Clonal Differences in the Formation of Turions are Independent of the Specific Turion‐inducing Signal in Spirodela polyrhiza (Great Duckweed)

Abstract

Abstract: Turion (survival organ) formation in Spirodela polyrhiza includes a switch in the programming of the primordia from the formation of vegetative fronds toward resting turions. The specific turion yield (SY; number of turions formed by one frond) is used to evaluate the effect of three turion‐inducing signals: low phosphate concentration (depleted due to frond growth), low temperature (15 °C) and exogenously applied abscisic acid (1 μM). The formation of turions was observed in the presence of any of the turion‐inducing factors in all three clones of S. polyrhiza investigated (clones 9256 from Finland, SJ from Germany and SC from Cuba). The clone SC showed no specific induction by low temperature or phosphate limitation in one nutrient medium. Regardless of the specific signal applied, the SYs were highest in clone 9256 and lowest in clone SC, demonstrating signal‐independent clonal differences. Clonal differences are therefore located in the developmental‐specific common phase of the transduction chains leading to turion formation. We intend to use clonal differences in the molecular analysis of turion formation, e.g., by cDNA‐based amplified fragment length polymorphism, to distinguish signal‐specific and developmental‐specific gene expression. In contrast, the total turion yield is useful in an ecological context to evaluate the number of turions available to support the survival of a population of plants but gives little information about the physiological process.