Phenotypes and the onset of competition in spring barley stands of one genotype: daylength and density effects on tillering.

摘要

In field trials in 1978 near Clermont-Ferrand, France, spring barley cv. Berenice seeds from the same seedlot were sown at the end of the winter at three altitudes: 320 m (end of February), 880 m (beginning of April) and 1120 m (beginning of May), and at the end of May at the lowest site, at low or high sowing rates and with or without N fertilizer. This experimental design in natural conditions gave differences in initial daylengths (12, 14 and >15 h at the 3 altitudes, respectively, and >15 h atthe later sowing at the lowest site) and different levels of competition. The tillers in the axils of the first and the second leaf were lacking on many plants growing in the long-day treatments in the low density stands, and this increased up to 70-90%in the high density stands. It was suggested that this was due to far-red light signals affecting emerging seedlings under conditions which induce floral development, before any competition can occur. The cessation of tillering as a result of the onset of competition was delayed during stem elongation in the stands established under long days. Such phenotypes showed strongly reduced growth potentials.