Question

2. a. Describe three physiological changes that occur within a plant during drought. ​​​​​​​​​​​​​

b. Write an essay on importance of Biological Nitrogen Fixation (BNF) in sustainable agriculture.​​​​​​​​​

Answer 1

Loss of water and dry soil with high transpiration rate makes the plant experience drought stress.Growth rate slows because of drought stress and some parts of the plant development compromised.Water is the major component of plant cells.Without adequate water ,food preparation in the plants will not occur properly.Reduced photosynthesis means reduced plant growth including root growth.Root system is responsible for water uptake.The first part of the soil is affected by dry soil conditions.The water reducing capacity of the plant is severely reduced with the loss of root hairs.

2 . Biological nitrogen fixation is a process by which the atmospheric nitrogen is converted into a plant usable form of nitrogen.It is a process by which molecular nitrogen in the air is converted into nitrogeneous compounds in the soil including ammonia.

Nitrogen fixation is carried out by microorganisms called diazotrophs.Aetobacter and archaea are included in diazotrophs.All biological nitrogen fixation is affected by enzymes called nitrogenases.It is a iron containing enzymes.Nitrogen fixation is essential for agriculture and manufacture of fertilizer.Biological nitrogen fixation occurs when atmospheric nitrogen is converted into ammonia by nitrogenase enzymes.Nitrogenase are rapidly degraded by oxygen.So many bacterias stops production in the presence of oxygen.Conditions with Only in anaerobic ,binding the oxygen with a protein called leghemoglobin most nitrogen fixing organisms exist.

For the important process of agricultural productivity biological nitrogen fixation is important.Plants that contribute to nitrogen fixation include the legume family fabaceae.They contain symbiotic bacteria in their root systems that produces nitrogen compounds.When the plant dies the fixed nitrogen is released and make it available to other plants

Biological nitrogen fixation helps to convert atmospheric nitrogen into plant usable form .Symbiotic systems cann be a major source of nitrogen in most cropping systems .Azetobacter plays an important role in the nitrogen cycle and has a role in nitrogen fixation.Rhizobium hasbeen used as an efficient nitrogen fixer and it increases the yield by converting atmospheric nitrogen into uasable form.