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

Proteins of plant origin - vegetable proteins, Proteins of Plant Origin ...

Proteins of Plant Origin Vegetable Proteins: Fresh vegetables are not considered to be a very good source of proteins. On fresh weight basis, the average protein content of s

Explain the functionality of carboxymethyl cellulose, Functionality of CMC ...

Functionality of CMC CMC is soluble in cold water and mainly used for controlling viscosity without gelling. As its viscosity drops during heating, it may be used to improve t

Effect of temperature, Effect of Temperature Certain plants such as th...

Effect of Temperature Certain plants such as the winter rye (Secale cereale) and the biennial strain of henbane (Hyoscyamus Niger) require exposure to low temperature conditio

Cranial nerves, The cranial nerves are composed of twelve pairs of nerves...

The cranial nerves are composed of twelve pairs of nerves which emanate from the nervous tissue of brain. In order to reach their targets they should ultimately exit/enter the cr

How to calculate the raw score for each scale, How to calculate the raw sco...

How to calculate the raw score for each scale The raw score for each scale is the sum of the 0, 1 and 2 item scores. Thus, the higher the score, the poorer the performance. Th

What body system hiv impairs, Given that most AIDS victims die from overwhe...

Given that most AIDS victims die from overwhelming infections or rare types of cancer, what body system do you think HIV (the AIDS virus) impairs?

Digestive system - teeth, TEET H - Study of teeth is odontol...

TEET H - Study of teeth is odontology. Accumulation of oral bacteria & their products on teeth is plaque. Some acids are secreted by bacteria causing carries.

Hyphae and the mycelium of pluricellular fungi, Q What are the hyphae and t...

Q What are the hyphae and the mycelium of pluricellular fungi? The major structures of pluricellular fungi are the hyphae threadlike filaments made of contiguous uni or multinu

Animal viruses, Chart of taxonomy of animal viruses

Chart of taxonomy of animal viruses

Frog, why frog respire through skin

why frog respire through skin

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