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

Procedure for quantitative determination of viable microbes, Explain for Pr...

Explain for Procedure Quantitative Determination of Viable Microbes? Now carry out the exercise following the steps included herewith: 1. Label the diluent tubes from 10 -1

What causes the signs, In the case story, Reggie presented with three typic...

In the case story, Reggie presented with three typical signs of hip fracture-shortening, adduction, and the lateral rotation of the affected limb. What causes these signs? (HINT-th

What are phenotypical & genotypical proportions in f1 & f2, According to th...

According to the Mendel's second law, in the crossing between homozygous individuals concerning two pairs of nonlinked alleles, AABB x aaBB, what are the phenotypical and genotypic

What is the reduction of stress on the implant, Reduction of stress on the ...

Reduction of stress on the implant - Removal of prosthesis when it is in the non aesthetic areas - Occlusal adjustment - Reducing Cantilever length - Occlusal splint

Explain waste produced during surgical process, Q. Explain Waste produced d...

Q. Explain Waste produced during surgical process? Some of the waste products produced during a surgical process are dressings, sponges, gloves or other soft material dripping

Which of structures is the nuclear membrane composed, Q. which of structure...

Q. which of structures is the nuclear membrane composed? Eukaryotic cells have nucleus delimited with two juxtaposed membranes that continue with the membrane of the endoplasmi

Define aids, Which one of the following statements is correct with respect ...

Which one of the following statements is correct with respect to AIDS? 1. The HIV can be transmitted through eating food together with an infected person 2. Drug addicts are

Ecological significance - conservation of wildlife, Ecological Significance...

Ecological Significance - Conservation of Wildlife  Besides serving as a valuable genetic reservoir, each species interacts with other species and plays a role in the transfe

Sericulture, i want to know about sericulture for assignment degree level

i want to know about sericulture for assignment degree level

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