XVI International Botanical Congess
A number of studies have addressed responses of leaf spectral reflectance, transmittance or absorptance to physiological stress. Stressors included dehydration, ozone, herbicides, disease, insufficient mycorrhizae and N fertilization, flooding and insects. Species included conifers, grasses and broadleaved trees. Increased reflectance with maximum responses near 700 nm wavelength occurred in all cases. Varying the chlorophyll content in leaves or pigment extracts can simulate this effect. Thus, common optical responses to stress result from decreases in leaf chlorophyll contents or the capacity of chloroplasts to absorb light. Leaf optics can be quite sensitive to any stressor that alters soil-plant-atmosphere processes.