Seedlings of medicinal plants treated with either a cytokinin antagonist (PI-55) or an inhibitor of cytokinin degradation (INCYDE) are protected against the negative effects of cadmium

Cytokinins are plant hormones that regulate diverse processes during plant growth and development. Targeted manipulation of their metabolism or perception has already shown benefits in agriculture. Recently, we described substances that can affect plants' endogenous cytokinin status: a cytokinin antagonist, PI-55, and an inhibitor of cytokinin degradation, INCYDE (2-chloro-6-(3-methoxyphenyl)aminopurine). The effects of these substances on seedling growth in the medicinal plant Bulbine natalensis Baker (Asphodelaceae) and the metal tolerant Rumex crispus L. (Polygonaceae) under abiotic stress caused by cadmium (Cd) were tested. Cd is known for its negative effects on plant growth and its toxicity to humans. Treatment with either PI-55 or INCYDE had positive effects on seedling shoot and root growth and the fresh weight of treated seedlings grown in the presence of Cd. Even a single application of either compound at sub-micromolar concentrations was sufficient to reverse the inhibitory effects of Cd. Our results demonstrate that modulating cytokinin status with inhibitors of cytokinin perception and/or degradation may be useful in protecting plants against the adverse effects of high Cd levels.