The exine of a pollen grain is not a continuous layer because it has openings called germ pores or colpi, which allow for the entry of pollen tubes during fertilization. These pores are necessary for the reproductive success of the plant as they facilitate the transfer of genetic material from the male gametophyte to the female reproductive structures.
The three parts of a pollen grain are the exine (outer layer), intine (inner layer), and the cytoplasm containing the male gametes. The exine is composed of sporopollenin and helps protect the pollen grain during transportation and fertilization.
Depending on the type of pollinators, the pollen grains may be sticky or light. Exine present on the pollen grains as the outermost covering layer is contributed by the tapetum cells. Reaching on the stigma after pollination, the stigmatic cells interact with the material of exine to determine the compatibility of the pollen to allow its germination for fertilization.
A single pollen grain contains the generative material that forms the male gametes. It also contains the material that will form the pollen tube when the pollen lands on the pistil. These are covered by a thin layer called the intine or endospore as well as a thick protective wall called the exine or exospore.
The outer covering of the grain is called Husk. :) - HAO -
The deepest layer of the epidermis is called the stratum basale which is actively mitotic and gives rise to all the more superficial layers.
The three parts of a pollen grain are the exine (outer layer), intine (inner layer), and the cytoplasm containing the male gametes. The exine is composed of sporopollenin and helps protect the pollen grain during transportation and fertilization.
In botany 'exine' is the outer coat, or the outer layer, of the wall of a pollen grain. It is composed of a durable organic polymer
Sporoderm is the outermost protective wall around the pollen grain or microspore. It is made up of many layers. The two main layers are Exine and Intine. Exine is outer while Intine is inner layer of sporoderm.
Depending on the type of pollinators, the pollen grains may be sticky or light. Exine present on the pollen grains as the outermost covering layer is contributed by the tapetum cells. Reaching on the stigma after pollination, the stigmatic cells interact with the material of exine to determine the compatibility of the pollen to allow its germination for fertilization.
A single pollen grain contains the generative material that forms the male gametes. It also contains the material that will form the pollen tube when the pollen lands on the pistil. These are covered by a thin layer called the intine or endospore as well as a thick protective wall called the exine or exospore.
What is usually meant by pollen case is the outer protective coat of the pollen grain. It is a highly modified cell wall, with two layers. The interior layer is largely pectocellulose (a combination of pectin and cellulose) with a bit of callose, and the exterior is made of sporopollenin. Sporopollenin is so tough that its exact chemical structure has not been figured out. Atop the sporopollenin layer is a deposit of sticky goo made of pollenkitt and/or tryphine.
Sporoderm stratification refers to the layering of the sporoderm, which is the outer layer of a pollen grain or spore. This stratification can consist of different layers with distinct compositions and functions, such as protecting the genetic material inside the pollen grain or aiding in dispersal. The structure and composition of sporoderm layers can vary among different plant species.
The outer covering of the grain is called Husk. :) - HAO -
Endocardium
Epicardium is the outer layer of heart tissue. When considered as part of the pericardium, it is the inner layer, continuous with the serial layer.
The Crust of the Earth ?
The pollen is actually nothing but sperm in a protective layer. The pollen is given to various organisms which give to other plants, and then the plants take the fertilization and use it to reproduce, to make fruits, and various other things depending on the species.