Answer:Nitrogen in its gaseous form (N2) can’t be used by most living things. It has to be converted or ‘fixed’ to a more usable form through a process called fixation. There are three ways nitrogen can be fixed to be useful for living things:
Biologically: Nitrogen gas (N2) diffuses into the soil from the atmosphere, and species of bacteria convert this nitrogen to ammonium ions (NH4+), which can be used by plants. Legumes (such as clover and lupins) are often grown by farmers because they have nodules on their roots that contain nitrogen-fixing bacteria. (Learn more about this process in the article The role of clover.)
Through lightning: Lightning converts atmospheric nitrogen into ammonia and nitrate (NO3) that enter soil with rainfall.
Industrially: People have learned how to convert nitrogen gas to ammonia (NH3-) and nitrogen-rich fertilisers to supplement the amount of nitrogen fixed naturally
Explanation:
The cell has little compartments called organelles. These organelles are similar to our organs, which carry out life processes for our bodies to survive. Organelles are just tiny organs within a cell
The substance that will help in seed germination and indicates to the plant that the stem must elongate to reach the light is <u>Auxin.</u>
The substance responsible for cell elongation is auxin. This phytohormone is formed in cells at the tip of the shoot and is then passed from cell to cell. As such, the hormone is shuttled through many cells of the plant before it reaches its final destination.
<h3>What is the role of auxin?</h3>
Even though many subsequent observations have supported this model, up to now there has been no definite proof that auxin is in fact involved in this process. Prof. Christian Fankhauser from UNIL (Université de Lausanne) in Switzerland explains why: "Up to now, all plants with a known defect in auxin transport showed a normal phototropism. How then could auxin transport be essential for this process?"
It was found that when several of the PIN and kinase components were missing, plant growth was completely unresponsive to the light signals that trigger phototropism. The auxin transport mechanism in these mutant plants was severely impaired: The plants grew upwards, away from the gravitational pull, irrespective of the light source. This helped the scientists prove for the first time that the hormone auxin definitely is the substance that drives phototropism.
Learn more about auxin
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