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

Describe how homologous recombination happening, Write about embryonic stem...

Write about embryonic stem cell invitro methord in which transgenic animal were generated and efficient show how homologous recombination happening?

Classifications of carbohydrates based on number of carbon, Define the Clas...

Define the Classifications of carbohydrates based on number of carbon?   A chain-form monosaccharide that has a carbonyl group (C= O) on an end carbon forming an aldehy

What is panspermia, What is panspermia? The Panspermia is a hypothesis ...

What is panspermia? The Panspermia is a hypothesis that describes life on earth as not originated from the planet. The thought is that the first living beings that colonized th

What is the typical shape of poriferans, What is the typical shape of porif...

What is the typical shape of poriferans? Sponges have bodies in the type of tubular vases or globes open in the upper extremity. They have an internal central cavity and porous

Where in eukaryotic cells does mrna synthesis occur, Where in eukaryotic ce...

Where in eukaryotic cells does mRNA synthesis occur? To where do these molecules migrate? Messenger RNA molecules are synthesized within the nucleus, pass by pores of the nucle

How does the excretory system of nematodes work, Q How does the excretory s...

Q How does the excretory system of nematodes work? The metabolic residuals of nematodes are together by two longitudinal lateral excretory channels that open in one single excr

Examples of human cells that produce proteins, Q. What are few examples of ...

Q. What are few examples of human cells that produce proteins for exportation? Which cytoplasmic organelle is expected to be abundant and well-developed in those cells? Special

Explain taxonomic concepts and their development, Explain Taxonomic Concept...

Explain Taxonomic Concepts and Their Development? The history of classification is an exciting aspect of plant taxonomy. The discovery of the use of plants for food and later

Define the term - lateralisation and localisation, Define the term - latera...

Define the term - lateralisation and localisation Discriminative validity studies including lateralisation and localisation achieved satisfactory results, but the localisation

Components of treatment of nkhdc, The components of treatment of NKHDC are:...

The components of treatment of NKHDC are: 1) control of water loss. 2) control of sugar using insulin. 3) adjust electrolytes like sodium and potassium. 4) control infe

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