waste can use in other processes, some exit via leaf organ
O2, CO2, Water / vapour, other unwanted chemical substances
light: phs > rsp -> released O2 > used / CO2 used > released
Net effect: O2 in excess = waste product (vs night: no phs so only O2 used)
gas in excess diffuses out thru stomata (excretion)
most water vapour lost NOT metabolic waste -- drawn up frm roots in transpiration stream
cells break down molecules to chemical substances not needed
cant convert to useful compound = removed
stored in dying tissues - falls off plant to remove eg in autumn turn orange bc of waste
