Root system development in Caucasian clover cv. Monaro and its contribution to seed yield

A sand bed was used to investigate root system development and the relation ship between the root system and seed yield of Caucasian clover (Trifolium ambiguum). During vegetative growth (September to November) root dry matter (DM) accumulated more rapidly than shoot DM, and the root to shoot ratio w as 2.52 by mid November. However, as reproductive growth accelerated the ra te of root DM accumulation decreased, and by early February the root to sho ot ratio was 0.78. Plants developed primary, secondary, and tertiary crowns in this first growing season, with both primary and secondary crowns produ cing reproductive shoots. The protracted flowering period five months was a result of an initial production of reproductive shoots from primary crowns , and an extended production of reproductive shoots from secondary crowns w hen primary crown shoot production had ceased. A single primary crown produ ced an average seed yield of 3.8 g compared with 0.81 g seed from an averag e secondary crown. However, as there was only one primary crown but there w ere 26 secondary crowns per plant, the total seed yield from secondary crow ns reached 21.1 g per plant. Seed yield per plant was, therefore, almost en tirely dominated by the number and size of the secondary crowns. Root DM wa s highly correlated (R-2 = 0.80-0.97) with the number of leaves, reproducti ve shoots, and inflorescences, as well as the number of secondary crowns, s uggesting that the potential for seed production is strongly influenced by the size of the root system prior to reproductive development.