(a) What are nastic movements, their types and mechanism ? Explain. 15 (b) How is the transport of electrons and pumping of…

(a) Nastic movements: types and mechanism

Nastic movements are non-directional responses of plant organs to a stimulus, where the direction of movement is fixed by the structure of the organ and not by the direction of the stimulus (unlike tropisms).

Types (by stimulus):

• Seismonasty (thigmonasty): response to touch or shock, as in Mimosa pudica, and Dionaea and Drosera (haptonasty).
• Nyctinasty: sleep movements of leaves and flowers with day and night, as in Albizia and Oxalis.
• Photonasty: response to light, e.g. opening of Portulaca flowers.
• Thermonasty: response to temperature, e.g. tulip and crocus flowers.
• Chemonasty: response to chemicals, e.g. insect capture in Drosera.
• Epinasty and hyponasty: downward or upward bending of leaves due to faster growth of the upper or lower surface.

Mechanism:

• Turgor-based: in Mimosa, a touch causes an action potential, which opens ion channels in the motor cells of the pulvinus; K⁺ and Cl⁻ move out and water follows, so the cells on one side lose turgor and the leaflets fold and the petiole droops. Slow recovery is by active uptake of ions and water, restoring turgor.
• Growth-based: in epinasty, petal movement in flowers, and many thermonastic and photonastic responses, differential cell elongation on the two sides, often regulated by auxin and ethylene.

(b) Electron transport, proton pumping and ATP synthesis in mitochondria

Mitchell's chemiosmotic hypothesis explains how electron flow drives ATP synthesis in the inner mitochondrial membrane.

Electron transport: NADH gives electrons to Complex I; FADH₂ (from Complex II, succinate dehydrogenase) gives them to ubiquinone. Electrons pass from ubiquinone to Complex III (cytochrome bc₁), then to cytochrome c and Complex IV (cytochrome c oxidase), and finally to O₂, which is reduced to water.

Proton pumping: Complexes I, III and IV pump H⁺ from the matrix into the intermembrane space; Complex II does not. This builds a proton-motive force, made of a pH gradient and a membrane potential.

ATP synthesis: protons flow back to the matrix through ATP synthase (F₀F₁). F₀ is the membrane-embedded channel; its rotation drives conformational changes in F₁, which makes ATP from ADP and Pi (binding-change mechanism). The yield is about 2.5 ATP per NADH and 1.5 per FADH₂ (P/O ratios). Uncouplers, such as DNP, collapse the gradient, and inhibitors such as oligomycin block ATP synthase.

(c) Importance of biodiversity conservation and steps taken in India

Importance:

• Ecological: ecosystem services such as pollination, nutrient cycling, soil and water protection, and climate regulation.
• Economic: food, medicines, fibre and timber, and the gene pool for crop and livestock improvement.
• Ethical, cultural and aesthetic: the intrinsic right of species to exist, and the value to culture and tourism.
• Insurance: a rich community is resilient to change, and extinction is irreversible.

Steps in India:

• Legal: Wildlife (Protection) Act, 1972; Forest (Conservation) Act, 1980; Environment (Protection) Act, 1986; Biological Diversity Act, 2002 (amended 2023), with the National Biodiversity Authority and local biodiversity management committees for access and benefit sharing.
• In situ: national parks, sanctuaries, biosphere reserves, tiger and elephant reserves (Project Tiger, 1973; Project Elephant, 1992), sacred groves and Ramsar wetlands.
• Ex situ: botanical gardens, seed and gene banks (NBPGR), cryobanks, and zoos.
• Policy and international: the National Biodiversity Action Plan, and commitments under the CBD (the Kunming–Montreal Global Biodiversity Framework), CITES and Ramsar.
• Community: Joint Forest Management and recognition of forest rights.