Semiquantitative strigolactone (SL) quantification, 3H‐GR24 transport and leaf senescence in wild‐type (WR) and PDR1 OE Petunia hybrida leaves. (a) Germination rate of Phelipanche ramosa seeds with leaf and stem extracts of WT and PDR1 OE plants. (b, c) Decays min–1 (DPM) of 3H‐GR24 present in leaf unloaded sap relative to 3H‐GR24 leaf content (b) and 3H2O leaf content (c). (d) Senescence‐related leaf phenotypes in 3‐month‐old WT and PDR1 OE plants from the last leaf grown before the transition to flowering time (leaf −1) up to leaf −23. (e–g) Gene expression levels of petunia ORE1like,SAG12like and SAG13like in leaves −5/−6, −9/−10 and −15/−16. Bars, 2 cm. Values are means ± SE. *, P < 0.05; **, P < 0.005; ***, P < 0.0005.