Does chloropyll a cause the red colors of autumn leaves?

No, chlorophyll a does not cause the red colors of autumn leaves. During autumn, as temperatures drop and sunlight decreases, chlorophyll breaks down, revealing other pigments present in the leaves, such as carotenoids (which produce yellow and orange colors) and anthocyanins (which can produce red and purple hues). The production of anthocyanins, in particular, can be influenced by environmental factors like light and temperature, contributing to the vibrant red colors seen in some trees during fall.