SEASONAL CHANGE

Environmental Explorations

Mr. Velazquez

Why the change? As summer ends and autumn comes, the days get

shorter and shorter. This is how the trees "know" to begin getting ready for

winter. During winter, there is not enough light or water for

photosynthesis. The trees will rest, and live off the food they stored

during the summer. 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. 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.

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.

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)

Anthocyanins ( reds 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. Hickories Ash Maples Aspen Birch Cottonwood

Aspen

Maple

Hickory

Birch

Seasonal Fall Peak for Deciduous Trees

Chlorophyll

Green

Anthocyanin

Purple Red

Carotenoids

Yellow

OrangeBrown

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 PO4.