Scientific publications

The abiotic stresses, such as soil flooding as well as drought, can have negative effect on growth of plants that can give reduced or lost of yield in annual harvest. In trees the problem sometime is under considered in view that one season stress may have relative less effect on long living species. In West European countries reforestation progamms encountered wide interest and economical support either at European Union, National, and Regional levels. The request of planting material is increasing for wide range of ecological habitats, hilly or plain lands, dry or water rich area, hot or temperate climate. In this view studies to select the best genotypes for each habitat are important points to reduce environmental effect on growth rate and stem quality to obtain trees with low defect in wood at the moment of the cutting some year decades after planting. Experiments were carried out on walnut (Juglans regia), well known for the high nutritive value of fruits and one of the more appreciated wood tree in Italy and South Europe for furniture production and on black locust (Robina pseudoacacia), also an interesting tree for its hardwood suitable for handwork other then for the quality of its honey. Working on those two tree species the aim was to search and test physiological and or biochemical parameters useful in the selective process for genotypes suitables for specific habitat area. In the last ten years about 20 varieties or provenances for J. regia as well as for R. pseudoacacia has been compared, in soil flooding or soil drought growing conditions, investigating radial stem growth, photosyntetic and transpistarion rates, osmotic potential, and its main components amino acids and soluble sugars, and stress marker compunds like ethylene, ethanol. The comparison of two significant genotypes of walnut and back locust are presented and compared. The studies give indication that comparing different genotypes is possible to have indication of the presence between them of a different degree of resistance to flooding or drought stressses. The use of daily course stem diameter evolution seems to be an indicator of stress status. Experiences indicate that flooding or drought could have negative effect on cambial activity and consequently on wood formation also in the successive growing seasons. Furthermore there are evidence that flooding or drought act in different ways and different intensity also in relation of tree species or genotypes. The use of physiological and biochemical markers can contribute to obtain indication useful for selection of stress resistance aptitude. In particular ethylene or ethanol presence and evolution can be markers for hypoxia resistance and osmotic potential seems relateted to drought conditions in young trees. Long time experiments are necessary to evaluate the response on elder trees and the stresses consequence on wood characteristic and quality.