What is the Difference Between Microphylls and Megaphylls

The main difference between microphylls and megaphylls is that microphylls are leaves having a single, unbranched vein, whereas megaphylls are leaves with multiple veins. Furthermore, in microphylls, the single vein originates from the protostele without having a leaf gap while megaphylls contain leaf gaps. Moreover, microphylls are the leaves, which occur early in the fossil record up to date while megaphylls develop independently from euphyllophyte leaf precursor structures. 

Microphylls and megaphylls are two types of structures that occur in leaves of vascular plants. 

Key Areas Covered 

1. What are Microphylls
     – Definition, Structure, Examples
2. What are Megaphylls
     – Definition, Structure, Examples
3. What are the Similarities Between Microphylls and Megaphylls
     – Outline of Common Features
4. What is the Difference Between Microphylls and Megaphylls
     – Comparison of Key Differences

Key Terms 

Euphyllophyte, Leaf Gap, Leaf Vein, Megaphylls, Microphylls

What are Microphylls 

Microphylls are one of the two types of leaves that independently evolved from the euphyllophyte leaf precursor structures in plants. The main characteristic feature of microphylls is the presence of a single vein, which is unbranched. Also, this single vein emerges from protostele without leaving a leaf gap. Generally, the leaf gap is the small area above the leaf node. Moreover, the vascular tissue in the leaf gap is diverted into the leaf.

Figure 2: Clubmoss

Furthermore, microphylls occur in lycophytes, including club moss, quillworts, and selaginella. They also occur in horsetails. However, horsetails along with whisk ferns and true ferns make the phylum Pteridophyta. Generally, the members of Lycophyta and Pterophyta are seedless vascular plants. 

What are Megaphylls 

Megaphylls are the other leaf structures that occur in vascular plants. They are derived from the euphyllophyte structures independently. Therefore, microphylls and megaphylls are analogous structures which have different anatomical structures but, similar functions. Generally, the main function of both microphylls and megaphylls is to undergo photosynthesis. In comparison, the main structural feature of megaphylls is the presence of multiple veins. Also, they contain leaf gaps.

Figure 2: Megaphylls in Hillebrandia sandwicensis

Moreover, megaphylls contain several main veins, which are either branching apart or running in parallel. These main veins are interconnected by a network of small veins. Generally, the leaves of angiosperms and gymnosperms and fronds of ferns are examples of megaphylls. However, some gymnosperms contain needle-like leaves with a single vein. Basically, these leaves are complex leaves derived from megaphylls. 

Similarities Between Microphylls and Megaphylls 

• Microphylls and megaphylls are two types of leaf structures, which occur in vascular plants. 
• Both develop independently from euphyllophyte leaf precursor structures. 
• They are not homologous structures. 
• Moreover, they differ from each other by means of leaf veins and leaf gaps. 
• However, their main function is to undergo photosynthesis. 

Difference Between Microphylls and Megaphylls 

Definition 

Microphylls refers to a type of very shortleaf, such as in moss or clubmoss, with a single unbranched vein and no leaf gaps in the stele while megaphylls refer to a type of leaf with several or many large veins branching apart or running parallel and connected by a network of smaller veins. 

Veins 

Microphylls contain a single vein which is unbranched while megaphylls contain multiple veins. 

Leaf Gap 

In microphylls, the single vein derives from the protostele without having a leaf gap while megaphylls contain leaf gaps.  

Occurrence 

Moreover, microphylls occur in lycophytes and horsetails while megaphylls occur in angiosperms, gymnosperms, and the fronds of ferns. 

Conclusion 

Microphylls are the leaves with a single vein, which is unbranched. They also do not contain leaf gaps. Generally, microphylls occur in lycophytes and horsetails. In contrast, megaphylls are the other type of leaves with multiple veins and leaf gaps. They occur in angiosperms, gymnosperms, and fronds of ferns. Therefore, the main difference between microphylls and megaphylls is structure and occurrence. 

References:

1. Tomescu, Alexandru M.F. “Megaphylls, Microphylls and the Evolution of Leaf Development.” Trends in Plant Science, Elsevier Current Trends, 11 Dec. 2008,  Available Here. 

Image Courtesy:

1. “Fir-Clubmoss” By Homer Edward Price (CC BY 2.0) via Flickr
2. “Starr-110713-7393-Hillebrandia sandwicensis-flowers and leaves-Ainahou Bowl Koolau Gap-Maui (25099679695)” By Forest & Kim Starr (CC BY 3.0 us) via Commons Wikimedia