Practicing Success

Target Exam

CUET

Subject

Biology

Chapter

Sexual Reproduction in Flowering Plants

Question:

Read the passage given below and answer the following question.

The pollen grains, serve as the male gametophytes in flowering plants. Upon touching the opened anthers of flowers like Hibiscus, one can observe the deposition of yellowish powdery pollen grains on their fingers. When these grains are sprinkled on a glass slide with a drop of water and observed under a microscope, a fascinating variety of architecture, including sizes, shapes, colors, and designs, can be seen among the pollen grains from different species.Pollen grains are generally spherical and have a diameter ranging from 25 to 50 micrometers. They possess a two-layered wall, with the outer layer composed of sporopollenin, which exhibits intricate patterns and designs. The inner wall of the pollen grain is a thin and continuous layer. When mature, the pollen grain contains two cells: the larger vegetative cell and the smaller generative cell. The vegetative cell holds abundant food reserves and a large, irregularly shaped nucleus, while the generative cell floats within the cytoplasm of the vegetative cell.In the majority of angiosperms (over 60 percent), pollen grains are shed at the 2-celled stage, where they contain vegetative and generative cells. However, in the remaining species, the generative cell undergoes mitotic division to produce the two male gametes before the pollen grains are shed, resulting in a 3-celled stage.

Pollen grain exine has prominent apertures. What are these known as?( Question 2)

Options:

Spindles

Vacuoles

Germ pores

Vegetative cells

Correct Answer:

Germ pores

Explanation:

The correct answer is Option (3)- Germ pores

The prominent apertures present in the exine of a pollen grain are known as germinal or pollen apertures.

Apertures are specific regions on the pollen grain's surface where the exine is thinner or absent, allowing for the release of pollen tubes during germination.

These apertures serve as entry points for pollen tube growth, which is crucial for the pollen grain to deliver the male gametes (sperm cells) to the ovule for fertilization.

The number, size, shape, and arrangement of apertures can vary among different plant species and are often important characteristics used in the identification and classification of pollen grains.