title: Transpiration modulates phosphorus acquisition in tropical tree seedlings.
abstract: Several experiments were conducted with tropical tree and liana seedlings in which transpiration ratio and leaf phosphorus to carbon ratio (P:C) were measured. Transpiration ratio was expressed as kg H(2)O transpired&emsp14;g(-1) C incorporated into plant biomass, and leaf P:C as mg P&emsp14;g(-1) C. Leaf P:C was positively correlated with transpiration ratio across 19 species for plants grown under similar conditions (R(2) = 0.35, P < 0.01, n = 19). For five species in the dataset, multiple treatments were imposed to cause intra-specific variation in transpiration ratio. Within four of these five species, leaf P:C correlated positively with transpiration ratio. The slope and strength of the correlation varied among species. In one experiment, whole-plant P:C was measured in addition to leaf P:C. Patterns of correlation between whole-plant P:C and transpiration ratio were similar to those between leaf P:C and transpiration ratio. Together, these observations suggest that transpiration can influence the rate of P uptake from soil in tropical tree and liana seedlings. We suggest that this occurs through transport of inorganic phosphate and organic P compounds to root surfaces by transpiration-induced mass flow of the soil solution. The positive correlation between leaf P:C and transpiration ratio suggests that leaf P:C could decline in tropical forests as atmospheric CO(2) concentration rises, due to decreasing transpiration ratios.
authors.affiliation: Research School of Biology, The Australian National University, Canberra, Australian Capital Territory 0200, Australia. lucas.cernusak@anu.edu.au
authors.forename: Lucas A
authors.initials: LA
authors.lastname: Cernusak
authors.forename: Klaus
authors.initials: K
authors.lastname: Winter
authors.forename: Benjamin L
authors.initials: BL
authors.lastname: Turner
mesh_terms: D002244:Carbon / Q000378:metabolism*; D010758:Phosphorus / Q000378:metabolism*; D018526:Plant Transpiration; D036226:Seedlings / Q000502:physiology; D014197:Trees / Q000502:physiology*; D014329:Tropical Climate
chemical_list: D010758:Phosphorus; D002244:Carbon