What is a Vascular Plant?
The vascular plant is one of several plants with specialized vascular tissue. The two types of vascular tissue, xylem, and phloem, are responsible for the movement of water, minerals, and the products of photosynthesis in the plant.
Unlike a non-vascular plant, a vascular plant can grow much larger. The vascular tissue inside offers the ability to transport water to great heights so that a vascular plant can grow upwards to catch the sun.
Structure of Vascular Plants
Within a vascular plant, the structure is very different from that of a non-vascular plant. In non-vascular plants, there is little or no differentiation between the different cells. In vascular plants, the specialized vascular tissues are arranged in unique patterns depending on the division and species to which the vascular plant belongs.
The xylem, which consists mainly of the structural protein lignin and dead cells, specializes in the transport of water and minerals from the roots to the leaves. A vascular plant creates pressure on the water on several fronts.
In the roots, water is absorbed by the tissue. The water flows into the xylem and creates upward pressure. Water is used on the leaves and evaporates from the stoma. These small pores are supposed to transpire, which pull up on the water column in the xylem.
Through the effects of adhesion and cohesion, the water moves up through the xylem like a drink through a straw. This process can be seen below.
Photosynthesis takes place in the leaves. A vascular plant uses the same process as the lower plants and algae to draw energy from the sun and store it in glucose bonds. This sugar is converted into other forms and has to be transported to parts of the plant that cannot photosynthesize, such as the trunk and roots.
The phloem was specially designed for this purpose. In contrast to the xylem, the phloem consists of partially living cells that facilitate the transport of sugar via transport proteins in the cell membranes. The phloem is also associated with the xylem and can add water to dilute and move the sugar. Harvested commercially, this is known as juice or syrup like maple syrup.
Vascular Plant Lifecycle
Like all plants, vascular plants show a generation change. This means that there are two forms of the plant, the sporophyte, and the gametophyte. The sporophyte, a diploid organism, goes through meiosis to produce the haploid spore.
The spore grows into a new organism, the gametophyte. The gametophyte is responsible for producing gametes, which can fuse together during sexual reproduction.
These gametes, the sperm, and the egg fuse to form a zygote, the new generation of diploid sporophytes. In some plants, this zygote develops directly into a new organism. In other cases, the zygote develops into a seed that is dispersed and must have a dormant phase or an activation signal in order to grow.
A vascular plant closer in terms of the mosses and non-vascular plants is more likely to have independent alternating generations. Seed plants tend to have a greatly reduced gametophyte that typically depends entirely on and lives in the sporophyte.
The distinction between the two organisms is barely discernible, apart from the amount of DNA they carry in their cells (haploid vs. diploid) and the cell division processes they use.
Classification of Vascular Plants
The vascular plants are embryophytes, which are a large group or related group consisting of both non-vascular and vascular plants. The embryophytes are further broken down into bryophytes, including mosses, liverworts, and non-vascular plants, as well as tracheophyta. Since the trachea is a passage for air in humans, the term tracheophyte refers to the vascular tissue in vascular plants.
The tracheophytes are further divided into departments. The subdivisions differ mainly in how their spores and gametophytes function. In ferns and club moss, the gametophyte becomes a free-living generation.
In gymnosperms (conifers) and angiosperms (flowering plants) the gametophyte is dependent on the sporophyte. The gametes developed in it become a seed and form the next generation of sporophytes. While every vascular plant exhibits a generational alternation with a dominant sporophyte, they differ in how they distribute spores and seeds.
Examples of a Vascular Plant
Annual Vs. Perennial
Some plants, the annuals, complete their life cycle within a year. If you bought a yearbook from the store, planted it in your yard, and collected any seeds it dropped, the plant wouldn’t come back next year.
Annuals are usually herbaceous, meaning their stems and roots, and not heavily structured and rigid. While the plants can stand tall, this is mainly due to the effects of turgor pressure on the plant’s cell walls.
A perennial plant is a little different. While it can also be herbaceous, even if you collect all of the seeds, the plant will return for several years. The vascular plant can store sugar in the roots in winter and avoid complete freezing.
In the spring, the plant can grow again and try again to produce offspring. While methods of reproduction reflect millions of years of evolution, they do not reflect vascular plants compared to non-vascular plants.
Monocot Vs. Dicot
There is a large split within the angiosperms or flowering plants. While monocots and dicots are both vascular plants, they differ in the way their seeds form and how they grow. A monocot grows underground as individual leaves start near the roots and grow upwards.
Corn is a monocot, as are many types of grass, including wheat and barley. In other seed plants, such as beans and peas, there are two cotyledons that make them dicots. The vascular tissue of the monocot can be seen in the picture at the bottom right.
In a dicot, the point of growth is above the ground, which causes the plants to branch in different directions. As such, the vascular tissue is branched in a dicot where it runs parallel in a monocot. Notice how the vascular tissue in these plants forms organized bundles.
This pattern creates easy branching opportunities. These changes in vascular tissue represent the different methods of leaf formation to collect light seen in the two species of a vascular plant.