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#culture medium

2 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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Animal Tissue Culture 1

The pink to yellow color change in DMEM indicates:

Metabolic basis for color change reflects shift toward glycolytic phenotype characteristic of rapidly dividing cells in vitro despite ample oxygen availability phenomenon termed Warburg effect observed initially in tumors but also in normal proliferating cultures. Cells convert glucose to pyruvate via glycolysis then lactate via lactate dehydrogenase tetramer reducing NADH to NAD+ maintaining redox balance, exporting lactate plus proton via monocarboxylate transporter MCT4 SLC16A3 electrogenic process acidifying extracellular milieu even when mitochondrial oxidative phosphorylation functional. Simultaneously citric acid cycle produces carbon dioxide diffusing across lipid bilayer hydrating to carbonic acid via membrane associated carbonic anhydrase IX expressed under hypoxia inducible factor one alpha. Both lactic acid pKa 3.86 and carbonic acid donate protons to bicarbonate buffer consuming HCO3- converting to H2CO3 that dissociates to CO2 plus water removed in incubator exhaust. Accumulation of protons lowers medium pH from 7.4 toward 6.8 shifting phenol red equilibrium to protonated yellow form as absorbance at 560 drops and 430 rises perceived yellow.

Ref: Eagle 1973 lactate acidification Warburg glycolysis MCT4; Gibco Cell Culture phenol red yellow acid pink alkaline contamination cue.

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