Partial desiccation enhances induction of secondary xylem-like tracheary elements from calli of hybrid poplar (Populus sieboldii x P. grandidentata)

Abstract

Calli of hybrid poplar that had been exposed to desiccation in air before transfer to the induction medium differentiated into tracheary elements at higher rates than calli without air desiccation. Cells of hybrid poplar (Populus sieboldii x P. grandidentata) in culture can be induced to differentiate into secondary xylem-like tracheary elements that form the highly developed bordered pits and broad regions of cell walls in contrast to helical or reticulate wall thickenings in primary xylem elements. We attempted to increase the rate of differentiation of tracheary elements from calli using a combination of hormonal stimulation and partial desiccation. Calli that had been exposed to desiccation in air in a clean hood for 90 min before transfer to the induction medium differentiated into tracheary elements at higher rates than calli without air desiccation. The partial desiccation treatment had no effects on the features of the induced tracheary elements and the frequencies with which they appeared. Our results show that partial desiccation can increase, approximately threefold the rate of differentiation of secondary xylem-like tracheary elements from calli of hybrid poplar. This improvement in the rate of differentiation tracheary elements in vitro should facilitate detailed future analysis of the differentiation of secondary xylem.