Which of the following statements is true for pollination by water ?

Options

A. Pollen grains of water pollinated plants are small and spherical .
B. The flowers of water pollinated plants are not very colourful.
C. Female flowers of Vallisneria remain submerged in water and male flowers release the pollen inside the water causing pollination deep with water .
D. Nelumbo nucifera (India lotus) is an aquatic plant pollinated by water.

Answer

To determine which statement is true for pollination by water, we can analyze the characteristics and examples of water pollination. Here’s a step-by-step solution:

### Step 1: Understand Pollination
Pollination is the process of transferring male gametes (pollen) from the anther (male part) to the stigma (female part) of a flower. It can occur through various agents including water, wind, and insects.

**Hint:** Remember that pollination is essential for fertilization and reproduction in flowering plants.

### Step 2: Identify Water Pollination
Water pollination is relatively rare among flowering plants but is observed in certain species, particularly in monocots. Examples include plants like Hydrilla, Valisneria, and Joistra.

**Hint:** Focus on the specific examples of plants that utilize water for pollination.

### Step 3: Characteristics of Pollen Grains
In water-pollinated plants, pollen grains are often long and ribbon-like, allowing them to be carried passively through the water. Additionally, these pollen grains are usually protected from wetting by a mucilaginous covering.

**Hint:** Pay attention to the structure and protection of pollen grains in aquatic environments.

### Step 4: Color and Nectar Production
Flowers that are pollinated by water are generally not colorful and do not produce nectar, as these traits are more common in insect-pollinated flowers.

**Hint:** Consider the adaptations of flowers based on their pollination method.

### Step 5: Specific Examples and Their Characteristics
For instance, in Valisneria, the female flowers remain submerged while the male flowers release pollen into the water. The female flowers then reach the surface of the water via a long stalk, allowing for successful pollination.

**Hint:** Look at how the structure of the flowers aids in the process of water pollination.

### Step 6: Evaluate the Given Statements
Now, we can evaluate the statements provided in the question:
1. Pollen grains are small (This is incorrect; they are long and ribbon-like).
2. Water-pollinated flowers are not very colorful (This is correct).
3. Female flowers of Valisneria remain submerged and male flowers release pollen inside the water (This is incorrect; the female flowers reach the surface).
4. Nymphaea (water lily) is an aquatic plant pollinated by water (This is incorrect; it is typically insect-pollinated).

**Hint:** Analyze each statement carefully to determine its accuracy based on the characteristics discussed.

### Conclusion
The true statement regarding pollination by water is that water-pollinated flowers are not very colorful.

**Final Answer:** The correct option is the second statement: Water-pollinated flowers are not very colorful.