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

Define neurological disorders of non- nutritional etiology, Define Neurolog...

Define Neurological disorders of non- nutritional etiology? Some of the common disorders are Alzheimer's disease, Parkinson's disease, epilepsy, and spinal and neuro trauma.

Psychiatric emergencies, Psychiatric Emergmcy: Psychiatric  Emergmcy i...

Psychiatric Emergmcy: Psychiatric  Emergmcy is  the treatment of disorders of mood, thought and behavior in  an emergency  setting. Psychiatric emergencies are conditions in w

Explain measurement of cell mass - microbial estimation, Explain Measuremen...

Explain Measurement of Cell Mass - Microbial Estimation? You may recall reading earlier that filamentous bacteria and moulds cannot be counted satisfactorily by employing plate

What are the symptoms causes of fever, During a fever in a human, A. sh...

During a fever in a human, A. shivering can happen when the actual body temperature is higher than the set point for body temperature during the fever. B. the control system

Determine the categories of drug and nutrient relationship, Determine the C...

Determine the Categories of Drug and nutrient relationship? Drug and nutrient relationship can be categorized into two aspects: 1. Effect of nutrition on drugs: the influenc

Photosynthesis, in a school laboratory, what is usually regarded as evidenc...

in a school laboratory, what is usually regarded as evidence that photosynthesis has occurred in plants

Biological challenges, Biology is becoming a more quantitative science, a t...

Biology is becoming a more quantitative science, a trend that has motivated and been recently spurred by advances in computing power and data-gathering technologies. Nowhere is th

In hormonal terms why does menses occur, In hormonal terms why does menses ...

In hormonal terms why does menses occur? Menses is the endometrial monthly desquamation that happens as the estrogen and progesterone levels fall after the regression of the co

Pollen biology, Pollen Biology Fluorescence microscopy coupled with bi...

Pollen Biology Fluorescence microscopy coupled with biochemical analysis has helped resolve the differential activity of the enzyme, β-l, 3- glucanase that catalyses the disso

Incomplete digestive and a complete digestive system system, Q What is the ...

Q What is the difference between an incomplete digestive and a complete digestive system system? How are these types of digestive tubes associated or not to extracellular digestion

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