The colours of autumnDeciduous trees are those that shed their leaves every year, as opposed to the

The colours of autumnDeciduous trees are those that shed their leaves every year, as opposed to the evergreens, which do not. While the latter are often associated with conifers, one should remember that there are varied other trees such as oaks with species that keep their leaves year round. The former is associated with trees that live or evolved in regions with a long dark and cold winter, and leaf shedding is a mechanism to conserve energy in the face of temperatures cold enough to freeze off the leaves and too little light to make photosynthesis worthwhile while still facing the threats of ice and wind. As light levels and day length diminish, hormonal cascades pass through the trees, which start to withdraw metabolically expensive chemicals such as green chlorophyll and red orange opsins into their depths, eventually taking most of the sap out of the periphery as well.The peripheral branches are then left in suspended animation while the vitality of the tree focusses back into the rootball, which outside permafrost zones at least is kept insulated by the covering blanket of soil. The process is not instantaneous, and the chemicals are withdrawn in sequences before the husk of the leaf is allowed to fall off, becoming insulating mulch for the base of the tree, and slowly releasing its remaining nutrients back into the soil (which is why excessive dead leaf removal by humans is not necessarily the best thing for the trees while conforming to most people’s aesthetics). Here we have a maple from Japan from the Acer family caught at the stage where nearly all the chlorophyll is gone but the red opsins remain in all their intense glory.LozImage credit: Falcor88 -- source link

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