2019 ASHS Annual Conference

Pepper (Capsicum annuum L.) transplants are generally more susceptible to transplant shock and establish slower in the field than tomato (Solanum lycopersicum L.) transplants, although they both belong to Solanaceae. Transplant shock is caused by the imbalance between root uptake capacity and shoot demand for water and nutrients. In this study, we used a scanner-based rhizotron system to examine their different post-planting growth from the perspective of root development. Each rhizotron had 2655 cm³ of soil volume with a 22×30 cm scannable window on each side. Soil was collected from the field and packed in rhizotrons using the field bulk density. After tomato and pepper seedlings were transplanted in rhizotrons, root image analysis and growth measurements were performed periodically over 17 days. Tomato seedlings developed new roots at 3 days after transplanting (DAT), which reached the bottom of rhizotrons (30 cm) at 12 DAT. By contrast, pepper seedlings developed new roots at 5 DAT, most of which remained in the upper half of rhizotrons (15 cm). At 17 DAT, the longest primary root of tomato seedlings was 39% greater than that of pepper seedlings. Root image analysis also revealed that tomato seedlings had 24% to 52% larger root surface area than pepper seedlings at 5 to 7 DAT, indicating different root establishment rates in the two crops. Shoot growth differences between the two crops became apparent from 10 DAT. At 17 DAT, tomato seedlings had 117% larger canopy area and 163% greater nitrogen accumulation than pepper seedlings. These results suggest that different post-planting growth in tomato and pepper transplants can be explained in part by their different root initiation and exploration for soil nutrients immediately after transplanting. Strategies to promote initial root development may improve the stand establishment of pepper transplants.