2018 ASHS Annual Conference

Grafted plants offer several advantages for tomato growers including resistance/tolerance to soil borne pathogens and increase in yields. In the US, the demand for grafted vegetable seedlings has increased in the last few years. Precision Indoor Productions (PIP) systems offer advantages for the propagation of grafted seedlings such as control of the environment and increase in spatial and temporal plant uniformity. However, these systems are energy intensive due to the use of electrical lighting as the energy source for plants. CO₂ supplementation is inexpensive for closed systems and has shown to improve yield for many crops. The objective of this experiment is to decrease the light requirements and increase CO₂ levels to produce a high-quality tomato seedling while reducing energy consumption. Two tomato cultivars were grown scion ‘Rebelski’, and rootstock ‘Maxifort’. Plants were subject to three different light treatments 100PPF (103 ± 7.4), 150PPF (152 ± 5.8), and 200PPF (200 ± 11) photosynthetic photon flux (mmol m^-2 s^-1) (18 h) with a percent photon flux ratio of 60Red:40Blue. Furthermore, plants were also exposed to End-of-day far-red light at 5 mmol m⁻²·d⁻¹. Plants were also subjected to three different CO₂ treatments of 400CO₂ (439 ± 23) (ambient), 1000CO₂ (1018 ± 42), and 1600CO₂ (1589 ± 10) μmol mol^-1. The room air temperature was 24.3°C ± 0.5/16.7°C ± 1.1(day/dark) (22.4°C average), and 51.9 ± 8.2% RH. Tomato seedlings were grown until the grafting stage (1.8-2.0 mm stem diameter). Daily morphological measurements were taken to observe the growth response over time. In addition, dry mass and other morphological and physiological data was collected to quantify the effects of each treatment. Preliminary results show that under 200PPF-1600CO₂, ‘Rebelski’ reached grafting stage at day 14, 12% earlier than the control (200PPF-400CO₂). ‘Maxifort’ grown at 200PPF-1600CO₂ reached grafting stage at day 17, 6% earlier than the control (200PPF-400CO₂). In addition, the same plant growth was obtained under 25% less PPF and elevated CO₂ (1000-1600 μmol mol^-1) as with standard growing conditions (ambient CO₂ at 200 mmol m^-2 s^-1).