Root is the part of the plant that remains inside the ground and anchors the plant while beneath the soil. It is the descending part of the plant. The main function of the root is to absorb water and minerals from the soil, and then the water and minerals are conducted to different parts of the plant through the xylem of the plant. It is the non-green part of the plant and does not bear nodes, internodes, leaves or buds. Roots can be of mainly two types—taproot and fibrous root. Absorption, conduction, storage and anchorage are the main functions of the root.
Root Absorption Pathways
Root hairs present on the tip of the roots absorb water and other minerals through the process called diffusion. Let’s learn more about the root water absorption pathway and the meaning of root absorption pathways.
➨ Once the root hairs take up the water, they need to pass it further down into deep root layers by two distinct pathways:
- Apoplast Pathway
- Symplast Pathway
Apoplast Pathway:
➨Apoplast refers to the non-protoplasmic components of a plant, including the cell wall and the intracellular spaces. This pathway does not provide any restrictions to water movement, as water movement is through a mass flow system. In apoplast, the water movement occurs by passive diffusion.
➨ Mass flow of water arises due to the cohesive and adhesive properties of water.
Symplast Pathway:
➨ Symplast refers to the continuous arrangement of protoplasts of a plant, which are interconnected by plasmodesmata. In symplast, the water movement occurs by osmosis.
➨ Surrounding cells are connected through cytoplasmic strands, which extend through plasmodesmata.
➨ In this type of pathway, the water has to travel through the cell membrane, and thus, the movement is relatively slower and down the potential gradient as usual.
➨ Symplastic movements are aided by cytoplasmic streaming also.
Note:
- Majorly, the flow of water in roots occurs via apoplast as the cortical cells are loosely packed and thus offer no barrier to water movement.
- Water movement through root layers is ultimately symplastic in the endodermis.
Root pressure:
➨ Root Pressure can only provide a moderate push in the overall process of water transport, and also, they do not play any major role in water movement up tall trees.
➨ The main work of the root pressure is to re-establish the chains of water molecules in the xylem, which frequently gets broken under tremendous pressure created by the process called, Transpiration.
➨ It is not responsible for the majority of the water transport, as most of the plants meet their requirement through transpiration pull.
Guttation
➨ We get to observe the effect of root pressure in the early morning or at night, when the rate of evaporation is pretty low.
➨ Excess water gets collected in the form of small droplets over openings of veins near the tip of grass blades and leaves of many herbaceous parts of the plant. Such loss of water in the liquid phase is known as Guttation.
Conclusion
Root is the underground part of the plant that helps in the absorption of water, nutrients and minerals from the soil. Absorption, conduction, storage and anchorage are the main functions of the root. There are four main regions present in the root: the region of maturation, the region of elongation, the region of cell division and the root cap. The root cap is also known as calyptra. It acts as the covering of the apical part of the root. The root cap is produced by the apical Meristem and is a multi-layer cup-shaped structure present in the roots of almost all crop plants. It represents the region that faces potential damage and friction from the particles present in the soil. The main function of the root cap is to enable the growth of the root in a downward direction (with gravity). It protects the delicate stem cells which are present inside the root tip. It also plays an important role in receiving and transmitting environmental signals to the root system.