AP Bio question

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Discus: SAT/ACT Tests and Test Preparation: April 2004 Archive: AP Bio question
By Jenesaispas (Jenesaispas) on Monday, April 19, 2004 - 07:20 pm: Edit

Alright, as I was reviewing about plants, I stumbled across the sentence, "Soil that contains humus is nutritious for plants. Humus is acidic; therefore, it retains positively charged minerals until plants take them up."

Uh, don't acidic things have a HIGH concentration of positive hydrogen ions, which would mean they would "retain" negatively charged minerals, or have I been under this huge misconception for all of high school?

By Jenesaispas (Jenesaispas) on Monday, April 19, 2004 - 07:24 pm: Edit

So I guess I am asking for a clarification or if this is in error.

By Jenesaispas (Jenesaispas) on Monday, April 19, 2004 - 08:17 pm: Edit


someone must know the answer

By Lahlahlah (Lahlahlah) on Monday, April 19, 2004 - 08:28 pm: Edit

high conc of negative ions ... think HCL-

By Aim78 (Aim78) on Monday, April 19, 2004 - 11:51 pm: Edit

From what I know, humus is positively charged, and clay is negatively charged. A humus-clay complex has a net negative charge and attracts positive ions, which most minerals in the soil are. Read around that sentence, does it mention anything about clay?

By Adidasty (Adidasty) on Tuesday, April 20, 2004 - 09:49 am: Edit

almost there Aim. he is right. CLAY is negative. It attracts positive ions like ca2+ that are needed by the plant. the plants root hairs release H+ ions which forms a gradient to attract the positive ions into the plant.

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