The Effect of Root and Shoot Temperatures on Growth of Ceanothus greggii Seedlings

The effect of varying independently nutrient solution temperature(5, 15, 25 C) and air temperature (10, 20, 30 C) on hydroponicallygrown Ceanothus greggii (Rhamnaceae) seedlings was studied.Increasing both air and solution temperatures caused higherroot and shoot biomass and larger root and leaf areas. Root/shootbiomass ratio increased with increasing solution temperatureand decreased with increasing air temperature. The surface areaof individual leaves decreased with higher air temperaturesbut did not change with solution temperatures. These resultsare opposite to what is predicted from Davidson's balanced rootand shoot activity model. We suggest that nutrient solutiontemperature directly affected root growth and that air temperaturedirectly affected shoot growth. Ceanothus greggii (Trel.) Jeps., root temperatures, soot temperature, plant growth, biomass allocation