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

Define the axons of all the baroreceptors in the body, The axons of all the...

The axons of all the baroreceptors in the body were destroyed at 2 AM. All else is normal.  Which of the following statements is true for the system at 2:10 AM when compared to the

Difference between reproduction system of man and rabbit, Difference betwee...

Difference between Reproduction System of man and rabbit -   S.No.   Man   Rabbit   1.   2.   3.

Describe the part of the female reproductive system, Q. What is the part of...

Q. What is the part of the female reproductive system where fecundation occurs? Fecundation in general occurs in the Fallopian tubes but it can also take place within the uteru

Bacteria - type of microorganisms, Q. Bacteria - type of microorganisms? ...

Q. Bacteria - type of microorganisms? Many of us know bacteria only as "germs," invisible to naked eyes that can invade our bodies and make us sick. Few know that many bacteria

Nature and structure of community, Nature and Structure of Community E...

Nature and Structure of Community Every place on earth -grasslands, forests, and ponds, edge of the river or sea is shared by many coexisting organisms. Plants, animals and mi

What is the elimination of the sliding clamp, Which of the following result...

Which of the following results from the elimination of the sliding clamp? A. DNA polymerase will no longer be processive and will fall off the double helix after synthesizing

Define most probable number (mpn) method, Define Most Probable Number (MPN)...

Define Most Probable Number (MPN) Method? The MPN method is like agar shake tube method where no agar is used. The dilutions of the microbial suspension are made in liquid medi

Peak flow velocity, Peak Flow Velocity  fs  derived  from Doppler  shift by...

Peak Flow Velocity  fs  derived  from Doppler  shift by  rearranging Doppler equation: V = C/2 x ΔF/Fo Various  information can be obtained from spectral display

Explain aerobic cellular respiration during muscle exercise, What happens w...

What happens when the oxygen supply is insufficient to maintain aerobic cellular respiration during muscle exercise? If oxygen from hemoglobin or myoglobin is not enough for th

Atoms, the mass number is used to calculate the number of _________in one a...

the mass number is used to calculate the number of _________in one atom of an elemement. In order to calculate the number of neutrons you must subtract the _______from the ______.

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