Changes of ion absorption, distribution and essential oil components of flowering Schizonepeta tenuifolia under salt stress

Abstract

In this paper, a pot experiment using quartz sands was conducted to study the effects of different concentrations of NaCl (0, 25, 50, 75, 100 mmol·L⁻¹) on the ion absorption, distribution and essential oil components of flowering Schizonepeta tenuifolia. The results showed that as NaCl concentration increased, Na⁺ content of root, stem, leaf and flower increased significantly, and that of the aerial parts was in a higher level than in the root. Regarding the K⁺ content, it decreased in the root but increased in stem, leaf and flower. Some changes were detected in the Ca²⁺ content, but not significant on the whole. The value of K⁺/Na⁺ and Ca²⁺/Na⁺ reduced as a result of increasing NaCl concentrations. The content of essential oil increased under medium salt treatment (50 mmol·L⁻¹ NaCl). However, the synthesis and accumulation of essential oil was inhibited by the serious salt treatment (100 mmol·L⁻¹ NaCl). Over 98% of the essential oil components were terpenes, in which pulegone and menthone were the most two abundant compounds. Varieties of essential oil components did not change significantly under salt stress but their relative proportions did. The transformation of pulegone to menthone was enhanced and the value of pulegone/menthone based on their relative contents decreased with NaCl concentration increasing. Consequently, menthone ranked the most abundant compound by replacing pulegone. Relative content of D-limonene increased under medium and serious salt stress, and that of β-caryophyllene only increased under mild treatments. So our research could provide references for the standard cultivation on saline soil of S. tenuifolia.