The question asks to identify a macronutrient among the given options, which are essential for plant growth. We need to recall the classification of essential plant nutrients into macronutrients and micronutrients based on the quantity required by plants.
A) Nitrogen (N) is a primary macronutrient. Plants require it in large quantities for various vital functions, including protein synthesis, chlorophyll formation, and overall growth.
The question asks to identify the specific enzyme responsible for nitrogen fixation by Rhizobium in legume root nodules. This process is crucial for converting atmospheric nitrogen into a usable form for plants. We need to recall the key enzymes involved in nitrogen metabolism, particularly those associated with biological nitrogen fixation.
Correct Option: D) Nitrogenase is the enzyme complex responsible for catalyzing the reduction of atmospheric nitrogen (\(N_2\)) to ammonia (\(NH_3\)) in nitrogen-fixing organisms like Rhizobium in legume root nodules. This process is central to biological nitrogen fixation.
The question asks about the function of leghaemoglobin in the root nodules of legumes. This requires knowledge of symbiotic nitrogen fixation and the specific role of leghaemoglobin in this process.
Correct Option: A) Protect nitrogenase enzyme from oxygen by acting as an oxygen scavenger
The question asks about the elements whose deficiency causes chlorosis (yellowing of leaves) due to reduced chlorophyll synthesis. We need to identify the elements that are crucial components of chlorophyll or play a direct role in its formation.
B) Magnesium (Mg) and Nitrogen (N) — Magnesium is the central atom of the chlorophyll molecule, and nitrogen is a major component of its porphyrin ring. Deficiencies in both these elements directly impair chlorophyll synthesis, leading to chlorosis.
The question asks to identify the mineral nutrient that forms a structural component of the chlorophyll molecule. This requires knowledge of the chemical structure of chlorophyll and the role of various mineral nutrients in plant biology.
C) Magnesium (Mg) is the central metal ion in the chlorophyll molecule, making it a direct structural component. Without magnesium, chlorophyll cannot be formed, and photosynthesis cannot occur.
The question asks why plant growth is described as 'indeterminate' or 'open'. This term refers to the continuous growth potential of plants throughout their lifespan, unlike animals which have determinate growth. We need to identify the biological reason behind this continuous growth.
A) Plants retain meristematic tissue throughout their life, allowing unlimited growth. This is the fundamental reason for indeterminate growth in plants. Meristems are regions of active cell division that continuously produce new cells, enabling the plant to grow throughout its life.