The influence of open-top chambers on the growth and development of field bean

In 1988, open-top chambers (OTCs) based on the Raleigh (USA) design were used to investigate the effect of ambient pollutants on field-sown Vicia faba cv, Ticol. This paper reports an aspect of this study in which the effect of the chamber itself on crop growth and development was investigated. Non-filtered chamber (NF OTC) microclimates were typically 0.8°C warmer, with 20% less radiation and reduced wind speeds compared with open-field sub-plots (AA treatments). These differences are sufficient to induce alterations in the growth and development of V. faba. Plant development progressed more quickly inside the chambers in response to the faster accumulation of thermal time. Chamber-grown V. faba were up to 20 cm taller and had fewer branches (0.7 compared with 1.2 per plant) than plants grown in the AA treatments. Larger leaf areas developed on the NF plants, and there were fewer stomata per unit leaf area in this treatment (34 compared with 42 mm^-2 , P= 0.01). Enclosure within an OTC did not alter the number of flowers per plant or the number of flowers which formed pods. However, at harvest, chamber-grown plants had a 13% higher yield than the plants grown in open-field plots. These differences in growth are described in relation to the microclimate differences between AA and NF treatments.