Difference Between Vascular and Non-vascular Plants

Main Difference – Vascular vs Non-vascular Plants

Plants can be divided into two major categories known as vascular and non-vascular plants according to the presence or absence of a vascular system. The vascular system of a plant contains xylem and phloem. The main difference between vascular and non-vascular plants is that vascular plants contain a specialized xylem and phloem tissues for the transportation of water and foods, while non-vascular plants do not contain specialized vascular tissues for transport. Vascular plants are known as higher plants while non-vascular plants are known as lower plants. Vascular plants become tall due to the structural support gained from its lignified xylem. Non-vascular plants grow on the surface of the ground or on tree trunks.

This article explains,

1. What are the Vascular Plants
     – Definition, Characteristics, Phylogeny
2. What are the Non-vascular Plants
     – Definition, Characteristics, Phylogeny
3. What is the difference between Vascular and Non-vascular Plants

What are Vascular Plants

The plants containing a xylem and a phloem are referred to as vascular plants. The xylem transports water and minerals from roots to leaves whereas phloem transports sucrose and other organic nutrients throughout the plant. Vascular plants first appeared 430 million years ago. The evolution of the vascular tissue allowed the dominance of these plants on land by gaining the structural support from lignified xylem, and long-distance movement of water and nutrients through xylem and phloem respectively. Vascular plants are also known as tracheophytes or higher plants. This group includes all seeding plants (Gymnosperms and the Angiosperms) and the pteridophytes (ferns, lycophytes and horsetails).

Since vascular tissues can transport water and nutrients for long distances, these plants can grow to form tree-like structures. Seed plants (the Gymnosperms and Angiosperms) produce an embryo within the seed. Since the embryo is protected by a hard, outer coating, it is resistant to conditions such as drought and predation. Seeds can remain dormant until proper conditions arrive for germination. Flowering plants produce flowers and fruit or wood. Seedless plants such as Lycopodiophyta (clubmosses), Equisetophyta (horsetails) and Psilotophyta (whisk ferns), produce free-swimming sperms. They require water for fertilization. Vascular plants are well-differentiated into roots, stems, and leaves. The dermal tissue system of these plants consists of cutin, which is a waxy substance forming the cuticle. The cuticle produces a protective covering throughout the plant body against desiccation of water. it also regulates the gas exchange through stomata, the pores within the cuticle.

What are Non-vascular Plants

Non-vascular plants are plants which do not have a specialized vascular tissue. However, some of these plants possess similar tissues for the internal transport of water. Non-vascular plants are small in size due to the poor transport of water and gas. Thus they do not possess true roots or true leaves. Some non-vascular plants contain leaf-like structures which can not be defined as leaves due to the lack of the vascular tissue. Root-like structures of non-vascular plants are called rhizoids. Since non-vascular plants do not possess a vascular system in their rhizoids, they have to depend on diffusion and osmosis. Thus, these plants are restricted to moist habitats in order to contact the cell surfaces with water. On the other hand, non-vascular plants withstand the dehydration to recover without any damage to the plant. Hence, they are known as poikilohydric. Dominant stage of the life cycle is the haploid gametophyte. The gametocytes are green in colour thus they are photosynthetic. Non-vascular plants are divided into two groups: Bryophytes and Algae. Bryophytes have three divisions: Bryophyta (mosses), Marchantiophyta (liverworts) and Anthocerotophyta (hornworts).

Figure 2: Bryophyta

Difference Between Vascular and Non-vascular plants

Definition:

Vascular Plants: Vascular plants are the plants that bear a vascular system containing the xylem and phloem.

Non-vascular Plants: Non-vascular plants are plants that don’t have a vascular system.

Size:

Vascular Plants: Vascular plants are larger in size due to their vascular system.

Non-vascular Plants: Non-vascular plants are small.

Reproduction:

Vascular Plants: Vascular plants reproduce via seeds.

Non-vascular Plants: Non-vascular plants reproduce via spores.

Principal Generation Phase:

Vascular Plants: The principal generation phase of vascular plants is sporophyte. The sporophyte is large, dominant and nutritionally-independent stage.

Non-vascular Plants: The principal generation phase of vascular plants is gametophyte. The gametophyte is photosynthetic.

Ploidy of the Principal Generation Phase:

Vascular Plants: The sporophyte is diploid, bearing two sets of chromosomes per cell.

Non-vascular Plants: The gametophyte is haploid, bearing only one set of chromosomes per cell.

Water for Fertilization:

Vascular Plants: The seeds tolerate desiccation and remain dormant until the right conditions arrive for the germination. Seedless plants still require water for the fertilization.

Non-vascular Plants: Fertilization requires water.

Structure:

Vascular Plants: Vascular plants have specialized roots, stems and leaves. They also contain a lignified xylem.

Non-vascular Plants: Non-vascular plants have the least specialized tissues and no lignified xylem.

Transpiration:

Vascular Plants: Cuticles prevent desiccation and stomata facilitate the gas exchange.

Non-vascular Plants: Non-vascular plants do not have specialized dermal tissues either to resist water loss or to facilitate gas exchange.

Absorption:

Vascular Plants: Roots of the vascular plants absorb water passively in the absence of transpiration pull through osmosis.

Non-vascular Plants: Non-vascular plants depend on diffusion and osmosis.

Examples:

Vascular Plants: Clubmosses, Horsetails, True ferns, Conifers, Flowering plants

Non-vascular Plants: Green algae, Bryophyta, Mosses

Conclusion

Non-vascular plants require moisture throughout their life cycle. They are unable to resist water against dry environmental conditions in the plant body. Thus non-vascular plants are limited to swamps, bogs and shady locations. On the contrary, vascular plants are well specialized to transport and store water throughout the plant. Hence, they are distributed in a wide variety of habitats. Seed plants, which are the Gymnosperms and Angiosperms produce flowers, fruits, and wood. This is the difference between vascular and non-vascular plants.

Reference:
1. Holsinger, K. E., Reproductive systems and evolution in vascular plants. PNAS. 2000 97(13): 7032-7042
2. Stanton, D. E., Reeb, C., Morphogeometric Approches to Non-vascular plants. Front. Plant Sci. 7:916. doi: 10.3389/fpls.2016.00916

Image Courtesy:
1. “Conifers, Lydcott Wood – geograph.org.uk – 191022” By Kevin Hale (CC BY-SA 2.0) via Commons Wikimedia
2. “Bryophyta 1627” By I.Sáček, senior – Own work (Public Domain) via Commons Wikimedia