Racemes of Big Bend bluebonnet (Lupinus havardii Wats.), a winter annual native to far west Texas with attractive blue flowers, are currently being produced commercially as a specialty cut-flower crop. Our studies indicated that the key determinants of postharvest longevity and performance are flower abscission and flower senescence, both of which can be influenced by ethylene. Therefore, this study was undertaken to evaluate the role of some ethylene biosynthesis inhibitors (aminooxy acetic acid = AOA; cobalt = CO++; salicylic acid = SA) and an ethylene action inhibitor (silver thiosulfate = STS) on flower abscission and flower senescence of bluebonnet racemes. Depending on the concentration used (10 μM - 1 mM), AOA and CO++ exhibited variable effects on flower abscission, flower senescence and vaselife. SA (10-100 μM) slightly delayed senescence but did not affect abscission, while higher levels of SA (500 μM - 2 mM) slightly promoted abscission and also significantly enhanced the senescence of flowers on cut racemes. The effects of SA were found to be pH-dependent. However, STS nearly eliminated flower abscission and enhanced vaselife. The results also demonstrated that the abscission of bluebonnet flowers, in particular, is highly sensitive to ethylene.
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