Reply to thread

Message: <blockquote data-quote="punaruwan" data-source="post: 11058977" data-attributes="member: 174822">Scientists solve riddle of why autumn leaves fall off and are different shades in Europe and North America Leaves changing colour and then floating to the ground before winter sets in is a familiar and beautiful autumn sight. And captured here is the contrast between birch trees (yellow), beech (red) and evergreen pines in a forest near  Gdynia in Poland's Pomerania. But  scientists now believe they have answered the question of why plants  might expend energy producing red pigment in leaves only for them to  fall off and why they tend to be a brighter red colour in North America  than in Europe.As  leaves die, the chorophyll inside them - used by the plants to  photosynthesise - diminishes. Yellow and orange pigments become visible.  But some plants actually produce a new pigment called anthocyanin - a  vivid red colour, seen here in the beech trees on the outside of the  picture.<img src="http://i.imgur.com/yn71b.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /> A  view over a lake in a forest with trees changing colour in Autumn in  Kashubia. The contrast between the evergreens and deciduous trees shows  how different plant families evolved to cope with local conditionsA new study has found trees evolved to become deciduous after a  series of ice ages and dry spells and their leaves were turned red to  help protect against insects that attacked them.  But the key difference in North America was as the ice age went on  plants and insects were able to migrate fairly freely while in Europe  the plants became trapped in ice, along with herbivorous insects,  meaning the majority of these bugs largely died out.So according scientist Simcha  Lev-Yadun of the University of Haifa, Israel. 'The anti-herbivore  component in red leaf colouration was relaxed, and Northern Europe  became dominated by trees with yellow autumn leaves,' but North American  trees continued to need the bright red to fight the insects, he says.<img src="http://i.imgur.com/KWGwa.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" />A  person walks past the trees at Westonbirt Arboretum, near Tetbury,  Gloucestershire, where the leaves are beginning to change to their  Autumn colours.<img src="http://i.imgur.com/vg1bl.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /> A dogwalker passes trees in the same area, which will turn from red to yellow quickly compared to U.S. treesIt seems nonsensical that a plant might 'decide' to spend energy  on a pigment for leaves that are about to drop off. But a series of  recent scientific papers provide the answer, according to an essay,  published in  New Scientist this week.The  pigment isn't an unnecessary 'expense' - in fact, for some plants, it's  an essential tool for survival. It also 'explains' why the changing of  the seasons can have markedly different colours depending on where in  the world you are.William  Hoch of Montana State University found that the pigment had a function -  it allowed the plants to send nutrients to the roots for winter. If  they 'blocked' plants from producing it, their leaves became vulnerable  to sunlight. The  reason for this was revealed in a  study of sweetgum and red maple by a team in North Carolina, led by  Martha Eppes. She found that leaves in nutrient-poor soils tend to be  redder - to shield leaves for longer, and allow them to 'keep doing  their job' of sending nutrients to the roots. <img src="http://i.imgur.com/CecCr.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" />This American tree stays a distinct red for longer as it fights insects not really found in Europe</blockquote>

Verification: Hathara warak wissa keeyada? (Hathara wadi karanna 20)

Top Bottom