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

How would contrast single covalent bonds, 1. In modern blimps, the gas of c...

1. In modern blimps, the gas of choice used to inflate them is helium rather than hydrogen. Hydrogen would be lighter, but helium is safer. Compare and contrast the atomic structur

Define the community ecology of disease, Define the Community ecology of di...

Define the Community ecology of disease? Lyme disease is a debilitating infectious disease which has emerged in North America in the last two decades in the landscape context o

Explain chymotrypsin, Chymotrypsin Chymotrypsin  is secreted in an ina...

Chymotrypsin Chymotrypsin  is secreted in an inactive form  'chymotrypsinogen',  which  is activated by  trypsin. Chymotrypsin  is specific  for  peptide  bonds containing unc

Determine the chance of developing cancer, A typical chest x-ray exposes th...

A typical chest x-ray exposes the patient to a radiation dose of 0.01 rem. If a man receives 10 such x-rays in a lifetime, what is his chance of developing cancer as a result of th

What are blood stem cells, Q. What are blood stem cells? Stem cells are...

Q. What are blood stem cells? Stem cells are undifferentiated cells able to differentiate into other kinds of specialized cells. The stem cells of the bone marrow originate

The human impact on the environment, put the following events in the most p...

put the following events in the most probable order. A. Dead algae decomposed by bacteria B.excess nitrate and phosphate discharge into rivers C. Fish die of suffocation D.bacteria

What are the main purpose of changes in life style, What are The main purp...

What are The main purpose  of changes in life style The main purpose  of changes in life style are to: - control blood sugar. - maintain the body weight of the patients.

Urinary system, Structures that l pyramidenaform the r

Structures that l pyramidenaform the r

Botany, what is affinites of gymnosperm

what is affinites of gymnosperm

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