Carbon source commonly used in plant tissue culture is:
Sucrose is standard carbohydrate and energy source in plant tissue culture employed at 2 to 4 percent w/v, most commonly 30 grams per liter, because in vitro explants are predominantly heterotrophic due to limited photosynthetic capacity under low irradiance 40 micromoles per square meter per second and low CO2 in closed vessels. Plant cell wall invertases cleave sucrose into glucose and fructose which enter glycolysis generating ATP and NADPH through oxidative pentose phosphate pathway and provide carbon skeletons for amino acid, nucleotide, cell wall polysaccharide synthesis. Additionally sucrose acts as osmoticum stabilizing water potential roughly 0.2 MPa and as signaling molecule modulating SnRK1 energy sensor and TOR growth regulator to balance proliferation versus differentiation. Compared to glucose sucrose causes less browning and phenolic oxidation and supports better organogenesis and embryo maturation because its hydrolysis rate maintains steady hexose supply avoiding catabolite repression. Although maltose lactose and fructose are used for specific applications like cereal embryo culture where slower metabolism improves quality, sucrose remains default carbon source providing optimal growth kinetics in MS based media.
Ref: Calvin & Bassham photosynthesis; Plant Tissue Culture Bhojwani Chap. 2 sucrose role.