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

Determine the symptoms of dehydration, Determine the Symptoms of Dehydratio...

Determine the Symptoms of Dehydration? The symptoms of dehydration are: Thirst Loss of appetite Decreased urination Impaired physical performance Nau

Is water a non-polar or a polar molecule, Q. Is water a non-polar or a pola...

Q. Is water a non-polar or a polar molecule? What is the consequence of that characteristic for the function of water as solvent? Ans. Water is made of two atoms of hydrog

Pathophysiology of cardiac tamponade, Q. Pathophysiology of Cardiac tampona...

Q. Pathophysiology of Cardiac tamponade? Progressive increase in pericardial fluid results in progressive increase in intrapericardial pressure, till a critical volume is reach

Is protein collagen has a high proportion of glycine, The protein collagen ...

The protein collagen has a high proportion (20% or more) of A. asparagine and glutamine B. proline and hydroxyproline C. glycine D. both A and B E. both A and C F

Reproduction, write about asexual reproduction in mucor

write about asexual reproduction in mucor

Contig, Contig:  Number of uses, all nouns. The term comes from the shorten...

Contig:  Number of uses, all nouns. The term comes from the shortening of the word 'contiguous'. A 'contig' might refer to the map showing placement of a set of clones which comple

What do all organic compounds contain, What do all organic compounds contai...

What do all organic compounds contain? The key element is carbon. Organic compounds are all carbon-having compounds. By definition, an organic compound having carbon. Alt

Pericarditis - nursing management, Pericarditis Nursing Management ...

Pericarditis Nursing Management Monitor-blood pressure, Pulse temperature, respiration, chills disphoresis, jugular pressure. Assess for signs of cardiac tarnponad

Explain the feeding 6-12 months infant, Explain the Feeding 6-12 Months Inf...

Explain the Feeding 6-12 Months Infant? As the infant grows older, mother's milk alone is not sufficient to meet his increasing needs. This could be seen in few infants between

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