ROD PLANCK / SCIENCE PHOTO LIBRARY ROD PLANCK / SCIENCE PHOTO LIBRARY
Gambel oak leaf. View of of a gambel oak leaf (Quercus gambelli) in autumn colour. The yearly colour change of the leaves of deciduous trees occurs as a biochemical process. A change is signalled by the accumulation of lipid droplets (fat) in the chloroplasts of leaf cells which contain the green chlorophyll pigment. As photosynthesis in the chloroplasts slows down due to shorter daylight hours and lipid production increases, leaf colour changes occur until finally the leaf loses its green colour. The gambel oak is a hardwood deciduous tree found in southwestern USA. Photographed in Zion National Park, Utah, USA.
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