[jbolanos2015]

I'm a freshman and I conducted an experiment in Biology. My question in the experiment was:
How do different pH levels in water affect plant growth?
It was an acid rain experiment on Marigolds. I had 4 6 packs of Marigolds. I labeled each pack A,B,C, and D. Plants in A received pH 7 water, plants in B received pH 6 water, plants in C received pH 8 water, and plants in D received pH 10 water. plants in A, C, and D thrived, while most plants in B started wilting and dying. I know that the pH of the water can affect the soil pH. I need a science concept of why most plants can't tolerate acidic pH levels. At alkaline pH values, phosphate ions tend to react quickly with calcium (Ca) and magnesium (Mg) to form less soluble compounds. At acidic pH values, phosphate ions react with aluminum (Al) and iron (Fe) to again form less soluble compounds. If that's true why did most of the plants in B die and the rest thrived? I need a concept explaining this.

[Borek]

What have you added to the water to controls its pH?

[jbolanos2015]

I used NaOH and HCl