Sure, here are examples of plants that reproduce through runners and offsets:

(i) Runner:

• Strawberries (Fragaria spp.): Strawberries reproduce through runners, which are also known as stolons. These are horizontal stems that grow along the ground and produce new plants at nodes. As the runner touches the soil, it roots and forms a new plant, which is genetically identical to the parent plant.

(ii) Offset:

• Hen and Chicks (Sempervivum spp.): Hen and chicks, also known as houseleeks, reproduce through offsets. These are small rosettes that form at the base of the parent plant. As they mature, they can be separated and replanted to grow into new individual plants.

The tapetum is a layer of cells found within the anther of a flowering plant. Its primary function is to nourish and support the development of pollen grains, which are the male gametophytes. If the tapetum malfunctions, it can result in the failure to produce viable male gametophytes for several reasons, but one significant reason is the lack of proper nutrition and support provided to the developing pollen grains.

The tapetum provides essential nutrients, such as carbohydrates, lipids, and proteins, to the developing pollen grains. It also helps in the removal of waste materials and facilitates the transfer of nutrients to the developing microspores. If the tapetum malfunctions, it may fail to provide these necessary nutrients and support, leading to impaired pollen development.

Without adequate nourishment and support from the tapetum, the male gametophytes may not undergo proper development, resulting in non-viable pollen grains. This can ultimately lead to the failure of successful pollination and fertilization in the plant, affecting its reproductive success.

The exine and intine of angiosperm pollen grains are primarily composed of organic materials.

1. Exine: The exine is the outer layer of the pollen grain wall and is primarily composed of sporopollenin, a highly resistant biopolymer. Sporopollenin is one of the most durable organic compounds known and is resistant to chemical and biological degradation. It is primarily made up of long-chain fatty acids and phenolic compounds. The exine layer provides protection to the pollen grain from various environmental stresses such as desiccation, UV radiation, and microbial attack. Additionally, the exine may also have elaborate sculpturing or ornamentation, which aids in pollen dispersal and recognition by pollinators.

2. Intine: The intine is the inner layer of the pollen grain wall and is composed of cellulose, hemicellulose, pectin, and proteins. Unlike the exine, the intine is relatively softer and less resistant to degradation. It plays a crucial role in pollen germination and pollen tube growth after pollination. The intine provides the necessary structural support and nutrients for the growing pollen tube to penetrate the stigma and reach the ovule for fertilization.

The exine and intine together provide structural integrity to the pollen grain and ensure successful pollen dispersal, pollination, and fertilization in angiosperms.