Responses of an old and a modern Indian wheat cultivar to future O level: Physiological, yield and grain quality parameters.

A field study was conducted to understand the physiological responses, yield and grain quality of an old (HUW234) and a modern (HD3118) wheat cultivar exposed to elevated ozone (O). The cultivars were grown under ambient O (NF) and ambient +20 ppb O (NF+) conditions using open-top chambers (OTCs). The comparative study of an old and a modern cultivar showed variable physiological responses under elevated O exposure. Elevated O in old cultivar caused high reductions in Rubisco activity (Vc) and electron transport rate (J) compared to modern cultivar with simultaneous reductions in the rate of photosynthesis and chlorophyll fluorescence. In modern cultivar, high stomatal density and conductance caused higher O uptake thereby triggering more damage to the adjacent stomatal cells and photosynthetic pigments coupled with reductions in photosynthetic rate and photosynthetic nitrogen use efficiency (PNUE). Modern cultivar also showed relatively high reduction in grain yield compared to old one under NF + treatment. Furthermore, grain quality traits (such as starch, protein and amino acids) of modern cultivar were better than old cultivar under ambient O, but showed more deterioration under NF + treatment. Results thus indicated that modern cultivar is relatively more susceptible to O and showed more negative impacts on plant performance, yield and quality of grains compared to old cultivar.