title: Interrelationships of petiolar air canal architecture, water depth, and convective air flow in Nymphaea odorata (Nymphaeaceae).
abstract: OBJECTIVE
  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. Petiolar air canals are the convective flow pathways. This study describes the structure of these canals, how this structure varies with water depth, and models how convective flow varies with depth. •
  
  
  METHODS
  Nymphaea odorata plants were grown at water depths from 30 to 90 cm. Lamina area, petiolar cross-sectional 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. •
  
  
  RESULTS
  Petioles of N. odorata 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 petiolar cross-sectional area. Petiolar and air canal cross-sectional areas increase with water depth. Petiolar area scales with lamina area, but the slope of this relationship is lower 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.
authors.affiliation: Department of Biological Sciences, Florida International University, Miami, Florida 33155, USA. Richards@fi u.edu
authors.forename: Jennifer H
authors.initials: JH
authors.lastname: Richards
authors.forename: David N
authors.initials: DN
authors.lastname: Kuhn
authors.forename: Kristin
authors.initials: K
authors.lastname: Bishop
mesh_terms: D018481:Convection; D005431:Florida; D005740:Gases / Q000378:metabolism*; D008954:Models, Biological; D030721:Nymphaea / Q000033:anatomy & histology* / Q000254:growth & development / Q000378:metabolism*; D018515:Plant Leaves / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism; D012212:Rheology; D014867:Water; D053833:Wetlands
chemical_list: D005740:Gases; D014867:Water