Effect of auxin (iaa) upon the proteolytic system in differentiating secondary xylem of pine (Pinus sylvestris L.)

Abstract

Effects of decapitation and IAA on proteolytic activity were studied in main stem of 4-7 year-old Pinus sylvestris trees. Proteolytic activity in the extract from differentiating secondary xylem was found to be totally reduced in decapitated 2-3 year-old segments of the main stem after a few weeks. Simultaneous application of IAA in lanolin paste prevented this reduction. Proteolytic activity reduced totally after decapitation was restored within 2 days when auxin was applied. Analogous responses to decapitated and auxin application were observed in respect to cambial activity and protein level. The latter effects were not correlated in time with the effects upon the activity of proteases. The differences were especially visible when phloem continuity between the decapited stem segment and the rest of the tree crown was broken by ring-barking. The results suggest dependence of a proteolytic system on the shoot apical control. In this epigenetic system of control the role of auxin seems to be directly associated with the seasonal meristematic activity of the cambium, which was observed in earlier studies.