The current study was conducted to evaluate the effects of indole-3-butyric acid (IBA) at 100 ppm with or without biostimulants (Agrobacterium rhizogenes, seaweed extract and coconut water) as either a spray or drench for 3 minutes or 1 hour on rooting and growth parameters of three cutting types (tip, middle and basal) of Conocarpus erectus L. The data showed that the rooting percentage, root and vegetative characteristics of rooted cuttings were significantly increased by all treatments of IBA and/or biostimulants compared to the untreated cuttings. The individual treatments of seaweed extract and coconut water were more effective than IBA or A. rhizogenes alone. Seaweed extract as drench with or without IBA surpassed those of seaweed extract treatments as spray. Besides, the response of cuttings treated with coconut water for 1 hour was better than coconut water for 3 min. Tip cuttings were significantly better than the middle and basal ones, especially in relation to rootability of cuttings. Maximum rooting percentage and shoot characteristics of plants were
obtained from tip cuttings treated with IBA + coconut water for 1 hour,
followed by IBA + seaweed extract as drench. The highest rooting
percentage was associated with high endogenous levels of phenols,
indole acetic acid (IAA) and gibberellic acid (GA) as well as the
lowest abscisic acid (ABA) level in cutting tissues and the anatomical
structure of rooted cuttings. So, it can be recommended treating tip
cuttings of C. erectus with either coconut water for 1 hour or seaweed
extract as drench combined with IBA for enhancing the rooting
percentage, root and shoot growth parameters as well as content of
endogenous root promoting substances.