'Volcano' plots illustrating the log2 of the fold-changes (i.e. the ratio of means for each gene) and inverse significance (i.e. log10 of the reciprocal of the Benjamini and Hochberg False Discovery Rate multiple test corrected P-value derived from a one-way ANOVA with the Benjamini and Hochberg FDR multiple testing correction) in gene expression differences between control and P-starved Brassica oleracea var. alboglabra cv. A12DHd. Total RNA samples were extracted from control B. oleracea shoots and from the shoots of plants grown in the absence of P for 100 h (n = 4). (a) no probe-selection used during transcriptome analysis, (b), (c), (d) using probe mask files during transcriptome analysis, generated at gDNA hybridisation intensity thresholds of 200, 400 and 1000 respectively. Data in Additional file 1.