PHYTOCHELATINS IN CADMIUM-SENSITIVE AND CADMIUM-TOLERANT SILENE VULGARIS - CHAIN-LENGTH DISTRIBUTION AND SULFIDE INCORPORATION

In response to a range of Cd concentrations, the root tips of Cd-toler ant plants of Silene vulgaris exhibit a lower rate of PC production ac companied by a lower rate of longer chain PC synthesis than those of C d-sensitive plants. At the same Cd exposure level, stable PC-Cd comple xes are more rapidly formed in the roots of Cd-sensitive plants than i n those of tolerant plants. At an equal PC concentration in the roots, the PC composition and the amount of sulfide incorporated per unit of PC-thiol is the same in both populations. Although these compounds mi ght play some role in mechanisms that contribute to Cd detoxification, the ability to produce these compounds in greater amounts is not, its elf, the mechanism that produces increased Cd tolerance in tolerant S. vulgaris plants.