Effect of Light Quality and Quantity on Leaf Growth in Lolium perenne L.

Abstract

In a sward, the quantity and quality of light are modified by the canopy, with in particular a decrease of red – far red ratio and a decrease of blue light. Plants react to these modifications by altering their shoot morphogenesis. In particular, in grasses, modification of light composition induces leaf growth changes. The objective of this study was to evaluate the effect of light quality and quantity on leaf growth in a set of perennial ryegrass genotypes. Ten clones of ten perennial genotypes highly variable in leaf length were used. Four light treatments were applied: a standard treatment (transparent filter), decreased PAR (neutral filter decreasing all the wavelengths similarly), low red – far red ratio associated with low blue (green filter, simulating the effect of a canopy), and low blue (red filter). After a growing period of three weeks, plants were defoliated and the light treatments were applied. Leaves three and four following defoliation were measured in order to obtain leaf elongation rate (LER), leaf elongation duration (LED) and adult leaf length. Strong genotype and light effects were observed on all traits. The low blue treatment had a particularly large effect, increasing adult leaf length by increasing both LER and LED. The differences in adult leaf length between genotypes were explained by both LER and LED. The genotypic × treatment interaction was significant but low in comparison to the principal effects.