Genotypes of Brassica rapa respond differently to plant-induced variation in air CO2 concentration in growth chambers with standard and enhanced venting

Theor Appl Genet (2009) 119:9911004 DOI 10.1007/s00122-009-1103-5

ORIGINAL PAPER

Genotypes of Brassica rapa respond differently to plant-induced variation in air CO2 concentration in growth chamberswith standard and enhanced venting

Christine E. Edwards Monia S. H. Haselhorst Autumn M. McKnite Brent E. Ewers David G. Williams Cynthia Weinig

Received: 26 March 2009 / Accepted: 25 June 2009 / Published online: 15 July 2009 Springer-Verlag 2009

Abstract Growth chambers allow measurement of phenotypic differences among genotypes under controlled environment conditions. However, unintended variation in growth chamber air CO2 concentration ([CO2]) may affect the expression of diverse phenotypic traits, and genotypes may differ in their response to variation in [CO2]. We monitored [CO2] and quantied phenotypic responses of 22 Brassica rapa genotypes in growth chambers with either standard or enhanced venting. [CO2] in chambers with standard venting dropped to 280 lmol mol-1 during the period of maximum canopy development, *80 lmol mol-1 lower than in chambers with enhanced venting. The stable carbon isotope ratio of

CO2 in chamber air (d13Cair) was negatively correlated with [CO2], suggesting that photosynthesis caused

observed [CO2] decreases. Signicant genotype 9 chamber-venting interactions were detected for 12 of 20 traits, likely due to differences in the extent to which [CO2] changed in relation to genotypes phenology or differential sensitivity of genotypes to low [CO2]. One trait, 13C discrimination (d13C), was particularly inuenced by unaccounted-for uctuations in d13Cair and

[CO2]. Observed responses to [CO2] suggest that genetic variance components estimated in poorly vented growth chambers may be inuenced by the expression of genes involved in CO2 stress responses; genotypic values estimated in these chambers may likewise be misleading such that some mapped quantitative trait loci may regulate responses to CO2 stress rather than a response to the environmental factor of interest. These results underscore the importance of monitoring, and where possible, controlling [CO2].

Introduction

Growth chambers are widely used integral tools in plant biology because they allow researchers to control and manipulate environmental conditions such as air temperature, humidity, light intensity, and photoperiod. Controlled growth settings are commonly used by molecular geneticists interested in annotating gene function. For instance, to understand genetic components of the photoperiod pathway for owering time (e.g., Corbesier and Coupland 2005; Onouchi and Coupland 1998), day length may be manipulated while...