Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
Release of Microspores
Up to the tetrad stage, there is no cellulosic wall around the microspores. As you will come to know in the next unit, a unique feature of the pollen is the ornamentation of the pollen wall. This ornamentation is seen on the outer layer of the pollen or exine. The exine is made up of sporopollenin, one of the most resistant (to physical and biological decomposition) substances known in the biological world. Pollen grains of prehistoric plants are well preserved as fossils because of their exine. There is enormous variation in the ornamentation of the exine, and it is a characteristic feature of a given species. Often pollen grains of particular group of plants can be identified on the basis of their exine pattern.
The blue print of exine, termed primexine is laid down below the callose wall after the basic structural features of the exine including the position of the germ pore (a region in the pollen wall through which the pollen tube emerges) are demarcated in the primexine. This important morphogenetic event takes place while the microspores are still enclosed in the callose wall, in groups of four or at the tetrad stage. Thus, the pattern of mature exine is laid down before the spores are set free. The callose wall seems to play an important role in the orderly deposition of primexine. You will read more about this in the next unit. After the development of exine, the callose wall dissolves. The enzyme callase which dissolves the callose wall is produced by the surrounding tapetal cell pen plasmodium. The development of the male gametophyte begins after the liberation of individual microspores.
Describe the Applications of vitamin b1 The steadily increasing consumption of white flours (insufficiently ground and thus low in vitamin content) by large sections of the po
How are secondary cell walls different from primary cell walls? Primary cell walls are assembled on the surface of the plasma membrane whereas the cell is growing. They can gro
Are organic solvents like benzene and ether polar or non-polar substances? Benzene and the ethers are molecules without electrically charged portions and therefore they are non
Valacyclovir (Valtrex) - Valacyclovir is an L-valyl ester of acyclovir that is metabolized to acyclovir after oral administration, resultingin higher serum concentrations than
poor metabolism phenotype will have
What would happen to a cell and its offspring if the cells did not go by a G1 phase during their cell cycle? Describe Without a G1 growth phase, the cells would not grow to th
Endocrine and exocrine pancreatic cells, thyroid and parathyroid endocrine cells, adenohypophysis, adrenal and pineal endocrine cells, the lot of types of gastric exocrine and endo
Explain mixture in basic chemistry? Mixtures : Mixtures are produced by combining two or more substances. In contrast to the substances in compounds, the substances that com
Explain Fetal Development? The medical profession divides pregnancy into three-month stages called trimesters. At the end of the first trimester, the fetus is only about 5 cm l
What is a population? The population is a set of individuals of the same species found in a given place in a given time.
Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!
whatsapp: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd