Light quality

Abstract: The primary issues regarding the lack of protocol reproducibility among laboratories are environmental factors. Light (quantity and particularly quality), is one of those main factors, and studies seldom present the spectral quality of the light sources used. With the advent of light-emitting diode (LED) technology, impressive progress has been made in environmental controls and morphogenetic responses, as directed by the light used in the culture shelves. A wide array of LED lights with different spectra are currently available and light is important in large-scale propagation, especially liquid bioreactor systems. LED technology continues to evolve rapidly and has created additional possibilities. This laboratory has dedicated extensive efforts to implement photoautotrophic propagation, and light is a key component of the system. This review presents relevant topics on the influence of light in various plant tissue culture-based techniques.

Abstract: Light filtered through the forest canopy is the most variable physical factor in tropical forests, both in space and time. Vegetation geometry, sun angle, and weather generate five light environments, which greatly differ in intensity and spectrum. Forest light spectra can directly affect photosynthesis, plant morphogenesis, visual communication, and the effectiveness of plant-animal interactions. For animals, the apparent simplicity of five light environments is complicated by different types of contrast with the optical background which greatly modify the conspicuousness of visual signals. The purpose of this paper is to describe peculiarities of light in tropical forest, and to review the effects of light intensity and especially quality on plants and animals. Ecophysiological adaptations of plants to cope with contrasting light environments operate at daily, seasonal and life time-scales. Ambient light quality acts as a signal for both animals and plants, and consequences on plant growth, colour display, and signal design are examined. An analysis of the range of spectral parameters along a deforestation gradient is presented, testing if sites with more variation in light could support more species which are light-environment specialists. It is suggested that light quality measurement may be used to estimate the structural impact of forest exploitation, and that gives us the information necessary for a functional explanation of anthropogenic effects on tropical forest diversity.