Fig 1.
Increasing stomatal density enhances P accumulation.
Mean total [33P] concentrations (ng g−1) taken up directly by whole plants over 5 hours (n = 5). Bars with no letters in common are significantly different, P<0.05, (Tukeys test after one-way ANOVA). Error bars represent SE.
Fig 2.
Stomatal density correlates with root area.
(A) Histochemical staining of seedlings expressing pEPF1::GUS (top) indicates EPF1 expression in guards cells but not in roots, and pEPF2::GUS (bottom) indicates EPF2 expression in early stomatal lineage cells and not in roots. (B) Representative scans to illustrate root size of plants grown in rhizotrons. (C) Linear regression showing a significant relationship between stomatal density and the rooting area of plants grown in rhizotrons (P = 0.0083). (D) Increased root hair length in plants with increased stomatal density. (E) Increased root hair density in plants with increased stomatal density. (F) Representative micrographs of plants grown in agar to assess root hair length and density. Bars with no letters in common are significantly different, P<0.05, (Tukeys test after one-way ANOVA). Error bars represent SE.
Fig 3.
Plants with altered root hair density and length display correspondingly opposite alterations in stomatal conductance and stomatal density.
(A) Mean steady state stomatal conductance rates for genotypes with decreased (rsl4rhd6rsl1; white symbols), or increased root hair length and density (RSL4OE; black symbols) in comparison to controls (Col-0; grey symbols) at 1000 μmol.s-1m-2 light, 400 ppm CO2 over 20 minutes. (B) Mature leaf abaxial stomatal densities of RSL4 overexpression or rsl4rhd6rs1 genotypes. Bars with no letters in common are significantly different, P<0.05, (Tukeys test after one-way ANOVA). Error bars represent SE.
Fig 4.
The promotion of root hair development is more likely to be due to an increased capacity for water loss rather than an enhanced demand for phosphate.
(A) Two proposed models to explain the enhanced root development and phosphate accumulation observed in the epf1epf2 mutant. (Top) Increased water loss promotes root hair development. (Bottom) increased frequency of stomata incurs a phosphate cost which leads to phosphate stress and the subsequent promotion of root hairs. (B, Left) A relationship exists between conditions which reduce leaf boundary layer resistance and rooting length. The X axis denotes distance from a moving air source with 1 being the closest. (B, Right) Plants grown under identical conditions without the presence of a moving air source. A relationship between transpiration/stomatal density and rooting length exists. (C) Plants grown under phosphate limiting conditions display normal levels of stomatal density. Bars with no letters in common are significantly different, P<0.05, (Tukeys test after one-way ANOVA). Error bars represent SE.