The filiform apparatus is a structure found in the mature embryo sac of angiosperms (flowering plants). Its primary function is to guide the pollen tube towards the embryo sac during fertilization. The filiform apparatus consists of several elongated cells with highly specialized wall structures located near the micropylar end of the embryo sac. These cells produce chemicals that attract and guide the pollen tube, facilitating the successful fertilization of the ovule.

To determine the number of male gametophytes produced by the Abilobed, dithecous anther with 100 microspore mother cells per microsporangium, we need to understand the process of microsporogenesis.

Microsporogenesis involves the formation of microspores from microspore mother cells (also known as pollen mother cells) within the microsporangium. Each microspore mother cell undergoes meiosis to produce four haploid microspores. Therefore, if there are 100 microspore mother cells per microsporangium, each microsporangium will produce 4 * 100 = 400 microspores.

Each microspore has the potential to develop into a male gametophyte (pollen grain). Hence, the number of male gametophytes produced by the anther would be the same as the number of microspores produced, which is 400.

Therefore, the Abilobed, dithecous anther can produce 400 male gametophytes.

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.

In angiosperms, the male gametophyte, also known as pollen grain, consists of two cells enclosed within a tough outer layer called the pollen wall or exine. These two cells are the generative cell and the tube cell, and they play distinct roles in the process of fertilization.

1. Generative Cell:

   • The generative cell is typically larger and more centrally located within the pollen grain.
   • Its primary function is to undergo mitosis to produce two sperm cells.
   • These sperm cells are eventually involved in fertilization, where one fuses with the egg cell to form the zygote, and the other fuses with the polar nuclei to form the endosperm nucleus, leading to the development of the endosperm, a nutrient-rich tissue within the seed.

2. Tube Cell:

   • The tube cell is smaller and usually located towards the periphery of the pollen grain.
   • Its main role is in pollen tube formation. After pollination, the pollen grain lands on the stigma of a compatible flower, where it germinates.
   • The tube cell elongates and develops into a pollen tube, which grows down through the style of the pistil towards the ovule.
   • The pollen tube serves as a conduit for the sperm cells to reach the female gametophyte (embryo sac) for fertilization.

In summary, while both cells are enclosed within the pollen grain of angiosperms, the generative cell gives rise to the sperm cells responsible for fertilization, while the tube cell develops into the pollen tube, facilitating the transport of sperm cells to the female reproductive structures.