Trees absorb nutrients and water through a process known as the cohesion-tension theory, which posits that evaporation from leaves creates negative pressure in the xylem, pulling water from the soil. During winter, deciduous trees shed their leaves to conserve resources and reduce the risk of damage from snow load and wind. This adaptation is crucial for survival in cold climates, as it minimizes the energy required to maintain leaves and protects the tree from freezing temperatures. The discussion also highlights the role of capillary action and the potential for cavitation in xylem cells, which can disrupt water transport.
PREREQUISITESBotanists, horticulturists, environmental scientists, and anyone interested in plant physiology and adaptations to seasonal changes.
Wiki once more.anorlunda said:May I inject a related question please? I've searched books about trees without finding this answer.
How do the nutrients formed by photosynthesis is the leaves get transported down to the trunk and the roots? Actually, I'm thinking of molecules more than complex nutrients. The trunk and roots have lots of carbon that I think was captured from the atmosphere. I'm trying to imagine how it got down there from the leaves.
Brian in Twisp said:phloem
256bits said:
Plants have been grown on scales many times. The water flow you mention makes it difficult to measure the up and down differences. And a great deal if the new mass is not sent to the roots. A tree adds a new ring, branches get longer. A plant adds mass above the roots, and has water flowing continuously upward. You could easily measure root mass and mass above the surface. But I'm not sure what question you are getting at. Plants mobilize resources. That is known. It is not hard to grow plants, and weigh them, either cut up or whole.anorlunda said:Thank you both. Phloem was the key word I lacked. The wiki article helped.
I'm curious if anyone has done a very physics-oriented non-biological-oriented experiment on trees -- a mass balance.
Let's say that a tree adds one metric ton of wood mass in one growing season. Applying conservation of mass, the mass of nutrients going up to the crown, must be at least one metric ton less than the mass of nutrients in the sap flowing down in the phloem. Measuring that mass balance would be an interesting and challenging experiment to perform. Has it been done to your knowledge?
Water makes it more challenging. The mass of water need not balance because water can be absorbed by roots and evaporate in the crown. Also, the mass of wood added in the season would have to be corrected for the water content of the new wood.
Drakkith said:I'm not sure, but I don't believe photosynthesis uses UV light at all. I think it uses different parts of the visible spectrum depending on the exact pigments used.
Hornbein said:It isn't suction or capillary action. Tree cells actively pump water.
jim hardy said:I'd sure love to read about that.
It might validate my long held but utterly baseless opinion that alternate tension/compression{think deflection in a beam) as they sway in the breeze provides the motive force.
Edison Bias said:Maybe we should not consume so much sugar because it is pure energy :)