IDENTIFICATION Unambiguous identification of degradation products required
the specific radiolabeling of Chl in the porphyrin moiety. Feeding of
[4-14C]ALA during greening of etiolated plantlets of barley (121) or to expanding
and greening canola cotyledons (35) resulted in the specific radiolabeling of
Chl for the study of catabolism. As Chl disappeared during subsequent senescence,
the radiolabel was progressively recovered in the water-soluble fraction
of leaf extracts, indicating that Chl degradation is associated with hydrolysis
into the phytol and porphyrin moieties. In barley plantlets developing under natural
conditions, the label incorporated into the pyrrole units of Chl was retained
in the senescent leaves (119); there was no indication of export of radiolabel
from the senescent primary leaf to other parts of the plant