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.
Clinical Evaluation of Infants and Young Children Approaches to clinical practice advanced in recent year are mostly directed at older children and adolescents. There has not b
Effects of long term malnutrition on children The effects of long time malnutrition are more severe in children. Unlike adults children do not have sufficient amounts of c
What is the vascular cambium? What is its function? Vascular cambium is the secondary meristematic tissue that in roots and in the stem creates the vascular tissues (xylem and
Locomotion in Mollusca The major locomotor organ in Mollusca is the foot, which is a characteristic feature of these animals. In its simplest form the foot is a flit ventral
Carbomedics Valve : Almost similar to StJude Medical valve, his is a low profile bileaflet valve made of pyrolitic carbon. On echo cardiography four small jets of regurg
Normal nutrition: a base of therapeutic diet Normal nutrition is the foundation upon which the therapeutic modifications are based. The primary principle of diet nutrition the
Food require during thyphoid So remember the foods to be included are: Juices, soups, dal water, broths. Refined cereals and their products (e.g. maida, rava, bread, rice
write about complementary genes
How are metarterioles different from arterioles? Explain how fenestrated capillaries are different than continuous capillaries in terms of their structure and function.
Nature of Metabolites in Sieve Tubes The phloem sap contains three major classes of organic compounds - organic acids, amino acids and sucrose besides some cations, anions and
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