GROWTH OF LEAF LETTUCE UNDER FLUCTUATING LIGHT CONDITIONS

The growth of leaf lettuce (Lactuca sativa var. crispa L.) was compared in three experiments under conditions of static lighting and fluctuating lighting at the same average light intensities, 58, 85 and 108 μmol m^-2 s^-1 PAR. Fluctuating light was achieved by means of an electric motor which moved the high pressure sodium lamps forwards and backwards above the vegetation.

Generally, fluctuating light appeared to affect lettuce growth negatively with foliage dry and fresh weights and numbers of true leaves being reduced.
The higher the light intensity, the smaller was the difference in dry weight of lettuce under static and fluctuating light.
The greatest reduction in numbers of leaves was obtained under fluctuating light at the lowest light intensity.
The nitrate content in leaves was commonly higher in plants grown under fluctuating light.
The results indicate that lettuce may show shade responses under conditions of continuously fluctuating light.

II Workshop on Environmental Regulation of Plant Morphogenesis

J. Autio, I. Voipio

greenhouse, Lactuca sativa, supplementary light

https://doi.org/10.17660/ActaHortic.1997.435.18