Isolation and developmental characterization of temperature-sensitive carrot cell variants.

Carrot cell lines multiply indefinitely in the presence of the auxin 2,4-D. If auxin is removed, the cells regenerate plantlets in a process that closely resembles embryogenesis in vivo. We isolated a temperature-sensitive variant, ts 2, which is unable to regenerate at 31 °C (non-permissive temperature), but does form embryos and plants at 24 °C (permissive temperature). The temperature treatment had no effect on fully differentiated ts 2 plantlets. In other variants (ts 5 and ts 11) cell proliferation was inhibited at the restrictive temperature. These lines were leaky with respect to the inhibition of embryogenesis at 31 °C.