What is lignin in plants? (And its distribution )

1. what is lignin in plants

•  Lignin is a natural plant substance that is widely present in various plants.

In plants, a large amount of lignin is produced annually through photosynthesis.

•  lignin function：

In natural plants, lignin is like an adhesive, distributed around the fibers and between the small fibers inside the fibers, making it a strong skeletal structure.

The reason why trees can stand erect for tens or even hundreds of meters without falling is because of the adhesive force of lignin.

2. Distribution of lignin in nature
 

•  In natural surroundings, lignin exists in various seed plants

•  It is generally believed that lignin is not present in algae plants.

• There is currently doubt about whether moss plants possess lignin.

•  Lignin is also commonly present in soil and sediments of rivers, lakes, and seas, and even in some natural water bodies.

After plant death and decomposition, lignin will be washed into rivers, lakes, and seas.

The special structure of lignin gives it high chemical stability and the ability to resist microbial degradation. When dead plants, leaves or fruits fall into the soil and rot, lignin remains in the soil. After being washed by rainwater or flowing water, it becomes an organic component in the sediment of rivers, lakes, and seas.

Lignin in sediments is a good biomarker for terrestrial organic matter in marine environments, and its application in marine biology and geochemistry has high scientific value.

3.Different plant species and genera result in differences in lignin content

•  Lignin with different structures and molecular weights exists in the roots, stems, leaves, skins, fruit shells, and seeds of mature plants.

•  The more mature a plant is, the higher its lignin content.

The chemical composition of plants varies greatly depending on their genus, and there are differences in lignin content among different genera of trees.

Lignin content in different plants:

Gymnosperms ＞  Coniferous wood ＞  Broad-leaf wood  = Gramineae plants

 such as:

① Gymnosperms

Gymnosperms have a higher lignin content than angiosperms, and tropical wood has a slightly higher lignin content than temperate wood.

② Coniferous wood

Coniferous wood has a slightly higher lignin content than broad-leaf wood.

③ Broad-leaf wood

The average lignin content of broad leaf wood is 21%.

Quaking aspen:16%,  American elm:24%,  White birch:19% , Yellow birch:21% , Sugar maple:24%

while the average lignin content of coniferous wood is 29%.

Balsam fir:29%,  Chinese arborvitae：31% ,    Canadian hemlock：33%,     Jack pine ：29%,   White spruce:27%,   Tamarack:29%

④ Gramineae plants

Bamboo in the Gramineae family has a lignin content that is similar to that of broad leaf wood:

Anhui Lu bamboo:19%,     Sichuan Xifeng bamboo:23% ,   Sichuan Yellow bamboo:24%

And similar to that of coniferous wood:

Fujian Mao bamboo:31%,    Sichuan sinocalamus affinis:31%,     Jiangsu henon bamboo：33%

The lignin content of other Gramineae plant is similar to that of broad leaf wood :

Wheat straw stem:22%，Reed: 20%，Miscanthus:20%，Miscanthus sacchariflorus：19%，Sugarcane:20%，Chinese alpine rush:14% ，Achnatherum splendens:17%，Corn stalk:18%，Sorghum stem:23%.

4. Differences existing in different parts for the same plant

For example, the lignin content in the trunk, branches, phloem, and outer bark of spruce trees is 28%, 34%, 16%, and 27%, respectively;

The lignin content of rice straw stems is only 12%, while the lignin content of panicles, nodes, leaves, and leaf sheaths is as high as 33%, 27%, 30%, and 30%.

5.  The correlation between lignin content and climate and dimension is not significant for the same plant.

The differences in lignin content between populations are very small.

The differences in lignin content are not closely related to the latitude, longitude, frost free period, annual average temperature, and annual rainfall of the source, and are not related to the diameter at breast height and ring width.