The far red radiation reflected by plants changes the far red ratio. This ratio is the early signal of competition within the community. The phytochrome is able to detect this ratio and transfer the eletronic excitation transforming it into a celular signal, that changes celular metabolism and affects plant growth and development. Determination performed in low density crops, where competition per light among plants is small, have shown that the presence of neighbour plants alter substantially the amount of far red received by the shoot. The lower amount of fertile tillers observed in winter cereals cultivated in Southern Brazil has rised a serious question related to the role of tillers in the yield formation of small grains. In this sense, to understand the changes in light quality verified during the stablishment of a crop is fundamental to compreehend the whole tillering process. Therefore, the answer to the question formulated in the title depends on the investigation of light quality effects on the following points of small grain development: (i) are the small grain cereals able to detect early in their life cycle the competition that will established in the future? (ii) are the small grain able to use this information to modify their tillering pattern? (iii) is there genetic variability among Brazilian cultivars about this characteristcs ?
radiation; competition; phytochrome