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

What is chromatography, Question 1 What is chromatography? List various me...

Question 1 What is chromatography? List various methods of chromatography. Add a note on applications of chromatography in diagnosis Question 2 Discuss the applications of co

What type of feedback loop is, The client was admitted to the hospital with...

The client was admitted to the hospital with hypertension (high blood pressure). The development of arteriosclerosis (plaque buildup in the arteries) has increased peripheral resis

How is the excretory system of molluscs characterized, Q. How is the excret...

Q. How is the excretory system of molluscs characterized? Molluscs have one or two pair of spongelike nephridia, similar to kidneys

What is tyrosinemia, Q. What is Tyrosinemia? There are two forms of her...

Q. What is Tyrosinemia? There are two forms of hereditary tyrosinemia. They are tyrosinemia Type I and tyrosinemia Type II. Type I was thought to be due to a deficiency of para

Parthenogenesis- asexual reproduction, Normal 0 false false ...

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

Gametogenesis - human development, Gametogenesis - Human Development G...

Gametogenesis - Human Development Gametogenesis as you are responsive is the process of formation and development of specialized reproductive cells, ova in females and sperms

Visceral larva migrans, Visceral larva migrans Visceral larva migrans,...

Visceral larva migrans Visceral larva migrans, also known as larval granulomatosis, is a clinical syndrome produced by the extra-intestinal migration of larval nematodes and i

Define type of chemical reaction used in volumetric analysis, Define the Ty...

Define the Type of chemical reaction used in volumetric analysis? The titration has to be based on some rapid chemical reaction. Although any type of chemical reactions may be

How many are the pulmonary veins, Q. What and how many are the pulmonary ve...

Q. What and how many are the pulmonary veins? The pulmonary veins are part of the pulmonary circulation they are vessels that carry oxygen-rich (arterial) blood from the lungs

Fats and lipids, Composed of C, H and O (fewer polar OH bonds than carbohyd...

Composed of C, H and O (fewer polar OH bonds than carbohydrates) Can be used at energy storage, components of cell membranes, chemical signals & thermal insulation Are

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