Resolving early growth variation in Pinus radiata : Effective indoor phenotyping of juvenile trees

Indoor plant phenotyping facilities provide high‐resolution, dynamic trait data not achievable with other systems, but are rarely applied to trees due to size constraints. Using the model conifer Pinus radiata , this study evaluated whether early growth variation among three clonal genotypes can be detected and reliably resolved using indoor phenotyping. Clonal seedlings were grown in three growth media under controlled conditions and phenotyped over 84 days using a LemnaTec RGB (red‐green‐blue) imaging system. Smoothed projected shoot area (sPSA) was derived from multi‐angle images, with absolute growth rate (sAGR) and relative growth rate (sRGR) calculated to quantify growth dynamics. Phenotyping‐derived traits consistently discriminated clones ( p < 0.05) but not growth media ( p > 0.05), and no clone × media interaction was detected ( p > 0.1). Clone 2 exhibited greater sPSA than Clones 1 and 3 from 48 days after planting onwards. Absolute growth rates differentiated treatments by overall growth magnitude, with media effects present but clonal effects dominant ( p < 0.001). Relative growth rates showed similar patterns, with Clone 2 exhibiting the highest intrinsic growth ( p < 0.001). Using six to seven replicates per clone‐soil treatment, indoor phenotyping enabled clear separation of clonal differences in early growth. These results demonstrate that juvenile conifers express measurable phenotypic variation that can be reliably captured under controlled conditions, supporting the application of indoor phenotyping for high‐resolution early‐stage tree research.