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 abbe condenser of microscope, Define Abbe Condenser of Microscope? ...

Define Abbe Condenser of Microscope? It is present beneath the stage, as shown in Figure. It collects and focuses a cone of light on the slide. Its position can be adjusted ver

Define systematic botany - taxonomy, Define Systematic Botany - Taxonomy? ...

Define Systematic Botany - Taxonomy? We will now learn something mare about systematic botany. The early recognition of harmful and useful plants was the beginning of systemati

Therapeutic diets - qualitative methods, Therapeutic diets - Qualitative me...

Therapeutic diets - Qualitative methods Qualitative methods: This  is where  you  give  the individual choices,  clear guidelines, menu guidance and supporting  information  su

Which are the phases of the menstrual cycle, Which are the phases of the me...

Which are the phases of the menstrual cycle? The menstrual cycle is separated into two main phases: the follicular (or menstrual) phase and the luteal (or secretory) phase.

What is determined by tube feet, What is determined by tube feet? Hollo...

What is determined by tube feet? Hollow and fluid-filled tubes which are part of the water vascular system in Echinoderms. Muscles associated with tube feet allow them to be hy

Reagent for determination of blood glucose by nelson somogyi, Define Reagen...

Define Reagent for Determination of Blood Glucose by Nelson Somogyi? 1. Alkaline copper reagent a) Dissolve 15 g of sodium potassium tartarate and 30 g of anhydrous N

Human embryo, Human embryo: After fertilization the human embryo divide...

Human embryo: After fertilization the human embryo divides mitotically and develops two membranes: 1) Chorion 2) Amnion Functions of the membranes: i) Chorion : It

Which of groups is not ionizable, Which of the following groups is NOT ioni...

Which of the following groups is NOT ionizable? Select one: a. Guanidinium b. Imidazole c. Phosphoryl d. Amine e. Aldehyde

Investigating, What is scientific investigation?

What is scientific investigation?

Explain what is fungi, Explain what is Fungi? The fungi are spore-beari...

Explain what is Fungi? The fungi are spore-bearing eukaryotic organisms without chlorophyll and having absorptive nutrition. These reproduce sexually as well asexually. Primari

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