$ Fertilization with the help of a pollen tube is called Siphonogamy.
! Entry of pollen tube into the ovule through integuments is called Mesogamy.

Options

A. If both As and R are correct and R is correct explanation of As
B. If both As and R are correct but R is not correct explanation of As
C. If As is correct, R is wrong
D. If both As and R are wrong.

Answer

To solve the question regarding the definitions of siphonogamy and mesogamy, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding Siphonogamy**:
- Siphonogamy is defined as the process of fertilization in plants that involves the use of a pollen tube. The pollen tube carries male gametes to the ovule for fertilization.
- In this process, the pollen tube grows from the pollen grain and penetrates the ovule at the micropyle, which is the opening of the ovule.

2. **Identifying the Components of the Ovule**:
- The ovule consists of several important structures:
- **Antipodal Cells**: These are located at the chalazal end of the ovule.
- **Egg Apparatus**: Located at the micropilar end, it consists of two synergids and one egg cell.
- **Filiform Apparatus**: This structure is found in the synergids and helps guide the pollen tube to the egg cell.

3. **Understanding Mesogamy**:
- Mesogamy refers to the entry of the pollen tube into the ovule through the integuments. The integuments are protective layers surrounding the nucellus of the ovule.
- In mesogamy, the pollen tube penetrates the integuments before reaching the nucellus and ultimately the egg cell.

4. **Conclusion**:
- Both statements in the question are correct:
- Fertilization with the help of a pollen tube is indeed called siphonogamy.
- The entry of the pollen tube into the ovule through the integuments is correctly referred to as mesogamy.

### Final Answer:
- **Siphonogamy**: Fertilization involving a pollen tube.
- **Mesogamy**: Entry of the pollen tube into the ovule through integuments.

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