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 why meat products causes diabetics, Explain why Meat products cause...

Explain why Meat products causes diabetics Diabetics can have meat products in case they eat non-vegetarian food. Baking, roasting or grilling is preferable to frying. Patient

Homeostasis, using a specific example describe how hormones have an importa...

using a specific example describe how hormones have an important role in the regulation of body functions and also, what happens if there is an over secretion or an under secretion

Illustrate steps of polymerase chain reaction , There are three steps of PC...

There are three steps of PCR a) Denaturation.  The reaction combination is heated to 95°C for a short time period (about 15-30 sec) to denature the goal DNA into one strands w

How to increased co2 levels in the atmosphere, Increased CO 2 levels in th...

Increased CO 2 levels in the atmosphere are correlated with rising global temperatures, leading many scientists to believe that the first phenomenon has caused the second. What wo

What is the difference between dna and rna, Q. Concerning their biological ...

Q. Concerning their biological function what is the difference between DNA and RNA? DNA is the source of information for RNA production (transcription) and thus for protein syn

Closed style - style of stigma interaction, Closed Style - Style of Stigma ...

Closed Style - Style of Stigma Interaction Cotton shows an epidermis with stomata, a cortex of thin-walled parenchyma with several vascular bundles and strands of transmitting

State the article - one hundred tests, Regarding the article "One Hundred T...

Regarding the article "One Hundred Tests" which of the following is a false statement? A. Genetic tests like the one developed by Counsyl can examine the multilevel genetic net

Drawbacks of fats and sweets in diabetics, Drawbacks of Fats and Sweets in ...

Drawbacks of Fats and Sweets in diabetics Diabetics should eat less fats and sweets. Fats found in burger, cheese and butter etc. should especially be avoided. Even when  a pat

Evolutionary innovation presented by nematodes, Q. What is the major evolut...

Q. What is the major evolutionary innovation presented by nematodes? What is the benefits of that innovation? The major evolutionary innovation of nematodes is the complete dig

What are the cells responsible for the antibodies, Q. What are the cells re...

Q. What are the cells responsible for the production of antibodies? The cells that produce antibodies that is the cells of the humoral immune system are the B lymphocytes (B ce

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