Explain what happens to the movement of sugar in winter when a tree has no leaves
http://www.abc.net.au/science/articles/2014/06/11/4022947.htm
When a tree has no leaves in winter, the movement of sugar, also known as sap, is affected. To understand what happens, we need to know how sugar moves within a tree.
In trees, sugar produced by the leaves during photosynthesis is transported through a network of tissues known as phloem. Phloem helps in moving sugars from the leaves to other parts of the tree, such as the stem, branches, and roots. This movement occurs through a process called translocation.
During the winter, most trees enter a dormant state. They stop photosynthesizing and conserve energy to withstand the cold temperatures. This dormancy period affects the movement of sugar within the tree.
Since the leaves are absent in winter, there is no source of sugar production. Without new sugars being produced, the existing sugars stored in the tree can be utilized for metabolic activities and growth, such as maintaining cell function and repairing tissues. However, the movement of sugar from storage sites to other parts of the tree is limited.
One of the reasons for this restriction is that translocation in the phloem is driven by the pressure gradient created due to sugar production in the leaves. In winter, this pressure gradient is significantly reduced or absent due to the lack of photosynthesis. This limitation prevents efficient movement of sugar throughout the tree.
However, it's important to note that some trees, like evergreens, do retain their leaves throughout the winter. These trees can continue photosynthesizing and producing sugars, which facilitates the movement of sugar within the tree even during winter.
In summary, when a deciduous tree has no leaves in winter, the movement of sugar in the tree is restricted due to the absence of sugar production and reduced pressure gradient in the phloem.