Nutrients and nutrition - class-XII

Potassium (K) and Chloride (Cl) ions are the primary minerals responsible for maintaining the osmotic potential and cation-anion balance within plant cells.

In plant physiology, any mineral ion concentration that reduces the dry weight of tissues by about 10% is defined as the toxic concentration.

In 1860 Julius von Sachs, Professor of Botany at the University of Wurzburg, published the first standard formula for a nutrient solution that could be dissolved in water and in which plants could be successfully grown. The technique was termed “nutriculture”.  Now it is called Hydroponics.
Answer is B.

In the Z-scheme of photosynthesis, the primary electron acceptor from the excited chlorophyll molecule (P680) of photosystem II is Pheophytin, which is a type of Quinone.

The criteria for the essentiality of mineral elements in plants were established by Arnon and Stout in 1939.

Potassium is involved in stomatal opening, enzyme activation, and protein synthesis, but it is not directly responsible for the translocation of carbohydrates; that is primarily the role of Boron.

Magnesium (Mg) is essential for the activation of enzymes involved in respiration and photosynthesis. Manganese (Mn) is also a key activator for several respiratory enzymes, including those in the Krebs cycle.

Hydroponic systems include various methods like nutrient film technique (NFT) and aeroponics. All the statements provided accurately describe the principles of these specific soilless culture techniques.

Pepsin enzymes are the enzymes that help in degradation of the proteins into various components like peptones. These enzymes are mostly found in stomach which has acidic pH.

Deficiency symptoms of Ca, K, Mg and P appear initially as localized tissue necrosis leading to stunted plant growth, necrotic leaf margins on young leaves or curling of the leaves, and eventual death of terminal buds and root tips.

Essential elements that plants absorb from the soil in inorganic form are classified as mineral elements. Non-mineral elements like carbon, hydrogen, and oxygen are typically obtained from air and water.

Law of minimum is popularly known as Leibig's law of minimum. 

Cellular respiration uses molecular oxygen to oxidize and breakdown nutrient molecules like glucose, releasing energy in the process.

Hydroponics is a method of growing plants without soil, using mineral nutrient solutions in a water solvent. It is the definition of soilless culture.

Mycorrhizal associations help plants primarily by absorbing essential minerals from the soil, most notably phosphorus, and transferring it to the plant roots.

Molybdenum is a crucial micronutrient for plants and acts as a structural component of the nitrate reductase enzyme system involved in nitrogen assimilation.

Justus von Liebig is famous for formulating the Law of the Minimum, which states that plant growth is dictated not by total resources available, but by the scarcest resource.

Hydroponics is defined as the technique of growing plants in nutrient-rich water solutions without the use of soil as a growth medium.

Photoautotrophs like Chlorobium use light (3), Chemoautotrophs like Nitrosomonas use chemical energy (4), Photoheterotrophs like Rhodospirillum use light and organic compounds (2), and Chemoheterotrophs like E. coli use organic compounds (1).

Phosphorus deficiency leads to lower leaves turning purplish due to anthocyanin accumulation, potassium causes marginal discoloration, manganese causes chlorosis in patches or stripes, and calcium affects cell walls causing dead tissues around margins.

Mo is a cofactor for enzyme nitrogenase, which is the most crucial enzyme for nitrogen fixation.

Potassium (K) is essential for various physiological processes, including the activation of enzymes and the maintenance of turgor pressure, which is critical for cell division and apical meristematic activity.

Hydroponics or soilless culture helps to know the essentiality of mineral elements, deficiency symptoms developed due to non-availability of particular nutrient, toxicity to plant when element is present in excess, possible interaction among different elements present in plants and role of essential element in the metabolism of plant.

Cultivation of plants by placing the roots in the nutrient solution (in complete absence of soil) is called hydroponics. It is necessary to aerate the solution to provide roots with adequate oxygen supply. The result obtained from soil-less culture may then be used to determine deficiencies under field conditions.

Micronutrients are defined as essential elements required in small quantities, specifically less than 10 millimoles per kilogram of dry matter.

Wilhelm Knop is credited with developing nutrient solutions that demonstrated the essential role of inorganic minerals in plant growth.

Heart rot in beet root is a deficiency in the minor, nonmobile element Boron, $B$. It shows necrotic cross-hatching inside the leaf petiole. Young leaves turn brown and die, resulting in a rosette of small dead leaves at the top of the beet. In the fleshy root, internal and external black spots of necrotic tissue develop.

Phosphorus deficiency is a plant disorder associated with an insufficient supply of phosphorus. Darker green leaves and purplish or red pigment can indicate a deficiency in phosphorus. It is most common in lower leaves that are older. This condition is associated with the accumulation of sugars in P-deficient plants. Stems are thinner and leave acquire a leathery texture and tend to curl upwards, sometimes shedding prematurely. 

Soil solution is very dilute $10^{-3}M$. It is in equilibrium with minerals adsorbed over colloidal particle.

Plants absorb water and mineral salts simultaneously through root hairs, not sequentially. The statement that plants absorb one thing at a time is incorrect because absorption of water and minerals occurs concurrently through the same root tissues. Mineral absorption does primarily occur through active transport methods.

Active transport is an energy-requiring process that moves molecules and ions across cellular membranes against their concentration gradient.

Heavy metals like mercury (Hg2+) act as non-competitive or irreversible inhibitors by binding to the sulfhydryl groups of enzymes, thereby denaturing them or blocking their active sites.

Plants obtain minerals from the soil, which are derived from the weathering and breakdown of rocks. Therefore, all these sources contribute to the mineral content available to plants.

Mushrooms are often called 'vegetable meat' because they contain a significant amount of protein, making them a good plant-based protein source.

Phytochelatins are cysteine-rich peptides that bind to heavy metals, allowing plants to sequester and detoxify them within vacuoles.