How well do you know your growth chambers? Testing for chamber effect using plant traits

Abstract

BackgroundPlant 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.Results and discussionFour 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 (δ13C) 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.Conclusion(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) δ13C, 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.

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“…Ideally CO 2 treatments would be repeated or run in parallel in a number of different chambers to fully test for chamber effects; effects driven entirely by the chamber which are independent of growth conditions (Porter et al . ). Whilst this approach is feasible when comparing two different CO 2 concentrations this approach would quickly become untenable when comparing multiple species across multiple CO 2 treatments.…”

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“…Plants were rotated between the two chambers every 2 weeks to negate any chamber effects (e.g., Porter et al, 2015). The chamber conditions were set to a 17-hr photoperiod with a 30-min simulated dawn and dusk.…”

“…Growth light levels (photosynthetically active radiation) varied between 100 and 500 μmol·m −2 ·s −1 depending on plant height. Plants were rotated between the two chambers every 2 weeks to negate any chamber effects (e.g., Porter et al, 2015).…”

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“…To minimize the potential environmental variations among chambers, plants were randomly rotated within and among OTCs at a 1 week interval. 28 N concentrations in each chamber were kept at 0.06 (low N) and 0.24 g N kg −1 soil (high N). Within a chamber, each N treatment was repeated eight times.…”