© 2000 Heron Publishing—Victoria, Canada
Changes in cellular structures and enzymatic activities during browning of Scots pine callus derived from mature buds
Hanna Laukkanen (1), Lea Rautiainen (1), Erja Taulavuori (1) and Anja Hohtola (1)
1. Department of Biology/Botany, University of Oulu, PO Box 3000, FIN-90401 Oulu, Finland / Received March 29, 1999
Summary
Visible browning is a typical feature of callus cultures derived from shoot tips of mature Scots pine (Pinus sylvestris L.). Because the ability of callus to regenerate is low, we determined the effect of browning on growth and changes in cellular
structure during culture. Striking alterations in cellular structure were detected by LM (light microscopy), EM (electron
microscopy) and SEM (scanning electron microscopy). Accumulation of phenolic substances was shown by histochemical staining.
Staining for β-glucosidase activity of soluble proteins that had been subjected to polyacrylamide gel electrophoresis indicated
lignification of cells. The measured growth rate of callus was low compared with a hypothetical growth curve. Peroxidase activity
increased rapidly soon after the start of the culture period, but especially between the second and third weeks of culture.
At this time, the degradation of cell membranes and browning began coincident with the loss of chlorophyll. We conclude that
browning is associated with cell disorganization and eventual cell death, making tissue culture of mature pine especially
difficult.
Keywords:
extracellular matrix, growth, beta-glucosidase, phenolics, Pinus sylvestris, peroxidase, recalcitrance, tannin.
