Elongation and Branching of Seminal and Nodal Roots in Wheat Grown under Field Condition.

Abstract

Growth and development of seminal and nodal roots in wheat were examined. After the experimental site was plowed and fertilized, a Japanese wheat cultivar was planted. Root system distributed in the top 30 cm of soil was taken using the monolith method every 2 weeks throughout the growing season. In each sampling, all seminal and nodal roots of three selected plants with normal size were identified and the number of root axes were recorded. Then the length of the root axes and the total root length including all lateral roots were measured, and the branching degree was examined as well. The total number and length of root axes in the seminal roots increased and almost reached a constant value soon after planting. The total root length of seminal roots, on the other hand, increased thereafter due to well-developed root branching, reached a maximum value and then decreased becouse of possible loss of lateral roots. On the contrary, the total number and length of nodal roots on main stems increased in the later growth stages followed by development of nodal roots emerged from tillers. Root branching of nodal roots was poorly developed compared with seminal roots. In the former growing period, most shallow roots consisted of seminal roots with well-developed laterals, whereris nodal roots increased to occupy a large portion in the later stages because of the increase in the total number of nodal roots as well as the decrease in the total length of seminal roots.