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

Decomposers - biotic components, Decomposers - Biotic Components Also ...

Decomposers - Biotic Components Also known as saprotrophs. Mostly, these are microscopic and are heterotrophic in nature. Decomposer organisms obtain their energy and nutrient

Explain the parasite-amoeba, Normal 0 false false false ...

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

Empirical validity of test procedures, Empirical validity of test procedure...

Empirical validity of test procedures Reitan's great concern has always been with the empirical validity of test procedures. Such validity can only be established by the collec

Strain of fusarium moniliforme, Q. Strain of Fusarium moniliforme? It w...

Q. Strain of Fusarium moniliforme? It was first obtained from a strain of Fusarium moniliforme isolated from southern leaf blight- damaged corn seed as a water soluble toxin.

Diffrence between fish epidermis and amphibian epidermis, Q. How different ...

Q. How different is the fish epidermis from the amphibian epidermis? The fish epidermis is very contains and thin mucus-secreting cells the fish skin doesn't present keratin, t

Peak flow velocity, Peak Flow Velocity  fs  derived  from Doppler  shift by...

Peak Flow Velocity  fs  derived  from Doppler  shift by  rearranging Doppler equation: V = C/2 x ΔF/Fo Various  information can be obtained from spectral display

Northern blot, Northern blot is a technique for analyzing mixtures of RNA ...

Northern blot is a technique for analyzing mixtures of RNA by transfer of size-separated RNA fragments to a synthetic membrane, the presence and rough size of one particular type

Epithelial tissue, conclusion for epithelial tissue when finish experiment?...

conclusion for epithelial tissue when finish experiment?

What is a bio regenerative system, What is a bio regenerative system? Why i...

What is a bio regenerative system? Why is it essential? Nutritional requirements for long flights have been refined, placing more demands on food development. Despite the techn

What are the main harms caused by vitamin a deficiency, What are the main h...

What are the main harms caused by vitamin A deficiency? How does this vitamin act in the physiology of vision? Deficiency of vitamin A (retinol) might be cause night blindness

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