VARIATIONS IN TILLER DYNAMICS AND MORPHOLOGY IN LOLIUM-MULTIFLORUM LAM VEGETATIVE AND REPRODUCTIVE PLANTS AS AFFECTED BY DIFFERENCES IN RED FAR-RED IRRADIATION

Lolium multiflorum Lam. plants were grown in a growth room under two light sources with red/far-red ratios of 1.62 and 0.84 but similar photosynthetically active radiation. In both situations the capacity to produce new tillers and the light available per tiller decreased with canopy growth. Tillering was further reduced by the low red/far-red ratio while light interception and plant dry weight were unaffected by this treatment. In both reproductive and vegetative plants under the lower red/far-red ratio the time between leaf expansion and the appearance of a tiller in its axil was increased and the proportion of ''mature buds'' that developed was reduced. Irradiation with low red/far-red advanced the reproductive development and increased the number of fertile tillers per plant. It also caused longer leaf sheaths, blades and reproductive shoots. The results suggest that as canopy density increases the lower light interception per tiller and the photomorphogenic effect of low red/far-red ratios may reduce the capacity to produce new tillers.