Release of microspores, Biology

Assignment Help:

Release of Microspores

Up to the tetrad stage, there is no cellulosic wall around the microspores. As you will come to know in the next unit, a unique feature of the pollen is the ornamentation of the pollen wall. This ornamentation is seen on the outer layer of the pollen or exine. The exine is made up of sporopollenin, one of the most resistant (to physical and biological decomposition) substances known in the biological world. Pollen grains of prehistoric plants are well preserved as fossils because of their exine. There is enormous variation in the ornamentation of the exine, and it is a characteristic feature of a given species. Often pollen grains of particular group of plants can be identified on the basis of their exine pattern.

The blue print of exine, termed primexine is laid down below the callose wall after the basic structural features of the exine including the position of the germ pore (a region in the pollen wall through which the pollen tube emerges) are demarcated in the primexine. This important morphogenetic event takes place while the microspores are still enclosed in the callose wall, in groups of four or at the tetrad stage. Thus, the pattern of mature exine is laid down before the spores are set free. The callose wall seems to play an important role in the orderly deposition of primexine. You will read more about this in the next unit. After the development of exine, the callose wall dissolves. The enzyme callase which dissolves the callose wall is produced by the surrounding tapetal cell pen plasmodium. The development of the male gametophyte begins after the liberation of individual microspores.


Related Discussions:- Release of microspores

Define starch retrogradation, Starch Retrogradation The starch paste or...

Starch Retrogradation The starch paste or solution obtained after the gelatinisation is not stable and generally produces a viscoelastic, firm  and rigid gel. Structural transf

Explain rectangular full mucoperiosteal flaps, Explain Rectangular Full Muc...

Explain Rectangular Full Mucoperiosteal Flaps - Endodontic Surgery      a. Releasing and relaxing "vertical" incisions, with the Horizontal incision, b. Causes re

Define about blood pressure control, Normal 0 false false f...

Normal 0 false false false EN-IN X-NONE X-NONE

Difference between living and non-living beings, DIFFERENCE BETWEEN LIVING ...

DIFFERENCE BETWEEN LIVING AND NON-LIVING BEINGS - S .No. C h a ra cte r L i v i n g be ings N o n - l i v i n g be

Locomotion, discuss locomotion in annelids

discuss locomotion in annelids

What do you mean by synapses, Q. What do you mean by synapses? Synapses...

Q. What do you mean by synapses? Synapses are the structures that transmit the neural impulse between two neurons. When the electric impulse arrives the presynaptic membrane

Introduction to parthenogenesis, Parthenogenesis The development of egg...

Parthenogenesis The development of egg to form an animal without fertilization is called as parthnogenesis. Parthenogenesis was discovered by Charles Bonnet in the egg of se

Explain spray-drying method, Spray-drying method Spray-drying is the co...

Spray-drying method Spray-drying is the common drying method in the production of ISP. The primary physical form of ISP in commerce, is that of fine powders. Structured form

Synovial fluid and amniotic fluid collection, Synovial fluid Collection: ...

Synovial fluid Collection: The technique of obtaining synovial fluid is called arthrocentesis. It is used to characterize type of arthritis and to differentiate inflammatory

Human impact on environment, questions and answers on human impacts on envi...

questions and answers on human impacts on environment

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