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Which of the following statements is not correct?
A. Pollen germination and pollen tube growth are regulated by chemical components of pollen interacting with those of the pistil.
B. Some reptiles have also been reported as pollinators in some plant species.
C. 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.
D. Insects that consume pollen or nectar without bringing about pollination are called pollen/nectar robbers.

Last updated date: 20th Jun 2024
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Hint: The pollen grain germinates on the stigma to produce the pollen tube through one of the germ pores only when the right pollen reaches the pistil, it germinates on the stigma.

Complete step by step answer: Pollen grains of other species are not compatible and do not germinate on the stigma of a flower of different species. A number of pollen tube of the same species can grow into a style. A pollen grain germinates and the pollen tube grows down the style toward the ovary. The pollen tube passes through the micropyle and discharges a pair of sperm into the female gametophyte within an ovule. The style is the elongated part of the pistil, i.e. the female reproductive organ of a flower which connects the stigma of a plant to the ovary of that plant, whereas a pollen tube is a tube which is formed by the pollen grains after the landing on the stigma. Pollen grains are male gametes. These are formed in another sac-like structure called anther by meiosis. Each microspore mother cell produces four microspores or pollen grains. Pollen is the powder-like substance that consists of pollen grains which are male microgametophytes that produce male gametes. Pollen in plants is used for transferring haploid male genetic material from the anther of a single flower to that of the stigma of another in cross-pollination. Pollen grains of one species can't germinate on a stigma of some other species. The stigma of a flower may receive much pollen even from other species also, but they do not get germinated because they do not get the required conditions.
Hence, the correct answer is option C.

Note: The pollen germination starts when the pollen grain lands on the stigma.
The cell of the pollen grain divides into two types; one of these is smaller in size. It is called the generative cell and the bigger one is called the tube cell. The intine grows out through the germ pore and forms a pollen tube.