The exine layer, Biology

Assignment Help:

The Exine Layer

It consists of two layers, inner (nexine) which is continuous and an outer (sexine) the sculptured one. The outer layer has ornamentations comprising rod-like bacula showing terminal expansion which sometimes fuses to form a roof like tectum perforated by micropores. During pollen development, the tapetum releases a mixture called tryphine, consisting of carotenoid lipid droplets and fibrogranular proteins into the thecal cavity. These fibrogranular proteins are enclosed in membrane bound cisternae. In tectate pollen, the released substances of tapetum become incorporated on the surface of pollen grains where cisternae membrane ruptures and protein released through micropores enter the tectum and accumulate in the interspaces of bacula.

Pollenkitt is the pigmented lipid fraction left on the surface of the tectum. Unlike intine, the exine held proteins exhibit only one enzymatic activity. The hydration of pollen is described to be stimulatory in releasing the proteins held in the pollen wall layers. The calculated time taken by the exine held proteins of sporophytic origin to pass out is 30 seconds while the intine of gametophytic origin takes a few minutes. This time difference in the protein release has made it easy to collect both samples separately. In SSI systems therefore the rejection reaction is faster than in GSI system.

 


Related Discussions:- The exine layer

Oogenesis., write breif notes on oogenesis

write breif notes on oogenesis

Illustrate artificial active immunization, Q. What are artificial active im...

Q. What are artificial active immunization and natural active immunization? Natural active immunization is that in which a previous natural infection induces the primary immune

Membrane potential, a solution of 5mMol/L CaCl2 is separated from a solutio...

a solution of 5mMol/L CaCl2 is separated from a solution of 1 micromole/L CaCl2 by a membrane that is selectively permeable to Ca+2 but is impermeable to Cl-1 what are the magnitu

What is etherification, What is Etherification The act or process of m...

What is Etherification The act or process of making ether; specifically, the process by which a large quantity of alcohol is transformed into ether by the agency of a small am

Describe the pulmonary artery, Q. Describe the pulmonary artery? The ma...

Q. Describe the pulmonary artery? The main pulmonary artery is seen on the PA view, as its left border forms the pulmonary bay. The right pulmonary artery runs horizontally to

Explain thermal destruction of enzymes during sterilization, Explain about ...

Explain about Thermal Destruction of Enzymes during Sterilization? Before we move on to canning, we need to emphasize here that like thermal destruction of microorganisms, ther

How many progeny flies have vestigial wings, In the fruit fly Drosophila, a...

In the fruit fly Drosophila, a rudimentary wing called "vestigial" and dark body color called "ebony" are inherited at independent loci and are recessive to their dominant wild-typ

Excretion, Normal 0 false false false EN-IN X-NONE ...

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

Define miscellaneous functions of protein, Define Miscellaneous Functions o...

Define Miscellaneous Functions of Protein? Besides the functions enumerated above certain other important miscellaneous functions of proteins are included herewith. These inclu

What is non specific defence, What is Non specific defence Non specifi...

What is Non specific defence Non specifi c:  These relate to  the  physical barriers  like  skin  and mucous membrane. They form the first line of defence against entry of mic

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

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!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd