ICAR AIEEA PG Plant Biotechnology 14 July 2023 Shift-1 Paper

Electrogenic proton pumps in plant cells:

• In plants, primary active transport across both the plasma membrane and tonoplast (vacuolar membrane) is mediated predominantly by proton pumps ($H^+\text{-ATPases}$ and tonoplast $H^+\text{-PPiase}$).
• These pumps hydrolyze ATP to pump $H^+$ ions out of the cytosol into the apoplast or vacuole, generating a membrane potential ($-120$ to $-180\text{ mV}$) and a proton motive force (PMF).
• Secondary transport of sugars, amino acids, $K^+$, $\text{NO}_3^-$, and other ions is driven by this established proton electrochemical gradient.

Vernalization requirement in crops:

• Vernalization is the acquisition of a plant's ability to flower in the spring by exposure to the prolonged cold of winter.
• Winter barley (Hordeum vulgare) and biennials like carrot (Daucus carota) have an obligate or quantitative cold requirement (vernalization) to induce flowering.
• Sunflower (Helianthus annuus) and ragi/finger millet (Eleusine coracana) are tropical/subtropical annual crops that do not require vernalization.

Agricultural production statistics by state:

• Chickpea (Gram): Madhya Pradesh is the largest producer in India: (A)-(II).
• Cotton: Maharashtra/Gujarat lead in acreage and production: (B)-(III).
• Rapeseed & Mustard: Rajasthan is by far the leading producer ($\gt 40\%$ of national production): (C)-(IV).
• Pigeonpea (Arhar): Karnataka is a premier producer listed in this group: (D)-(I).

Chemicals for breaking seed dormancy:

• Potassium nitrate ($\text{KNO}_3$, $0.2\%$) and Thiourea ($0.5-3\%$) are the standard, officially recommended chemicals (ISTA rules) used to substitute for light requirements and break dormancy in photodormant seeds (like lettuce, oats, gladiolus corms, tobacco).
• Potassium nitrate stimulates the pentose phosphate pathway, while thiourea overcomes inhibition by seed coat phenolics and abscisic acid.
• NAA is a synthetic auxin used for rooting and fruit set, not for breaking photodormancy.