Root pressure is absent in

Options

A. rapidly transpiring plants.
B. conifers.
C. plant growing in cold soils.
D. all of the above

Answer

To solve the question "Root pressure is absent in," we will analyze each option provided and determine whether root pressure is present or absent in the given scenarios.

### Step-by-Step Solution:

1. **Understand Root Pressure**:
- Root pressure is defined as the positive pressure within the xylem of plants that helps to push water upward from the roots to the leaves. It is particularly effective in small plants and during times of low transpiration.

2. **Evaluate Each Option**:
- **Option A: Rapidly transpiring plants**:
- In plants that transpire rapidly, the rate of water loss is high. This means that water is being pulled up through the xylem due to the transpiration pull rather than being pushed by root pressure. Therefore, root pressure is typically absent in rapidly transpiring plants.
- **Conclusion**: Root pressure is absent.

- **Option B: Conifers**:
- Conifers are tall gymnosperms. In tall plants, the height can limit the effectiveness of root pressure because the gravitational pull on water is stronger over long distances. While root pressure may be present, it is not sufficient to move water to the heights that conifers reach. Thus, root pressure is often considered ineffective in very tall plants.
- **Conclusion**: Root pressure is often absent or ineffective.

- **Option C: Plants growing in cold soils**:
- In colder regions, the rate of transpiration is generally lower due to reduced temperatures. However, root pressure can still occur in some cases. But in many cold environments, the physiological processes can slow down, leading to less effective root pressure.
- **Conclusion**: Root pressure may be absent or less effective.

3. **Final Evaluation**:
- All the options provided indicate conditions where root pressure is either absent or ineffective. Therefore, the correct answer is that root pressure is absent in all of the above scenarios.

### Final Answer:
Root pressure is absent in **all of the above** (Option D).