Autumnal luminosity of the leaves in the October light

by Silva Wischeropp

These autumnal leaves of the wig bush were taken on 28 October 2018 in a park in the Berlin district of Pankow.
Autumn, as one of the four meteorological and astronomical seasons, is the season between summer and winter. In temperate zones, it is the time of harvest and leaf fall. In autumn in the northern hemisphere, the sun appears to move from the celestial equator to the Tropic of Capricorn. Astronomically, autumn begins here with the equinox on 22 or 23 September, but meteorologically and biologically it is usually set for early September. For the southern hemisphere, the astronomical start is on 20/21 March. Autumn ends astronomically on 21 or 22 December in the northern hemisphere and on 21 June in the southern hemisphere (winter solstice). Approximately, autumn is assigned to the months of September, October and November in the northern hemisphere, or March, April and May in the southern hemisphere. In autumn, the leaves on the trees change colour before they fall off. This is caused by the slow withdrawal of the plant juices into the trunk or roots. The chlorophyll is broken down and other leaf pigments provide the colour. These pigments are, for example, carotenoids and anthocyanins. Some of them are already present in the leaf, others are newly formed, as in the case of anthocyanins. The pigments have a protective function against sunlight, so that the juices present in the leaf can be transferred to the stem before it finally falls off (see leaf fall).