Root response to above-ground light quality – Differences between rhizomatous and non-rhizomatous clones of Festuca rubra

Abstract

Root response to reduced red/far red ratio above ground was studied in an experiment with 12 vegetatively propagated clones of Festuca rubra, a rhizomatous grass species. A new method suitable for describing the node position within rhizome systems was developed. It uses a combination of developmental and functional directions of ordering, adopting methods of topology. At each node the root structure was defined as consisting of three root types: unbranched, long branched and fine branched. Root system size was expressed as the number and length of roots of these individual types. Rhizomatous and non-rhizomatous clones of Festuca rubra differed in the size and structure of their root systems and in the response to lowered red/far red light ratio. This response was caused more by the behaviour of the rhizomes than of the roots alone. In rhizomatous clones, the largest differences in root system structure were between the mother-nodes and the nodes on the rhizomes. The size of the root system also depended on the node position. Response to the red/far red ratio was clone specific only in some of the root parameters, especially in traits of unbranched roots at young nodes. The role of the three root morphotypes in the plant's ontogeny, nutrient uptake and ability to cope with environmental heterogeneity both above- and below ground, is discussed.