or shoots through submerged stems to another set of emergent leaves or shoots. This mass flow supplies oxygen to the submerged parts of the plant and flushes out carbon dioxide and methane. When the ventilation system is working, the increased soil aeration in the roots’ vicinity can substantially alter wetland biogeochemistry by changing the soil redox state and thus availability of nutrients, altering microbial populations, and preventing the build-up of soil phytotoxins. On a global scale, convective flows enhance methane efflux from submerged sediments. Because wetlands have been estimated to provide between 20 and 39% of this greenhouse gas’s annual emissions, and because vegetation is the dominant route for these emissions, convective flow also has a major impact on global climate change. This report should be of interest to research scientists in academia and the USDA-ARS who are studying methane generation by plants and its effect on global climate change.
Technical Abstract: Premise of the study--Nymphaea odorata grows in water up to 2 m deep, producing fewer, larger leaves in deeper water. This species has a convective flow system that moves gases from younger leaves through submerged parts to older leaves, aerating submerged parts. Petiole air canals are in the convective flow pathway. This study describes the structure of these canals, including their differences among water depths, and models how convective flow varies with depth. Methods--N. odorata plants were grown from 30 to 90 cm water depths. Lamina area, petiole XS area, and number and area of air canals were measured. Field-collected leaves and leaves from juvenile plants were analyzed similarly. Using these data and data from the literature, we modeled how convective flow changes with water depth. Key results--N. odorata petioles produce two central pairs of air canals; additional pairs are added peripherally, and succeeding pairs are smaller. The first three pairs account for 96% of air canal area. Air canals form 24% of petiole XS area. Petiole and air canal XS area increase with water depth. Petiole area scales with lamina area, but the slope of this relationship is less in 90 cm water than at shallower depths. In our model the rate of convective flow varied with depth and with the balance of influx to efflux leaves. Conclusions--Air canals in N. odorata petioles increase in size and number in deeper water but at a decreasing amount in relation to lamina area. Convective flow also depends on the number of influx to efflux laminae.