A controlled environment room for producing advective white or black frost conditions

Abstract

The ability to frost plants in controlled environment facilities allows the research worker to have complete control over the nature, intensity and duration of low temperature conditions. This facilitates studies into factors responsible for frost tolerance in plants and allows plant breeding and selection programs to progress more rapidly and with much greater precision than is possible in the field. A large walk-in controlled environment room capable of precisely reproducing advective, white or black frost conditions is described. Air temperature can be controlled from 15°C maximum to −20°C ± 0·5°C minimum. Maximum to minimum and minimum to maximum temperature changeovers are independently programmed and controlled and can occur over 1, 2, 3, 4, 6, 8 or 10 h periods in either 16 or 64 proportional steps. Changeover rates typically vary between 1°C h −1 and 20°C h −1. Separate equipment is provided to maintain root temperatures above 0°C if required. Air relative humidity is controlled; white frosts are produced using saturated low-temperature air, and black frosts are formed with cold air of low moisture content. Lighting systems permit irradiance levels of up to 170 W m −2 (photosynthetically active radiation) during frost conditions. The solid state control systems and modified commercial refrigeration systems are described. Design features allow the maintenance of low temperature conditions for long time periods without control loss during evaporator coil defrosting.