వృక్ష శాస్త్రము

వృక్ష శాస్త్రము - Sakshi


 UNIT-IV

 Plant Systematics

 This Unit includes only one chapter ie. Taxonomy of Angiosperms. Plant systematics is not just taxonomy of Angiosperms. It is the study of diversity of plant kingdom. In chapter 4 we have already studied the Taxonomy of lower plants.


Since the earlier days, as the knowledge regarding microscopic organisms is lacking, plant systematics is equated with Taxonomy of Angiosperms. Hence for the classical studies in Botany Taxonomy of Angiosperms has become an essential requirement. In Intermediate syllabus, regarding the classifications given by ancient people are also mentioned in first few paragraphs of chapter 3. For EAMCET point of view this information is also very important. Information regarding the criteria for classification and other features of Prasara's classification and other Western philosophers classifications have to be remembered.

 

 Criteria for classification   changes over time


 In the beginning of this chapter certain basic aspects of Taxonomy is given. Terms like "Alpha Taxonomy" and "Omega Taxonomy" are clearly explained. Besides this different types of classifications are given like Artificial, Natural and Phylogenetic systems of classifications with examples and criteria for these classifications. A student should know the difference between these classifications as well as the difference between Alpha taxonomy and Artificial classification. For Telugu medium students both these terms are  treated as synonyms due to lack of exact and similar words in telugu language. Classification is grouping of plants where as Taxonomy is rules and regulation for the classification. Titles of books written by different Taxono- mists and basic information relating to these are also important for examination point of view. As the criteria for classification changes new classification types developed.



The drawbacks or demerits of the earlier classification are drawn on the basis of latter classifications. Every classification is a classical work for that time period. Regarding this we have to see a sentence written in the text under Natural systems of classification, "Usually, the floral characters were given greater importance since they are more conserved and do not change due to the effect of environment". This statement is not tenable in Natural system of classification. During the popular period of natural system of classifications concept of conserved organs, an evolutionary concept, is unknown. The statement is totally misleads the student. In assertion and reasoning questions this type of information will be a draw back to the student.

 

 Semi-Technical Description has no place in Taxonomy

 In the next sub-topic semi-technical description of a typical plant is given. It is difficult to understand how even at this stage a semi-technical description will help a student. In future studies of taxonomy, if a student wishes to join a graduation course, this will not help in any way. In graduation student must have the knowledge of detailed description of plants as he has to deal with more than 20 different families directly. Even with complete description sometimes it will be difficult to identify a plant. Identification is one of the primary requirements for the classification.



Before describing the three families included  in the syllabus, the basic methods to be followed is given. The symbolic representation of the flower as floral formula and pictorial representation of the flower in floral diagram is explained. Student should learn the detailed meaning and representations of the floral diagram and floral formulae. Many questions are possible like "Which character of the flower cannot be represented in the floral diagram or in floral formula". In the same sub-topic example of floral diagram and floral formula of Brassica ceae family is given this can be a basis for different questions. Else where we have seen many characters regarding Brassicaceae. This information like number of stamens (6), number of caly x(4) and their arrangement is to be remembered.



This information must also to be clubbed with meiosis. The description of families needs holistic approach. Families should be studied with information regarding their habits, habitats and morphology of vegetative and floral characters besides pollination methods and economic importance. Information that has already come across is to be added here.  In the description of the three families, included in the syllabus, unfortunately their classification and position in Bentham and Hooker's classification is not given. Regarding the families student of Intermediate is generally scary. He has to remember names of the plants in each family both their scientific and vernacular names.



All together in the families he has to remember more than 40 plant names and their common names. Student must write all the plant names one below the other in alphabetical order with numbers to remember and recollect easily. Objective type questions generally cannot be segregated chapter wise. All the information regarding a particular plant must be clubbed for a holistic view. For example "Number of pollen formed in a flower of Allium if each pollen sac contains 20 pollen mother cell".This needs knowledge regarding the number of stamens and whether stamens are bithecous or monothecous in Allium and how many cells form after meiotic division.



 Questions are simple but without proper exposure to this type of questions before exam they look difficult and confusing. Student has to read these families as many times as possible before the exams. Long intervals make them forget easily. At least a glance for every few days is the best possible way to remember things in these easily.   


 Learning thoroughly information given in the families also help the student to perform well in the practicals as the description of the twig in technical terms is a major question in practical examinations. Practical marks also play an important role in the ranking of EAMCET.  

 

 IPE carries little weightage for this unit. For IP Exams this chapter got very little importance with 6 marks weightage. This can be one of the reasons for a student not able to do better in objective questions from this chapter. Mostly one Short Answer Question and one Very Short Answer Question  can be asked from this Unit. For SAQ's diagrams must be drawn neatly. Description of the essential parts also required to be written with all the important characters given in the text. Student should not forget to mention important and specific characters of that particular family.



Without that full marks cannot be awarded

 For EAMCET point of view for regular students they have to put lot of hard work at least 3 questions we can expect from this unit. The information regarding each and every plant if any has to be correlated to the morphology chapter. Practicing few model questions help them enormously. For long term students this chapter will not pose any problems as they have studied descriptive part thoroughly.

 

 Important Points

 

 *    Several medicinal plants and their uses were described in Atharvana Veda.

 *    Parasara written two books- Krishi Parasaram and Vriksha yurveda.

 *    Krishi Parasaram is oldest book on agriculture and about weeds.

 *    Different types of forests and medicinal plants are described in Vrikshayurveda.

 *    Gaspard Bauhin identified 6000 plants. He introduced Binomial Nomenclature.

 *    The term Taxonomy is coined A.P.de Condole. De Condole is a Natural system classifier.

 *    Alpha taxonomy is descriptive taxonomy.

 *    Omega taxonomy includes information from other branches of botany.

 *    Classification is grouping of plants based on certain criteria.

 *    Taxonomy is rules and regu lations for the classification.

 *    Artificial classification depends on one or two external features

 *    Aristotle's classification is artificial. His criteria is form of the plant.

 *    Theophrastus classification is artificial. His criteria is also form of the plant.-Herbs, Shrubs, Trees.

 *    Theophrastus book is de Historia Plantarum.

 *    Linnaeus classification is artifi cial. His criteria are stamens and carpels. He classified plants into 24 groups.

 *    Linnaeus book is Species Plantarum. He described only plants in this book. Both Crypto games and Phanerogams are classified.

 *    Carolus Von Linnaeus populari- zed Binomial nomenclature.

 *    Artificial characters gave equal importance to both vegetative and sexual characters.

 *    Vegetative characters are not stable as plants adopt to envir-onment.

 *    In Natural system of classi- fications natural affinities are considered for classification.

 *    Beginning of the natural system classifications usually starts with two groups. As the classification proceeds more and more groups are seen.

 *    Natural systems naturally show many evolutionary tendencies.

 *    Flowers are considered as they have many parts and variations suitable for classification.

 *    Bentham and Hooker's classi- fication is Natural system of classification even though it is published after Darwin's theori- es of evolution.

 *    Bentham and Hooker's book is 'Genera Plantarum'.

 *    His classification mainly of only flowering plants.

 *    All flowering plants are classi-fied into only three classes are .

 *    His classification shows 21 series, 25 cohorts and 202 natural orders (families).

 *    Cohorts are present day orders. Natural orders are present day families.

 *    Angiosperms classified into 198 families. Among them Dicots are 165 and Monocots are 34.

 *    Monochlamydae sub class and Monocotyledonae class are divided directly into series.

 *    Natural systems are very popular as plant identification is very easy.

 *    Post-Darwinian classifications are phylogenetic.

 *    Primitive plants are placed in the beginning of the classi-fications.

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