| Summary: | Drought is among the most important abiotic stresses on plants, so research on the physiological regulation mechanisms of plants under drought stress can critically increase the economic and ecological value of plants in arid regions. In this study, the effects of drought stress on the growth status and biochemical indicators of <i>Iris japonica</i> were explored. Under drought stress, the root system, leaves, rhizomes, and terrestrial stems of plants were sequentially affected; the root system was sparse and slender; and the leaves lost their luster and gradually wilted. Among the physiological changes, the increase in the proline and soluble protein content of <i>Iris japonica</i> enhanced the cellular osmotic pressure and reduced the water loss. In anatomical structures, <i>I. japonica</i> chloroplasts were deformed after drought treatment, whereas the anatomical structures of roots did not substantially change. Plant antioxidant systems play an important role in maintaining cellular homeostasis; but, as drought stress intensified, the soluble sugar content of terrestrial stems was reduced by 55%, and the ascorbate peroxidase, glutathione reductase, and monodehydroascorbate reductase (MDHAR) activities of leaves and the MDHAR activity of roots were reduced by 29%, 40%, 22%, and 77%, respectively. Overall, <i>I. japonica</i> was resistant to 63 days of severe drought stress and resisted drought through various physiological responses. These findings provide a basis for the application of <i>I. japonica</i> in water-scarce areas.
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