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In the Calvin cycle, RuBP combines with CO₂ to form 3-PGA (3-carbon compound), which is the first stable product detected in C3 plants.

Mitochondria is the powerhouse of the cell and produces ATP through oxidative phosphorylation. Chloroplasts produce ATP through photophosphorylation.

Rhizobium bacteria form symbiotic associations with legume roots, fixing atmospheric N2 into ammonia. The bacteria live in root nodules. This symbiotic relationship is agriculturally significant and frequently tested in competitive exams.

Chlorophyll absorbs blue and red light but reflects and transmits green light, making plants appear green. This is why plants cannot utilize green light efficiently for photosynthesis - a fundamental physics-biology concept.

Monocots typically have fibrous root systems with adventitious roots. They lack secondary growth (no cambium) and have scattered vascular bundles. Dicots have tap roots and show secondary growth.

Stomata generally close at night (except CAM plants) to reduce transpiration. Guard cells are rich in mitochondria and chloroplasts to provide ATP and regulate osmotic potential. This circadian regulation is fundamental to plant physiology.

Ethylene is the senescence hormone that promotes leaf yellowing, abscission, and fruit ripening. Cytokinins antagonize ethylene effects. This hormone physiology is important for understanding plant development.

The correct radial arrangement in dicot stems is Epidermis (outermost) → Cortex → Vascular bundles (Phloem outer, Xylem inner) → Pith (center). This NCERT-based concept is frequently asked in SSC exams.

In hypertonic solutions, water moves out of the cell due to osmosis, causing protoplasm to shrink away from the cell wall - this is plasmolysis. This is a fundamental osmotic principle tested in SSC/Railway exams.

Transpiration is the loss of water vapour from aerial parts of plants, primarily through stomata during daytime.