Differential ozone-induced alterations in the photosynthetic apparatus and chlorophyll fluorescence dynamics of two pea cultivars (Pisum sativum L.)

The phytotoxic nature of tropospheric ozone (O₃) has led to substantial declines in global crop productivity. Given their nutritional richness, legumes serve as vital dietary staples, valued for their high protein, oil, and fiber content. A field experiment was conducted to assess the physiological plasticity of two pea (Pisum sativum L.) cultivars, K Agaiti (O₃-sensitive) and K Damini (O₃-tolerant), under elevated O₃ (ambient + 15 ppb). The Ball-Woodrow-Berry (BWB) model revealed a greater change in the intercept for K Agaiti compared to K Damini, indicating stronger stomatal disruption. Analysis of A/Ci and A/Q curves and chlorophyll fluorescence transients demonstrated cultivar-specific variations in both light and dark reactions. While K Agaiti exhibited significant PS II impairment, K Damini showed moderate reductions linked to feedback inhibition of dark reactions. Vcmax of elevated O₃-exposed plants decreased by 3.5% and 7.35% at the vegetative stage, and by 4.91% and 8.45% at the reproductive stage in K Damini and K Agaiti, respectively. Similarly, seed weight per plant declined by 2.55% in K Damini and 15.29% in K Agaiti. These findings highlight the resilience of K Damini’s photosynthetic machinery under O₃ stress, demonstrating cultivar-specific adaptability and providing insight into the physiological basis of ozone tolerance in pea.