BACKGROUND: Drought and heat stress are among the most critical environmental challenges limiting plant growth, physio-biochemical performance, and seed germination, particularly as a result of climate change. This study investigated the effects of drought stress using three irrigation levels: non-drought (ND) (80% of field capacity (FC)), moderate drought (MD) (60% of FC), and severe drought (SD) (40% of FC), and heat stress using three temperature regimes: low (LT) (15-25 °C), standard (ST) (25-35 °C), and high (HT) (35-45 °C), on growth, physio-biochemical responses, and seed quality in Lallemantia iberica and L. royleana. RESULTS: Moderate drought combined with standard temperature (MD × ST) significantly increased photosynthetic activity and antioxidant enzyme activity in both species. This treatment combination also promoted the accumulation of proline and sugars, and effectively reduced oxidative damage markers such as hydrogen peroxide and lipid peroxidation. Notably, MD × ST produced the highest seed yield, germination, and fatty acid levels, underscoring its positive influence on seed quality. Between the species, L. iberica outperformed L. royleana in seed yield (10.1%), oil content (13%), linoleic acid (61.3%), and germination (15%), and this was associated with a higher net photosynthetic rate (74.1%) and greater seed weight (17.8%). In contrast, L. royleana exhibited superior antioxidant defense, including higher catalase activity (46.53%), and ascorbate peroxidase activity (29.8%), along with elevated proline (11.45%), total flavonoids (8.6%), total phenols (20.4%), and sugars, suggesting stronger biochemical stress resilience. CONCLUSION: The interaction of MD × ST conditions improved both plant growth and seed quality in Lallemantia species, offering insights into species-specific responses and potential strategies for enhancing crop productivity under future drought and heat scenarios. © 2026 Society of Chemical Industry.
Paravar et al. (2026) studied this question.