title: Stabilization of pH in solid-matrix hydroponic systems.
abstract: 2-[N-morpholino]ethanesulfonic acid (MES) buffer or Amberlite DP-1 (cation-exchange resin beads) were used to stabilize substrate pH of passive-wicking, solid-matrix hydroponic systems in which small canopies of Brassica napus L. (CrGC 5-2, genome : ACaacc) were grown to maturity.  Two concentrations of MES (5 or 10 mM) were included in Hoagland 1 nutrient solution.  Alternatively, resin beads were incorporated into the 2 vermiculite : 1 perlite (v/v) growth medium at 6% or 12% of total substrate volume.  Both strategies stabilized pH without toxic side effects on plants.  Average seed yield rates for all four pH stabilization treatments (13.3 to 16.9 g m-2 day-1) were about double that of the control (8.2 g m-2 day-1), for which there was no attempt to buffer substrate pH.  Both the highest canopy seed yield rate (16.9 g m-2 day-1) and the highest shoot harvest index (19.5%) occurred with the 6% resin bead treatment, even though the 10 mM MES and 12% bead treatments maintained pH within the narrowest limits.  The pH stabilization methods tested did not significantly affect seed oil and protein contents.
authors.affiliation: Department of Horticulture, Purdue University, West Lafayette, IN 47907-1165, USA.
authors.forename: J
authors.initials: J
authors.lastname: Frick
authors.forename: C A
authors.initials: CA
authors.lastname: Mitchell
mesh_terms: D017738:Alkanesulfonic Acids; D001937:Brassica / Q000254:growth & development*; D002021:Buffers; D002197:Capillary Action; D002411:Cation Exchange Resins; D003470:Culture Media; D006863:Hydrogen-Ion Concentration; D018527:Hydroponics / Q000379:methods*; D009025:Morpholines; D010938:Plant Oils / Q000032:analysis; D010940:Plant Proteins / Q000032:analysis; D018517:Plant Roots / Q000254:growth & development*; D012639:Seeds / Q000737:chemistry
chemical_list: D017738:Alkanesulfonic Acids; D002021:Buffers; D002411:Cation Exchange Resins; D003470:Culture Media; D009025:Morpholines; D010938:Plant Oils; D010940:Plant Proteins; C004550:2-(N-morpholino)ethanesulfonic acid