Development of Nodal and Lateral Roots in Potato under Field Conditions

Development and distribution of nodal and lateral roots under field conditions were investigated using two to four varieties of potato.Approximately 90% of nodal roots had already emerged by the fourth leaf stage, thereafter, their diameters increased.Maximum values of both number and diameter of nodal roots were achieved during the initial flowering stage.Within up to 30 cm of soil from the surface, the number of first-order lateral roots per cm of nodal root was about 9, while the number of second-order lateral roots per cm of first-order lateral root was about 4. Diameters for both lateral roots were almost the same, 0.2-0.3mm, much thinner than the diameters of nodal roots, which were about 1.0 mm.Maximum root extension depth in soil during the growing season was about 60 cm for early varieties and 100 cm for late varieties.The roots, especially the lateral roots, concentrated at the site just beneath hill center at depth of 10-20 cm, where fertilizers had been applied.About 97% of total root length, to a depth of 100 cm, consisted of lateral roots.Average specific root length (length per unit dry weight) was 17 m g-l for nodal roots and 295 m g-l for lateral roots.