EFFECTS OF INFECTION BY PHYTOPHTHORA CINNAMOMI AND DIFFERENT WATERING TREATMENTS ON WATER RELATIONS OF OAKS AND CHESTNUT
C ROBIN and ML DESPREZ-LOUSTAU
INRA Bordeaux, Pathologie Végétale, BP 81, 33 883 Villenave D'Ornon, France
Background and objectives
The aim of this study was to investigate how P. ;cinnamomi infection and different watering treatments may affect tree-water relations.
Materials and methods
Results and conclusions
The water withholding had no significant effect on root loss and taproot infection in oaks. The repetitive flooding episodes induced a decrease in the root weight, in controls as well as in inoculated plants. Whatever the flooding treatment and the species, the PIT was greater than 50%. Fungal infection induced an early significant decrease in PLWP of inoculated plants of chestnut and holm oak. A simultaneous significant effect was always observed on gs. In cork oak, the decrease induced by infection was significant on PLWP only after 10 wai, but significant on gs as soon as 5 wai. No effect was observed in red oak. No significant interaction between watering treatments and infection was observed on gs. However, in holm oak, there was a synergistic effect of floodings and fungal infection on PLWP.
In conclusion, we showed that root infections results in a decrease in PLWP, which is explained by a decrease in water absorption capacity and appears to be quantitatively related to the root loss. Root infection also induces a stomatal regulation, which leads to a stomatal closure. As in the case of droughts this regulation occurs before the reduction in PLPW. Although the water stress did not increase the root necrosis, it is likely that infected plants are more vulnerable to drought or flooding and these effects are additive or synergistic to P. ;cinnamomi root infection effects on water relations.References
1. Brasier CM, 1996. 53, 347-358.
2. Robin C, Desprez-Loustau ML, Capron G, Delatour C, 1997. Annals of the Science of Forestry, in press.