Unlike some other flower stems
The root of sunflower is composed of main root, lateral root and fibrous root. The taproot is deeper into the soil, and generally grows about 0.3-1.2 meters deep in the soil. The US Department of Agriculture has measured that there was a sunflower root that was 1.5 meters long. Lateral roots grow from the main root and grow horizontally; there are many fibrous roots on the lateral roots. The lateral roots and fibrous roots have root hairs.
The main root grows vertically downwards and connects to the smaller lateral roots and fibrous roots, which helps the structure support the sunflower's weight. The tap root is the main root of sunflower, receiving most of the nutrients and water obtained by the plant. Sunflower roots are well-developed and widely distributed in the soil. About 60% of the roots are distributed in the 0-40 cm soil layer. The growth rate of sunflower roots has always been faster than that of stems. The roots grow fastest before and after the flower disc is formed. When the seeds begin to mature, the roots no longer grow and gradually wither. In addition, a large number of water roots (aerial roots like corn) can grow under suitable conditions. 
Unlike some other flower stems, sunflower stems cannot stretch out to support other flowers, but stems support a flower. The stalk can grow to 3-5 meters. Sunflowers have a dicotyledonous stem structure with round and upright stems, rough surface and bristles. The stem is composed of cortex, xylem and spongy pith, and provides nutrients and water to the plant through all stages of its growth and life cycle. The outer layer is called the epidermis, which protects the stem. In the later stage of growth, the stem is lignified, and the pith in the stem forms a multi-layer hollow. The embryo stems of sunflowers are green, lavender, deep purple, etc., which are important indicators for identifying varieties at the seedling stage. The height of the stem varies greatly between different types of varieties. The height of the same variety is affected by the sowing date and cultivation conditions. The growth rate of the stems is the fastest from budding to flowering. At this time, the growth height accounts for about 55% of the total height. Later, the growth rate slows down to only about 5%. The branching of sunflowers is determined by heredity and the latter is caused by environmental conditions. [6