Seven enzymes of carbon metabolism, including three Calvin cycle isozymes, are present in the secondary cell wall thickenings of the developing xylem tracheary elements in pea leaves

Antibodies directed against chloroplast aldolase and chloroplast fructose bisphosphatase and against cytosolic fructose bisphosphatase, cytosolic P-glycerate kinase, and cytosolic glyceraldehyde-3-P dehydrogenase recognize antigens in the secondary cell wall thickenings in the developing xylem tracheary elements in pea (Pisum sativum L.) leaf mesophyll cells. The isozyme specificity indicates sorting and selection during cell death and xylem formation. Antibodies directed against ADP-glucose pyrophosphorylase, sedoheptulose bisphosphatase, triose-P isomerase, and the photosynthetic electron transport component plastocyanin also recognize secondary cell wall components. It seems possible that these proteins are being recycled and put to some alternate use in the developing xylem.