photorespitation in C₃ plants strats from

1. phosphoglycerate
2. phosphoglycolate
3. glycerate
4. glycine

photorespiration in C3 plants start from phosphoglycolate.C3 plants(95% of plants: use only Calvin cycle)
("3" because first cycle product has 3 carbons)
normal supply of CO2 favors photosynthesis, but in dry conditions the high O2 level causes rubisco to attach O2 instead of CO2 to RuBP (called photorespiration) <-essentially waste CO2 and ATP
reduces efficiency of sugar production because cells lose CO2 and ATP