Release of microspores, Biology

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.

Posted Date: 1/23/2013 1:02:19 AM | Location : United States







Related Discussions:- Release of microspores, Assignment Help, Ask Question on Release of microspores, Get Answer, Expert's Help, Release of microspores Discussions

Write discussion on Release of microspores
Your posts are moderated
Related Questions
55yrs old woman had burns and has lost 6% body fluid.She weighs 50Kg.How much fluid does she need to replace the lost fluid.

What is Flap tearing Poor preoperative surgical planning can result in flap of small size with inadequate exposure of the underlying bone. In an effort to increase the visibili

Define Nutrition Support in Postoperative Nutritional Care? Aggressive nutritional support is important to avoid postoperative complications and mortality. Routine postoperativ

Explain the Air Sampling? Microorganisms may be present in air of processing facility and have an impact on the quality and safety of foods processed and handled there. To avoi

State the term- Hue Hue  is the dominant spectral colour (rainbow) and is related to the wavelength of light. In Munsell system there are five principal hues; red (R), yellow (

General characteristics of phylum

Q. Carbohydrates requirement during myocardial infarction? The protein intake generally remains the same as per the RDI i.e. 1.0 gm protein per kg body weight per day. Adequate

Write the meaning of Life Style Modification (LSM) Life style modification means diet control and doing exercises. Diet control and exercise should be planned on individual bas

Sources of vitamin C It is found in many of the natural foods like fresh citrus fruits like limes, lemons and oranges are rich sources of vitamin C. The best and the chea

Protein Classification Based on Shape There are three types of proteins on the basis of shape - Fibrous, Globular, Intermediate 1 .       FIBROUS PROTEINS They ar