A temporary immersion bioreactor (10) for in vitro production of differentiated plant biomass comprises a growth chamber (12) having one or more transparent side walls (14) and a mesh bottom (16), the mesh bottom (16) defining a plurality of pores (18) to receive plant material. The bioreactor (10) includes a flexible bag (20) formed from a transparent material, the flexible bag (20) having a sealable opening and being dimensioned to receive the growth chamber (12) together with a liquid medium (22). The bioreactor (10) also includes an outer chamber (24) having one or more transparent side walls (26). the outer chamber (24) is formed to correspond in shape to the growth chamber (12) and dimensioned to receive the growth chamber (12) within the flexible bag (20) so that the mesh bottom (16) of the growth chamber (12) faces a bottom (28) of the outer chamber (24) that in use is intended to rest on a support surface. Movement of the growth chamber (12) within the outer chamber (24) is restrained to movement along a single axis such that the mesh bottom (16) of the growth chamber (12) moves towards and away from the bottom (28) of the outer chamber (24). The bioreactor (10) further includes a driving mechanism (30) arranged to selectively drive movement of the growth chamber (12) along a single axis (A), when the growth chamber (12) and flexible bag (20) are received in the outer chamber (24), between a first position in which the mesh bottom (16) of the growth chamber (12) is located at or towards the bottom (28) of the outer chamber (24) and a second position in which the mesh bottom (16) of the growth chamber (12) is spaced from the bottom (28) of the outer chamber (24).Un bioréacteur à immersion temporaire (10) pour la production in vitro de biomasse végétale différenciée comprend une enceinte de croissance (12) possédant une ou plusieurs parois latérales transparentes (14) et un fond en treillis (16), le fond en treillis (16) délimitant une pluralité de pores (18)
