Bamboo, tall and straight, has no gorgeous posture, but looks like a painter, but has the ambition of Lingyun. It has become a symbol of many beautiful things in China people's aesthetic habits and occupies an important position in people's minds. But from the perspective of a bamboo researcher, many excellent qualities of bamboo are closely related to its unique internal structure, which is still beautiful. The beauty of bamboo is unique, both inside and outside.

Bamboo is widely used because of its various excellent qualities. It has high strength, good elasticity, stable performance and low density, so it is used in building and furniture manufacturing. It is rich in fiber components, so it is used in the paper industry. It is green and tall, evergreen all the year round, so it is used for greening landscape and garden construction. It grows rapidly and has important applications in environmental protection and ecological restoration. It is delicious and nutritious, so it is deeply loved by people. These qualities are related to the microstructure of bamboo, which is determined by the type, size, shape and arrangement of cells and the structure and composition of cell walls.

Therefore, as a researcher of bamboo microstructure, I not only like the external beauty of bamboo, appreciate their good temperament, but also appreciate their internal beauty.

The research history of 1 is not long.

Compared with the cultivation and utilization history of bamboo for thousands of years, the history of in-depth research on the internal structure of bamboo is less than 50 years. Microscopic anatomy of bamboo belongs to the scope of wood anatomy. In order to make better use of wood, it is necessary to carry out various microscopic anatomical studies on wood. Only by understanding the microstructure of all kinds of wood in detail can we turn the experience gained in practice into quantifiable scientific indicators. At present, some large wood processing plants in the world have their own micro-anatomy research institutions.

Like wood utilization, in order to make better use of bamboo, it is necessary to conduct various anatomical studies on the microstructure of bamboo. In the research field of bamboo anatomical structure, Professor Li from Peking University and Professor W. Liese from Hamburg University have made the greatest contributions.

In the early 1960s, in order to better study the properties of various bamboo materials, Professor Li invented the steam slicing method. That is, the collected bamboo samples are boiled for a period of time, then sliced and blown with steam to soften the bamboo. This method overcomes the difficulty of bamboo being hard and difficult to make, and lays a foundation for the microscopic study of bamboo in the future. Professor Li studied the anatomical structure of 25 bamboo species in China and compiled the first classified key table based on anatomical characteristics in China.

Later, in 1970s and 1980s, Professor W. Liese studied and analyzed the unique vascular bundle structure in 52 species of bamboos belonging to Asia 14 genus, and compared the differences of this structure between different heights of the same bamboo and individuals of the same bamboo. The ultrastructure of bamboo fiber cell wall was observed by scanning electron microscope and transmission electron microscope, and the structure model of bamboo fiber cell wall was put forward.

Why does bamboo grow so fast?

There is a very interesting phenomenon in the growth of bamboo, that is, there are as many knots as there are on the ground. How thick bamboo shoots are, how thick bamboo grows. This strange phenomenon is determined by the unique microstructure of bamboo.

Bamboo shoots are developed from the buds of underground bamboo stems, and the shell that wraps bamboo shoots layer by layer is called tuo. The top of the internal structure of bamboo shoots is called apical meristem. At the place where the leaves come out, the apical meristem cells divide and differentiate to form nodes, which are the bamboo nodes after the bamboo grows. Nodes divide meristem into several nodes from bottom to top, and each node is a node. Growing up between nodes is a section of bamboo we see. In tender bamboo shoots, the internodes are very short, and the whole internode is a kind of cell, which we call mesophyll. Metameristem plays a decisive role in the growth of bamboo.

After bamboo shoots grow out of the ground, the cells that formed nodes earlier will stop dividing and differentiating, so there will be no new nodes. Therefore, as many knots as there are in bamboo shoots, there are as many knots as there are in grown bamboo. Since then, the growth of bamboo is the result of the activity of "mesophyll". The cells of this tissue have a characteristic that they can only divide along the long axis of bamboo stems, and the expansion and elongation of cells are also carried out along the long axis of bamboo stems. If you can't increase the number and width of cells in the horizontal direction, you can't increase the thickness of bamboo stems, so bamboo shoots can only grow as thick as before. In the same bamboo shoot, the "mesophyll" of each node grows at the same time, so macroscopically, it shows the rapid growth of bamboo shoots. Most kinds of bamboo shoots can grow 8- 15cm a day on average, and can grow 1m day and night when they grow fastest.

Bamboo shoots are delicious and nutritious because the cell walls of various cells of bamboo shoots are not lignified and are rich in cellulose, hemicellulose and pectin. In addition, the basic tissue cells of bamboo shoots contain a lot of starch polysaccharides. When the bamboo shoots grow into new bamboos and the cell walls are lignified, the bamboo becomes hard and flexible and can't be eaten any more.

For bamboo, the period when bamboo shoots have just become new bamboo is the most dangerous period in their lives. At this time, bamboo has grown very tall, but the mechanical tissue in the body is not fully developed, especially at the node, which is the place where the intercalated meristem stops moving at the latest, and it is easy to break under the condition of external damage (wind, human or animal invasion, etc.). ). And this period is also a period when bamboo is very sensitive to pests and diseases and bad environmental conditions. Therefore, the Bamboo Farmers Association has given more careful care to the bamboo garden.

When is bamboo the hardest?

Most kinds of bamboos will stop growing rapidly after one year of growth, the height will not increase, and the internal structure has basically developed. Polarization microscope observation showed that the cell walls of basic tissues and cells had thickened, and the lignification process was basically completed.

Although the internal structure of three-year-old and seven-year-old bamboos is basically the same as that of one-year-old bamboos, through careful observation of the microstructure, scientists found that with the increase of bamboo age, the cell wall of bamboos is still further thickened, showing a multi-layer structure. The research by Professor W. Liese and others shows that even after 12 years of growth, the thickness, layers and lignification degree of bamboo cell wall are still increasing.

The thickness, layers and lignification degree of bamboo cell wall directly affect the quality of bamboo. Therefore, the age of bamboo is closely related to its mechanical strength. Generally speaking, the mechanical strength of bamboo increases with the increase of bamboo age, but when bamboo ages, especially after flowering, the strength will decrease rapidly, and the material will become brittle and easily broken.

In the south of China, bamboo farmers often use their own marker to mark the year of birth on each bamboo, and then cut down 4-6-year-old bamboos. Although the age of bamboo can be estimated according to its color, texture and other characteristics, the quality of bamboo can be guaranteed by accurately recording the age of each bamboo stem and cutting it on time. Because after 4-6 years of bamboo, although the cell wall will thicken and lignification will continue, the mechanical strength of bamboo has basically reached a stable value, and then the improvement of strength is very limited. If we wait for these years, it will not be cost-effective for bamboo farmers.

Why is bamboo hard and elastic?

Among all plants, bamboo is one of the best raw materials for structural materials. It is light and hard, with thick and hollow skin and strong bending tension, which fully shows the mechanical beauty of nature. Compared with wood or even ordinary steel, it is superior in strength and rigidity, and can be widely used in construction engineering. For example, bamboo scaffolding is more resistant to hurricanes than steel scaffolding. The microstructure determines the macroscopic properties, and the mechanical properties of bamboo are also determined by its microstructure.

Bamboo is mainly composed of vascular bundles that play a bearing role and basic tissue cell matrix that plays a connecting role and transmits loads. On the same cross section of bamboo wall, the changes of the shape, size and density of bamboo stem vascular bundles show obvious regularity. From the outside to the inside, the volume of vascular bundle increases from small to large, and then changes slightly when it approaches bamboo yellow (the innermost wall of bamboo). The density changes from dense to sparse, and it is slightly dense near the bamboo yellow surface. The hard surface layer system (bamboo green) composed of epidermis and hypodermis and the pith ring (bamboo yellow) composed of multiple layers of stone cells constitute the inner and outer sandwich walls of bamboo, which tightly sandwich vascular bundles and basic tissues, and play a very good role in stabilizing the properties of bamboo. This is why bamboo is hard.

The cell wall of bamboo fiber is very different. It has multi-layer uneven thickened secondary wall, forming a multi-layer structure with alternating width. This layered structure is of great significance to the bending strength of bamboo. In addition, the structure that the density of vascular bundles and fibers in bamboo poles gradually increases from the inside out is also the best adaptation to the bending load of wind. This is the secret of bamboo flexibility.

However, bamboo also has its disadvantages. For example, the content of starch, reducing sugar and protein in bamboo is more than that in wood, which makes bamboo and its products prone to mildew during storage, transportation, processing and use, affecting its quality and reducing or even completely losing its use value. In order to prevent it from mildew, bacterial rot and moth-eaten, after bamboo is harvested and processed, necessary physical methods such as cooking, drying and chemical reagent treatment must be carried out.

Bamboo has conquered people's hearts with its beautiful eyebrows and straight appearance, and its diverse uses have been loved by people. With the development of science and technology, the secret of bamboo microstructure is being revealed day by day. In the laboratory, under the microscope, life scientists showed a little-known side of bamboo, which made everyone see its other beauty and gave it more meaning.