Spinach (Spinacea oleraceae) is one of several vegetable crops commercially grown in Controlled Environment Agriculture (CEA). Recent research has indicated differences in root morphology and architecture among various crops may influence performance and environmental stressor tolerance. Specifically, fast-growing cultivars have shorter life cycles, develop more extensive and specialized root systems with increased root order differentiation in response to their growth systems. Contrastingly, slow-growing cultivars have greater heat-tolerance and produce simpler root systems with less root-order differentiation and fibrous roots. These root traits may be exploited to increase yield, promote efficient nutrient use, and mitigate environmental stressors. Novel studies have revealed an ideal root system archetype, known as “Subsoil Foraging Ideotype (SFI)”, wherein a well-penetrating taproot is able to easily maintain nutrient and water flow while optimizing resource efficient root development. We designed an experiment to measure differences between various spinach cultivars in CEA systems to reveal morphological variation which can aid in the development of SFI architecture cultivars. Our experiment utilized two growth systems located in a walk-in greenhouse, standalone NFT hydroponic systems with two inch net pots and expanded clay aggregate media, and one gallon pots to replicate field conditions. Seeds from fast-growing “Income”, medium-growing “Darkside” and slow-growing “El-Majestic” cultivars were transplanted into different growing systems. Supplemental light totalling 200 µmole/m2/s with 12 hour photoperiod and periodic fertigation was used. Harvests were conducted on days 15, 30, and 45, with the collection of leaf and root biomass. Collected data included scanning of root systems in WinRhizo software, measuring length, root volume, root diameter, surface area, classification by diameter, forks, tips, and crossing numbers. On day 45, four plants per cultivar were selected for anatomical analysis through microscopy evaluation and underwent JB4 embedding protocol. Anatomical analysis of five root orders included diameter, vascular development, and rhizodermis characteristics. Preliminary results suggest there is an interaction effect between cultivar, growth system, and developmental stage on spinach root morphology. All cultivars developed more extensive, specialized root systems under hydroponic conditions versus field counterparts where extensive root development was limited to fast-growing cultivar. Root diameter was greater in fast-growing cultivars, with decreased root order diversification of slow and medium-growth cultivars. These results affirm previous research which links root morphology to growth systems and environmental conditions. Cultivars which possess resilient traits may be further developed in conjunction with SFI archetypes. Such advances would further nutrient use efficiency and shrink growth cycles in CEA.
