Bioreactor Cultures of Embryogenic Suspensions of Barley (Hordeum vulgare L.) and Maize (Zea mays L.)

Embryogenic suspension cultures of barley (Hordeum vulgare L.) and maize (Zea mays L.) were cultured in a 2-L bioreactor. A bioreactor developed for mammalian tissue culture could be used for plant suspension cultures after reduction of the agitation speed to 60 rpm. Initial experiments were performed using a non-embryogenic barley suspension. Growth characteristics (increase in fresh weight as well as pH, osmolarity and conductivity of the medium) were determined daily. The bioreactor conditions optimized with a non-embryogenic barley suspension could be successfully transferred to the culture of embryogenic suspensions of barley and maize when the agitation speed was increased to 70 rpm. Plants could be regenerated from barley suspensions grown for 8 days in the bioreactor. In the case of maize, morphogenesis could be obtained even after 60 days in semicontinuous culture. In contrast to embryogenic cultures, non-embryogenic cultures of both barley and maize grew to twice the cell density until they reached the stationary growth phase. This could be due to conditioning factors released into the culture medium, which induce or prevent further growth. Since bioreactors allow the culture of large volumes of suspensions in a very reproducible manner, the use of this system to analyse conditioning factors will be discussed.