The growth and physiological responses of Alhagi sparsifolia to root cutting and subsequent rewatering

Alhagi sparsifolia is the dominant phreatophyte in the southern margin of the Taklimakan Desert and has become seriously degraded; however, its root system has strong regenerative ability. In this study, we investigated the regrowth and changes of leaf structural and physiological characteristics of A. sparsifolia under three root-cutting and rewatering treatments (CK, natural growth; DG, root cutting; DW, root cutting and rewatering) to elucidate the main growth and physiological responses of A. sparsifolia to these treatments. The results showed significant decreases in leaf thickness, saturated water content, and specific leaf area but significant increases in malonaldehyde content of A. sparsifolia under DG and DW treatments during the initial 3 days after root cutting (P < 0.05). All parameter changes were significantly higher than that under CK treatments at each sampling time. These results implied that the A. sparsifolia plants were subjected to obvious water stress under DG and DW treatments. There were no significant changes in leaf thickness, saturated water content, and specific leaf area under DG and DW treatments after the third day of root cutting. However, there were significant increases in leaf tissue density, dry matter content, soluble sugar, proline, and starch contents under DG and DW treatments on the third compared to that on the first day after root cutting. Although these changes were beneficial for A. sparsifolia to adapt to water stress, the reduction in leaf water content was irreversible. All of the shoots of A. sparsifolia under DG and DW treatments withered to death on the 10th day after root cutting. However, new shoots under DW treatment sprouted from the rhizomes of A. sparsifolia on the 30th day after root cutting. These findings indicated that the shoot growth and physiological traits of A. sparsifolia were severely and even irreversibly affected from the third day by root cutting. However, the rhizomes of A. sparsifolia under DW treatment could sprout again because of the rewatering treatment. Therefore, the effects of root cutting on the original aboveground growth of A. sparsifolia can likely be disregarded during future transplantation efforts.