2018 ASHS Annual Conference

Eight tomato cultivars (Accession LA-1994, ‘Nacgarlang’, ‘Saladette’, ‘Campbell-28’, ‘Moskvich OG’, ‘Amana Orange’, ‘Solar Set’, and ‘Solar Fire’) previously identified as heat tolerant or intolerant based upon photosynthesis and/or yields were compared for variation in root respiratory temperature thresholds. Root respiration rates were measured at temperatures ranging from 44.1-59.1C (+/- 0.4C) by measuring changes in oxygen concentration in sealed containers over a thirty-minute sampling period. Roots and their associated media were heated in a water bath (in a sealed tray) from 44.1 to 59.1 ^oC (at 3^oC sequential increments) and were then transferred to sealed jars at each media temperature with vertically mounted oxygen sensors to evaluate oxygen depletion rates. Absolute oxygen concentration in jars was measured every second for 30 min after samples were placed in jars. Only data from 15 - 30 min was used for analysis, as data collected from 0 to 15 min was highly variable and impacted by the initial adjustment of sensors to conditions within the jars. A linear function was fit to the data, with the slope of that line representing oxygen depletion (root respiration rate) over time. Root respiration rates were divided by root sample fresh and dry mass (after washing media from roots) to determine root respiration rate per unit mass. Data were analyzed to determine whether there was an association between reported above ground heat tolerance and the heat tolerance of roots as identified by maximum temperatures at which root respiration still occurred.