Na compound fertilizer promotes growth and enhances drought resistance of the succulent xerophyte Haloxylon ammodendron

Abstract

Haloxylon ammodendron (C. A. Mey.), a C4 perennial woody species native to the desert areas of northwest China, is a succulent xerophyte belonging to Chenopodiaceae (Haloxylon) with excellent adaptability to adverse arid environments. Our previous investigations showed that sodium (Na+) has a positive effect on the growth of Zygophyllum xanthoxylum under drought conditions, which was closely related to high Na+ accumulation in leaves. To reveal the effects of Na compound fertilizer on the growth and drought resistance of Haloxylon ammodendron and its ecological environment, plants were treated with Diammonium phosphate and Na compound fertilizer and then were subjected to water deficit (30% of field water capacity) in pot and field culture experiments (Apri1 to September 2008). One-year-old plants were transplanted to a desert habitat in Apri1 2009 and harvested in September 2009. The results (take the pot culture experiment, for example) indicate that Na compound fertilizer could significantly mitigate deleterious impacts of drought stress on the growth of Haloxylon ammodendron. The fertilizer encourages plant height, crown diameter, main root length and biomass and raises survival rate of transplanting and, concomitantly, accumulates a higher concentration of Na+ than potassium (K+) in the photosynthesizing stems for osmotic adjustment. The contribution of Na+ to the osmotic potential (compared with the control) varied from 14% in plants subjected to diammonium phosphate and, surprisingly, to 95% in plants grown in the presence of Na compound fertilizer under water deficit (April 2008 to September, 2009). Furthermore, the distribution characteristics of the total Na+ (1296 mg) in the Na compound fertilizer showed that 756 mg (58%) is absorbed by plants, 344 mg (27%) remained in the pot and 184 mg (15%) leached, which accounted for 6.2% of the nursery soil, respectively (April 2008 to September 2009). The positive effect of Na compound fertilizer on the growth and drought resistance of Haloxylon ammodendron and ecological environment were also confirmed in field culture experiments (April 2008 to September 2009). These findings suggest that Na compound fertilizer popularization and application can be one of the most effective strategies to restore and reconstruct degraded vegetation in many arid and semi-arid areas.