Enhanced expression of 4-Cl-IAA and 6-Cl-IAA by touch stimulus for rapid and differential growths of the Madeira vine

Madeira vine (MV) grows 30 times faster after encountering a support. In vivo x-ray diffraction made on live MV stems revel the appearance of crystallized IAA (C10H9NO2), 4-Cl-IAA (C10H8ClNO2) and 6-Cl-IAA (C10H8ClNO2) in the stems. Small angle neutron scattering spectra of the IAA extracted from MVs stem reveal a progressive increase in the size of crystallized IAA transported downward from the apex of the shoots. High resolution X-ray diffractions made on the extracted IAA reveal significantly larger amounts of 4-Cl-IAA and 6-Cl-IAA in the climbing MVs than in the swaying around MVs. The gas chromatography-mass spectrometry spectra reveal the production of 9% more IAA and 90% more 4-Cl-IAA+6-Cl-IAA at the apexes of climbing MVs than swaying MVs. More 4-Cl-IAA+6-Cl-IAA were transported to the contact-free side than to the contact side of the vine. In vivo neutron tomography of naturally climbing MVs reveals a substantially higher H+ concentration in the contact-free parts than in the contact parts. The absorption spectra also reveal more expansin in the contact-free parts than in the contact parts. These results provide a view, at the molecular level, of what triggers the faster and differential growths in MVs in response to touching a support. ### Competing Interest Statement The authors have declared no competing interest.