Vertical gradient in soil temperature stimulates development and increases biomass accumulation in barley

We have detailed knowledge from controlled environment studies on the influence of root temperature on plant performance, growth and morphology. However, in all studies root temperature was kept spatially uniform, which motivated us to test whether a vertical gradient in soil temperature affected development and biomass production. Roots of barley seedlings were exposed to three uniform temperature treatments (10, 15 or 20 degrees C) or to a vertical gradient (2010 degrees C from top to bottom). Substantial differences in plant performance, biomass production and root architecture occurred in the 30-day-old plants. Shoot and root biomass of plants exposed to vertical temperature gradient increased by 144 respectively, 297%, compared with plants grown at uniform root temperature of 20 degrees C. Additionally the root system was concentrated in the upper 10 cm of the soil substrate (98% of total root biomass) in contrast to plants grown at uniform soil temperature of 20 degrees C (86% of total root biomass). N and C concentrations in plant roots grown in the gradient were significantly lower than under uniform growth conditions. These results are important for the transferability of normal greenhouse experiments where generally soil temperature is not controlled or monitored and open a new path to better understand and experimentally assess rootshoot interactions.