Effects of elevated CO₂ on development and morphology of spring wheat grown in cooled and non-cooled open-top chambers

Abstract

Facilities for studying effects of elevated CO₂ on crops affect the microclimate in the crop. Open-top chambers may increase temperature by 1–3˚C compared to ambient conditions.

This paper describes a newly developed cooling system for open-top chambers. In 1995 and 1996, experiments were carried out to test the system and analyse the effects of temperature on crop phenological and morphological response to elevated CO₂. Spring wheat (Triticum aestivum L. cv. Minaret) was subjected to ambient and doubled CO₂ concentration in both cooled and non-cooled chambers.

The cooling system reduced temperature by 1.6–2.4˚C, and this delayed maturity by 10 days. In contrast, elevated CO₂ did not affect phenological development. Elevated CO₂ reduced tiller density, green leaf number per tiller and specific leaf area, thereby reducing the capacity for light interception of the crop. Crop height growth before anthesis mainly responded to temperature, but after anthesis it was only affected by CO₂, indicating a shift from sink- to source-limited growth. For none of the parameters studied, a significant statistical interaction of CO₂ and temperature was found.

The cooling system proved effective. Atemperature difference of about 2˚C affected crop development and morphology more strongly than CO₂ doubling. However, the absence of CO₂-temperature interaction suggests that CO₂ effects may validly be investigated even without a cooling system.