Figure 1.

Preliminary comparison of accessions of P. tricornutum grown in artificial medium depleted in N or P. A, Geographical origin and major morphotypes of Pt accessions. The origin areas of sampling of Pt accessions are shown: Pt1 off Blackpool, United Kingdom; Pt2 and Pt3 off Plymouth, United Kingdom; Pt4 near the island of Segelskå; Pt5 in the Gulf of Maine; Pt6 off Woods Hole, Massachusetts; Pt7 off Long Island, New York; Pt8 near Vancouver, Canada; Pt9, Territory of Guam, Micronesia; PtHK, near Hong Kong; and Pt10, in the Yellow Sea. The genomic strain Pt1 8.6 derives from the Pt1 accession. Pt3 is a stress form deriving from Pt2. Major morphotypes observed for each accession in artificial seawater are indicated (i.e. the triradiate, fusiform, and oval morphotypes; from De Martino et al. [2007]). B, Accumulation of nonpolar lipids in N-limiting conditions. Cells in the exponential phase of growth were harvested by centrifugation and transferred to a fresh replete (1N1P; black bars) or N-depleted (0N1P; red bars) ESAW medium. Nonpolar lipid accumulation was measured after 3 d by Nile Red staining and expressed as fluorescence intensity normalized by cell number. C, Accumulation of nonpolar lipids in P-limiting conditions. Cells in the exponential phase of growth were harvested by centrifugation and transferred to a fresh replete (1N1P; black bars) or P-depleted (1N0P; blue bars) ESAW medium. Nonpolar lipid accumulation was measured after 8 d by Nile Red staining and expressed as fluorescence intensity normalized by cell number. r.f.u., Relative fluorescence units.