Heat Priming Impacts on Root Morphology, Productivity and Photosynthesis of Temperate Vegetable Crops Grown in the Tropics

Many plants have an inherent basal thermotolerance and they are able to survive temperatures over the optimum for growth and development. This project aimed to investigate if heat stress priming at the root-zone (RZ) could be used to induce thermotolerance through the studies of root morphology, productivity and photosynthesis of temperate vegetables aerponically grown in the tropics. Two high valued temperate vegetable crops were used for this study: Lactuca sativa (cv. Canasta) and Eruca sativa (cv. Arugula). Heat stress at the RZ priming was studied by exposing the plants to three different root-zone temperature (RZT) treatments: (1) 25C-RZT, (2) 25C-RZT→42C-RZT (defined as non-hardening) and (3) 25C -RZT →38 CRZT→42C–RZT (defined as hardening). It was found that RZ heat stress priming did not have any negative effects on the root morphology for both vegetable crops. Compared to Arugula, Canasta had heat hardening effects which increased productivity at high RZT of 42C with better photosynthetic performance. Since RZ heat hardening stimulated shoot growth of Canasta, this finding has practical significance on using RZ heat stress priming to induce thermotolerance of certain temperate vegetable crops grown in the tropics that could enhance productivity at low production cost.