Pollen tube growth, Biology

Assignment Help:

Pollen Tube Growth

There are significant differences in the fine structure of the tips of pollen tubes in compatible and incompatible pistils such as Lilium. Tubes growing in compatible pistils show deep embayment but no compartments (tubes in incompatible pistil have a compartmented cap). The compatible tubes undergo a transition from autotrophic nutrition (characterized by compartmented cap of golgi derived vesicles) to heterotrophic condition in which the secretion product from the stylar canals enter the pollen tubes through the deep embayments (tubes growing in incompatible pistils are unable to make this transition and thus are unable to continue growth due to the exhaustion of endogenous food reserves).

The pollen tube wall is composed mainly of polysaccharides. Since the pollen grain carries limited food reserves and a relatively large amount of new pollen wall material is synthesized during growth, it has been assumed that at least a part of the substance needed for pollen tube wall is contributed from the polysaccharides present in the pistil tissues. It has been shown that the polysaccharide component of the stigmatic exudate of L. longiflorum is incorporated into the cytoplasm of the growing pollen tubes and later a specific fraction of the incorporated exudate is extensively metabolised before being utilized for pollen tube wall biosynthesis.


Related Discussions:- Pollen tube growth

Describes why okazaki fragments are not observed in pcr, Which of the follo...

Which of the following best describes why Okazaki fragments are not observed in PCR? A. DNA primase is used for the entire reaction therefore eliminating the production of Okaz

Are microorganisms directly or indirectly affects our lives, Describe 5 way...

Describe 5 ways that a microorganisms directly or indirectly affects our lives.

Acid rain, what are the two main pollutants that contribute to acid rain

what are the two main pollutants that contribute to acid rain

What is the formula for photosynthesis, What is the formula for photosynthe...

What is the formula for photosynthesis? H 2 O + 6CO 2 + Light Energy ----> C 6 H 12 O6+ 6O 2 6 molecules of water + 6 molecules of carbon dioxide --->1 molecule of glucose

Tetrasporic embryo sacs, Tetrasporic Embryo Sacs In this group neithe...

Tetrasporic Embryo Sacs In this group neither of the meiotic divisions is accompanied by wall formation so that at the end of meiosis all the four haploid nuclei remain in a

Write the positive ion isoelectronic with neon, Write the positive ion isoe...

Write the positive ion isoelectronic with neon The positive ion isoelectronic with neon must have 10 electrons and 11 protons, and thus must have an  atomic number = 11. This i

Procedures for diagnosis - immune responses and biomarkers, Demonstration o...

Demonstration of immune responses and biomarkers: This may be done either on the basis of sero-conversion study on paired sera samples or by challenge (protection) test.

Define harvard step test - aerobic capacity, Define Harvard Step Test - aer...

Define Harvard Step Test - aerobic capacity? In this test, the subject steps on and off an 18-inch platform at a rate of 30 times per minute. The evaluator records the subject'

Determine the term anapsid , Determine the term Anapsid ? The type of s...

Determine the term Anapsid ? The type of skull found in reptiles and seen today only in turtles. Behind the opening of the orbits the skull is solid and lacks temporal openings

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