A chamber for the simulation of radiation freezing of plants

Frost injury to plants can occur following episodic radiation frosts. In th e UK this is particularly important to spring sown crops such as potatoes. Most laboratory based frost studies simulate freezing using either conducti ve or convective freezing chambers. Such frost tests do not simulate overni ght freezing events adequately. A freezing chamber based on radiative cooling is described which mimics ove rnight radiative freezing. The chamber is rectangular in design (1 m x 1 m x 2 m high) with a radiative cooling plate at the top of the chamber cooled to -40 degrees C to -45 degrees C using HFC coolants, which acts as a cold black body. The sides of the chamber are also cooled to variable temperatu res down to -5 degrees C in order to prevent the chamber walls radiating to the plant material during testing. Using thermocouples to measure air temperature and plant temperature the ch amber has been characterised to simulate the radiative cooling conditions f ound in the UK during autumn and spring. Exotherm detection upon plant free zing is simplified by virtue of the reduction in temperature fluctuation no rmally experienced at the plant surface during natural freezing. Radiation frosts and subsequent frost damage to potatoes have been recorded in the te mperature range -4 degrees C to -5 degrees C. The equipment is recommended for studies of frost damage to plants normally caused by episodic radiation frost events.