To solve this problem, we need to analyze each statement and determine which one is not correct.$\newline \bullet$Option 1:$\newline$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.$\newline$This statement is correct. It describes the process of pollen-pistil interaction where only compatible pollen tubes grow through the style.$\newline \bullet$Option 2:$\newline$Insects that consume pollen or nectar without bringing about pollination are called pollen/nectar robbers.$\newline$This statement is correct. Pollen/nectar robbers are insects that feed on pollen or nectar without contributing to pollination.$\newline \bullet$Option 3:$\newline$Pollen germination and pollen tube growth are regulated by chemical components of pollen interacting with those of the pistil.$\newline$This statement is incorrect. While pollen germination and pollen tube growth are influenced by interactions between pollen and pistil, the statement implies that this regulation is solely due to chemical components, which is an oversimplification.$\newline \bullet$Option 4:$\newline$Some reptiles have also been reported as pollinators in some plant species.$\newline$This statement is correct. Certain reptiles, such as some lizards, have been observed to act as pollinators.$\newline$Therefore, the statement that is not correct is Option 3.$\newline$Thus, the correct answer is Option 3.