The effect of auxin and auxin inhibitor application on induction and proliferation of protocorms in immature fruit Phalaenopsis amabilis in vitro culture

Abstract. Cahyaningsih AP, Pitoyo A, Solichatun. 2019. The effect of auxin and auxin inhibitor application on induction and proliferation of protocorms in immature fruit Phalaenopsis amabilis in vitro culture. Cell Biol Dev 3: 49-55. Auxin is a hormone that plays an important role in the ovulum development of moth orchid Phalaenopsis amabilis after pollination. Using immature fruit 60 days after pollination as explants are presumed to cause cessation of endogenous auxin distribution due to early fruit harvesting. The research was aimed to investigate the effect of exogenous auxin addition on induction and proliferation protocorm in moth orchid immature fruit explant through in vitro culture. This study used NAA (?-Naphthaleneacetic acid) as auxin in MS medium with 4 treatments: (i) control, (ii) NAA 1 ppm, (iii) NAA 5 ppm, and (iv) TIBA (2,3,5- triiodobenzoic acid) 5 ppm. Observed data include explants' color change, development, anatomy after planting, and protocorm development. Morphological and anatomical data were presented descriptively, and protocorm measurement data were analyzed using One Way ANOVA and followed by a DMRT test of 5% level. The results showed that the culture of immature fruit P. amabilis 60 DAP with the addition of NAA 1 and 5 ppm in immature fruit culture induced protocorm. Still, the protocorm was not able to develop further. Without adding exogenous hormone-induced protocorm formation, immature fruit culture developed some protocorm to form leaf primordia. Next, adding TIBA as auxin transport inhibitor, 5 ppm induced protocorm and developed all protocorms to form leaf primordia.