వృక్ష శాస్త్రము

వృక్ష శాస్త్రము

UNIT-III
 The third unit consisting of the chapters 6th and 7th. The entire unit deals with the methods and process of reproduction in the plant kingdom. Reproductive methods of Monera and Protista are also dealt here. More elaborately reproduction in Angiosp-erms is discussed in the seventh chapter. In both the chapters the description as usual is very brief with many questions and directions to the students.

History of the discovery of the sexuality in plants is completely ignored. Except Maheswari's name no other scientist's names are mentioned in the entire unit. Topic on Artificial Hybridization, an applied aspect, is an aberration in the unit. In the sub-topic 'significance of fruit and seed', less is written about the significance.
 *    Reproduction is intriguing in the plants..
 Reproduction is essential for living organisms for continuity of the species. The most interesting part of the plant life is its reproduction. Sexual reproduction is basically similar in all living organisms; both plants and animals. It involves union of gametes. But plants show, besides sexual reproduction, vegetative and asexual reproduction. Lower as well as higher plants adopt different methods of vegetative and asexual reproduction and in each group and individual plant methods are different. So the process of vegetative and asexual reproduction is much varied in the plant kingdom.

This is where student has to concentrate to answer knowledge based questions. For examples gemmae are vegetative propagules in Bryophytes and sporangiospores in Rhizopus. In evolution the reproductive process underwent changes. These changes are quite evident in the plant kingdom. Prokaryotes like Bacteria undergo binary fission which is a very primitive form of reproduction. In higher plants sexual reproduction is well developed resulting in much variation in the progeny. At the same time most of the higher plants also reproduce vegetatively and this process is also well developed. Many higher plants do not produce flowers regularly and some like Chrysanthemum and Jasminum lost the ability to produce fertile seeds and has to entirely depend on the vegetative propagation. Vegetative propagation does not produce variation in the progeny. In lower plants like fungi sexuality is much reduced in the evolution. Asexual reproduction is a normal feature in the plants. Spore germination is asexual reproduction. Spores never form in the animal kingdom. Another interesting feature in the Plant kingdom is the presence of a haploid stage with varied nutritional status and morphological structure.

This we cannot see in the animals. Haploid structures or stages, compared to diploid structures do not ha-ve stability in the nature. Peculiarly in Pteridophytes both haploid and diploid stages live independently. With such an enigmatic and wonderful nature, reproduction must be understood very clearly in plant kingdom. A separate unit for this is aptly justified. Even though the student has been studying this process from the lower classes Intermediate is the correct stage to study and understand this difficult process. Studying an example for every group make it easy for the student.
 *    This Unit must be correlated to Chapters 2 & 4.
 The content of this entire unit must be correlated and coordinated with chapters 2 and 4 of unit-I. Once a student read the unit-I after the unit-III he understands easily many aspects written in Unit-I.
 Actually the chapter 6 is a redundancy of the earlier chapters. Information given in the earlier chapters 2 & 4 are presented differently here but without much effect. The definition and explanation given thereof of reproduction is of very low standard. Certain things student will understand only after reading many times. For example statement like "When two parents (opposite sex) participate in the reproductive proce-ss and also involve fusion of male and female gametes, it is called sexual reproduction". It may be true in higher animals. In lower plants same plant produces both the gametes and results in sexual reproduction.
 Regarding asexual reproduction-examples and methods, much is written in the chapter 5. Same things are once again repeated here but not before creating a confusion. For better understanding of asexual reproduction vegetative reproduction must be separated from it. Definition of spore is given in the glossary of chapters 4 & 6, sporophyte in the glossary of chapters 4 & 7 and sporangium in the glossary of chapter 7. A student need to go through all these chapters twice or thrice before understanding something about these structures.

 In the chapter 6 the explanation regarding sexual reproduction is confusing. Student feels like reading once again from the beginning. For example we can see a statement here "All organisms have to reach a certain stage of growth and maturity in their life, before they can reproduce sexually and this stage is known as vegetative phase in plants". With this knowledge, understanding of life cycle of an angiosperm plant is very difficult. For competitive exams this kind of confusion will be a drawback.

 For IPE examination point of view this chapter does not have much importance. The entire unit carries 12 marks weightage. One Long Answer Question (LAQ) from this unit is invariable. LAQ is not possible from chapter 6. As entire chapter is a repetition of earlier chapters other type of questions can be answered easily. But regarding the EAMCET point of view no chapter can have a certain weightage. So the student has to go through this chapter carefully and thoroughly and should correlate with other chapters for better understanding.