Q.1. Thiobacillus is a group of bacteria helpful in carrying out (2019)
(b) Nitrogen fixation
(c) Chemoautotrophic fixation
Denitrification is the process opposite to nitrogen fixation in which nitrates (NO-3) get converted into N2 gas by bacteria Pseudomonas denitrificans and Thiobacillus denitrificans.
In the process of denitrication nitrates are reduced to gaseous compounds of nitrogen. Common bacteria causing denitrification of soil are Thiobacillus denitrificans, Pseudomous denitrificans, etc.
Q.2. Which of the following bacteria reduce nitrate in soil into nitrogen? (2019)
Q.3. Which of the following elements is responsible for maintaining turgor in cells? (2018)
Potassium helps in the maintenance of cell turgidity and opening and closing of stomata.
Q.4. In which of the following forms is iron absorbed by plants? (2018)
(c) Free element
(d) Both ferric and ferrous
Iron is absorbed by plants in the form of ferric ions.
Q.5. Which is essential for the growth of root tip? (2016)
Calcium (Ca) is necessary for the proper growth and functioning of root tips and meristems.
Q.6. In which of the following all three are macronutrients? (2016)
(a) Molybdenum, magnesium, manganese
(b) Nitrogen, nickel, phosphorus
(c) Boron, zinc, manganese
(d) None of the above
From the given options, Option b has a better answer with macro nutrients - Nitrogen, nickel and Phosphorus.
All other options have only micronutrients and thus 'D' turns the correct answer.
The primary macronutrients: nitrogen (N), phosphorus (P), potassium (K) the three secondary macronutrients: calcium (Ca), sulfur (S), magnesium (Mg) the micronutrients/trace minerals: boron (B), chlorine (Cl), manganese (Mn), iron (Fe), zinc (Zn), copper (Cu), molybdenum (Mo), nickel (Ni).
In relatively large amounts, the soil supplies nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur; these are often called the macronutrients. In relatively small amounts, the soil supplies iron, manganese, boron, molybdenum, copper, zinc, chlorine, and cobalt, the so-called micronutrients. Nutrients must be available not only in sufficient amounts but also in appropriate ratios.
So, the correct answer is option b.
Q.7. In which of the following, all three are macronutrients? (2016)
(a) Boron, zinc, manganese
(b) Iron, copper, molybdenum
(c) Molybdenum, magnesium, manganese
(d) Nitrogen, nickel, phosphorus
(Bonus) Nitrogen, phosphorus, potassium, calcium, sulfur and magnesium are the macronutrients. In the above given options no three element denotes macronutrients.
Q.8. Minerals known to be required in large amounts for plant growth include: (2015)
(a) Calcium, magnesium, manganese, copper
(b) Potassium, phosphorus, selenium, boron
(c) Magnesium, sulphur, iron, zinc
(d) Phosphorus, potassium, sulphur, calcium
Phosphorus, potassium, sulphur and calcium play an important role in plants growth. These minerals are required in large amount. Phosphorus is required for all phosphorylation reactions and constitution of cell membrane, nucleic acids and some proteins. Potassium is related with protein synthesis, closing and opening of stomata and activation of enzyme. Calcium regulates metabolic activities, function of cell membrane and stabilizes the structure of chromosomes. Sulphur is the main constituent of the amino acids, cystine and methionine, coenzymes and vitamins.
Q.9. Which one gives the most valid and recent explanation for stomatal movements? (2015)
(a) Potassium influx and efflux
(b) Starch hydrolysis
(c) Guard cell photosynthesis
The opening and closing of stomata are caused by influx and efflux of potassium ions (K+). The increase of K+ results in opening of stoma and decrease of K+ causes closing of stoma. The turgidity of guard cells induces to open the pores of stomata found on the surface of leaves.
Q.10. Deficiency symptoms of nitrogen and potassium are visible first in: (2014)
(a) Senescent leaves
(b) Young leaves
The parts of the plants that show the deficiency symptoms also depend on the mobility of the element in the plant. For element that are actively mobilised within the plants and exported to young developing tissues, the deficiency symptoms tend to appear first in the older tissues. For example, nitrogen, potassium and magnesium are visible first in the senescent leaves.