EXTENT AND LONGEVITY OF THE SEMINAL ROOTS OF CERTAIN GRASSES

Grasses possess two distinct root systems. The primary or seminal root system begins development immediately upon the germination of the seed and consists of one to several main roots and their branches, the number varying with the species. The young plant is entirely dependent upon this primary root system for water and soil nutrients. Later, especially during the period of tiller production, a secondary or nodal root system develops from the lower nodes of the parent culm and from the tillers. The seminal roots are often designated as temporary in general texts and even in special books on grasses. Hitchcock (1) states: "The primary root persists only a short time after germination, its place being taken by secondary roots produced from the nodes of the young culm." It has been observed by Locke and Clark (5) that where extremely dry surface soil or soil drying or crusting prevented normal development of nodal roots, the seminal roots furnished sufficient moisture to maintain the growth of the wheat plant to maturity. Weaver, Jean, and Crist (13), after numerous investigations on the root systems of several cereal crops, concluded that the seminal roots remain alive and active until the time of harvest. Simmonds and Sallans (12) found that the wheat plant may produce seed when dependent almost entirely upon the seminal roots. Simmonds (ll) states that the seminal roots of wheat remain functional throughout the entire life of the plant. Records on absorption of water and salts from water cultures by Krassovsky (3) have shown that the seminal roots of wheat, barley, and rye are active up to the time of harvest. These findings were later confirmed by plants grown in soil (4). Pavlychenko (9) states that in the several annual grasses studied in arid climates, seminal roots functioned throughout the entire growing season and were frequently the only roots supporting the plant from emergence to maturity. Studies on seminal roots of perennial grasses, however, are very few, and usually mention of their development is only incidental. The purpose of this study was to ascertain the extent of their development among perennial grasses ; how long they remain alive and functional after the secondary root system is established and how much growth grasses can make when supported by the seminal roots alone.