RED AND BLUE LIGHT EFFECTS DURING GROWTH ON HYDRAULIC AND STOMATAL CONDUCTANCE IN LEAVES OF YOUNG CUCUMBER PLANTS
In greenhouses at high latitudes artificial lighting (AL) is applied in winter as supplementary light source to increase photosynthesis and plant growth. Additionally, AL is already solitary used in closed systems for commercial plant production. The spectral composition of AL (light quality) usually deviates from solar light, causing long-term morphological and developmental changes as well as short-term functional responses in plants. Light quality directly influences leaf photosynthesis via changes in stomatal aperture and photosynthetic quantum efficiency. Stomatal conductance (gs), however, also depends on leaf characteristics such as the size, number, and distribution of stomata over the upper and lower surfaces of a leaf, which develop on the long-term. Besides, stomatal aperture is also influenced by leaf water status, while vice versa, leaf water status depends on transpiration and gs. Leaf water status is also affected by its internal conductance for (liquid) water transport through the leaf (Kleaf). It has often been suggested that gs and Kleaf should be properly dimensioned for appropriate control of gs in relation to water stress. We investigated long-term effects of light quality on Kleaf and gs in leaves of young cucumber plants, which were grown under red (R), blue (B) or combined red and blue (RB) LED (light emitting diode) light. Light quality-induced differences in gs were largely due to differences in stomatal density, which were mainly due to differences in epidermal cell size. Kleaf was influenced by light quality and positively correlated with changes in gs across the applied light qualities. Our results show that in horticultural production systems where AL is used, light quality effects on both plant photosynthesis and plant water relations are important for the efficient production of high quality plants.
van Ieperen, W., Savvides , A. and Fanourakis, D. 2012. RED AND BLUE LIGHT EFFECTS DURING GROWTH ON HYDRAULIC AND STOMATAL CONDUCTANCE IN LEAVES OF YOUNG CUCUMBER PLANTS . Acta Hort. (ISHS) 956:223-230
Cucumis sativus, leaf hydraulic conductance, light quality, stomatal conductance