Photosynthesis, Phytohormone Signaling and Sugar Catabolism in the Culm Sheaths of Phyllostachys edulis

Abstract

Culm sheaths play an important role in supporting and protecting bamboo shoots during the growth and development period. The physiological and molecular functions of bamboo sheaths during the growth of bamboo shoots remain unclear. In this study, we investigated the morphological anatomy of culm sheaths, photosynthesis in sheath blades, storage and distribution of sugars, and the transcriptome of the sheath. Respiration in the base of the culm sheath was higher than that in the sheath blades; chloroplasts matured with the development of the sheath blades, the fluorescence efficiency Fv/Fm value increased from 0.3 to 0.82; and sucrose and hexose accumulated in the sheath blade and the culm sheath. The sucrose, glucose, and fructose contents of the middle sheath blades were 10.66, 5.73, and 8.84 mg/g FW, respectively. Starches accumulated in parenchymal cells close to vascular bundles. Genes related to the plant hormone signaling pathway and sugar catabolism were highly expressed in the culm sheath base. These findings provide a research basis for further understanding the possible role of bamboo sheaths in the growth and development of bamboo shoots.

Emerging Insights into the Roles of the Rhizome–Culm System in Bamboo Shoot Development through Analysis of Non-Structural Carbohydrate Changes

“…The functions of bamboo sheaths have received increasing attention in recent years. Some researchers believe that sheaths not only play the role of protecting, supporting, and providing a suitable environment for the growth of bamboo shoots but also participate in water, carbon metabolism, and even photosynthesis [ 6 , 7 , 8 ]. Bamboo sheaths had complete photosynthetic system genes, and the photosynthetic capacity of sheath blades was improved with their development.…”

“…Since underground shoot buds were unable to photosynthesise, NSCs were transported from the bud itself through the vascular bundles to the sheaths and stored in them [ 7 , 49 ]. Some studies have shown that starch granules were also present in the sheaths during the elongation growth [ 6 ], and the starch granules at this time may originate from their own photosynthesis or may be transported to the sheaths together with water from parent bamboo, which is still a mystery and still needs to be further researched.…”

“…Non-structural carbohydrates (NSCs), as direct products of photosynthesis, including soluble sugars and starch, are involved in plant metabolism and impact growth rhythms [ 5 ]. Some studies have pointed out that shoot sheaths have the potential for photosynthesis because of the complete photosynthesis-related genes and a large number of chloroplasts [ 6 , 7 , 8 ]. Chen et al indicated that the shoot sheaths of Bambusa multiplex can even provide about 40% of the energy for the growth of bamboo shoots [ 9 ].…”