Morpho-physiological, anatomical and molecular responses of Porang (Amorphophallus muelleri Blume) to drought stress

Porang is a tuberous plant commodity that has the potential as an alternative food due to its high glucomannan content, so the demand for porang is always increasing. The main problem in efforts to fulfill and increase the demand for porang is climate change which can cause drought in various regions in Indonesia. Drought stress is one of the most damaging types of abiotic stress because it can reduce plant growth, so it becomes a limiting factor in plants. Plants are able to survive and grow in abiotic stress conditions such as drought through morpho-physiological and molecular adaptation. Therefore, this study investigates the drought resilience mechanisms of porang (Amorphophallus muelleri) by integrating morpho-physiological, anatomical, and molecular analyses, with a focus on glucomannan biosynthesis genes (SuSy2, CSLA3) under progressive drought stress (75% to 0% field capacity). We demonstrate that porang prioritizes glucomannan accumulation (130.3% increase at 50% FC) via CSLA3 upregulation (3.11-fold), revealing a novel drought adaptation strategy distinct from other tuber crops. This study was conducted for 21 days with the treatment stress level based on field capacity of 75%, 50%, 25%, and 0%. Data were analyzed using ANOVA One-Way and followed by Tukey Test. The result showed that drought stress negatively induced various morphological responses such as the reduction in root lenght, weight and diameter of tuber, and leaf area. However, plant height did not show a significant difference compared to the control. However, drought stress significantly increased the percentage of stomata closure and stomata density. The physiological response shows a decreased chlorophyll content, while the net assimilation rate showed no significant difference compared to the control. Interestingly, glucomannan content at 50% field capacity and transpiration rate were increased under drought treatment. Molecular responses were characterized by the expression of glucomannan biosynthesis gene, SuSy2 and CSLA3. Relative expression of SuSy2 was increased up to 1.3-fold at 75% field capacity and decreased at 25%-0% field capacity. While CSLA3 was increased up to 3.11-fold at 50% field capacity. As an implication of the results of this study, it can be seen that drought stress of 50% FC increases the highest glucomannan production so that porang can be used as an alternative food source.