Study on the cause of peeling and withering in Isodon rubescens stems in winter

Abstract

Objectives: The living stems of Isodon rubescens (Hemsley) H. Hara peels and withers when the air temperature is below 0 °C in winter. The peels and withers evidently hamper the growth of I. rubescens. This report analyses the reason that causes I. rubescens stems to peel and wither in winter. Methods: The field investigation and paraffin sections of I. rubescens stems (peeled and intact) were performed. Results: The results showed that I. rubescens stems extruded ice ribbons at air temperature below 0 °C. The enlarged ice ribbons separated the phloem from the xylem, burst the phloem and even the whole bark of the I. rubescens stems. Conclusions: The phloem was separated from the xylem by the enlarged ice ribbons. The phloem and the whole bark of the I. rubescens stems were torn when ice ribbons appeared. The damaged stem could not transport water and nutrition to the upper section. The upper stem above the ice ribbons withered because it could not receives water and nutrition.

Keywords

• Isodon rubescens
• Stem
• Ice ribbons
• Peel
• Wither