[GpsFrontier]

From what I can understand of your words, you are saying the roots get fed only during daylight when transpiration occurs. I have trouble understanding how that can be

Yes, that's basically what I'm saying, but in general terms because there is always exceptions. Because without the process of transpiration, there would be no movement of the fluid. Like if a persons heart stopped, there would be no movement of blood thought the body, and to the cells. The process of transpiration is in effect, the plants heart. I have herd that some flowers/fruit actually grow at night. I don't know exactly if this is true or not (but wouldn't be surprised), and/or witch plants it would apply to. But I would not relate it to the plant feeding, rather I would see it as cell division. Humans and animals don't feed 24/7 but their body's are constantly dividing cells, even while sleeping, and I can't see any reason why plants wouldn't do the same.

I guess what I'm trying to find (thank you for including the pictrue by the way) would be a diagram/timeline that show the flow of substances in the Xylem and in the Ploem with emphasis on when there is flow and when the substances are stagnant.

No problem, it helped me to visualize everything. So I thought it might help others also. I just copied it from Phloem - Wikipedia, the free encyclopedia Although I have not seen any images with a time line.

P.S. To whom it may concern, all images on Wikipedia are not supposed to be copyrighted according to there terms of use agreement.

I'm trying to relate this ebb and flow throughout the plant with cell-division/growth. When do the roots grow ? When do the leaves grow ? Is it when they are fed ? When are they fed ?

As far as I can tell growth/cell division can happen 24/7. But they would do best when the cells are well feed. At night (in darkness) it may very well slow down, but likely continue.

In particular I am trying to find out if a shorter than 24 hour cycle might "pump" more nutrients up and food down if light and dark cycles were speeded up to say just for an example, an hour or so of each.

In all likelihood you would just confuse the plant with cycles of 1 hour on, one hour off all day. At best you would just stunt the growth because that would only allow 12 hours of light. Light is what the plant needs for the chlorophyll to do its job, and is vital to plant growth. By cycling the light in such short intervals you only confuse the plant, and don't add any benefit. In fact it would be far better to extend the daytime for more growth.

Alaska is well known for producing GIANT produce because of there long days. There known as "the land of the midnight sun", and during summer (depending on where in Alaska you are) the sun never sets. It hits the horizon and stays twilight for a couple of hours, then it rises again. Extending the daylight to virtually 24 hours a day. For me that makes it clear, more light more growth. In some plants the length of darkness tigers the plant to produce fruiting/flowering. Shorter verses longer (not the actual length of time), the change is what's important

Am I wrong in asuuming the dark cycle is necessary because it controls some hydraulic properties which help sustain the plant.

In fact the hydraulic properties that sustain the plant are done through transpiration (daytime). Transpiration is the act in witch evaporation takes place, this evaporation actually sucks up water/nutrients from the soil (or nutrient solution) to replace what evaporates through the leaves. When it's dark and the pores that the evaporation takes place through close, the water inside the stems and leaves remain in place (but not flowing) or the plant would wilt.

Think of it like a hydraulic car jack, when transpiration is taking place, its like pumping the handle on the car jack up and down, making the car lift because of the fluid flowing through tubes. When transpiration stops, it's like you stopped pumping the jack handle, and thus the car stays where it is. It dosen't rise or drop (unless your jack leaks).