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

Closed heart surgery, Closed Heart Surgery Blind operations and access...

Closed Heart Surgery Blind operations and access is obtained into the heart through incision on the ventricular or atrial wall. Commonest closed heart surgery done is m

What is the difference between amnion and chorion, Q. What is the differenc...

Q. What is the difference between amnion and chorion? Amnion is the membrane that covers the embryo and Chorion is the membrane that covers the amnion the allantois and the yol

Define advantages of using bacteria as a source of protein, Define Advantag...

Define Advantages of using Bacteria as a source of protein? Advantages of using Bacteria as a source of protein are as follow: 1. High yield of protein (60-80%) 2.

What is the meaning of narcolepsy, What is the meaning of Narcolepsy Th...

What is the meaning of Narcolepsy This is an inappropriate attack of sleep, the affected person has an overwhelming impulse to fall asleep or simply collapses into sleep at inc

Calcium channel blockers, Calcium antagonists are not recommended for the t...

Calcium antagonists are not recommended for the treatment of CHF because of their negative inotropic effects. However, second-generation dihydropyridine-type calcium antagonists su

Adrenaline and noradrenaline, Both these neurotransmitter strengthen memory...

Both these neurotransmitter strengthen memory when they are released into the blood stream following learning. Stressful events stimulate release of stress hormones from the adrena

Define the future challenges of spatial processes, Define the Future challe...

Define the Future challenges of spatial processes? Understanding the dynamics of stochastic spatial systems, systems with a multitude of spatial scales, and systems along with

Introduction to biodiversity, Biological diversity is the new buzzword, the...

Biological diversity is the new buzzword, the magic door to international funding and global travelling. We share the earth with million of other living beings. Just as we humans m

Transplant procedure and immunosuppression, TRANSPLAN T PROCEDURE - Op...

TRANSPLAN T PROCEDURE - Operation is done under general anaesthesia, duration 3-4 hrs. Cut is given in the lower abdomen. Donar's kidney is transplanted retroposistonicaly

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