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.
Hydroxyapatite coating Hydroxyapatite coating has been recommended for clinical use. These implants are superior with respect to the degree and rate of fixation in the bone as
M a g n etic resonance imaging (MRI): It is in use as a clinical diagnostic tool since 1980. The distribution of hydrogen nuclei (protons), present in cellular wa
Q. Dietary tips for hyperlipideinic patients? It is important to note here that the dietary modifications need to be individual in each patient and these should be tailored lo
How do mineral salts participate in osmotic regulation? Osmotic pressure depends on the number of particles dissolved in a solution and not on the nature of such particles. Min
What are some similarities between proteins, carbohydrates, and nucleic acids?
Reproductive Cycle The whole reproductive cycle consists of an ovarian cycle and a uterine cycle. Figure illustrates one complete reproductive cycle. You can observe in the fi
sample assignment on tagmatizatio
Unsaturated fatty acids require some additional processing before they can be degraded completely by β-oxidation. The Unsaturated fatty acyl CoAs with double bonds at odd-numbered
Q. Are hookworms monoxenous or heteroxenous? The Monoxenous are Hookworms that is their life cycle depends only on one host.
Dideoxy Sequencing is the enzymatic determination and consideration of DNA or RNA sequence by the rechnique of Sanger and colleagues, based on incorporation of the chain terminati
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