Fig. 5

Bracts of cannabis genotype a SQ and b MD at 6 weeks of inflorescence development with abundant trichome development. Arrows point to approximate position where bracts were sampled. c To quantify trichome density, the bracts were excised, placed under the dissecting microscope (× 50 magnification) and the Polygon Lasso tool was used to trace the outline of each segment, as shown. The position of each capitate trichome was marked using a pen of 15 px thickness and then counted. d Spatial distribution of capitate trichomes on bracts of SQ (A, C) and MD (B, D) at 3 weeks and 6 weeks, respectively. Locations of trichomes are shown as black dots on bracts. e Density of capitate trichomes on the adaxial (upper) and abaxial (lower) surface of bracts at 6 weeks into the flowering period. Bars followed by different letters denote significant differences (P = 0.05, t-test). The lower bract surface contained more trichomes than the upper surface. f Average trichome density on upper bract surfaces as a function of number of weeks in the flowering period. Asterisk (*) denotes significant difference at P = 0.05 between the two genotypes according to ANOVA and Student’s t-test (n = 24). Genotype SQ produced significantly more trichomes than MD at all time periods. g Density of capitate trichomes on bracts as a function of position of sampling within the inflorescence (top, middle, bottom). Data are from week 6 of the flowering period. There were no significant differences due to sampling position. Vertical bars represent standard errors of the mean