why photorespiration is a wasteful product?
In photorespiration, instead of CO2 being added by RuBisCo to RuBP, O2 (Oxygen) is instead. This is a result of hot & dry weather in which a plant closes certain pores called stomata so that water doesn't evaporate from its cells. The outcome caused by photorespiration is thus considered wasteful because when O2 travels through the Calvin Cycle rather than CO2, the end result is a release of CO2 into the surrounding atmosphere and NO production of sugar which the plant needs as a source of energy. Not to mention, the light reactions of photosynthesis which normally produce products needed by the Calvin Cycle to convert CO2 to sugar (stored energy), are simply wasted in photorespiration because nothing essential to the cell is produced.