ICAR AIEEA PG 2024 - Plant Biotechnology

Photoperiodic classification:
Sugarbeet (Beta vulgaris): Obligate/qualitative Long-Day Plant (LDP) requiring long days and cold vernalization for flowering.
Potato (Solanum tuberosum): Functions as a Long-Day Plant (LDP) with respect to floral induction and flowering (though tuberization is favored by short days).
Tobacco (Nicotiana tabacum, cv. Maryland Mammoth): Classical Short-Day Plant (SDP) in which photoperiodism was first discovered by Garner and Allard.
Cotton (Gossypium spp.): Day-Neutral Plant (DNP).

In plant root tips, gravity sensing (graviperception) occurs within the columella cells of the root cap. These specialized cells contain heavy, starch-filled non-pigmented plastids called Amyloplasts, which function as 'statoliths'. Due to their high density relative to the cytosol, amyloplasts sediment to the lowest physical side of the cell in response to gravity. This physical sedimentation triggers a signal transduction cascade that polarizes the PIN family of auxin efflux carriers, redirecting auxin accumulation to the lower side of the elongation zone and directing downward root growth (positive gravitropism).

Crop water requirements vary widely depending on photosynthetic pathway, duration, and leaf transpiration rates:
In sequence (D): Pineapple is an obligate CAM xerophyte requiring minimal water (~300–400 mm); Amaranthus is an efficient $C_4$ vegetable requiring moderate water (~400–500 mm); and Cotton is a long-duration commercial crop requiring substantial irrigation (700–1300 mm). Thus, Pineapple < Amaranthus < Cotton is fully correct.

• is false because Sugarcane (1500–2500 mm) requires far more water than Cowpea (300–450 mm).
• is false because Pearlmillet (250–350 mm) requires less water than Sunflower (500–650 mm).
• is false because Rice (1200–1500 mm) requires far more water than Sorghum (450–550 mm) and Redgram (500–600 mm).