The objective of this two-year field study was to assess the influence of stand establishment methods (direct seeding or transplanting) on root growth dynamics, shoot morphology, leaf physiology, yield, and quality of globe artichoke (Cynara cardunculus). Three artichoke cultivars were evaluated, 'Green Globe Improved' (GGI), 'Imperial Star' (IS), and 'Romolo' (ROM). Plants established with the transplanting method had higher mean root length intensity (La), root length, and root surface area as compared to plants established by direct seeding. The topsoil (0-20 cm) had on average higher La, root length, and root surface area than deeper soil profiles. Transplanted plants had higher plant shoot width and leaf area index (LAI) chlorophyll content index (SPAD) than direct seeded plants at the vegetative stage in 2015. The improvement of root and shoot growth in transplants (compared to direct seeding) also resulted in higher (p < 0.05) marketable yield (21.1 vs. 19.9 ton ha-1 in 2015 and 18.3 vs. 13.7 ton ha-1 in 2016). Additionally, 46-50% of the total yield occurred during the first 30 days of harvest in the transplanting method compared to 13-38% for direct seeding. No significant differences were found between planting methods or cultivars in leaf-level gas exchange (photosynthesis, stomatal conductance, and transpiration) and cynarin concentration in the marketable heads. Although chlorogenic acid was similar in both establishment methods in 2015, direct seeding had higher concentration in 2016. Comparing cultivars, GGI had higher root length, surface area, root volume, and earlier and higher marketable yield than ROM. However, ROM had higher mean root length intensity (La; total root length per specific area in soil profile) than GGI in both growing seasons. This study showed significant and consistent improvements in root and shoot traits, and yield for transplants as compared to direct seeded plants.
Keywords: Cynara cardunculus; SPAD; chlorogenic acid; minirhizotron; root length; yield.