In commercial practice of Dutch greenhouses, roses are often
lighted till 20 h a day and the light intensity obtained at the
canopy level is usually between 100 and 200molm−2 s−1. However,
under the common lighting systems (lamps at the top of the
canopy), light is not uniformly distributed along the leaf layers.
Particularly, it has been calculated that, considering a crop with
LAI = 3, even when the light intensity at the top of the plant is
400molm−2 s−1, roughly 33% of the leaves in the lower and inner
zone of the canopy receive less than 100molm−2 s−1 because of
self shading (data not shown).