The Effect of Light Quality on Shoot Extension Growth in Three Species of Grasses

The effect of light quality on the extension growth of vegetative shoots and on the final size of their leaves was investigated in plants of Lolium multiflorum, Sporobolus indicus and Paspalum dilatatum. Three experimental approaches were used, (a) red or far-red end-of-day irradiations of sunlight-grown plants, (b) different red/far-red ratios of white light in a growth room and (c) sunlight enrichment with radiation of different red/far-red ratios or with different amounts of far-red light during the photoperiod. Plants treated with end-of-day far-red or low red/far-red ratios throughout the photoperiod developed longer leaves and, as a result, longer shoots. This effect was more marked in leaf sheaths than in blades. Tiller extension and leaf sheath length increased with the amount of far-red added to sunlight in a simple hyperbolic relationship. These results show that vegetative grass shoots respond to light quality in a way similar to internodes of dicotyledonous plants.