which of the following statements is true with reference to cross pollination in angiosperms?

Options

A. It most often results in higher yield of plants
B. It occurs only in unisexual flowers
C. It can fail to occur due to distance barrier
D. It requires production of large nuumber of pollen grains.

Answer

To determine which statement is true with reference to cross-pollination in angiosperms, let's analyze each option step by step.

### Step 1: Understand Cross-Pollination
Cross-pollination is the transfer of pollen grains from the anther of one flower to the stigma of a different flower, typically of the same species but on a different plant. This process is crucial for genetic diversity in plants.

### Step 2: Evaluate Each Statement

1. **"It most often results in higher yield of plants."**
- This statement is **incorrect**. While cross-pollination can produce better offspring in terms of genetic diversity, it does not necessarily lead to a higher yield. Factors such as pollen compatibility and the number of pollen grains that successfully reach the stigma affect yield.

2. **"It occurs only in unisexual flowers."**
- This statement is also **incorrect**. Cross-pollination can occur in both unisexual and bisexual flowers. Some bisexual flowers have mechanisms to prevent self-pollination, ensuring that cross-pollination occurs.

3. **"It can fail to occur due to distance barrier."**
- This statement is **incorrect**. Cross-pollination can occur over long distances, especially when facilitated by pollinators like wind, water, insects, or birds. Therefore, distance is not a barrier to cross-pollination.

4. **"It requires production of a large number of pollen grains."**
- This statement is **correct**. Cross-pollinated plants often produce a large number of pollen grains because many of them are lost during the transfer process. This ensures that enough pollen reaches other flowers for successful fertilization.

### Conclusion
The true statement with reference to cross-pollination in angiosperms is: **"It requires production of a large number of pollen grains."**

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