This results in the buildup of cork cambrium, which interrupts the flow of materials between the stem and leaves. This causes the death of the leaves, and the breakup of the chloroplasts.
Chloroplasts are plastids, organelles that can contain pigments.
Chloroplasts, which function in photosynthesis, contain a green pigment that causes the leaves to appear green. Other pigments can show after their disintegration, resulting in the fall colors. The cork cambrium buildups are points of weakness, however, and the leaves drop off the stems.