October 05, 2009

What Is In An Autumn Leaf...

The turning of the foliage is something we are very familiar with, at least those of us who live in parts of the world that experiences the four seasons. We accept and relish in the colours of golden, reds, purples and browns that turn the landscape into warm paintings created as if by brush strokes of a skillful artist.

But only few of us ever consider the reason and the means by which this natural phenomenon take place. So, why do leaves change colour?

Interestingly enough, the complete details of this process are not yet understood, but scientist do know enough to be able to explain the basics.
Leaves are the food factory of the tree. Water is transported from the ground through their roots and together with carbon dioxide from the air and sunlight, plants can produce glucose, a kind of sugar. This process is called photosynthesis. Glucose is what we might consider being the food for plants, which makes them thrive and grow.

Leaves do naturally contain several colours, even reds and browns, but the dominating colour during the spring and summer is green, which comes from the pigment called chlorophyll, an important chemical vital for the process of photosynthesis.

When summer comes to its ends and autumn arrives, the days become shorter and the absence of light is obvious - this onset of darkness is the signal that prompts the trees to begin getting ready for winter. During winter, there is not enough light or water for photosynthesis and it shuts slowly down, commencing in the fall. The green chlorophyll disappears from the leaves and as it fades away, we begin to see the yellow, red and orange colors. The intensity, the onset and the duration of this turn depends very much on the weather, the climate and the latitude. Sunny, warm days and cold nights produce the most stunning colour displays. The color variation also depends on the bushes and trees and the variety and amounts of the pigment stored in their foliage.

As autumn progresses and reaches its end, the veins that carry fluids into and out of the leaf gradually close off, producing chemicals that will seal the leaf off from the tree branch. This is on order to prevent the leaf to freeze and damage the trees. Once this separation is complete, the leaf is ready to fall.

The tree then enters a state of winter dormancy, not shutting down completely, but resting. Some metabolic and developmental processes do take place in it's buds and twigs, while it prepares for spring and the onset of yet another yearly growth cycle.

23 comments:

Jill said...

My science lesson for the day! What beautiful leaves you have in your photographs...you caught all the colors and they are so pretty. Ours are really starting to turn right now.

Tom Bailey said...

These leaves remind me of leaf presses that I did as a kid. Now I connect leaves like these with football.

Keith said...

Great post. Very informative. I learned a lot. One of my favorite things about this season is the changing colors of the leaves.

Hilary said...

I love it when you get all scientist with us! ;) Great post, Z.. and wonderful autumn leaf images to boot!

Betsy said...

My very favorite thing about this autumn season...and I never really knew why before! ;)

Donna said...

Very interesting. I love the changing of the leaves this time of year...reds, golds, oranges, just beautiful!

Valentine said...

Oh wow! The things I learn from you... I dont know if we have autumn here.. I guess we do because I sometimes find red, yellow and bright orange leaves strewn about. hehe.. They say spring is the most beautiful time of year.. but I think it should be autumn. Hibernating trees! hehe..

xx

Sumandebray said...

What beautiful colors.... the colors that can never be replicated!
From where we belong there used to be 6 seasons. But here in the Middle its only two ... summer in and summer out

Helen McGinn said...

I love this time of year like no other; the colour of the leaves, the cold, crisp, sunny days and the reflections have me leaping out of bed every morning. Of course, this is Scotland, 'cause then comes the rain............. ;O)

Diane said...

Your blog is way better than my high school biology class ;) xo

Claus said...

We take so much for granted, we never really care to stop and search the meaning of many things. What a wonderful explanation, especially because it explains why we never have Autumn, and hence orange and red leaves, here in Guatemala. We have sun and clear skies pretty much the entire year, so I suppose trees always have what they need to always be green. How fascinating!

Rosezilla said...

I love autumn leaves and we don't get any here. I do miss them. I always loved the fairy tale about the leaf fairy turning them different colors...

Blogaire said...

So very interesting as usual Z..
You remind me of my science teacher Miss Hughes (many years ago), her enthusiasm always made learning easy.

Lulda Casadaga said...

Lovely pics as always! Ours are just starting to turn..it seems like it is taking forever. I know one day I'll look up and no leaves will be on the trees...:D

Enjoy your week!

Fashion Chalet said...

Fall is finally upon us, not in Miami but surely where I will be 8 days from now.. excited about it all; but I won't lie, I will truly miss the year round summer and many of my favorite haunts... food and shopping a like, but change = adventure, right? =)



XO

Protege said...

=Jill,
thank you. I guess being a bit more south than me, everything is a bit later in your part of the world.;) Here we will be reaching the fall peak in about 2 weeks.;) xo

=Tom,
great comment, made me laugh.;) yes, we pressed leaves too, I completely forgot about that, thank you for bringing that memory back.;))

=Keith,
your are always so kind, thank you.;) Glad you enjoyed this a bit boring scientific recap.;)

=Hilary,
thank you.;)You know me; I am curious and need everything explained and investigated.;) Always love when you visit dear friend.;)xo

=Betsy,
glad you liked it and did not find it boring.;)) But I know you like to share a piece of scientific info from time to time yourself.;)xo

=Donna,
thank you and I agree; I recall the beauty of the fall foliage in NC.;) xo

=Valentine,
glad to see you back! Yes, it is funny that trees are like animals and hibernate.;) We had a storm this weekend and I got to think about you, hope all is well.xo

=Sumandebray,
6 seasons, wow.;) That made certainly for some changes.;) Must be difficult to be living with only two now. Always glad when you stop by.;)

=Helen,
agree with you completely.;) And we get the rain and dark too comes November.;) xo

=Diane,
you always say the greatest thing, made me laugh!;) Hehe.;) Enjoy you busy life off blogging dear friend.;) xo

=Claudia,
so right you are.;) I am sure the sufficient daylight in your part of the world makes the trees keep the leaves. I bet you too have quiet a different fauna as well.;) Always so happy when you stop by my dear friend;) xo

=Rosezilla,
I guess you get plenty of heat and sunshine instead.;) I love to imagine a Fall Fairy turning the leaves.;) xo

=Blogaire,
thank you.;) I hope it is a good thing I remind you of your old teacher.;) I hope she was young and lovely and not old and plain.;) Hehe. Always happy when you stop by dear friend.;)

=Lulda,
you are so right. If we get too much wind and too many storms, the foliage will be gone in no time. Already this weekend the storm has taken most of the beautiful colours away...
So glad every time you stop by.;)xo

=Erika,
ah, enjoy your trip.;) I guess it is as exciting to you to visit places in the North as it is for us to travel south.;)
Thanks for finding the time to stop by.;) xo

Kcalpesh said...

Lovely leaves! They've got a very beautiful color!

- Pixellicious Photos

steviewren said...

I always forget what makes for a colorful autumn and what doesn't. Sunny warm days and cool nights. Hmmmm, so far we aren't set for a colorful season here. We've only had a couple of cool nights and way too much rain this year.

Gal Friday said...

Love the colorful collage you created, of the leaves, and you explained the science behind the changing colors of the leaves in fall beautifully.

sallymandy said...

Hi Z, once again you've given us a science lesson about something beautiful and poetic from nature. I do remember from school learning about photosynthesis and chlorophyll, but I didn't know what makes the leaf actually fall.

Fascinating. Thank you!

Protege said...

=Kcalpesh,
thank you so much.;)xo

=stevie,
I hope that sunny days with cool nights will arrive soon in your part.;) xo

=Tina,
you know me, always the scientist.;) Glad you liked this and always happy to see you stop by.;) xo

=sallymandy,
ah, glad to see you visit, thank you for your kind words. I am happy you enjoyed this science bit; but I know you love trees.;) xo

gaelikaa said...

Scandinavia's a place I always associate with evergreen trees..

Protege said...

=gaelikaa,
we have spruce tress, that are green year around, but we have many leaf-trees that loose leaves during the fall.;)