Abstract
The physiological function of bamboo shoot sheaths is still unclear. In the present study, we investigated the anatomical and physiological influences of bamboo shoot sheaths on internode elongation by longitudinally striping parts of sheaths. The internodes would bend toward the bare sides during night. The results showed that amounts of water leaked at the cut of shoot sheaths during night, which impeded the increase of water, water pressure and assimilate transport rates, and decreased starch and soluble sugar catabolism in the bare side of the internodes. A higher level of water pressure and sugar metabolism increased the vacuole expansion and promoted the cell expansion in the outer sides as compared to the bare sides. The bending growth of internodes was mainly due to the significant differences in cell expansion, which was led by the difference in water pressure and sugar hydrolysis levels between the inner and outer sides. Bamboo internode elongation mainly relied on the increase of water pressure and soluble sugar concentration. Shoot sheaths played an important role in the rapid growth of bamboo shoots as a controller in water and assimilate transportation. This study gave a new insight into understanding the rapid growth mechanism of bamboo plants.
Highlights
Bamboo plants are the fastest growing plants worldwide, and their culms can complete their height growth in one growing season (Panda, 2011)
We have reported that culm sheaths and sheath blades were the main transpiration and respiration organs for bamboo shoots and young elongating culms; their transpiration rate and the stomatal conductance of culm sheaths were significantly higher than those of foliage leaf blades (Wang et al, 2018), but their physiological functions are still not very clear
When a strip of culm sheath was peeled off instead of a black plastic film enclosing the bare internodes, it would still bend during the night. This phenomenon implied that the internode bending growth is unrelated to the changes of light or temperature
Summary
Bamboo plants are the fastest growing plants worldwide, and their culms can complete their height growth in one growing season (Panda, 2011). The mechanism underlying the rapid growth of bamboo shoots is a hot research topic. The anatomical and physiological characteristics of young shoots during their rapid growth have been neglected. Bamboo shoot sheaths are one important morphological characteristic in systematic bamboo classification (Janzen, 1976). They are green or some other color but are usually persistent to a Internode Bending Growth of Fargesia yunnanensis certain degree even after turning brown, and enclose the bamboo internodes for some time (Wong, 2004). Most studies have focused on their mechanical functions, but few on the physiological functions. Wong (2004) considered that shoot sheaths play an important role in protecting the tender lower part of a bamboo internode. Other studies showed that sheaths could avoid possible damage by providing crucial stiffness (Niklas, 1990, 1998; Zebrowski, 1992)
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