Which of the following statements is not correct

Options

A. Insects that consume pollen or nectar without bringing about pollination are called pollen/nectar robbers
B. Pollen germination and pollen tube growth are regulated by chemical components of pollen interacting with those of the pistill
C. Some reptiles have also been reported as pollinators in some plant species
D. Pollen grains of many species can germinate on the stigma of a flower, but only one pollen tube of the same species grows into the style

Answer

To determine which statement is not correct regarding pollination and pollen tube growth, we will analyze each statement provided in the options.

### Step-by-Step Solution:

1. **Analyze Statement A**: "Insects that consume pollen or nectar without bringing about pollination are called pollen or nectar robbers."
- This statement is correct. Insects that take pollen or nectar without aiding in the pollination process are indeed referred to as pollen or nectar robbers.

2. **Analyze Statement B**: "Pollen germination and pollen tube growth are regulated by the chemical components of pollen interacting with those of the pistil."
- This statement is also correct. The interaction between the chemical components of the pollen and the pistil is crucial for pollen germination and the growth of the pollen tube.

3. **Analyze Statement C**: "Reptiles have also been reported as pollinators in some plant species."
- This statement is correct as well. Certain reptiles, such as some species of lizards, have been observed to act as pollinators for specific plants.

4. **Analyze Statement D**: "Pollen grains of many species can germinate on the stigma of a flower, but only one pollen tube of the same species grows into the style."
- This statement is incorrect. While pollen grains from various species may land on a stigma, they typically do not germinate if they are from a different species due to incompatibility. Only pollen grains from the same species can germinate and grow a pollen tube into the style.

### Conclusion:
- The statement that is not correct is **Statement D**.