The Season of Fall & The Leaves-What makes the leaves change color and fall off of the trees?4-21-08?

Question

Have you ever been walking and you see a tree looking like this

http://images.search.yahoo.com/search/images?p=fall+trees&js=1&ni=18&ei=utf-8&y=Search&fr=yfp-t-501&xargs=0&pstart=1&b=253

What makes the leaves on the trees change colors and fall off the tree to the ground, does the evergreen ever change color, and does the tilt of the earth have anything to do with it,and when do trees know it's the season Fall or Autem?

Answer 1

The loss in color and eventual dropping of the leaves is called leaf senescence. In preparation for the winter months which are unsuitable for growth the plant leaves die, first losing their chlorophyll (which makes them turn from green to yellow/orange/red) and then other photo-pigments if present (making them turn brown). In winter many plants enter a stage of dormancy-essentially hibernating-in order to survive the lean months.

Plants are able to detect the amount of sunlight (technically the amount of darkness), which is related to the tilt of the earth and the seasons. The light detection ability is also used when plants flower

Evergreen leaves are typically only ever green (alive) or brown (dead). They drop there leaves just not all at once.

Answer 2

That is correct that trees prepare for winter by dropping their leaves because photosynthesis would be inefficient, at best, in the winter.

They also scavenge many mobile essential elements before they drop their leaves.  The color changes from green, to red/orange to yellow to brown as the leaf resorps its photosynthetic pigments (process is resorption): chlorophyll (green), carotenoids (orange), and xanthophylls (yellow), leaving behind the nonmobile lignin and cellulose molecules.  This is why we see the colors changes during the fall.

Answer 3

I believe it's the change in the seasons or the climate change.

Answer 4

It is the way trees prepare for winter.

Sunlight is the primary source of energy for plant life. They are able to use the energy through a mechanism called photosynthesis and store it in a usable form.

During the summer time, there is plenty of sunlight and so trees sprout green foliage to make the most of it. This is the time when growth is most. During the winter time, sunlight is scarce and energy available is limited. At that time, these leaves would be kind of excess baggage to be maintained.

So at the time of autumn, trees prepare to shed all the leaves and twigs and this cause the change in colour and is called fall season.