[Grovenet] A bit of phun with physics . . . . . .

Fri Sep 29 09:45:54 PDT 2006

Thanks for the suggestion, Dale!

Geri

----- Original Message ----- 
From: "Dale Wiley" <dale.wiley at netzero.com>
To: "'Forest Grove local interests list'" <grovenet at rdrop.com>
Sent: Friday, September 29, 2006 9:10 AM
Subject: Re: [Grovenet] A bit of phun with physics . . . . . .

: An excellent trip to see fall foliage color is the train from Banks throught
: the Salmonberry Canyon to Enright. I believe they run a couple of more
: excursions in October.
: 
: -----Original Message-----
: From: grovenet-bounces at rdrop.com [mailto:grovenet-bounces at rdrop.com]On
: Behalf Of Jim Zaleski
: Sent: Thursday, September 28, 2006 10:51 PM
: To: Forest Grove local interests list
: Subject: Re: [Grovenet] A bit of phun with physics . . . . . .
: 
: 
: This is very interesting science!!!
:  ----- Original Message -----
:  From: Bob Browning
:  To: Grovenet
:  Sent: Thursday, September 28, 2006 5:32 PM
:  Subject: [Grovenet] A bit of phun with physics . . . . . .
: 
: 
:    The Science Behind Fall Foliage
:    By WeatherBug Meteorologist, Adam Bell
: 
:    After months of heat, humidity and ongoing drought, the time has come
: for summer to gracefully step aside. In its place the spotlight shines on
: autumn, a season renowned for cooler temperatures and the return of
: football. However, while attending a football game in the chilly weather can
: be invigorating after the stifling summer heat, that's not all the Fall
: season has to offer. Another popular feature of the post-summer months is
: the fall foliage.
: 
:    Starting in mid-September and lasting until early November, the changing
: leaf colors can be seen in the Pacific Northwest, the Rockies, Midwest, Ohio
: Valley, the eastern mountains as well as the mid-Atlantic and the Northeast.
: With these changes arriving very soon, let's take a look at what makes those
: leaves change color.
: 
:    First things first, why are leaves green during the spring and summer?
: One word: chlorophyll. This green pigment is abundant in leaf cells during
: the growing season. As a result, the chlorophylls' green color masks out any
: other pigments in the leaf.
: 
:    In order to understand the changing fall colors, we must learn how the
: leaf works. In addition to giving leaves their green color, chlorophyll also
: captures the sun's energy. Chlorophyll utilizes this energy to split water
: molecules, brought into the leaf via the roots, into hydrogen and oxygen
: atoms. Meanwhile, tiny pores on the surface of the leaf, called stomata,
: take in carbon dioxide from the air. Once the carbon dioxide reacts with
: sugars in the plant, it too is broken down to its simplest parts, carbon and
: oxygen.
: 
:    After all of the compounds have been simplified, the leaf begins the
: reconstruction process. Individual atoms of carbon, hydrogen and oxygen are
: joined together to make glucose, an energy-rich sugar that nourishes the
: plant. For every molecule of glucose that is produced, there are six
: molecules of oxygen leftover. The stomata release this gas into the air we
: breathe.
: 
:    This process, called photosynthesis, tends to destroy the chlorophyll.
: But the warm temperatures and strong incoming solar radiation during the
: spring and summer helps to create more chlorophyll to replace what is lost.
: Because the chlorophyll is constantly replenished, the green pigment is
: always present in the leaf, keeping the tree green.
: 
:    That's all well and good, but what gives the leaves that unmistakable
: fall color? During the autumn season, the Northern Hemisphere starts to tilt
: away from the sun. This shortens the window of daylight, which in turn
: lowers the temperatures. As this cooling takes place, a thin layer of cells,
: located at the junction of the leaf and stem, begin to swell and form a
: cork-like substance. This swelling cuts off the supply of water from the
: roots, thereby taking away one key ingredient of photosynthesis.
: 
:    Another important part of photosynthesis, the sunlight, is also in short
: supply due to the Earth's tilt. The lack of water and sunlight halts the
: photosynthetic process and therefore ceases chlorophyll production. With
: this absence of chlorophyll, other pigments in the leaves finally have a
: chance to come forward.
: 
:    One such pigment is carotenoid. Responsible for the yellows, oranges,
: browns and hues in between, carotenoids are also found in familiar foods.
: Corn, carrots and bananas are just a few that are colored by this pigment.
: Like chlorophyll, the carotenoids are present in the leaf cell during the
: entire growing season. The similarities stop there, however, as the
: concentration of carotenoids is much less than that of chlorophyll. Some
: species of trees that have higher amounts of carotenoids include hickories,
: birch, poplar, sugar maple and black maple.
: 
:    The reds and purples come from a pigment called anthocyanin. It too adds
: color to foods such as cranberries, red apples, cherries and strawberries.
: In contrast to chlorophyll and carotenoids, anthocyanins are not always
: present in the leaf cell. Their formation is dependent on low levels of
: phosphate in the leaf. Because there is a high level of phosphate during the
: growing season, the production of anthocyanins must hold off until that
: level drops, usually around late summer. A few trees that produce red and
: purple leaves in the Fall include the dogwood and the red maple.
: 
:    Weather plays a very large role determining how vibrant the fall color
: will be. A warm, wet period during the autumn will decrease the brightness
: of the foliage. A severe frost early in the season will likely kill the
: leaves, turning them brown and causing them to fall from the tree. Severe
: drought could delay the fall colors by two to three weeks.
: 
:    So what are the weather conditions for great fall foliage? While there
: is no magic recipe, the best colors tend to be seen when there is a warm,
: rainy spring, a summer that is not brutally hot and a fall season with sunny
: days and crisp, cool nights.
: 
:    Since a few of the northern states are already reporting signs of fall
: color, now is the time to start planning that foliage drive. For those who
: have never driven through the changing colors, you should make an attempt
: this autumn as the trip is truly scenic.
: 
: 
: 
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