了解干旱和盐胁迫下不同光合类型荒漠植物的响应特征,对预测气候变化下干旱区荒漠生态系统的植被组成和功能具有重要理论意义。碳氮稳定同位素组成能够指示植物对环境胁迫的响应和适应,可以作为许多植物生理整合过程的代用指标,以此分析不同水分和NaCl处理下新疆荒漠优势种C3植物长穗柽柳(Tamarix elongata Ledeb)和C_4植物梭梭[Haloxylon ammodendron (C. A. Mey. ) Bunge]一年生幼苗碳氮同位素组成的变化特征。结果表明:①梭梭和长穗柽柳叶片稳定性碳同位素组成(delta~(13)C)与盐度呈正相关关系;干旱处理下长穗柽柳的delta~(13)C值随水分的降低显著增大,而梭梭的变化不显著。2种植物的稳定氮同位素组成(delta~(15)N)与盐度呈负相关关系;干旱胁迫下,两者delta~(15)N值均显著减小。②随着处理时间的延长,梭梭delta~(13)C值减小而长穗柽柳delta~(13)C值增大;梭梭~(15)N含量增加而长穗柽柳~(15)N含量减少。③梭梭和长穗柽柳的delta~(13)C值与其他生理指标显著相关,表明delta~(13)C值对植物受环境胁迫的程度有较好的指示作用。
英文摘要:
Water is a primary factor affecting plant growth and reproduction in arid and semiarid regions. With the intensification of global climate change,precipitation pattern ( amount and timing) is likely to be altered,and it is predicted that both the frequency and intensity of drought events are increased. Water deficit and salinization usually occur together, which have been observed not only in farmland ecosystems but also in natural ecosystems. Salinization and migration of soil salts are likely to be influenced by the change of precipitation regime. Heat, drought and/or high salinity may alter C3 and C4 plants differently and change their proportions in vegetation composition. Therefore, it is of an important theoretical significance for predicting the vegetation composition and ecosystem function in future climate change to understand the plant photosynthetic type differences in response features,water adaptive strategies and resistance mechanisms to drought and salinity stress. In this study, we measured the carbon and nitrogen isotopic compositions under different water and NaCl treatments in the saplings of two dominant woody species in west China, C3 plant Tamarix elongata Ledeb and C4 plant Haoxylon ammodendron ( C. A. Mey. ) Bunge. The results are as follows :① For the two studied plant species,there were the positive correlations between carbon isotopic composition (delta~(13)C) and salinity. Drought stress induced an increase of delta~(13)C values in leaves of T. elongate,but had no significant effects on delta~(13)C in leaves of H. ammodendron. Low nitrogen isotopic composition ( delta~(15)N) values were detected under salinity and drought stress:② delta~(13)C and delta~(15)N values were influenced by the duration of salinity and drought stress, the delta~(13)C values in leaves of H. ammodendron were reduced over time, but those in leaves of T. elongata were increased. With the extension of stress time,15 N was enriched in leaves of H. ammodendron but depleted in leaves of T. elongata. These results suggested that H. ammodendron adapted the environment change quicker than T. elongate;③ There were the significant correlations between delta~(13)C values and other physiological parameters (such as leaf water potential,chlorophyll content,g_s ,T,C: N and Na/K) . Therefore,delta~(13)C values could be used as a robust indicator of the intensity of drought and salinity stress.