Effect of Bursaphelenchus xylophilus on the Assimilation and Translocation of 14 C in Pinus sylvestris.

The effect of wound, wound + water, wound + Bursaphelenchus xylophilus culture filtrate, or wound + lethal B. xylophilus doses on the assimilation and translocation of (1)C by 8-month-old Pinus sylvestris seedlings was tested. In two separate experiments, pine seedlings were exposed to 28.35 muCi of (1)CO for 20 minutes below or above (to the pine shoot leader) the point of nematode inoculation. After 2 and 4 hours of dark adaptation, 80% ethanol soluble (1)C tissue extracts were determined by liquid scintillation counting. Nematode infection significantly (P = 0.05) decreased (1)C assimilation. Treatments translocated less than 6% of the total amount of the fixed (1)C and translocation generally decreased with increasing size of nematode inoculum. However, infected pines translocated a greater proportion of the amount of (1)C fixed per gram of exposed nematode-plant tissue than did the control pines. The lower levels of photoassimilate entering the plant system probably resulted in a reduced metabolic capacity in B. xylophilus-infected pine seedlings. The effect on photosynthesis could be one of the key factors leading to death of pines through starvation, and it is possible that it was preceded by an effect on related physiological processes such as water uptake.