Growth and Attachment Strategy of Vanilla (Vanilla planifolia Jacks. ex Andrews) Adventitious Roots in Different Types of Support Post

Abstract

The adventitious roots (ARs) of vanilla (Vanilla planifolia Jacks. ex Andrews) are primarily responsible for the firm anchorage and vertical growth and development of this important spice. The effects of different types of supporting structures on the growth and attachment properties of ARs were investigated. The ARs attached to natural support posts (Gliricidia sepium [Jacq.] Steud. and Sphaerobambos philippinensis [Gamble] S.Dransf.) appeared to be flattened due to the significant increase in root width. In contrast, slender ARs attached to artificial support posts (GI wire [control treatment], polyvinyl chloride (PVC) pipes, concrete and styrofoam) were observed. The appearance of long and slender ARs attached to artificial posts and flattened ARs attached to natural support posts were probably adaptive root traits to increase water retention and improve phosphorus (P) and nitrogen (N) acquisitions. The maximum increment growth in length and width (2.1 mm and 0.25 mm d-1, respectively) of the ARs attached to G. sepium was achieved after 4 d. The attachment strength, the force that maintains the permanent attachment of ARs to the support post, was greatest when ARs were attached to G. sepium (935.44 ± 514.60 mN) while the least force was exerted when ARs were attached to S. philippinensis (179.70 ± 148.72 mN) which suggested that the texture of the support post was observed to primarily influence the attachment strengths of ARs.