CHAPTER III 

 ROOTS 



Development of Root Systems. — The root system of a 

 plant is the entire collection of roots. Let us trace out the 

 development of different root systems, starting with the 

 seed. If we examine soaked grains of wheat, or bean seeds, 

 or beet seeds, we observe that there is a young root already 

 formed within the seed. Three germinating stages in wheat 

 are shown in Fig. 2. The one principal root or primary 

 root we see in the grain is the first to appear. It breaks 

 through the root sheath (coleorhiza) which remains as a 

 collar about the root where it breaks through the grain coat. 

 Very soon two lateral roots appear; hence the primary root 

 system or temporary root system consists of a whorl of three 

 roots. Since these three roots were in the seed in the 

 embryonic condition they are called seminal (seed) roots. 

 The secondary roots appear in whorls at the joints on the 

 stems some distance above the three temporary roots. The 

 first whorl of permanent roots in wheat is generally about i 

 inch below the soil surface, no matter at what depth the 

 grain was planted (Fig. 3). One whorl of roots after 

 another is formed above the first one, and as a result there is 

 built up a fine network of roots, with their branches. A root 

 system such as described in wheat is called a fibrous root 

 system. 



We spoke above of the three seminal or seed roots, and the 

 development of whorls of roots from the nodes above as 

 shown in Fig. 3. Roots not arising from the seed or as 



