Pollen tube structure, Biology

Assignment Help:

Pollen Tube Structure

The pollen tube in the stigma is filled with cytoplasm containing numerous mitochondria and dictyosomes. The number of dictyosome cisternae is reduced in the tubes. Large vesicles associated with dictyosome seem to be incorporated in the tube wall. Abundant ER and polysomes which are either in free form or attached to ER can also be seen. The pollen tube wall in the stigma and style show two distinct regions: the outer part of the wall (PAS positive), and the inner portion which is thicker, more homogeneous (much less reactive to PAS), and rich in callose. The dense cytoplasm contains vesicles of various sizes, ER, ribosomes, and a few poorly-developed plastids with swollen outer membranes. Dictyosomes are quite numerous with 4 or 5 cisternae, and produce vesicles.

The vesicles appear to fuse with the plasma membrane of the pollen tube. A very large population of small, spherical vesicles are scattered throughout the pollen tube cytoplasm. The ER in the pollen grains and during early growth of the pollen tube has extended cisternae and apparently serves as a storage site for proteins. As the pollen tube grows down the style, the ER shows the common variety of narrow cisternae indicating that protein present is being gradually utilized during tube growth. The ultra structure of the distal region of the pollen tube and the wide variety of cell organelles are indicative of active carbohydrate and protein metabolism. The part of the tube immediately behind the tip region shows less dense cytoplasm and more dispersed organelles. The more mature parts of pollen tube contain only a thin layer of cytoplasm closely appressed to the wall and a large vacuole occupies the rest of the space. Plugs of the wall material, mostly callose serve to separate the older parts of the pollen tube from the growing distill region. The plugs originate as rings on the inner side of the wall and grow inwards like the closing of an iris diaphragm.


Related Discussions:- Pollen tube structure

Explain food applications of gum tragacanth, Food Applications of Gum traga...

Food Applications of Gum tragacanth Gum tragacanth finds various food applications. These include: In dairy products, it functions as stabilizer in ice cream, ice pops a

Recent concerns of food safety, Normal 0 false false fal...

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

Diverse proteins made by the same total number of amino acid, Q. Are there ...

Q. Are there diverse proteins made by the same total number of amino acids? Diverse proteins with the same total number of amino acids may exist. In such cases the discriminati

Aves, detail information about ave?

detail information about ave?

What are the diagnostic models, Diagnostic Models Study models made fro...

Diagnostic Models Study models made from impressions of the arches are invaluable for diagnosis and treatment planning. The model must be mounted on an adjustable or semi adjus

Identical chromatids bound, Q. What is the structure that to maintains iden...

Q. What is the structure that to maintains identical chromatids bound? The structure that to maintains identical chromatids bound is the centromere.

How long is the incubation period of the hiv, How long is the incubation pe...

How long is the incubation period of the HIV? What is meant by acute AIDS? The incubation period of the HIV (the time interval among the infection and the beginning of the immu

Phases of the cardiac cycle, The phases of the cardiac cycle are: 1)  At...

The phases of the cardiac cycle are: 1)  Atrial Systole This begins with the P-wave of the ECG. The atrio-ventricular valves are open and the ventricles are relaxed (diastole

Differentiate between a dossier and a submission document, Problem 1: H...

Problem 1: How do you differentiate between a dossier and a submission document? Define dossier Define submission document differentiate between a dossier and a

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