Penicillium crustosum requires Fe, Zn, Cu, Mo, B and d (+) biotin for its growth. It does not require the following trace elements and organic growth factors: Mn, Ca, Co, W, Ga, Sc, thiamine HC1, pyridoxine HC1,i-inositol, adenine sulphate, ascorbic acid, folic acid, guanine HO, nicotinamide, riboflavin, uracil, choline chloride and xanthine. In the deficiency of essential trace elements the mycelial dry weight is reduced, the contents of mycelial tips get vacuolised and exhausted, septa are formed at shorter intervals and sporulation is inhibited. Biotin deficiency also causes similar symptoms besides formation of distinct septa in conidiophoral apparatus with vacuolised contents.