Photosynthetic and Morphological Responses of Sacha Inchi (Plukenetia volubilis L.) to Waterlogging Stress

Abstract

Sacha inchi (Plukenetia volubilis L.) is an important oilseed crop that is rich in fatty acids and protein. Climate-change-related stresses, such as chilling, high temperature, and waterlogging can cause severe production loss in this crop. In this study, we investigated the photosynthetic responses of sacha inchi seedlings to short-term waterlogging and their morphological changes after long-term waterlogging stress. Sacha inchi CO2 uptake, stomatal conductance, and transpiration rate are affected by temperature and light intensity. The seedlings had a high CO2 uptake (>10 μmol m−2s−1) during the daytime (08:00 to 15:00), and at 32 and 36 °C. At 32 °C, CO2 uptake peaked at irradiations of 1000 and 1500 µmol m−2s−1, and plants could still perform photosynthesis at high-intensity radiation of 2000–3000 µmol m−2s−1. However, after 5 days of waterlogging (5 DAF) sacha inchi seedlings significantly reduced their photosynthetic ability. The CO2 uptake, stomatal conductance, Fv/Fm, ETR, and qP, etc., of the susceptible genotypes, were significantly decreased and their wilting percentage was higher than 50% at 5 DAF. This led to a higher wilting percentage at 7 days post-recovery. Among the four lines assessed, Line 27 had a high photosynthetic capability and showed the best waterlogging tolerance. We screened many seedlings for long-term waterlogging tolerance and discovered that some seedlings can produce adventitious roots (AR) and survive after two weeks of waterlogging. Hence, AR could be a critical morphological adaptation to waterlogging in this crop. In summary, these results suggest that improvement in waterlogging tolerance has considerable potential for increasing the sustainable production of sacha inchi.