Correlation between changes in cell ascorbate and growth of Lupinus albus seedlings

The growth of Lupinus albus seedlings is stimulated when ascorbate (Asc) content is experimentally raised; on the contrary, when Asc content is lowered by lycorine — an alkaloid inhibiting Asc biosynthesis — the growth is inhibited. The stimulation of growth by Asc is due to the promotion of cell division and cell expansion. Redox enzymes of the Asc system respond in different manners to the Asc changes. Asc peroxidase is the enzyme that is most affected by Asc changes in the cell: its activity increases or decreases in parallel with the Asc content. Dehydroascorbic acid (DHA) reduction capability is affected in the opposite way: when Asc content rises, the DHA reduction ability of the cells drops, while it rises when Asc decreases. Ascorbate free radical (AFR) reductase activity does not vary with changing Asc content. A possible regulatory function of Asc redox enzymes is discussed.