The hardest question ever!!?

Question

Scientists have meausured the circumfrence of trees at 2 A.M. and at 2 P.M. If they collect measurements when the ground has adequate moisture and the days are sunny and dry, they find that hte circumfrence (and therefore the diameter) of the tree trunk is smaller at 2 P.M. than at 2 A.M. From your knowledge of the mechanisms of water transport, suggest your reasons for this decrease in circumfrence.

Answer 1

Hi. Transpiration occurs faster in sunlight. http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/T/Transpiration.html

Answer 2

Photosynthesis occurs in in the day. Therefore there is a lot more transpiration occurring. Transpiration works because of the adhesive and cohesive properties of water. As water is lost through the stomata of a plant, water is also being pulled throughout the xylem. This is because a negative water potential is created, this is called tension. Sometimes tension within a tree is so great that it constricts the tree. This is why the diameter of the tree is smaller during 2 P.M. Think of an empty water bottle the bottle resembling the tree trunk. If you were to suck the air out of the bottle the sides of the bottle constrict or get crushed. Sucking air out of the bottle resembles transpirational pull, and the collapsing of the sides resembles the tension being created by the transpiration. hope this helps.

Answer 3

Since transpiration happens at a greater rate and with greater flow during daylight (when photosynthesis light reactions are happening), the vascular tissues dilate (via osmosis, creating turgid cells lining the xylem and forcing the tube to open wider) to allow increased water flow to the leaves.

At night, when less water is needed, the vascular tissues constrict, reducing the flow.

Answer 4

ummm....the water inside trees are used and dryed up when the weather is dry and sunny?

Answer 5

Someone entirely missed the point of "homework."