Monocot vs Dicot Roots
Root is one of the significant structures of a sporophyte of a vascular plant. It is the underground part of a plant, which has an important role in plant life. Absorbing nutrients, anchoring to the soil or another plant surface (i.e. epiphytes), storing of foods are some of the main functions of a root. The roots are attached to the stem through special regions called hypocotyl. Roots have two growth phases, namely primary and secondary growth. Roots have gravitropism ranging from positive gravitropism to diagravitropism with negative phototropism. Both these types of roots have commonly vascular tissues, pericycle, endodermis and cortex from the centre to the outside of the root respectively. Roots have distinctive regions such as maturation, elongation, cell division region and root cap.
Monocot roots are hair like adventitious roots, which lacks the tap root. The radical of the monocots is replaced by the adventitious roots at early stages. Monocot roots have pith in the centre. In monocot, secondary growth is absent, making young and older plants similar. Roots have three distinct regions namely, epidermis, cortex and vascular bundle.
Epidermis is the outmost layer, which consist of parenchymatic cells. Root hairs begin in this layer, and they are unicellular. Cortex, which is much thicker comparing to dicot cortex, is also made up of parenchymatic cells and barrel shaped cells. Outmost cortex consists of loosely arranged parenchymatic cells and inner most layer of cortex, which is called endodermis, is made up of barrel shaped cells. Inner to endodermis there is pericycle. Lateral roots begin from the pericycle. Vascular tissues, phloem, and xylem are arranged alternatively as a ring.
Dicot roots have two growth phases as primary growth phase and secondary growth phase. When a seed grows, the radical becomes the tap root combined with lateral roots. Epidermis, endodermis and cortex also present in dicot roots, which have the same function and structure. However, xylem and phloem are separated by conjunctive parenchyma, which later becomes the vascular tissue. Pith is reduced or absent in dicot roots. From the cells of pericycle and conjunctive tissues, cork cambium and vascular cambium originate in the secondary growth phase of a dicot root.
Vascular cambium arises between the xylem and phloem, and forms cells inside and outside from the cambium. Cells, which grow inside of the cambium, form the secondary xylem and cells formed outside of the plant form secondary phloem increasing the girth of the root. With the pressure of that, cork cambium forms the periderm.
What is the difference between Dicot Roots and Monocot Roots?
• Dicot roots have tap roots with lateral roots, whereas monocot root has adventitious root system, lacking a tap root.
• Monocot roots do not have secondary growth, while dicot roots have two growth phases.
• In secondary growth dicot roots have vascular cambium and cork cambium, which originate from the cells of pericycle and conjunctive tissues, whereas monocot roots lack those.
• Monocot roots have significant pith in the centre, but dicot either have very small pith compared to the monocot pith or lacks the pith.
• Because of the growth of vascular cambium, girth of the root increases, but the lateral dimension of the monocot root does not increase.