Practice question

Murashige and Skoog medium proposed in 1962 for tobacco pith culture remains gold standard and most widely used basal medium for plant tissue culture due to broad applicability and high salt formulation supporting rapid growth across herbaceous and many woody species. Its composition features high concentrations of macronutrients ammonium nitrate 1650 mg per L and potassium nitrate 1900 mg per L providing dual nitrogen source favoring both amino acid synthesis and pH buffering, plus calcium chloride, magnesium sulfate, potassium dihydrogen phosphate; chelated iron as Fe-EDTA, micronutrients manganese, zinc, boron, iodine, molybdenum, copper, cobalt; organic supplements thiamine, nicotinic acid, pyridoxine, glycine, myo-inositol; and sucrose 30 g per L as carbon source. High ammonium to nitrate ratio about 1 to 2 stimulates chlorophyll retention and proliferation rather than rooting. Ionic strength around 90 mM supports vigorous meristematic activity. While alternatives like B5 for protoplasts or WPM for trees exist, full strength MS with modifications half strength for rooting remains default choice referenced in textbooks, commercial laboratories and research protocols worldwide for callus induction, organogenesis, embryogenesis and protoplast culture.