LAUSR

Trichomes are potentially important for absorption of foliar fertilizers, yet little is known in this regard despite previous study showing that the non-glandular trichromes (NGTs) of sunflower (Helianthus annuus) accumulate high concentrations of foliar-applied Zn. This study investigated how foliar-applied Zn accumulates in the NGTs and the subsequent fate of this Zn. Time resolved synchrotron-based X-ray fluorescence microscopy and transcriptional analyses were used to probe the movement of Zn in the NGTs, with the cuticle composition of the NGTs examined using confocal Raman microscopy. The accumulation of Zn in the NGTs is both an initial preferential absorption process and a subsequent translocation process. The preferred absorption is likely because the NGT base has a higher hydrophilicity. The subsequent translocation is due to the presence of plasmodesmata, Zn chelating ligands and Zn transporters in the NGTs. Furthermore, the Zn that was sequestered in the NGTs eventually translocated out once the leaf Zn concentration had decreased, suggesting that the NGTs are also important in maintaining the leaf Zn homeostasis. This study demonstrates for the first time that trichomes have a key structural and functional role in the absorption and translocation of foliar-applied Zn.