Orchid fruit and root movement analyzed using 2D photographs and a bioinformatics pipeline for processing sequential 3D scans.

Premise: Most studies of the movement of orchid fruits and roots during plant development have focused on morphological observations; however, further genetic analysis is required to understand the molecular mechanisms underlying this phenomenon. A precise tool is required to observe these movements and harvest tissue at the correct position and time for transcriptomics research.

Methods: We utilized three-dimensional (3D) micro-computed tomography (CT) scans to capture the movement of fast-growing roots, and built an integrated bioinformatics pipeline to process 3D images into 3D time-lapse videos. To record the movement of slowly developing and fruits, two-dimensional (2D) photographs were used.

Results: The roots twisted and resupinated multiple times from early development. The first period occurred in the early developmental stage (77-84 days after germination [DAG]) and the subsequent period occurred later in development (140-154 DAG). While fruits twisted 45° from 56-63 days after pollination (DAP), the fruits of only began to resupinate a week before dehiscence (133 DAP) and ended a week after dehiscence (161 DAP).

Discussion: Our methods revealed that each orchid root and fruit had an independent direction and degree of torsion from the initial to the final position. Our innovative approaches produced detailed spatial and temporal information on the resupination of roots and fruits during orchid development.