ESSENTIAL MINERAL ELEMENTS PART 01 PDF Print E-mail
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Written by punjalak   
Friday, 15 August 2014 05:18

 ESSENTIAL MINERAL ELEMENTS: Most of the minerals present in the soil can enter plants through roots. Analyses of ashes of different plants reveal the presence of about 60 elements. All the 60 elements are not present in all plants. Only 16 elements are present in all plants. These elements are necessary for plants. Some elements are essential for certain plants only. Example: Sodium is essential only for C_4 plants and Halophytes. Silicon is essential only for Grasses and Cobalt is essential for Blue green algae.Daniel Arnon and Perry Stout carried out experiments on the essentiality of nutrients in Tomato plants. They laid down basic requirements to determine the essentiality of an element. These basic requirements are called Arnon's Criteria of Essentiality.
Arnon's Criteria for Essentiality:The element must be necessary for supporting normal growth and reproduction. In the absence of the element, the plants do not complete their life cycle or set the seeds.The requirements of the element must be specific and not replaceable by another element. In other words, deficiency of any one element cannot be met by supplying some other element.The element must be directly involved in the metabolism of the plant.
ESSENTIAL ELEMENTS:Based upon the Arnon's Criteria for Essentiality, 16 elements are found to be essential for plant growth and metabolism. Such elements are called essential elements. These elements are further divided into 2 categories based on their quantitative requirements.1 Macronutrients and 2 Micronutrients
Some plants require some additional elements for their growth and reproduction. These elements are called non-essential elements. Example: Sodium, Silicon, Aluminum, Cobalt, Selenium, Strontium, Vanadium.List of Macronutrients: These are 9 elements and generally present in plant tissues in large amounts. Micronutrients include: 1 Carbon 2 Hydrogen 3 Oxygen these three elements are obtained from 〖CO〗_2 and H2O 4 Nitrogen 5 Phosphorus 6 Sulphur 7 Potassium 8 Calcium and 9 Magnesium.These are absorbed from soil as mineral nutrition
List of Micronutrients: These are 7 elements needed in very small amounts hence they are also called trace elements. They include. 1 Iron 2 Manganese 3 Copper 4 Molybdenum 5 Zinc 6 Boron 7 Chlorine 8 Nickel
Categories of Elements based on their Functions:Essential elements are grouped into 4 categories based on their functions. 1 Structural elements: C, H, O and N. 2 Energy related chemical compounds: Example: Magnesium in chlorophyll and Phosphorus in ATP. 3 Enzyme Regulators: These either activate or inhibit enzymes. Example: 〖Mg〗^(2+)is an activator of RUBP Carboxylase-oxygenase and PEP Carboxylase. These are important in carbon fixation. 〖Zn〗^(2+)is an activator of alcohol dehydrogenase and M O of Nitrogenase during Nitrogen metabolism. 4 Osmotic potential: Example: Potassium plays an important role in opening and closing of stomata.
ROLE OF MACRO AND MICRO NUTRIENTS: Essential elements participate in various metabolic processes and perform several functions.

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