The greatest contribution of root pressure is to (A)____ the continuous chains of water molecules which often break by (B)_____

Answer

**Step-by-Step Solution:**

1. **Understanding Root Pressure:**
- Root pressure is defined as the osmotic pressure within the cells of the root system. It is generated when soil moisture levels are high, allowing water to be absorbed by the roots and pushed upward through the xylem.

2. **Understanding Transpirational Pull:**
- Transpirational pull refers to the negative pressure created at the top of the plant due to the evaporation of water from the leaves. This process pulls water upward through the plant's xylem.

3. **Analyzing the Contribution of Root Pressure:**
- The primary role of root pressure is to help maintain a continuous column of water in the xylem. This column can often be disrupted by the transpirational pull, which can cause breaks in the chain of water molecules.

4. **Filling in the Blanks:**
- The first blank (A) can be filled with "re-establish" because root pressure helps to restore the continuous chain of water molecules.
- The second blank (B) can be filled with "transpiration" since it is the process that breaks the continuous chain of water molecules.

5. **Final Answer:**
- The greatest contribution of root pressure is to (A) **re-establish** the continuous chains of water molecules which often break by (B) **transpiration**.

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