Effects of nitrogen and/or sulphur deprivation on the regulation of photosynthesis in barley seedlings

Abstract

The effects of nitrogen and sulphur deprivation on photosynthetic apparatus were investigated in barley grown in hydroponic culture: no difference was observed in AN, qP, and ETR/AN among control (C), nitrogen (-N), and sulphur (-S) deprivation. Conversely, plants grown in nitrogen and sulphur deprivation (-N-S) exhibited a reduction of AN and qP, a significant increase of NPQ and ETR/AN, as well as higher levels of glutathione and cysteine. The lowest total protein content was found in -N and -N-S plants. Data indicate that the simultaneous starvation of N and S leads to an alteration of plant metabolism that affects negatively photosynthesis. However, since no difference in Fv/Fm was found, it may be hypothesized that in -N-S seedlings processes other than photosynthesis and thermal dissipation are effective in photoprotection at low light. In -N-S plants, the highest glutathione content could represent a mean to face oxidative stress triggered within photosynthetic membranes by carbon fixation decline