When deciduous trees begin to change leaf colors in fall in response to short day length and cool night temperatures, it induces the formation of an abscission layer at the base of the leaf stem ...

In most deciduous trees, a group of cells grows between the branches and the leaves, called the abscission layer, and acts as a sort of off-valve for water and nutrients once daylight begins to wane.

However, in cultivated rice (japonica), the abscission layer isn’t formed at all. Credit Plant Breeding Lab. Graduate School of Agricultural Science, Kobe University ...

At the base of their stem (referred to as the petiole), leaves have a zone called the abscission layer, located near the branch to which they are attached. Figure 2.

Eventually, as the veins in the leaf close down, a layer of cells called the abscission layer forms at the base of the leaf stem before falling off.

In spring and summer, the leaf can replenish its stores of chlorophyll with no problem, but when the abscission layer forms, it doesn't have the materials to do so," the Week explains.

However even with this partial abscission layer junction, the seeds still tend to fall easily in a natural environment. Credit Ishikawa et al. (2022) PNAS Plant Breeding Lab. Graduate School of ...

Why have the leaves not fallen from trees in the Kansas City area? It’s a condition called marcescence, where leaves wither but don’t drop. It’s due to the sudden change in recent temperatures.