The objective of this project is to investigate changes in the physiology and biochemistry of coniferous trees induced by complex combinations of environmental factors.
The experiments will be mainly performed on Pinus halepensis, a species of economical importance in the Mediterranean countries, but the pollutant tolerance of which is not well known. Studies will be also conducted on Pinus sylvestris, another widespread pine species.
The investigations will comprise long term studies in the field and in open top chambers and short term studies with tightly controlled conditions in laboratories. The natural conditions in the field in Greece will allow following of the behaviour of the trees in their usual environment. The open top chambers will be used to compare polluted and unpolluted trees in exclusion experiments. Short term studies will combine the effects of gaseous pollutants (ozone and nitrous oxide), climatic factors (drought, frost) and nutritional parameters.
The key question with regard to forest decline is to define, at the physiological level, how the gaseous pollutants increased the susceptibility of the trees to natural stress factors. The experiments will focus on carbon and nitrogen metabolic sequences suspected to be sensitive to various stresses. The detoxifying processes requiring the reducing power provided by these pathways will also be studied. The presence of detoxifying enzymes and proteins in the extracellular fluid will be related to the behaviour of the plasma membrane. The accumulation of some secondary compounds (polyamines, etc), known to occur under stress, will be followed in order to establish a link with the observed changes at the level of the primary metabolism. The impact of the changes in ion content will also be evaluated. Finally, in order to integrate the work from the cell to the entire plant, carbon allocation will be followed by using carbon-14 dioxide feeding experiments. All these laboratory experiments, allowing to follow sp cific reactions of the trees to isolated or combined factors, could lead to a better understanding of the tree response in the field.
The long term experiments will be carried out in Greece and in Tarragona, Spain.
Besides the continuous measurement of growth, several sampling dates for biochemical studies are planned: during the spring period (dehardening and bud break) and the autumn (hardening). The short term experiments in closed chambers with young trees (2 to 3 year old trees) will start in spring 1991 and will concern the following.
Ozone alone at concentrations closed to those found in polluted sites. Moreover, some experiments will use pollutants to concentrations at least 3 times higher (100 parts per billion) than the realistic ones in order to reveal or to reinforce some changes too weak to be clearly apparent with lower pollutant levels. In addition, the use of different types of filter (active charcoal and Purafil) will allow verification of the relative importance of nitrogen monoxide.
Ozone and other factors such as drought, frost, acid rain and nitrogen supply.
Funding SchemeCSC - Cost-sharing contracts
LA1 4YQ Lancaster
NE1 7RU Newcastle Upon Tyne
1211 Genève 4