title: How well do you know your growth chambers? Testing for chamber effect using plant traits.
abstract: BACKGROUND
  Plant growth chambers provide a controlled environment to analyse the effects of environmental parameters (light, temperature, atmospheric gas composition etc.) on plant function. However, it has been shown that a 'chamber effect' may exist whereby results observed are not due to an experimental treatment but to inconspicuous differences in supposedly identical chambers. In this study, Vicia faba L. 'Aquadulce Claudia' (broad bean) plants were grown in eight walk-in chambers to establish if a chamber effect existed, and if so, what plant traits are best for detecting such an effect. A range of techniques were used to measure differences between chamber plants, including chlorophyll fluorescence measurements, gas exchange analysis, biomass, reproductive yield, anatomical traits and leaf stable carbon isotopes.
  
  
  CONCLUSIONS
  Four of the eight chambers exhibited a chamber effect. In particular, we identified two types of chamber effect which we term 'resolvable' or 'unresolved'; a resolvable chamber effect is caused by malfunctioning components of a chamber and an unresolved chamber effect is caused by unknown factors that can only be mitigated by appropriate experimental design and sufficient replication. Not all measured plant traits were able to detect a chamber effect and no single trait was capable of detecting all chamber effects. Fresh weight and flower count detected a chamber effect in three chambers, stable carbon isotopes (δ(13)C) and net rate CO2 assimilation (An) identified a chamber effect in two chambers, stomatal conductance (gs) and total performance index detected an effect only in one chamber.
  
  
  CONCLUSIONS
  (1) Chamber effects can be adequately detected by fresh weight measurements and flower counts on Vicia faba plants. These methods were the most effective in terms of detection and most efficient in terms of time. (2) δ(13)C, gs and An measurements help distinguish between resolvable and unresolved chamber effects. (3) Unresolved chamber effects require experimental unit replication while resolvable chamber effects require investigation, repair and retesting in advance of initiating further experiments.
authors.affiliation: School of Biology and Environmental Science, Earth Institute, O'Brien Centre for Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Amanda S
authors.initials: AS
authors.lastname: Porter
authors.affiliation: School of Biology and Environmental Science, Earth Institute, O'Brien Centre for Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Christiana
authors.initials: C
authors.lastname: Evans-Fitz Gerald
authors.affiliation: School of Biology and Environmental Science, Earth Institute, O'Brien Centre for Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: McElwain
authors.affiliation: School of Biology and Environmental Science, Earth Institute, O'Brien Centre for Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Charilaos
authors.initials: C
authors.lastname: Yiotis
authors.affiliation: School of Biology and Environmental Science, Earth Institute, O'Brien Centre for Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Caroline
authors.initials: C
authors.lastname: Elliott-Kingston
keywords: Chamber effect; Chlorophyll fluorescence; Controlled environment; Experimental design; Fresh weight; Gas analysis; Plant anatomy; Plant growth chamber; Stable carbon isotopes; Uniformity trials