Autumn is a spectacular time of year in the temperate parts of the world . Maples , Oaks , Sourwoods , Cherries , Dogwoods , Birches , Alders , Sycamores , and other trees are ablaze with fiery red , orange , and yellowed leave of absence . But why is it that these leaves change gloss and drop from deciduous tree every gloam ?
Why some tree leaves fall and others don’t.
The leaf of evergreens likepines , fir tree , rhododendrons , junipers , yew , box , arborvitae , and manyhollies , are coat with a kind of wax that assist protect their leave from moth-eaten and freezing temperature . Hence their classification as “ evergreen ” – their foliage does n’t fall from the tree or industrial plant based on the season .
Not so for deciduous trees , which disgorge their leaves and become dormant in winter . The tissues of deciduous leaves are cranky and the fluids that flow through the leaves are very susceptible to freezing . so as to hold open resources during winter , deciduous trees activate a variety of self - destruct chemical mechanism for shedding their foliage as fall draws near . Throughout the tree are chemicals that are raw to spark , called cryptochrome and phytochrome . These chemical are so sensitive that tree can register day length changes of as little as 30 minutes . It is these chemicals and others that touch off change in the trees that produce autumn coloring and falling leaves .
Why leaves change colors.
Chlorophyll masks every other pigment
Chlorophyll is the dominant pigment in a leaf . It ’s this chemical that conduct fleeceable color to leave-taking during the growing season . There is so much chlorophyll in a folio that all other gloss are block out , even though they ’re always present in the foliage .
Chlorophyll is full of life to the tree diagram ’s creation – it ’s necessary for photosynthesis , the process by which the plant conquer energy from sunlight to manufacture intellectual nourishment for the tree . Chlorophyll is continually being used up during the grow season , but the tree refill it rapidly so the supply remains as high as demand . Thus , the leaf remain green .
But once sidereal day distance begin to shorten in fall , the tree diagram produces less and less chlorophyl . Slowly , the other colour which have been hiding in the folio – flushed , yellow , or orange – are reveal . As fall progresses , all of this pigment easy deteriorate until only the brown tannins remain . Then the leaf dries and crumbles .
What creates yellow, orange, and red leaves?
Xanthophyll and Carotenoids are responsible for the brilliant yellowness and oranges ofautumn leaf . These are the same substances that make acarrotorange andcornyellow . Carotenoids and Xanthophyll are present in leaves at all times during the growing season ( they help absorb sunshine ) but are veil by the gullible pigment from chlorophyll . As chlorophyll diminishes in fall , the carotenoid and xanthophyll pigments are revealed , leave in brighter and brighter yellow-bellied or orange parting .
At the same time , some tree coinage like Maples , Dogwoods , and Oaks produce anthocyanins in the sap of their leaves . These are the same pigments that make cherries red . Bright visible radiation ramps up anthocyanins , which is why the leaves on a Red Maple tree on a clear , cheery day in earlyNovemberappear brighter than on a cloudy day .
The amount of carotenoids , xanthophyll , and anthocyanins in the parting are hooked on temperature , moisture , and sunshine throughout the growing season . That ’s why the intensity and hue of leaf can exchange each class due to the balance of these chemicals inside the leaf . During years with drought and heatwaves , you may see tree diagram foliage in fall that have less intense colour than the year before .
Why leaves fall from trees.
Chemicals in the tree recognize that days are getting shorter
Trees contain extremely sore chemic light receptor which signalize when the days are getting shorter . These chemical substance are so sensitive that trees can register twenty-four hour period duration changes of as little as 30 minutes . Phytochrome detects change in red wavelengths and cryptochrome detects change in dark wavelengths . It is these chemicals that trigger the chemical and physical variety in the Tree that produce autumn colors and begin the process of shedding leave .
Trees create zones that “scissor” the leaf from the tree
sloughing leaves starts when the tree diagram mould an “ abscission zona ” where the leaf attaches to the twig or branch . The abscission layer acts like a scissors that cut the leaf off the tree . The tree also creates structurally imperfect areas between the leaf and branch where idle words or any other force can aid in off the leaves .
The fragile layer of cells that make up the abscission layer slowly swell , limiting the period of water and nutrient into the leaves . This restriction have the amount of chlorophyll in the leaf to decrease , reduce the fleeceable pigment and drying the foliage . As autumn get on , the abscission level pay back thicker and blockheaded , finally pushing the foliage away from the fore completely , reserve it to be pull off by environmental forces ( soberness , wind , rain , etc ) . The unfastened lesion is then closed by other electric cell that block and protect the wound , form a scar . This bed of cubicle defend the tree from pests and theenvironment .
Is n’t it amazing to bring in that all of this happens when a tree recognise that the day have gotten shorter ?
source : School of Forest Resources , University Of Georgia(pdf),Loyola Center for Environmental Communication , National Wildlife Federation , Wikipedia .
