Anatomical structure of Camellia oleifera shell
Received: 4 January 2018 /Accepted: 28 May 2018
Springer-Verlag GmbH Austria, part of Springer Nature 2018
The main product of Camellia oleifera is edible oil made from the seeds, but huge quantities of agro-waste are produced in
the form of shells. The primary components of C. oleifera fruit shell are cellulose, hemicellulose, and lignin, which
probably make it a good eco-friendly non-wood material. Understanding the structure of the shell is however a prerequisite
to making full use of it. The anatomical structure of C. oleifera fruit shells was investigated from macroscopic to ultra-
structural scale by stereoscopic, optical, and scanning electron microscopy. The main cell morphology in the different parts
of the shell was observed and measured using the tissue segregation method. The density of the cross section of the shell was
also obtained using an X-ray CT scanner to check the change in texture. The C. oleifera fruit pericarp was made up of
exocarp, mesocarp, and endocarp. The main types of exocarp cells were stone cells, spiral vessels, and parenchyma cells.
The mesocarp accounted for most of the shell and consisted of parenchyma, tracheids, and some stone cells. The endocarp
was basically made up of cells with a thickened cell wall that were modified tracheid or parenchyma cells with secondary
wall thickening. The most important ultrastructure in these cells was the pits in the cell wall of stone and vessel cells that
give the shell a conducting, mechanical, and protective role. The density of the shell gradually decreased from exocarp to
endocarp. Tracheid cells are one of the main cell types in the shell, but their low slenderness (length to width) ratio makes
them unsuitable for the manufacture of paper. Further research should be conducted on composite shell-plastic panels (or
other reinforced materials) to make better use of this agro-waste.
Keywords Camellia oleifera shell
Camellia oleifera is a subtropical evergreen dunga-runga or
shrub widely distributed and grown in the middle and south-
ern provinces of China, including Hunan, Jiangxi, and
Guangxi. The current annual production of C. oleifera in
China is approximately 4 × 10
(Shen and Jiang 2006).
The main product of C. oleifera is the high-quality edible oil
extracted from the seeds, but a considerable amount of
byproducts including the shells remains, which account for
50–60% of total yield. The shells are mostly discarded or
underutilized and may even become a burden to the environ-
ment (Hu et al. 2015).
The primary chemical components of C. oleifera fruit
shells are cellulose, hemicellulose, and lignin, i.e., the same
major constituents as wood (Peng et al. 2016). In the past few
years, uses have been found for the fruit shells including tan-
nin, xylitol, and furfural extraction (Yoshida et al. 1994; Lee et
al. 2007; Zhang et al. 2017) as well as the production of
activated carbon, potassium carbonate, and deodorizer
(Siddiqui et al. 2007). Moreover, some components of the fruit
shells were discovered to be bioactive, including antitumor
and antioxidant activities of polysaccharides and free scaveng-
ing activities of biflavonoids (Jin 2012;Yeetal.2012).
Recently, the biological degradation of shells under the attack
of fungi and termites has also been investigated (Hu et al.
Jinbo Hu and Shanshan Chang contributed equally to this work.
Handling Editor: David McCurdy
* Shanshan Chang
College of Materials Science and Engineering, Central South
University of Forestry and Technology, Changsha 410004, China
Hunan Provincial Collaborative Innovation Center for
High-efficiency Utilization of Wood and Bamboo Resources, Central
South University of Forestry and Technology, Changsha 410004,
Chinese National Engineering Research Center for Oiltea Camellia,
Changsha 410004, China