Gibberellin and auxin applications confirm flower variation in porang (Amorphophallus muelleri Blume)

Indonesian konjac or iles-iles or porang ( Amorphophallus muelleri Blume.) produces inflorescence with many variations concerning the genetic purity in seed production. However, the cause of the variation is still unknown. This study aimed to evaluate the inflorescence growth and morphology by application of GA 3 and NAA. The research was carried out from August 2019 to February 2020 at the Leuwikopo Experimental Station, Bogor Agricultural University, West Java, Indonesia. The study consisted of two separate experiments, i.e., gibberellic acid (GA 3 ) and NAA (auxin) treatments. GA 3 and NAA were applied to the flower bud at concentrations of 0, 250, 500, 750, and 1000 ppm. The results showed that GA 3 application at 500 ppm tended to increase inflorescence height and stimulate the diameter of male and female zones. Increasing concentrations of both GA 3 and NAA increased the variability in cone shape and abnormalities of spathe shape and its number. Thus, the variability of A. muelleri flower is most likely related to excess concentration of GA 3 in the plant. The application of GA3 to stimulate flowering is recommended to be below 500 ppm to minimize the presence of abnormal inflorescence.