Which one of the following statements is not true?

Options

A. Tapetum helps in the dehiscence of anther
B. Exine of pollen grain is made up of sporopollenin
C. Pollen grains of many species cause severe allergies
D. Stored pollen in liquid nitrogen can be used in the crop breeding programmes

Answer

To determine which statement is not true regarding sexual reproduction in flowering plants, we will analyze each of the provided options step by step.

### Step-by-Step Solution:

1. **Analyze the First Statement:**
- The first statement claims that "Tiptum helps in the dehiscence of anther."
- **Evaluation:** This statement is incorrect. The tiptum is a layer of nutritive cells found within the anther, and its primary function is to provide nutrition for the development of pollen grains and to act as a precursor for the pollen coat. It does not play a role in the dehiscence (the process of opening) of the anther.

2. **Analyze the Second Statement:**
- The second statement states, "Exine of pollen grain is made up of Sporopollenin."
- **Evaluation:** This statement is correct. The exine is indeed the outer layer of the pollen grain, and it is composed of a highly resistant substance known as sporopollenin, which protects the pollen grains.

3. **Analyze the Third Statement:**
- The third statement mentions, "Pollen grains of many species cause severe allergies."
- **Evaluation:** This statement is also correct. Many species of pollen grains are known to be allergens and can cause allergic reactions in sensitive individuals.

4. **Analyze the Fourth Statement:**
- The fourth statement says, "Stored pollen in liquid nitrogen can be used in crop breeding programs."
- **Evaluation:** This statement is correct as well. Storing pollen in liquid nitrogen is a common practice in crop breeding to preserve genetic material for future use.

### Conclusion:
After evaluating all the statements, the first statement is the only one that is not true. Therefore, the answer to the question is that the first statement is incorrect.

### Final Answer:
The statement that is not true is: "Tiptum helps in the dehiscence of anther."

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