Revealing the Application of Synchrotron-Based X-Ray Computed Tomography in Healthy Versus Unhealthy Interior Lodgepole Pine (Pinus contorta var. latifolia) Conelets.

Abstract

The reproductive cycle of interior lodgepole pine spans approximately 26 months, with seed cones initiating in late summer, followed by pollen conelets emerging the next spring when pollination occurs. Fertilization and cone maturation occur in the subsequent spring and fall. Successful pollination, critical for seed conelet retention, requires an ~80% success rate. In June 2020, 30 pine clones (genotypes), with contrasting conelet abortion rates, were selected from a production seed orchard in Alberta, Canada. Sixty conelets per clone (30 aborted and 30 healthy) were collected for synchrotron radiation-based microcomputed tomography (SR-μCT) analysis. A subset of two contrasting clones (1401 and 596) was selected for detailed study. Conelets were transported to the Canadian Light Source in Saskatoon, Saskatchewan, for SR-μCT Phase Contrast Imaging (PCI), where samples were mounted and scanned using a PCO Edge 5.5 sCMOS camera and analyzed using Avizo software to visualize internal structures. Results showed that healthy conelets in clones 1401 and 596 had greater tissue volume (248.8 and 251.9 mm³, respectively) and more organized cavity spaces than aborted conelets (64.7 and 102.1 mm³, respectively), with differential internal air space volume (clone 1401: 8.7 mm³ in aborted vs. 17.5 mm³ in healthy; clone 596: 6.9 mm³ in aborted vs. 11.5 mm³ in healthy). Overall, SR-μCT imaging demonstrated significant advantages over traditional methods of visualization by providing a nondestructive, high-resolution analysis of internal structures. In addition, this technology enhances our understanding of pine reproductive processes, improving management practices in seed orchards-the delivery system for tree improvement programs.