Tunica corpus theory is a theory of plant development that explains how the shoot apical meristem (SAM) produces the various organs of the shoot. The theory was proposed by Ernst Münch in 1930 and was later elaborated on by other plant biologists.

Explanation:
The shoot apical meristem (SAM) is a group of undifferentiated cells located at the tip of the shoot. These cells divide and differentiate to produce the various organs of the shoot, such as leaves, stems, and flowers. The Tunica Corpus theory explains how this process occurs.

The theory is based on two distinct regions in the SAM: the tunica and the corpus. The tunica is a layer of cells that surrounds the SAM, while the corpus is the central region of the SAM. The tunica is further divided into three layers, known as L1, L2, and L3.

According to the Tunica Corpus theory, the L1 and L2 layers of the tunica produce the outermost layers of the shoot, such as the epidermis and the cortex. These layers are responsible for protecting the shoot from external damage and regulating water and nutrient uptake. The L3 layer of the tunica produces the cells that will eventually form the SAM itself.

The corpus, on the other hand, is responsible for producing the internal tissues of the shoot, such as the vascular tissues and the pith. These tissues are responsible for transporting water, nutrients, and other essential substances throughout the plant.

The Tunica Corpus theory explains how the SAM produces the various organs of the shoot by dividing and differentiating the cells in these two regions. As the cells divide and differentiate, they form the different types of tissues that make up the shoot.

In conclusion, Tunica corpus theory is a theory of plant development that explains how the shoot apical meristem produces the various organs of the shoot. The theory is based on two distinct regions in the SAM: the tunica and the corpus, which are responsible for producing the outer and inner tissues of the shoot, respectively.