Influence of salinity and high temperature on turion formation in the duckweed Spirodela polyrhiza

The influence of NaCl (salinity; 0–5 ‰) and higher temperature (heat stress; 32 °C) on yield of turion formation has been tested in the duckweed Spirodela polyrhiza for the first time. Turion formation was more sensitive to both stressors than the growth of the vegetative fronds: (1) the concentration of NaCl which produces half-maximal inhibition was lower for turion formation than for growth by the factor of five. (2) At 32 °C turion formation was completely blocked whereas growth rates decreased by only 20% as compared with 28 °C.

► Formation of turions is more sensitive to salt stress than vegetative growth.
► The same holds true for high temperature stress (32 °C).
► No adaptation of clones to salt stress or high temperature stress was observed.
► Neither salt stress nor high temperature induces turion formation.