44. Which one of the followings is NOT a cryoprotectant for plant tissue?
(A) Dimethyl sulfoxide
(B) Glycerol
(C) Ethylene glycol
(D) Liquid nitrogen

Liquid nitrogen is not a cryoprotectant for plant tissue; it serves as the cryogenic storage medium at -196°C. Common cryoprotectants like DMSO, glycerol, and ethylene glycol prevent ice crystal damage during freezing.​

Correct Answer

D) Liquid nitrogen

Liquid nitrogen acts as the ultra-low temperature storage agent in cryopreservation protocols but lacks cryoprotective properties. It does not penetrate cells or inhibit ice formation; instead, tissues are plunged into it after cryoprotectant treatment.​

Option Explanations

Dimethyl Sulfoxide (DMSO)

DMSO penetrates plant cells effectively, increasing viscosity to form a glassy state and preventing intracellular ice crystals during vitrification. Widely used in plant cryopreservation solutions for shoot tips and embryos.​

Glycerol

Glycerol serves as a key component in solutions like Plant Vitrification Solution 2 (PVS2), providing high viscosity and supercooling ability to protect meristematic tissues from freezing damage. Common in protocols for diverse plant species.​

Ethylene Glycol

Ethylene glycol functions as a penetrating cryoprotectant, dehydrating tissues osmotically while stabilizing membranes against cold stress. Frequently combined with other agents in plant cryopreservation.​

Liquid Nitrogen

Not a cryoprotectant, as it is merely the storage liquid (-196°C) used post-treatment. Cryoprotectants are applied beforehand to enable survival upon immersion.​