Question

Select out the incorrect match with respect to plant growth requirements among the following:

• A. Water $\to$ Cell metabolism
• B. Oxygen $\to$ Enzyme activation
• C. Minerals $\to$ Osmotic regulation
• D. Light $\to$ Flowering

Answer 1

The correct option is B Oxygen $\to$ Enzyme activation

Growth of an organism involves increased protoplasm synthesis, cell division, cell enlargement and cell differentiation. So, all the factors influencing the biosynthetic machinery like, the availability of $O_2$, $H_{2}O$, optimum light and temperature, minerals (both macro and micro) and absence of stress conditions, also affect growth of an organism.

Oxygen is essential for aerobic respiration and hence availability of energy for biosynthetic processes. Oxygen is not known to activate any enzyme. But it is known toi reduce the rate of photosynthesis by reacting with RuBisCO.

Water is required for cell elongation, maintenance of turgidity of growing cells and providing medium for enzyme action. Even slight deficiency of water reduces growth. It may, however, promote differentiation. Water stress completely stops growth.
Minerals are required for the increased synthesis of protoplasm and for maintenance of osmotic pressure. Few essential minerals required by plants for their growth and development are calcium, nitrogen, potassium, phosphorus, magnesium, sulfur, iron, etc.
The deficiencies of minerals like nitrogen, iron and sulfur result in stunted growth, insufficient chlorophyll in leaves, cell senescence etc.
Light is required for tissue differentiation, synthesis of photosynthetic pigments and photosynthesis. Its absence results in etiolation. Light also influences certain stages of growth. The phenomenon is called photoperiodism.
Other factors that influence plant growth are temperature and gravity. A temperature of ${28}^{\circ }C-{30}^{\circ }C$ is optimum for the proper growth in most plants. Higher temperature above ${45}^{\circ }C$ hinders growth due to excessive transpiration, denaturation of enzymes and coagulation of protoplasm. Lower temperature inactivates enzymes and also increases the density of protoplasm. Gravity vector determines the direction of shoot and root growth. Direction of light also determines the orientation of leafy shoots.