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

Biomedical waste management, Waste generated is termed as "Biomedical Waste...

Waste generated is termed as "Biomedical Waste" which means a waste that may contain human pathogens of sufficient virulence and in sufficient concentrations that exposure to it by

What can be deduced about the genotype, In pet rabbits, brown coat colour i...

In pet rabbits, brown coat colour is recessive to black coat colour. A black female rabbit gives birth to four black-coated and three brown-coated baby rabbits. What can be deduced

Explain about the water-soluble vitamin - riboflavin, Explain about the w...

Explain about the water-soluble vitamin - Riboflavin? Riboflavin (vitamin B 2 ), a water-soluble vitamin, was discovered in milk as a pigment possessing a yellow green fluore

Explain the loss of carotenoids, Explain the loss of carotenoids In pro...

Explain the loss of carotenoids In processing fruits and vegetables, loss of carotenoids into cooking or canning water is very slight. However, carotenoids undergo oxidation wh

Animal biodiversity, Ask question #M1. Discuss why Obelia is considered to ...

Ask question #M1. Discuss why Obelia is considered to be of special interest in Zoology as an animal showing an intermediate grade of organization. inimum 100 words accepted#

Coa to succinate in the citric acid cycle, Name the high-energy complex gen...

Name the high-energy complex generated during the conversion of succinyl CoA to succinate in the citric acid cycle GTP  or  ATP is  the high-energy  complex generated during th

What is enzyme kinetics, What is enzyme kinetics The study of the rate ...

What is enzyme kinetics The study of the rate at which an enzyme works is called enzyme kinetics.

CLASSIFICATION, WHY CORALS MAY SOMETIME BE CONFUSED WITH PLANT

WHY CORALS MAY SOMETIME BE CONFUSED WITH PLANT

Explain measles, Measles Adults born after 1956 who have not received ...

Measles Adults born after 1956 who have not received 2 doses of live measles vaccine (not the killed vaccine that was commonly used in the 1960s) after their first birthday an

Pathophysiology and assessment of purpura, Pathophysiolog y   Normal...

Pathophysiolog y   Normally the platelets are formed from megakaryocytes (stem cells) in the.  bone marrow. These cells mature, fragment and are released in  the blood strea

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