Veins are the visible characteristic of any leaf which provides different features to the leaves and ultimately to the plant. The arrangement of these veins in a leaf is called venation. Veins are the components of the vascular tissue (xylem and phloem) arising from the stem of the leaf as veins are composed of xylem and phloem, which are enclosed in the parenchyma, sclerenchyma, and bounded by the sheath cells. Vascular tissues (xylem and phloem) perform significant functions for the plant. Xylem helps in water transportation in the lamina, whereas phloem transports food, nutrients, and sugar produced by the process of photosynthesis to the whole plant. Both xylem and phloem provide mechanical support to the leaf.
The veins are of two types; primary veins and secondary veins. The veins which enter the leaf through the petiole are called primary veins or first-order veins. The leaf petiole is the stalk that connects the leaf blade with the stem. The secondary veins are the primary veins that enter and further divide into the branches. These are also called second-order veins. The primary veins have a higher diameter than secondary veins.
In a plant, venation or arrangement of veins in a leaf are of two types; parallel venation and reticulate venation. In parallel venation, the veins of the leaf blade show the parallel pattern from the base to the tip, whereas in reticulate venation, the veins of the leaf blade or lamina in the plants show the net-like or web-like pattern on both sides of the midrib.
The venation architecture is widely distributed among the different species of all plants, especially angiosperms. It has significance in the recognition and differentiation of plants according to their characteristics. Venation also helps the plant in mechanical support, protection, and coordination in the development.
Comparison Chart
| Basis for Comparison | Parallel Venation | Reticulate Venation |
| Definition | When the veins run parallel to one another in the whole the leaf blade or lamina is called parallel venation. | When the veins are arranged either network-like or web-like all over the leaf blade or lamina is called reticulate venation. |
| Orientation | Parallel to one another | Network or web-like structure |
| Occurs in | Monocot plants | Dicot plants |
| Types | Two types: pinnate parallel venation and parallel palmate venation | Two types: pinnate reticulate venation and palmate reticulate venation |
| Example | Bamboo, aloe vera plant leaves, banana, wheat, grasses, and maize, etc | Hibiscus, peepal mango, ficus, etc |
What is Parallel Venation?
In parallel venation, primary veins are arranged parallel to one another and at an equal distance in the whole leaf and converge towards the apex of the leaf. This converging is usually called anastomosis, which means “fusion towards the apex.” In angiosperms, the minor veins are abundant, which are associated with the primary veins. These veins function as the network of distribution of different substances for the leaf and provide mechanical support to the leaf. Parallel venation occurs mostly in monocot plants.
Types
Parallel venation is classified into two types based on the presence of midveins; pinnate parallel venation and palmate parallel venation.
- Pinnate Parallel Venation: In this type of parallel venation, the veins arise from the prominent midvein, which is present in the center of the leaf lamina from the base to the apex. The veins grow perpendicular to the midvein towards the margin and are parallel to one another. This type of venation is also called Unicostate parallel venation. An example of this venation is the leaf of the banana.
- Palmate Parallel Venation: In this type of parallel venation, there are numerous prominent veins that are parallel to one another. This type of venation is also known as Multicostate parallel venation.
Palmate parallel venation is further divided into two types; convergent and divergent parallel venation.
In convergent parallel venation, all midveins arise from the basal part and run parallel to one another, and fuse at the apex of the leaf. Leaves of grass are examples of convergent parallel venation. On the contrary, in the divergent parallel venation, the leaf lamina is lobed, and the veins enter into the distinct lobes from the base. Borassus is an example of this type of venation.
What is Reticulate Venation?
In reticulate venation, the arrangement of veins is in the form of a network. The leaves with reticulate venation possess a distinct primary vein that enters by the leaf petiole and runs through the center of the leaf. This vein connects the leaf and possesses numerous branches which give rise to small secondary veins. The secondary veins terminate at a structure in the leaf margin, which is known as hydathodes. The secondary veins develop further branching patterns of tertiary veins. These tertiary veins develop a network like a reticulate pattern. Reticulate venation is usually found in dicots.
Types
Reticulate venation is of two types; pinnate reticulate venation and palmate reticulate venation.
- Pinnate Reticulate Venation: This is also called Unicostate reticulate venation. In this pattern, only one midvein is present, and all other veins from the network-like structure. Pinnate reticulate venation can be seen in the leaves of Mangifera.
- Palmate Reticulate Venation: It is also called Unicostate reticulate venation. In this pattern, more than on midribs are present, whereas other veins are in the form of a network. Palmate reticulate venation is further divided into two types; convergent reticulate venation and divergent reticulate venation. Convergent reticulate venation occurs in unlobed leaf lamina in which veins arise from one midrib, from the network, and eventually, meet at the apex. This is also called pinnately reticulate. In divergent reticulate venation, the leaf lamina is lobed, and the midveins enter into different lobes separately. All small veins form the network. This type of venation is also called palmately reticulate.
Key Differences between Parallel and Reticulate Venation
- Parallel venation is the pattern of veins showing parallel arrangement to one another whereas reticulate venation is the network like arrangement of leaf veins all over the leaf blade.
- Parallel venation is the characteristic of monocot plants, whereas reticulate venation is the characteristic of dicot plants.
Key Similarities between Parallel and Reticulate Venation
- Both parallel and reticulate venation are the types of arrangement of veins of the leaf blade.
- Both types help in recognizing and differentiating the plants.
- Both types of venation have vascular bundles; xylem and phloem.
- Both parallel and reticulate venation provide mechanical support to the plants.
- Both also provide support and coordination in the development of the leaves.
Conclusion
In conclusion, parallel and reticulate venation are two different types of patterns on veins in the leaves. Both are present in different kinds of plants.