Effects of Root-Zone Temperature on Growth and Development of Roots of Two Potato (Solanum tuberosum L.) Clones as Influenced by Plant Age, Nutrient Supply, and Light Intensity

The effects of supraoptimal root-zone temperature (30 °C) on growth and development of roots were investigated in water and soil culture with cuttings of two potato clones DTO-2 (heat tolerant) and LT-1 (heat sensitive) at different plant ages, with different compositions of the nutrient solution, and different light intensities. It is suggested that the negative relation between cutting age and heat susceptibility observed in our experiments, is a reflection of the decreasing shoot/root dry weight ratio rather than of age. Heat damage of root systems increased with the concentration of the nutrient solution, nitrate being the main factor responsible. The influence of light intensity on temperature mediated restriction of root growth was relatively small. However the roots of plants grown under low light intensity (60 W m⁻² PAR) appeared to be less stressed by supraoptimal temperature, i.e. roots appeared brighter, thinner and more ramified than plants growing at high light intensity (190 W m⁻²).