[GpsFrontier]

There I read that nutrients which have been converted to sugars (plant food or sap) flow in both directions in the plhoem depending on where the food/sap is needed most.

I have printed those pages out also, but as of yet have not had time to read much of either printouts. But the plant food or sap flowing in either direction to where it's needed seems logical. After all, it would want to make the most of what it has to work with. Although, other than transpiration, I don't know of any other mechanism that would move (pump) fluids inside of a plant (but I an no expert, as mentioned before).

You also would have me believe that generally speaking in most plants, there is nothing produced at the roots from within the plant under favorable conditions. No reason for root exudate, therefore no root exudate normally without being triggered by some various mechanism.

I am not asking for anyone to believe me, and hopefully you don't feel that I am trying to be an expert. I am just trying to learn myself. Why? So I will have better crops in the future. But here is a quote from the link you posted:

"Survival of any plant species in a particular rhizosphere environment depends primarily on the ability of the plant to perceive changes in the local environment that require an adaptive response. Local changes within the rhizosphere can include the growth and development of neighboring plant species and microorganisms. Upon encountering a challenge, roots typically respond by secreting certain small molecules and proteins"

If I am to believe what you are telling me, then crop rotation is not necesary if enough nnutrient/fertilizer is used to replace the mineral contet that has been depleted by the previous crop.

No, I don't believe I ever said that at all. There is a wide variety of chemicals and compounds secreted into the soil by roots and can even change the chemical and physical properties of the soil. By simply replacing the nutrients/fertilizer depleted by the plants, you are NOT EXTRACTING the wide variety of chemicals and compounds secreted into the soil, by the roots. Therefor crop rotation would still be needed to allow time for these chemicals and compounds to break down and decompose, so they wont be in such high concentrations over time.

I know the thinking that if the root exudates are not needed they wont be secreted. But if the the chemical and compounds secreted into the soil by roots do change the physical properties of the soil, the soil itself would become unusable to the plants. You would need to change the soil, not just add fertilizer. Thus, crop rotation. Also (again depending on the plant) they might regularly secrete a compound as a preventive measure automatically, increasing the dosage if conditions warrant it.

But wait, you say plants in general excepting certain examples, do not release anyhting from the roots under ideal conditions.

Again I am not a botanist or even a biologist, and there are billions of types of plants. So such a general statement is needed to encompass them all. Also fertilizer conditions are not the only reason that roots secrete compounds into the rhizosphere. They also serve many other important roles, these quotes were also taken from the link you posted.

1. "the compounds secreted by plant roots serve important roles as chemical attractants and repellants in the rhizosphere"
2. "roots may regulate the soil microbial community in their immediate vicinity, cope with herbivores, encourage beneficial symbioses"
3. "and inhibit the growth of competing plant species"

Hmmm ... that previous link I included speaks of a viscous substance the roots exude mostly at night apparently, to help with taking in nutrients during daylight when transpiration is occuring.

As I just mentioned there are many reasons that plant roots exude compounds, possibly hundreds of thousands of different reasons, and even hundreds of thousands of different compounds. From what I have read (from your link), "Our understanding of the biology, biochemistry, and genetic development of roots has considerably improved during the last decade." So there is much the biology, and biochemistry community's do not know or understand yet (much less me).

For some reason I still belive there must be some sort of waste product besides O2 from the leaves, speaking in general terms for I realize there are exceptions, that the plant needs to rid itself of in order to be healthy, grow and produce blossoms. The waste would be put into the ground via the roots.

I don't know, or ever herd of any other wast product (that I can think of) from plants that are given off (roots or not) by all plants. That would involve the plants specific biology if it did exist (I'm sure).