 The most distal segments of the root system (unbranched root segments that end in root tips) are classified as first-order roots.When two roots of the same order converge, the root that results from their combination is assigned the next highest root order (so two first-order roots merge to form a second-order root).When two root segments of different orders meet, the resulting root is given the higher order of the two roots that merged (so a second-order and a first-order root combine to form a second-order root).