Competition for light and nutrients between natural populations of Dac- tylis glomerata.
Seedlings of cocksfoot populations from Norway and Portugal were planted-out 5 cm apart at the cotyledon stage into boxes equipped with partitions to eliminate root and shoot competition, then transferred to controlled environment. With full competition the population from Portugal was the more competitive at 7°C in 8-h photoperiods and the less competitive at 30°C in 16-h photoperiods. Similar effects occurred in the presence of root competition alone, but not in its absence irrespective of shoot competition. Possible mechanisms involved in root competition are discussed.