CONTROLLED ENVIRONMENT SYSTEM FOR STUDYING ROOT ZONE TEMPERATURE EFFECTS ON CUTTING PROPAGATION

Abstract

An experimental controlled environment system for plant propagation was developed to provide three replications of a gradient in root zone temperature treatments to poinsettia cuttings. The system consisted of three propagation chambers and a transpiration chamber for water status tests. Control of VPDair and PAR was also possible. A unique component of the propagation chambers was the system of thermogradient tables that provided controlled bottom heating of the cutting medium in the root zone. Two different constant temperature water baths provided water that flowed through aluminum channels welded to opposite sides of an aluminum plate. The temperature of the two water sources could be set to provide a temperature gradient along the width of the plate. Cuttings were propagated in covered aluminum trays oriented along the length of the thermogradient table to provide multiple cuttings at different media temperatures. The thermogradient table maintained root zone temperatures within 0.5.C of all five treatment setpoints. The same source of plant material may be used for the replications, thus reducing the variability caused by differences in stock plant health and maintenance. Performance of the propagation chambers, some demonstrative results of use, and some limitations in ability to maintain air temperature and relative humidity in high radiation situations are presented.