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Q1. Represent diagrammatically the development of root nodules in soyabean.  

Solution

Development of root nodules in soyabean:        

Q2. Name the elements responsible for delayed flowering.

Solution

Nitrogen, sulphur and molybdenum

Q3. With the help of examples explain the role of essential elements in activating or inhibiting enzymes.

Solution

Magnesium is an activator for ribulose bisphosphate carboxylase-oxygenase as well as for phosphoenol pyruvate carboxylase. Both enzymes play an integral role in CO₂ fixation in photosynthesis. Zinc ions activate alcohol dehydrogenase and the molybdenum of nitrogenase during nitrogen fixation.

Q4. Name parts of the plant where potassium is required in abundant quantities. State any two functions of potassium ions in plants.

Solution

Potassium ions are required in the meristematic tissues, buds, leaves and root tips. Potassium helps to maintain an anion-cation balance in cells. Potassium is required in all phosphorylation reactions.

Q5. Name the compound which when reacts with ammonia forms glutamic aid.  

Solution

α-ketoglutaric acid  

Q6. Explain the method of hydroponics.

Solution

In hydroponics, a series of experiments are conducted in which roots of plants are immersed in a nutrient solution. Then an element is either added or removed or provided in varied concentration in the solution according to its suitability to the plant and its growth. Plants are grown in tubes or troughs placed at a slight incline. A pump is provided which circulates the solution from a reservoir to the elevated end of the tube. The solution flows down the tubes and returns back to the reservoir. The roots of the plants get bathed continuously in an aerated solution.

Q7. Name the four categories of essential elements.

Solution

Four categories of essential elements are as follows:

Components of biomolecules

Components of energy-related compounds

Activator or inhibitor of enzymes

Elements which alter the osmotic potential of a cell

Q8. Name the element required for the photolysis of water during photosynthesis.

Solution

Manganous ions or chlorine ions

Q9. Name the substance present in the middle lamella which contains calcium.  

Solution

Calcium pectate  

Q10. When is an element considered toxic for plants?

Solution

Any mineral concentration which reduces the dry weight of plant tissues by 10% is toxic for plants.

Q11. State the role of Nitrobacter in nitrogen fixation.  

Solution

Nitrobacter oxidises nitrite into nitrate.  

Q12. What is the name given to the movement of ions?  

Solution

Flux  

Q13. Name any one bacterium which oxidises ammonia to nitrite.

Solution

Nitrosomonas/Nitrococcus

Q14. Excess of manganese induces deficiency of other elements in plants. Justify.

Solution

Many times, excess of an element inhibits the uptake of another element by the plant. Manganese when becomes toxic (i.e. present more than its required concentration) causes brown spots to appear around the chlorotic veins. Manganese competes with iron for uptake. It competes with magnesium for binding with enzymes. It inhibits the calcium translocation in the shoot apex. Hence, excess of manganese induces deficiency of other elements in plants.

Q15. Name the two amino acids which contain sulphur.

Solution

The two amino acids which contain sulphur are cysteine and methionine.

Q16. State the quantity of macronutrients required by plants. Name two macronutrients and micronutrients.

Solution

10 mmol of macronutrients are required per 1 kg of dry matter. Examples of macronutrients are nitrogen and phosphorus. Examples of micronutrients are nickel and chlorine.

Q17. Name the elements responsible for the following functions:    

Maintenance of the ribosome structure  

Activation of catalase  

Germination of pollen grains  

Photolysis of water  

Solution

Maintenance of the ribosome structure - Magnesium  

Activation of catalase - Iron  

Germination of pollen grains - Boron  

Photolysis of water - Chlorine  

Q18. Write the chemical equations of the two steps involved in the conversion of ammonia to nitrates.  

Solution

Step one: Ammonia to nitrite ions   Step two: Nitrites to nitrate ions  

Q19. Name the bacterium which can produce nodules on non-leguminous Alnus.  

Solution

Frankia  

Q20. Name the technique of growing plants in a nutrient solution.

Solution

Hydroponics is the technique of growing plants in a nutrient solution.

Q21. What is nitrogen fixation? State the two natural sources to provide energy for nitrogen fixation.

Solution

The process of conversion of nitrogen to ammonia is called nitrogen fixation. Ultraviolet radiation and lightning provide energy for nitrogen fixation.

Q22. State the reason due to which the minerals become available to the roots of plants.

Solution

Weathering and break down of rocks

Q23. What did Julius von Sachs demonstrate?  

Solution

Julius von Sachs demonstrated that plants could be grown in a defined medium in the complete absence of soil and such plants also attain maturity.  

Q24. Write any two forms in which nitrogen is taken up by plants.  

Solution

are the forms in which nitrogen is taken up by plants.  

Q25. Name the following:

Aerobic nitrogen-fixing bacteria

Anaerobic nitrogen-fixing bacteria

Solution

Aerobic nitrogen-fixing bacteria - Azotobacter

Anaerobic nitrogen-fixing bacteria - Rhodospirillum

Q26. Name the parts of the plants which require potassium ions more abundantly.

Solution

Meristematic tissues, buds, leaves and root tips require potassium abundantly.

Q27. Describe the importance of calcium in cell division.

Solution

Calcium pectate is necessary for the formation of the middle lamella, a part of the cell wall. Hence, calcium is important in the synthesis of the cell wall during cell division. It is required for the formation of the mitotic spindle.

Q28. Name the enzyme for which Zn²⁺ acts as an activator.

Solution

Alcohol dehydrogenase

Q29. Name the two amides found in plants.  

Solution

Asparagine and glutamine  

Q30. Draw a well-labelled diagram of a typical setup of nutrient solution culture.  

Solution

Typical setup of nutrient solution culture:        

Q31. Name the vegetables which are produced commercially by using hydroponics.

Solution

Seedless cucumber, tomato and lettuce

Q32. What is denitrification? Name the bacteria which perform denitrification.

Solution

Reduction of nitrate present in the soil into nitrogen is called denitrification. Bacteria Pseudomonas and Thiobacillus perform denitrification.

Q33. Name the deficiency symptom in which leaves turn yellow.

Solution

Chlorosis

Q34. Name the elements whose deficiencies are visible in senescent leaves.  

Solution

Nitrogen, potassium and magnesium  

Q35. Which element is responsible for the opening and closing of stomata to some extent?

Solution

Potassium

Q36. Name the first phase of uptake of ions in the outer space of cells.  

Solution

Apoplast  

Q37. State the criteria which decide the essentiality of elements.

Solution

Criteria which decide the essentiality of elements: The element must be necessary for plant growth and reproduction. In the absence of such elements, plants do not complete their lifecycles. The deficiency of the element cannot be met by supplying some other element. The element must be directly involved in plant metabolism.

Q38. Name the element found in plants growing near nuclear testing sites.  

Solution

Radioactive Strontium  

Q39. Name the minerals present in plant cells which are not released easily.  

Solution

Sulphur and calcium  

Q40. Name the element which activates the enzyme nitrogenase during nitrogen metabolism.

Solution

Molybdenum