Question

Which of the following statements is not correct?

• 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 pistil
• 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 grow into the style

Answer 1

The correct option is D

Pollen grains of many species can germinate on the stigma of a flower, but only one pollen tube of the same species grow into the style

The correct option is D.
Explanation of the correct option:

1. Other species' pollen grains are incompatible and do not germinate on the stigma of a flower of a different species.
2. A style can be formed by several pollen tubes of the same species.
3. When a pollen grain germinates, a pollen tube extends down the style toward the ovary.
4. The pollen tube enters the micropyle and releases two sperm into the female gametophyte within an ovule.
5. The style is an elongated portion of the pistil, which is the female reproductive organ of a flower that connects the stigma to the ovary, whereas a pollen tube is a tube generated by pollen grains after they settle on the stigma.
6. Male gametes are pollen grains. Meiosis creates them in another sac-like structure called an anther.
7. Each mother cell of a microspore produces four microspores or pollen grains.
8. Pollen is a powdery substance made up of pollen grains, which are male microgametophytes that create male gametes.
9. In cross-pollination, pollen is utilized to transfer haploid male genetic material from the anther of one flower to the stigma of another.
10. Pollen grains from one species cannot germinate on a stigma from another.
11. The stigma of a flower may receive a lot of pollen from other species, but it may not germinate because the conditions are not right.

Explanation of the incorrect options:
Option A:

1. Pollen/nectar thieves are insects that take pollen or nectar without pollinating it.
2. The pollen grain germinates on the stigma to generate the pollen tube through one of the germ pores only when the correct pollen reaches the pistil.

Option B:

1. The apical membrane F-actin produces formin, an actin-binding protein required for pollen tube tip development.
2. Formins are found in tip growth cells and are classified into two types: type I and type II.
3. When pollen from most species is placed in a solution of calcium, boron, and an osmotic, it germinates and grows a tube.

Option C:

1. Malacophily refers to snail pollination, whereas ophiophily refers to snake pollination.
2. Skinks that visit flowers pull off the calyptra, a particular floral structure that protects the style, anthers, and nectar.
3. They then ingest the calyptra as well as the nectar.
4. Although the lizards never carry pollen, their exposure to the style and anthers allows insects to fertilize the flowers.

Final answer: Pollen grains of many species can germinate on the stigma of a flower, but only one pollen tube of the same species growing into the style is the incorrect statement.