Effect of Substrate Volumetric Water Content on Performance of <i>Ardisia pusilla</i> Grown in Indoor Conditions

Most automated irrigation technologies focus on effective cultivation of horticultural plants in terms of efficient production, but it can also be applied to maintain the performance of ornamental plants. The present research study aimed to investigate the optimum substrate volumetric water content (VWC) needed for Ardisia pusilla to maintain its performance indoors. The threshold levels of substrate VWC were evaluated as 0.3, 0.4, 0.5, or 0.6 m3 ․m−3 using an automated irrigation system with capacitance soil moisture sensors and a datalogger. Plant height and width, number of leaves, leaf area, SPAD, relative water content of leaf, shoot fresh and dry weight, photosynthetic rate, and Fv/Fm were measured at 0, 1, 2, and 4 weeks after treatment (WAT) and irrigation amount of each pot was measured. No significant differences in growth and physiological responses were observed when comparing treatments at 1 WAT, but Fv/Fm decreased at 2 WAT for the lowest VWC treatment (0.3 m3 ․m−3). While no differences in physiological responses were observed at 4 WAT, decreases in plant growth parameters such as plant width, shoot fresh weight, shoot dry weight, leaf number, and leaf area were observed for the lowest VWC treatment. This suggests that Ardisia pusilla shows physiological responses relatively promptly compared with its growth responses. The amount of irrigation was highest for the 0.5 m3 ․m−3 treatment, and all the irrigation amount was correlated with shoot fresh weight irrespective of treatment. After accounting for convenience and efficient use of water, the 0.4 m3 ․m−3 treatment was determined to be the optimal level required to maintain the performance of Ardisia pusilla, grown indoors with efficient maintenance practices.