Changes in Hydraulic Properties of Seminal Roots During Wheat Evolution

Root architecture influences the ability of plants to extract water from the soil, and it reflects plants strategies to survive under limited resources. During wheat domestication, the number of seminal roots increased (from 3 to 5), and consequently, seedlings lost their ability to recover from water stress. Moreover, this increase in the number of seminal roots was associated with a decrease in water movement. Here we analyzed the changes in the root hydraulic conductivity in domesticated and wild wheat. Using anatomical, physiological and computational modeling, we examine the changes in root hydraulic properties associated with wheat evolution under domestication. Anatomical characterization of the seminal roots in wild emmer wheat (Triticum turgidum ssp. dicoccoides) and domesticated durum wheat (Triticum turgidum ssp. durum) revealed that while the total root surface area was similar between both lines, the wild accession had significantly larger metaxylem elements. Thus, the calculated axial conductance of the wild plants was significantly higher (24%) as compared with the domesticated seedlings. To test the hydraulic properties of the roots, we analyzed 11-days-old seedling of wild and domesticated wheat using pressure chamber. In agreement with the anatomical results, the wild plants had higher hydraulic conductivity. We used the anatomical and physiological information as inputs to a numerical model for water flow in soil and root system (RSWMS). This model enables to study how the different root architectures of wild and domesticated wheat affect water state in the soil and in the plant. A construct realistic scenarios, representing different environmental conditions relevant to wheat were tested. Our results shed new light on the modification in seminal root architecture and hydraulic properties involved in wheat domestication.