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 sports nutrition, What is Sports Nutrition? Sports nutrition i...

What is Sports Nutrition? Sports nutrition is a discipline which applies principles derived not only from nutritional but also biochemical and physiological scientific knowled

Types of embryogeny, Types of Embryogeny On the basis of the plane of...

Types of Embryogeny On the basis of the plane of division of the zygote and of the cells of the 2-celled proembryo, and also taking into account the relative contributions of

What is the endocrine function of the placenta, What is the endocrine funct...

What is the endocrine function of the placenta? The placenta is not a permanent gland of the endocrine system but it also has endocrinal function. The placenta produces estroge

Sucrose is non sugar but maltose and lactose are not. why?, Sucrose is a no...

Sucrose is a non-reducing Sugar while Maltose and Lactose are reducing due to the presence of free Aldehydic Functional Group in them. In SUgar the Aldehydic Group of both Glucose

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

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

Tools used in taxonomy, Q. Tools used in Taxonomy? Before you plan for ...

Q. Tools used in Taxonomy? Before you plan for a field trip decide the tools and equipment required. Certain, equipments are necessary for plant collection. A collecting pick i

What is the importance of uterine glycogen-producing glands, What is the im...

What is the importance of the uterine glycogen-producing glands? The uterine glands produce glycogen that can be degraded into glucose to nourish the embryo before the complete

Describe ps with vsd in tetralogy of fallot''s, Describe PS with VSD in Tet...

Describe PS with VSD in Tetralogy of Fallot's ? This group is also known as Tetralogy of Fallot's physiology. The classic example is Fallot's tetralogy characterized by: (1) Se

Comparison to healthy lungs, The nature of the sounds produced by percussio...

The nature of the sounds produced by percussion (tapping) a patient's chest can tell a physician a great deal about the condition of the organs within the thoracic cavity. Healthy,

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