Effects of temperature on parameters of root growth relevant to nutrient uptake: Measurements on oilseed rape and barley grown in flowing nutrient solution

Summary Effects of root temperature on the growth and morphology of roots were measured in oilseed rape (Brassica napus L.) and barley (Hordeum vulgare L.). Plants were grown in flowing solution culture and acclimatized over several weeks to a root temperature of 5°C prior to treatment at a range of root temperatures between 3 and 25°C, with common shoot temperature. Root temperature affected root extension, mean radius, root surface area, numbers and lengths of root hairs. Total root length of rape plants increased with temperature over the range 3–9°C, but was constant at higher temperatures. Root length of barley increased with temperature in the range 3–25°C, by a factor of 27 after 20 days. Root radii had a lognormal distribution and their means decreased with increasing temperature from 0.14 mm at 3°C to 0.08 mm at 25°C. The density of root hairs on the root surface increased by a factor of 4 in rape between 3 and 25°C, but in barley the highest density was at 9°C. The contribution of root hairs to total root surface area was relatively greater in rape than in barley. The changes in root system morphology may be interpreted as adaptive responses to temperature stress on nutrient uptake, providing greater surface area for absorption per unit root weight or length.