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.
Pulmonary edema is life-threatening condition and therefore, treated as a medical emergency. As is the case with chronic stable heart failure, identification and correction of any
The coronary sinus is the main vein of the heart and is about 3 cm. long. It lies in the coronary sulcus at the posterior surface of the heart in the posterior atrio-ventricular g
In high altitudes is it necessary for the blood to have more or less hemoglobin? In high altitudes the air is rarefied and oxygen concentration is lower than in low altitudes.
characterstics and classification of vertebrates
In detail describe the structure and function of the heart and blood flow. Include the conduction system and blood vessels. Make your response specific to your audience who are a g
Ways to adapt to stress Now that you know the nature of stress, let us see what type of strategies plants have acquired to adapt to stress. You know that biological functions
If a tissue was heated to 65ºC for 10 minutes, respiration would cease even if oxygen and food were supplied. Why is this? A temperature of 65°C for 10 minutes would denature
In which meiotic division does the separation of the homologous occur? What are the ploidies of the generated cells after the end of that process? The separation of the homolog
Q. What do you mean by Periodical? A periodical is a publication appearing at regular intervals. Each issue is called a number and collectively these numbers comprise a volume.
Determine Teenager mindset and the eating disorders? Self image is an important determinant of weight and figure. Mostly girls under eat as already mentioned earlier, in order
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