Characterization of Drought Stress Responses in Phalaenopsis amabilis Based on Survival Percentage and Stomatal Density

The moon orchid [Phalaenopsis amabilis (L.) Blume] is a highly valued ornamental plant designated as one of Indonesia’s national flowers due to its exceptional aesthetic appeal. Despite its economic importance, its growth is strongly influenced by environmental conditions, particularly drought stress. Drought can inhibit various physiological processes, such as reduced turgor pressure, stomatal closure, and disruptions in photosynthesis due to limited water availability. These conditions may decrease plant quality and reduce the success rate of seedling production, which is a crucial aspect for the commercial development of orchid commodities. This study aimed to determine the percentage of Phalaenopsis amabilis plants that survived under different concentrations of PEG 6000 used to induce drought stress and to characterize the changes in stomatal density on the leaves as an adaptive physiological–morphological response. The experiment was arranged in a Completely Randomized Design (CRD) with a single factor of PEG 6000 concentration: 0%, 10%, 20%, 30%, and 40%, each with five replications. Data were analyzed using ANOVA at a 5% significance level followed by the Honestly Significant Difference (HSD) test. The results showed that increasing PEG 6000 concentrations reduced plant survival percentages, yet led to an increase in stomatal density as an adaptive response. The 40% concentration exhibited the highest tolerance response, providing insights into the adaptive mechanisms of P. amabilis under drought stress.