Alternating thermal conditions enhance seedling morphophysiology, antioxidant activity and nutrient dynamics in eggplant

Partial dormancy in eggplant (Solanum melongena L.) seeds often delays germination and emergence, leading to poor and non-uniform seedlings development. Nonetheless, limited research has examined the effects of alternating temperature regimes on seedling vigour, antioxidant capacity, and nutrient dynamics in eggplant. To address this gap, the present study evaluated the responses of four commercial hybrids (‘Brigitte F1’, ‘Faselis F1’, ‘Karaefe F1’, ‘Hünkar F1’) and two hybrid rootstocks (‘Hawk F1’, ‘Köksal F1’) to two alternating temperature regimes (35/20 °C-16/8 h and 20/35 °C-16/8 h) compared with constant temperature (25 °C). A Completely Randomized Design was employed to assess germination, emergence, morphological and biomass traits, antioxidant enzyme activities (SOD, CAT, APX), and macro-and micronutrient uptake. The genotypes exhibited differential responses: the 35/20 °C-16/8 h regime significantly improved germination (up to 97.7%) and emergence (up to 94.6%), enhanced seedling length and biomass, and increased SOD, CAT, and APX activities compared with constant temperature. Nutrient uptake (Ca, Mg, P, K, Fe, Zn, Cu, Mn, B) was also highest under this regime, while Na accumulation decreased. Correlation and PCA analyses revealed strong positive relationships among germination, emergence, antioxidant activity, and nutrient accumulation, while mean germination and emergence times were negatively correlated with seedling vigour. These findings highlight the role of antioxidant mechanisms in conferring tolerance to thermal fluctuations thereby improving seedling quality and nutrient dynamics of eggplant. Consequently, the 35/20 °C - 16/8 h regime can be readily and economically adopted by commercial producers to enhance germination rates and improve seedling development in eggplant cultivars.