Sensitivity of tobacco tissue cultures to chloramphenicol and its photodegradation products

Abstract. Non‐differentiated tissue cultures (calli) of tobacco were found to be more sensitive to chloramphenicol (CAP) than differentiated tissues (shoots). The difference is especially manifested in darkness and at an irradiation regime lacking u.v. and blue light. Photodegradation of CAP solutions was demonstrated at moderate light fluence rates (6–15 Wm⁻²). The evidence indicates that the final products of photodegradation may be toxic or non‐toxic according to the irradiation regime. The implication of the present findings in establishing a selection system for resistance to chemicals, and especially CAP, using plant tissue cultures, is discussed.