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The process of converting ammonia to nitrate is known as . (ammonification, denitrification, nitrogen fixation, nitrification)

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The process which involves conversion of nitrates and nitrites into ammonia, nitrogen oxide and nitrogen is called _____. (denitrification, nitrification, ammonification)

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A haemoglobin like compound is synthesised in the root nodules of pea plants called _____. (leghaemoglobin, carotenoid, phycobilin)

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When mineral ion concentration in tissues reduces dry weight of tissues by about $10$ percent then it is considered _____. (deficiency symptoms, mineral toxicity, chlorosis)

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Magnesium is a_____. (trace element, micronutrient, macronutrient)

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Boron is a_____. (toxic element, micronutrient, macronutrient)

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Elements which are required in trace amounts are called_____. (macroelement, microelement, toxic element, deficient element)

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The main sources of ${\mathrm{O}}_2$ is _____ for land plants. (water, soil, atmosphere, rock)

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Plants cannot utilise the gaseous _____ directly. (oxygen, potassium, carbon, nitrogen)