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 do you mean by osseous cavity, Q. What is the osseous cavity where the...

Q. What is the osseous cavity where the pituitary gland is located? The hypophysis or pituitary gland is located in the sella turcica of the sphenoid bone (one of the bones in

Explain the occurrence of nictoinic acid, Explain the Occurrence of Nictoin...

Explain the Occurrence of Nictoinic acid Nictoinic acid occurs widely in the animal and vegetable kingdom in free as well as in bound form (in enzymes). Several animal organs

Welfare, what is welfare in biology

what is welfare in biology

Nursing assessment - anomalies of stomach and oesophagus, Nursing Assessmen...

Nursing Assessment  These children present with excessive salivation and droofing of saliva from the mouth, coughing, gagging, even choking and cyanosis at the lime of first f

Discuss the evolution of implants in dentistry, Q. Discuss the evolution of...

Q. Discuss the evolution of implants in dentistry? The first use of Implants dates back to 600 A.D. in the Mayan population where intraosseous implantation of animal teeth or t

Colibacillosis of newborn animals, Colibacillosis of newborn animals T...

Colibacillosis of newborn animals This is the commonest disease entity of newborn farm animals. In calves the disease  occurs in three forms, viz. enteric colibacillosis manif

What is a ph meter, What is a pH meter? A pH meter is a device used for...

What is a pH meter? A pH meter is a device used for measuring. pH of any unknown solution. It is composed of: a) A reference electrode b) Glass electrode whose potential

Life as an expression of energy changes, LIF E AS AN EXPRESSION OF ENERGY ...

LIF E AS AN EXPRESSION OF ENERGY CHANGES - Energy is explained as capacity of body to do work. Energy may be as potential (stored) or kinetic (expended) energy. It ex

What is the first polar body, What is the first polar body? How different i...

What is the first polar body? How different is it from the oocyte II? In oogenesis the oogonium differentiates into oocyte I (2n) and this cell enters meiosis. After finishing

Why are the recombinant dna technology, Why are the recombinant DNA technol...

Why are the recombinant DNA technology and the nucleus transplantation technology still dangerous? A recombinant DNA technology and the nucleus transplantation technology (clon

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