干旱区生态环境知识资源中心

in order to elucidate the seasonal and annual variation, leaves of Ammopiptanthus mongolicus were collected in 3 consecutive years from natural (drought stressed) and irrigated (water supplemented) fields at Shapotou in Tengger Desert, in which stable carbon isotope composition (delta C-13) and major osmotic solute such as proline, total soluble sugar (TSS), especially sucrose and glucose, as well as inorganic cations (K+, Ca2+, Mg2+, Na+) were measured. Contents of osmotic solutes involved in osmotic adjustment varied with growth periods. At the early stage, they were mainly soluble sugars and inorganic cations,. especially Ca2+ and Mg2+; among them, glucose was the principal osmotic agent. At the late stage, besides soluble sugar, inorganic cations, free amino acids, especially proline, also play an important role in osmoregulation due to contents of proline and potassium increased continually under both natural and water supplemented conditions. In all growth stage, relatively higher delta C-13 can be observed in natural site of A. mongolicus rather than in irrigated ones. Variations between contents of osmotic solute and delta C-13 value under two water conditions have been revealed by multiple variable regression analysis. Variation trends of osmotic solute and delta C-13 value coincided with precipitations in 3 years. The results obtained by the present study would help understand the seasonal and annual change of osmotic solutes and adaptive mechanism to severe environment of the plant as well as strengthen the protection of this endangered evergreen species in this area. (c) 2006 SAAB. Published by Elsevier B.V.