Changes in growth irradiance are reflected on H +ATPase activity of plasma membrane enriched vesicles from maize ( Zea mays L.) roots

Leaves change their photosynthetic activity in response to growth light conditions, but little is known about what may happen at the root level. The effect of irradiance level (high or low) on transport activities of root plasma membrane enriched vesicles was studied in maize ( Zea mays L.) plants. High irradiance appears to have a differential promoting effect on proton transport activity and ATPase activity, the most pronounced one on ATP-dependent H +-accumulation. Furthermore, our results put in evidence a correlation between increase in enzyme activity and increase in MHA2 gene transcription level. Finally, high irradiance results in increased uptake rates of nitrate and in a higher reduction rate of the anion. We suggest that high light-induced changes in plasma membrane H +ATPase activity and transcription might have an adaptive role in sustaining the higher request for the nitrate resulting from increased photosynthate availability.