The process by which deciduous trees drop their leaves is called abscission. Abscission is when the leaves are "cut away from" the tree.
Deciduous - "temporary"
There are Two Reasons why Deciduous Trees drop their leaves in the fall.
1. To keep from dehydrating in winter when the ground freezes. Decidous trees obtain water through their roots in the ground. When the ground freezes, water is no longer available to the cells in the tree. If a tree continued photosynthesizing during the winter, it would have to use the water within its cells to photosynthesize. The tree would dehydrate, and eventually die.
2. To reduce weight on the branches when winter snows fall. Branches on decidous trees reach toward the sky and break easily.
The Process of Abscission
1. Begins when chlorophyll breaks down. Nutrients and minerals in the leaves are storerd in the trees. The other color pigments (xanthophyll, xanthocyanin, tannin, carotene) begin to show throught.
2. Leaf produces a hormone (a chemical that causes change in an organism) that makes the petiole (stem of the leaf) swell at the end. This hormone is in the form of a gas, and is called ethylene.
3. Leaf produces an enzyme (a chemical that breaks things down). The enzyme breaks down the cellulose in the cell walls of the cells in the petiole. This makes the cell walls weak.
4. When autumn winds and rain come, the colored leaf falls from the tree.
Abscission - "to cut away from"
The process by which deciduous trees drop their leaves is called abscission. Abscission is when the leaves are "cut away from" the tree.
Deciduous - "temporary"
There are Two Reasons why Deciduous Trees drop their leaves in the fall.
1. To keep from dehydrating in winter when the ground freezes. Decidous trees obtain water through their roots in the ground. When the ground freezes, water is no longer available to the cells in the tree. If a tree continued photosynthesizing during the winter, it would have to use the water within its cells to photosynthesize. The tree would dehydrate, and eventually die.
2. To reduce weight on the branches when winter snows fall. Branches on decidous trees reach toward the sky and break easily.
The Process of Abscission
1. Begins when chlorophyll breaks down. Nutrients and minerals in the leaves are storerd in the trees. The other color pigments (xanthophyll, xanthocyanin, tannin, carotene) begin to show throught.
2. Leaf produces a hormone (a chemical that causes change in an organism) that makes the petiole (stem of the leaf) swell at the end. This hormone is in the form of a gas, and is called ethylene.
3. Leaf produces an enzyme (a chemical that breaks things down). The enzyme breaks down the cellulose in the cell walls of the cells in the petiole. This makes the cell walls weak.
4. When autumn winds and rain come, the colored leaf falls from the tree.