Ionenverteilung und Inhaltsstoffmuster in Blättern streusalzbelasteter Wiener Alleebäume: II. Stickstoff und lösliche Kohlenhydrate

Abstract

Summary In the leaves of healthy and salt damaged roadside trees of 13 different species within the urban environment of Vienna, the contents of total nitrogen, free amino acids, and soluble carbohydrates have been measured. Nitrogen content of injured leaves of Great, Norway, and Ashleaved Maples, Linden, Cherry, Locust, Walnut and Ash were lower as the corresponding values in healthy leaves, the ones of Birch, Chestnut, and Plane-tree were higher, whereas the contents in Hackberry and Oak remained unchanged. The lower levels of total nitrogen are probably the result of a restricted nitrogen uptake from highly salt-affected urban soils. However, in all species investigated, variations within the pool of free amino acids ocurred: Generally, in salt-damaged leaves the amounts of the main amino acid compounds (γ-amino butyric acid, aspartic acid, alanine, asparagine) decreased markedly, while the contents of glutamic acid, glutamine, serine and cysteine raised. Within the pattern of soluble carbohydrates, the sugar compounds exhibited no obvious alterations with increasing salt stress. In some trees the accumulation of speciestypical cyclitols (pinitol in Plane-tree, sorbitol in Cherry, scyllo-inositol in Hackberry, dulcitol in Ash, quercitol in Oak) contributed significantly to the total osmotic potential, which is mainly built up by high electrolyte levels. Variations of nitrogen and carbohydrate metabolism are discussed with respect to the specific salt tolerance of different species, and with respect to the additional water stress situation on roadside habitats.