Pivotal role of Indole-3-Acetic acid in the senescence and flower absicission of Lupinus mutabilis L. Sweet

The role of the most common auxin Indole-3-Acetic Acid (IAA) levels was determined all along the inflorescence of Lupinus mutabilis (L.sweet) during the senescence and flower abscission stage. Lupinus mutabilis Sweet is apparently unknown in the wild but is cultivated as an important food crop throughout the Andes and is also the focus of crop breeding and development elsewhere in Australia and Europe. Concentrations of indole-3-acetic acid were identified and quantified by CG-SIM-MS in different regions of the inflorescence and at different stages in the development. IAA levels were steady at first stages of the plant development. However, the IAA levels increased as the Senescence and Abscission Syndrome (SAS) of flowers and young pods starts. IAA concentrations were different depending on the stage of development of the process but it was detected an acropetal increase of the phytohormone levels. The results here presented strongly support the hypothesis that IAA plays a fundamental role in flower abscission in Lupinus Mutabilis. Moreover the region and staged analysis suggests the existence of a spatio-temporal gradient of IAA related to the Senescence and Abscission process. This data could clearly explain the sequential pattern of the plant senescence and pose new questions about the timing of IAA synthesis.