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#MS medium

3 public questions tagged with this topic.

Plant tissue culture 1

Which medium is specially designed for woody plants?

Woody Plant Medium WPM specially formulated by Lloyd and McCown in 1980 to meet nutritional demands of woody trees shrubs and hard to culture species which exhibit ammonium toxicity tip necrosis and vitrification on high salt MS medium. WPM lowers total nitrogen to roughly one quarter of MS, ammonium nitrate 400 mg per L versus 1650, calcium nitrate increased to improve lignification and middle lamella stability, potassium sulfate replaces potassium nitrate at lower level to reduce hyperhydricity, and microelements adjusted copper sulfate elevated for lignin biosynthesis polyphenol oxidase. Its ionic strength about 30 mM compared to 90 mM in MS prevents osmotic stress and phenol leaching inhibitory to woody explants rich in tannins. Inclusion of phloroglucinol or activated charcoal 0.1-0.5 percent adsorbs phenolic exudates preventing browning. WPM and derivatives DKW for walnut, Quoirin Lepoivre for fruit trees enable sustained shoot proliferation rooting and somatic embryogenesis of species like Rhododendron, Pinus, Eucalyptus, Quercus where MS fails. Thus WPM has become standard for forestry and woody horticulture micropropagation ensuring healthier shoots with expanded leaves and functional vascular development.

Ref: Lloyd & McCown Int Plant Prop Soc 1980 WPM; NCBI woody plant medium formulation.

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Plant tissue culture 1

Macronutrients in MS medium are required at concentration:

In plant tissue culture classification, macronutrients are defined as elements required at concentration greater than 0.5 millimolar, reflecting their roles as building blocks and osmotic regulators. They include nitrogen incorporated into amino acids, nucleotides, chlorophyll porphyrin and alkaloids; potassium acting as cofactor for over 40 enzymes, osmoregulator for stomatal opening; calcium essential for middle lamella calcium pectate crosslinking cell walls and as secondary messenger binding calmodulin during stress signaling; magnesium central atom of chlorophyll and bridge for ATP Mg complexes needed by kinases; phosphorus in nucleic acids phospholipids and high-energy ATP; sulfur in cysteine, methionine, coenzymes and Fe-S clusters. In MS medium macronutrients occur at tens of millimolar, for example 20.6 mM NH4+, 18.8 mM NO3-, 20 mM K+, 3 mM Ca2+, 1.5 mM Mg2+. Deficiency below 0.5 mM rapidly causes chlorosis necrosis or hyperhydricity. Micronutrients conversely needed below 0.5 mM as catalytic cofactors, highlighting quantitative distinction guiding stock preparation where macro stock prepared at 10X and micro at 100X to prevent precipitation and toxicity.

Ref: Gamborg et al., Exp Cell Res; MS medium macronutrient composition, Plant Cell Culture Manual.

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Plant tissue culture 1

Most widely used plant tissue culture medium is:

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.

Ref: Murashige & Skoog Physiol Plant 1962; NCBI NBK26873 MS medium composition.

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