Physiological Mechanism of Internode Bending Growth After the Excision of Shoot Sheath in Fargesia yunnanensis and Its Implications for Understanding the Rapid Growth of Bamboos

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.