Abstract
Thermal imaging was applied to micropropagated plantlets to predict wilting after ex vitro transfer. Potato plantlets were cultured from nodal cuttings under photoautotrophic and heterotrophic/ mixotrophic culture conditions for various time periods. A pair of culture vessels, each with a single potato plantlet, was placed in a laminar flow hood. Images of the two plantlets were simultaneously acquired using thermal and digital cameras after removing the cover of the vessels to analyze the relationships between leaf temperature and the onset of wilting. Plantlets with lower leaf temperatures wilted earlier in all measurements. Plantlets grown under heterotrophic/ mixotrophic culture conditions had lower leaf temperatures than those grown under photoautotrophic conditions. Furthermore, these plantlets were more susceptible to wilting, suggesting greater water loss from poorly developed stomata and/or cuticle. The temperature reduction index (TRI) was developed to normalize the difference between air and leaf temperatures for comparing results from different measurements. A negative correlation was observed between the time to the onset of wilting and TRI just after opening the culture vessels. These findings suggest that thermal imaging can be applied as a non-invasive assessment of water loss in micropropagated plantlets and thus, contribute to the prediction of wilting after ex vitro transfer.
