• Iris halophila var. sogdiana exhibits exceptional dual tolerance to drought and waterlogging, withstanding moderate drought (50%±5% FC for 30 days) and severe waterlogging (20 cm inundation for 80 days) via divergent adaptive strategies. • The drought tolerance of is Iris halophila var. sogdiana dominated by physiological acclimation and waterlogging tolerance by morphological plasticity (aerenchyma expansion) and metabolic reprogramming. • The unique isobilateral leaf structure of Iris halophila var. sogdiana with differentiated palisade/spongy mesophyll and air space structure underpins bidirectional stress adaptation, making this species an ideal candidate for climate-resilient urban green infrastructure (e.g., rain gardens). Drought and waterlogging stress impair plant growth and reduce ornamental value, creating an urgent need for dually tolerant ornamental species in landscape design. This study systematically analyzed the growth and physiological responses of three-year-old Iris halophila var. sogdiana to four drought and two waterlogging treatments. Results showed that: 1) After 30 days of severe drought, shoot and root biomass decreased by 72.30% and 46.95%, respectively. Leaf and aerenchyma thickness were reduced by 62.53% and 92.99%, while the net photosynthetic rate declined by 97.66% and malondialdehyde (MDA) content increased 1.45-fold ( P < 0.05). Following 7 days of rewatering, photosynthetic capacity in moderately stressed plants fully recovered, whereas severely stressed plants regenerated new leaves from the basal meristem. 2) Severe waterlogging primarily reduced photosynthetic pigment content and induced transient oxidative stress (H₂O₂ content peaked at a 1.81-fold increase within 15 days before returning to the control level). The plants established and maintained a new physiological equilibrium after 30–40 days. 3) Drought tolerance was mainly attributed to osmotic adjustment (proline and soluble sugar content increased by 12.46-fold and 2.25-fold, respectively) and antioxidant defense (SOD activity increased by 5.76-fold). In contrast, waterlogging tolerance relied on morphological plasticity (e.g., leaf aerenchyma expansion) and metabolic reconfiguration. In conclusion, Iris halophila var. sogdiana exhibits remarkable dual tolerance to water stress, withstanding both moderate drought and severe waterlogging. Its unique palisade/spongy tissue differentiation provides the basis for this bidirectional morpho-functional regulation, making it an ideal candidate for rain gardens experiencing extreme water fluctuations.
Lv et al. (Sun,) studied this question.