Changes in plant life in autumn
In autumn days shorten, light decreases and temperature falls. In leaf cells chloroplasts and chlorophyll start to break down, so the green disappears and yellow-orange pigments already present are revealed; in some plants reddish pigments also form: leaves turn yellow, red or brown. An abscission layer of cork forms where the petiole joins the shoot and the leaf falls — this is leaf fall. Its meaning: falling leaves carry away waste accumulated over the year; in winter the root hairs cannot take up cold water, and evaporation from leaves could dry the plant out — shedding leaves prevents this. Oleaster, maple, almond, poplar and acacia shed their leaves early, while lilac, rose and privet stay green long. Dormancy begins in winter: making food, sap flow and respiration almost stop. Juniper, pine, spruce and boxwood are evergreen: their leaves (needles) are replaced gradually through the year. It is called “golden autumn” because many fruits ripen and leaves colour.
Observation and herbarium: collect leaves of 6 kinds of trees that have fallen to the ground, dry them between paper and group them by colour (yellow, red, brown, green). Record which tree sheds first. Safety: collect only fallen leaves, do not climb trees, do not touch poisonous plants, wash hands afterwards.