SEASONAL CHANGE Environmental Explorations Mr. Velazquez

Why the change? AAs summer ends and autumn comes, the days get shorter and shorter. TThis is how the trees "know" to begin getting ready for winter. DDuring winter, there is not enough light or water for photosynthesis. TThe trees will rest, and live off the food they stored during the summer. TThe green chlorophyll disappears from the leaves. As the bright green fades away, we begin to see yellow and orange colors. Small amounts of these colors have been in the leaves all along. We just can't see them in the summer, because they are covered up by the green chlorophyll.

Why leaves change colors?  The carotenoids occur with the chlorophyll pigments.carotenoids  This is why leaves can be green and yellow at the same time.  They are always present in the leaf structure that’s why some plants have a yellow green color even during summer.

Why leaves change color? During the summer the phosphate are at a very high level. The chlorophyll is the most abundant pigment.phosphate In fall the phosphate levels alone with other chemicals and nutrients moves from the leaf into the stem of the plant. This leads to the production of other pigments like Anthocyanins. Anthocyanins

Color of leaves  Leaf are green because of a pigment known as chlorophyll.  The chlorophyll mask out the colors of any other pigments in the leaves cells.  There are other colors in the leaves:  Carotenoids ( yellow orange and browns) Carotenoidsyellow orange and browns  Anthocyanins ( reds and purples) Anthocyaninsreds and purples

How does weather affect autumn color?  The amount and brilliance of the colors that develop in any particular autumn season are related to weather conditions.  Temperature and moisture are the main influences.  The amount of moisture in the soil also affects autumn colors.  Like the weather, soil moisture varies greatly from year to year.  The countless combinations of these two highly variable factors assure that no two autumns can be exactly alike.

What triggers leaf fall?  In early autumn the shortening days and declining intensity of sunlight, leaves begin the processes leading up to their fall.  The veins that carry fluids into and out of the leaf gradually close off as a layer of cells forms at the base of each leaf.  Once this separation layer is complete and the connecting tissues are sealed off, the leaf is ready to fall.

Colors of Fall  Hardwood species are the ones that have the most color display during fall. Hardwood  Hickories  Ash  Maples  Aspen  Birch  Cottonwood Aspen Maple Hickory Birch

Seasonal Fall Peak for Deciduous TreesDeciduous

Chlorophyll Green

Anthocyanin Purple Red

Carotenoids Yellow Orange Brown

Chlorophyll  Its the pigment which gives plants its green color and is responsible for absorption of light, allowing photosynthesis to occur.

Pigment  Any substance whose presence in plant or animal tissues produces a characteristic color  Biological pigments include plant pigments and flower pigments.

Anthocyanins  The most important of the visible plant pigments, responsible for the reds, purples, and blues you see in plants.

Carotenoids  Any of a class of highly unsaturated yellow to orange and brown pigments occurring in plants.

Deciduous  Having leaves that fall off or are shed seasonally to avoid adverse weather conditions such as cold or drought.

Hardwoods  Trees that lose their leaves in autumn; also refers to the wood produced by these trees.  Hardwoods are the predominant type of tree in the deciduous forest.

Phosphate  Compounds of phosphorus, phosphates are an essential plant nutrient.  Its symbol is PO 4.