Use of an ultrasound cell retention system for the size fractionation of somatic embryos of woody species

The potential of ultrasonic standing waves for trapping suspended particles was utilized successfully for differential size fractionation of plant som atic embryos. In a flow-through resonator equipped with a 200-kHz piezocera mic transducer, embryos of different sizes corresponding to different devel opmental stages could be retained by varying the electric power input and f low speed. The system was initially established for carrot (Daucus carota) somatic embryos and subsequently adapted for the larger-sized embryos of th e woody species cork oak (Quercus suber), grapevine (Vitis Berlandieri x ru pestris) and cherry (Prunus incisa x serrula). Separation performance was c onfirmed by analysing the different fractions for the expression of homeobo x genes which are differentially expressed during embryogenesis. No inhibit ory effects of embryos on short- and long-term development could be observe d.