What is the key factor in the start of trees losing there leaves?

Question

What I am on about, is the triger that makes the tree start to shut down.

Answer 1

Plants use light from the sun, water and carbon dioxide to photosynthesize, i.e. make food for themselves. As the earth tips away from the sun starting in fall (in the northern hemisphere anyway), the sun's rays are less intense. Deciduous trees compensate for the diminished light and diminished ability to photosynthesize by losing their leaves and going dormant.

Answer 2

Light. All Flora and some Fauna react to the ambient light levels for their given area or topographical location. As soon as light levels start to decrease this triggers the tree into closing down and storing energy for the winter to be released in the spring when ambient light levels start to increase. Yes, cold air, cold winds, heavey rain all have a contributing factor as well but light is the main one.

Answer 3

What triggers leaf fall?
In early autumn, in response to 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. These clogged veins trap sugars in the leaf and promote production of anthocyanins. Once this separation layer is complete and the connecting tissues are sealed off, the leaf is ready to fall.

Answer 4

Nature

Answer 5

It depends on many factors.
The trees locally are currently losing their leaves due to drought.

Answer 6

Less Sunlight

Answer 7

The end of Summer.

Answer 8

It's a sesonal thing just like kickers on cent m/c's

Answer 9

The cold.

Answer 10

shorting of daylight