The difference between root and stem is due to the following properties:
Origination: Roots originate from the radicle through the germination of seed, whereas shoots originate from the plumule of the developing embryo.
Arrangement of vascular bundles: In roots, the vascular bundles reside within the central core, while shoots have dispersed vascular bundles.
Presence of nodes: Nodes are the growing units of the stem, which a root system lacks.
Apart from many differences, roots and stems are the structures that share some similarities like:
The occurrence of vascular tissues: Both root and stem possess vascular tissues, i.e. xylem and phloem.
Branching: Both can initiate lateral growth to form branches.
Content: Root Vs Stem
|Definition||Root requisites in a plant’s root system that usually grows downwards the plant axis and bears lateral rootlets, root hairs and a root cap.||Stem requisites in a plant’s shoot system that grows aerially or upwards and bears lateral stems, stem hairs, leaves, buds, flowers etc.|
|Part of||Root system||Shoot system|
|Geotropism||Shows positive geotropism||Shows negative geotropism|
|Phototropism||Shows negative phototropism||Shows positive phototropism|
|Hydrotropism||Shows positive hydrotropism||Shows negative hydrotropism|
|Origination||Originates from radicle||Originates from plumule|
|Presence of leaves||Absent||Present|
|Presence of buds||Absent||Present|
|Presence of flowers and fruits||Absent||Present|
|Presence of nodes and internodes||Absent||Present|
|Presence of hairs||Root comprises of unicellular root hairs||Stem comprises of multicellular stem hairs|
|Existence of cap-like structure||Root consists of a cap-like structure refers as root cap||It lacks such kind of structure|
|Branches||Root branches are endogenous||Stem branches are exogenous|
|Colour||Non-green||It is generally green coloured, during its young stage|
|Stomata||Absent||Present usually in the epidermis|
|Epidermis||Absorptive in function||Protective in function|
|Sclerenchymatous hypodermis||Absent||Present below the epidermis|
|Chloroplast||Invariably absent||It may contain in the outer cells of ground tissue|
|Pericycle||It is usually 1-2 layered, which participates in the root formation and secondary growth||It is multi layered, which does not participate in the secondary growth|
|Vascular bundles||Radial arrangement||Conjoint and collateral arrangement|
|Secondary vascular growth||Mediated by conjunctive parenchyma and pericycle||Mediated by intra or inter fascicular cambium|
|Fibers||Absent||Xylem and phloem contain fibers|
|Functions||Helps in anchorage of plant and nutrient absorption from the soil||Helps in photosynthesis, conduction and storage of food|
Definition of Root
Roots refer to a root system that grows downwards the plant axis or subterranean to the soil surface. It originates from the radicle of the growing seed as primary root and later gives off lateral branches as secondary or tertiary roots. A layer of epidermis surrounds the root surface and typically consists of three zones.
Root Hair or Piliferous Zone
It lies at the topmost region of the root system and comprises several outgrowths or unicellular root hairs. A permanent zone helps in anchoring and transporting nutrients to the plants.
Root Elongation Zone
lies between the piliferous region and meristematic zone, and its functional role is to promote root length.
Zone of Meristematic Cells
lies between the elongation zone and root cap. The meristematic cells undergo multiple cell divisions and differentiate into three layers:
- Outer layer: Here, the meristematic cells differentiate into Epiblema and root cap.
- Middle layer: Here, the meristematic cells mature to form the cortex.
- Central zone: The cells develop stele.
The dermatogen layer produces a root tip or root cap. A root cap performs a primary function by giving protection to the apical meristem against harsh soil particles. It has the capacity to regenerate. In aquatic plants, instead of the root cap, a loose root pocket is present.
Definition of Stem
Stems refer to a shoot system that grows upright to the plant axis or superterranean to the soil surface. It originates from the plumule of the growing embryo as the primary stem and later gives off lateral branches as secondary or tertiary stems.
Stems bear nodes (give rise to the formation of leaves) and internodes (separates two nodes). Stems also bear buds that can be terminal and lateral in position. A terminal bud or “Apical bud” grows towards the tip, and a lateral bud or “Axillary bud” grows laterally towards the axil of a leaf.
The primary meristems (apical and intercalary meristem) at the tips and nodes of the stem promote the stem’s primary growth. Secondary growth occurs in the secondary or lateral meristem, located in and around the vascular tissues, forming secondary vascular tissues and woody axis (bark).
Key Differences Between Root and Stem
- Root requisites in a plant’s root system usually grow downward the plant axis and bear lateral rootlets, root hairs and a root cap. Stem requisites in a plant’s shoot system that grows aerially or upwards and bears lateral stems, stem hairs, leaves, buds, flowers etc.
- Root emerges out from the first outgrowth of the developing seed or radicle. Stem emerges out from the plumule of the seed’s embryo.
- Stems are the part of the shoot system that flourishes above the soil surface and shows negative geotropism. Roots are the part of the root system that flourishes underground the soil and shows positive geotropism.
- Stems bend towards the light and are positively phototropic, while roots are negatively phototropic.
- Roots are the tubular structures that move towards the water and show positive hydrotropism, whereas stems are the branched structures that move away from the water and are negatively hydrotropic.
- Multicellular stem hairs are present throughout the body of the stem, whereas roots are always surrounded by unicellular root hairs.
- A thimble-like root cap is a structure found in a root system, differentiating it from the other parts of the plant.
- The growing point of the root is sub-terminal and giving rise to the endogenous root branches. Conversely, the growing point of the stem is terminal and giving rise to the formation of exogenous stem branches.
- Cuticle, sclerenchymatous hypodermis, stomata, chloroplast, fibres are absent in the cross-section view of the root system while present in stems.
- The epidermis of root comprises several root hairs that participate in water and mineral absorption and are absorptive in function. The epidermis of the stem is protective in function.
- Root possesses a broad cortex, and stem possesses a narrow cortex.
- The conjunctive parenchyma and pericycle promote the secondary growth of the root. On the contrary, intra or interfascicular cambium promotes the growth in stems.
- Root performs two functional roles like anchorage and nutrient absorption, whereas stem performs functions like preparation, transportation and storage of food in a plant system.
Therefore, we can conclude that a plant could not thrive without the working of roots and stems as both perform different roles to maintain the plant physiology.