EFFECT OF AUXIN (IAA) UPON THE PROTEOLYTIC SYSTEM IN DIFFERENTIATING SECONDARY XYLEM OF PINE (PINUS-SYLVESTRIS L)

Effects of decapitation and IAA on proteolytic activity were studied i n main stem of 4-7 year-old Pinus sylvestris trees. Proteolytic activi ty 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 p revented this reduction. Proteolytic activity reduced totally after de capitation was restored within 2 days when auxin was applied. Analogou s responses to decapitated and auxin application were observed in resp ect to cambial activity and protein level. The latter effects were not correlated in time with the effects upon the activity of proteases. T he differences were especially visible when phloem continuity between the decapited stem segment and the rest of the tree crown was broken b y 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 meris tematic activity of the cambium, which was observed in earlier studies .