PHOTORESPIRATION PROTECTS C3 PLANTS FROM PHOTOOXIDATION

PLANTS absorb light for photosynthesis but as light can itself be dang erous to plants, they need to protect themselves against its damaging effects, Here we show that photorespiration can act as such a defence mechanism, We constructed transgenic tobacco plants enriched or reduce d in plastidic glutamine synthetase (GS2), a key enzyme in photorespir ation. Those transgenic plants having twice the normal amount of GS2 h ad an improved capacity for photorespiration and an increased toleranc e to high-intensity light, whereas those with a reduced amount of GS2 had a diminished capacity for photorespiration and were photoinhibited more severely by high-intensity light compared with control plants, W e conclude that photorespiration protects C3 plants from photoinhibiti on.