Culm sheaths affect height growth of bamboo shoots in Fargesia yunnanensis

Abstract

Culm sheath is an important morphological characteristic of bamboos; however, its physiological functions are still unknown. The main goal of this study was to examine the physiological functions of culm sheaths and their effects on the height growth of Fargesia yunnanensis Hsueh et Yi shoots. The elongating internodes were analyzed for determining the soluble sugar and starch contents, as well as the water potential of different sections. The transpiration rates were also determined and compared between culm sheaths and foliage leaf blades. The effects of culm sheaths on the shoot height growth were also analyzed. The results showed that the outer zone had higher starch but lower soluble sugar contents than the inner zone in the developing shoots. The transpiration rate of culm sheaths was far higher than that of leaves. The water potential of the outer zone was lower than that of the inner zone in bamboo culms. The growth of bamboo culms decreased without culm sheaths. When one strip of culm sheaths was peeled off longitudinally from young culms, the bare side of the culms curved rapidly after one night, and the water potential gradient between the inner and outer zones significantly decreased, further demonstrating that sheaths have significant effects on bamboo culm height growth.