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

Briefly explain about the chromium, Briefly Explain about the Chromium? ...

Briefly Explain about the Chromium? As you will go through this section, you will realize that compared to other minerals, the essentiality of chromium was recognized very late

Classification of zoonoses disease , Classification of zoonoses More t...

Classification of zoonoses More than 300 zoonoses of diverse etiologies are recognized. Thus, a very large number of zoonoses call for classification, especially for teaching

Thermodynamics, Thermodynamics Thermodynamics  tells us that every tran...

Thermodynamics Thermodynamics  tells us that every transformation of matter chemical  transformation is  accompanied with  energy conversion .For example  when complex  molecul

Imaging techniques to test stress, Q. Imaging Techniques to test stress? ...

Q. Imaging Techniques to test stress? A screening exam with M-mode and limited Doppler should be performed at the start of the test, but a detailed echo examination is usually

Explain the effect on minerals of the human milk, Explain the effect on Min...

Explain the effect on Minerals of the Human milk? There appears to be no relationship between dietary intake and concentrations in milk for copper, iron or zinc. Iron supplemen

Determine protein needs during pregnancy period, Determine Protein needs du...

Determine Protein needs during pregnancy period? Altogether, 925 g of protein are deposited in a normal foetus and maternal accessory tissues and considering the dietary protei

Explain about the autodispensor, Explain about the Autodispensor? This ...

Explain about the Autodispensor? This is used to transfer accurate quantities of liquids that are difficult to pipette like concentrated acids, alkalis, etc. You will also use

Removal of testis, REMOVAL OF TESTIS - It is male hypogonadism. (1 ...

REMOVAL OF TESTIS - It is male hypogonadism. (1 ) BEFORE PUBERTY - Cestration before puberty results in permanent sterility. This condition is eunuchoidism & shows the

Are sex-linked diseases associated only to genes, Are sex-linked diseases a...

Are sex-linked diseases associated only to genes of the X chromosome? There are many X-linked diseases, like hemophilia A, hemophilia B and adrenoleukodystrophy, but called as

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