Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
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.
Principles of HACCP A) Determine the Critical Control Points (CCPs) B) Establish Critical Limit(s) C) Establish a System to Monitor Control of the CCP D) Esta
Q. Heavy Metals require for the normal finctioning of our body? Like the foods we consume, our bodies also contain many metallic elements. Most of these metals are actually r
BACK CROSS When F 1 individual (Tt) is crossed with one of the two parents, either tall (TT) or dwarf (tt), such a cross is called the back cross. There are two possibilities
Determine about the diseases Sleep attacks These are brief, often irresistible, episodes of sleep, probably slow wave, NREM, naplike sleep that last about 15 minutes and can oc
Define Interaction of pyridoxine with Ascorbic acid and Leucine? Ascorbic acid: Vitamin B 6 metabolism increases with. Higher levels of vitamin C intake. Whole blood a
TEST TUBE BABY - Ova are fertilized in laboratory dish (in vitra) containing a nutrient broth . It may be artificial insemination donor (AID) / Artificial insemination h
How does the swim bladder of fishes work allowing fishes to control their depth under water? From Hydrostatics it is called that an object does not sink if its density is equal
Explain briefly about the selenium Toxicity? There is a narrow margin between the beneficial and harmful intakes of selenium. The level at which selenosis occurs is not well-de
Adaptive Radiations The organisms all the time tend to establish harmony with their environment. This process, called adaptation, enables the organism to face the vagaries of
The client was admitted to the hospital with hypertension (high blood pressure). The development of arteriosclerosis (plaque buildup in the arteries) has increased peripheral resis
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!
whatsapp: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd