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.
Q. How be able to the excretory system of annelids be described? In each segment (metamere) of the being a pair of complete excretory structures known as metanephridium exists.
Explain Heat Preservation - Method of Food Preservation? The process of heating was used centuries before its action was understood. Food is heated up or cooked. Heat kills mi
Discuss the similarities and differences of transposable elements in E. coli, yeast, plants, and Drosophila.
Define Methods of Quantitative Analysis and Colorimetry? Many methods of quantitative analysis are based upon the production of coloured solutions in such a way that the intens
Cytoplasmic bridge formed during the conjugation of paramoec: The two paramoecia that undergo conjugation are called conjugants. During conjugation, the two conjugants com
what are lipids? how ther absorption takes place in human bodies?
Define the Beer's Law - Nutritional Biochemistry? Beer's law states that the concentration of a substance is directly proportional to the amount of light absorbed or inversely
excretory system in agama lizard
Q. How many ATP molecules are produced for every glucose molecule used in fermentation? And How many ATP molecules are produced for each glucose molecule used in aerobic respiratio
What does skin color in man shows?
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