How and why do species break a developmental trade-off? Elucidating the association of trichomes and stomata across species.

Premise: Previous studies have suggested a trade-off between trichome density (D) and stomatal density (D) due to shared cell precursors. We clarified how, when, and why this developmental trade-off may be overcome across species.

Methods: We derived equations to determine the developmental basis for D and D in trichome and stomatal indices (i and i) and the sizes of epidermal pavement cells (e), trichome bases (t), and stomata (s) and quantified the importance of these determinants of D and D for 78 California species.