2019 ASHS Annual Conference

Plant-derived protein biostimulants exhibit hormone-like activities promoting plant growth and yield, yet detailed investigations on hormonal function have remained limited. This study was conducted to investigate the effects of vegetal-derived-biostimulant on morphological and metabolic changes in cuttings of chrysanthemum (Chrysanthemum indicum L.) demonstrating different rooting ability in comparison to brassinosteroid and auxin. Unrooted cuttings were applied with or without biostimulant (1, 5, 10, 15, 20, and 30 mg L⁻¹), Brassinosteroid (24-Epbrassinolide;, 0.5,1, 2, 5, 10, and 15 μM) or auxin [1% indole-3-butyric acid (IBA) plus 0.5% 1-naphthaleneacetic acid (NAA); 200 mg L⁻¹] as a basal quick-dip, stuck into inert media, and evaluated at 20 days after placement under intermittent mist. Biostimulant required a significantly higher threshold for a series of adventitious rooting responses than auxin, and the maximum effectiveness was achieved at 1 mg L⁻¹ for biostimulant and between 5 and 10 μM for brassinosteroid. Adventitious rooting responses (dry mass and length) to biostimulant showed a gradual logarithmic rise as a function of increasing dosages, which was not in agreement with biphasic dose-response of auxin. Biostimulant significantly increased or tended to increase fine roots in the tested cuttings, which was not consistent with auxin. The results of cuttings with brassinosteroid are not significantly different from those of biostimulant. These results indicate that the hormonal effects of vegetal-derived biostimulant are primarily exerted by BR-mediated processes while involving interaction with auxin.