Plays a role in the inhibition of programmed cell death by converting the toxic proline catabolism intermediate (s)-1-pyrroline-5-carboxylate (P5C) to glutamate. (S)-1-pyrroline-5-carboxylate + 2 H2O + NAD(+) = H(+) + L-glutamate + NADH Amino-acid degradation; L-proline degradation into L-glutamate; L-glutamate from L-proline: step 2/2. Highly expressed in flowers (PubMed:11532180). Constitutively expressed at low levels in the other tissues (PubMed:11532180). Highly expressed in pollen grains and tissues undergoing cell death (PubMed:15548746). Expressed in old leaves, mature siliques and developing embryos (PubMed:15548746). Induced by treatment with proline (PubMed:11532180, PubMed:15548746). Induced by drought stress (PubMed:19635803). No visible phenotype under normal growth conditions, but mutant plants are hypersensitive to treatment with proline (PubMed:15548746). Hypersensitivity to heat stress (PubMed:19635803). Belongs to the aldehyde dehydrogenase family.