Figure 2.
Micrographs of microcalli derived from rice protoplasts. Rice protoplasts were plated in thin layers of agarose (0.4%) in a Petri dish at a density of 1.0 × 105 cells per ml. Agarose blocks were then cut into four pieces, transferred to Murashige and Skoog liquid medium containing 1.0 mg/liter 2,4-dichlorophenoxyacetic acid in the presence or absence of PSKs, and incubated at 25°C without shaking. After 4 weeks, total numbers of colonies (≥200-μm diameter) were scored under an inverted microscope. Colony formation frequency was as follows: 66.8% ± 7.5% [PSK-α, 1.0 × 10−6 M (A)], 39.4% ± 2.1% [PSK-α, 1.0 × 10−8 M (B)], 48.4% ± 3.0% [PSK-β, 1.0 × 10−6 M], 16.4% ± 0.8% [PSK-β, 1.0 × 10−8 M], and 13.7% ± 2.3% [control (C)]. (Bar = 500 μm.)