A vast majority of plants found on the planet today are vascular in nature; surprisingly though, not many people know what that actually means. On the basis of how water, nutrients, and the products of photosynthesis are transported to different parts, plants are categorized into two groups: vascular and non-vascular plants.
What are Vascular Plants?
Plants which have vascular or liquefied tissues that transport water, various nutrients, and products of photosynthesis―all of which are necessary for plant growth, to their different parts are referred to as vascular plants. As opposed to this, non-vascular plants do not have any such system. Plants with a vascular system are also known as higher plants. Though not quite popular, these plants are known as Tracheophyta and Tracheobionta in botanical studies.
In vascular plants, three different systems come into play to facilitate plant growth. These include the root system, i.e., the roots that help the plant absorb water and minerals from the soil, the stem system, which―along with the leaves―facilitates the process of photosynthesis, and the vascular system, by which water, nutrients, and photosynthesis products are transported to various parts of the plant. It is the vascular system which transports water and nutrients required for the process of photosynthesis to the leaves of the plant, and products of photosynthesis, such as glucose, to various parts of the plant. Basically, vascular tissues make sure that water and other nutrients necessary for plant growth reach every corner of the plant, owing to which these plants grow and attain a large size as compared to their non-vascular counterparts.
Simply put, vascular plants have the ability of circulating water and food to different parts of the plant―something which their non-vascular counterparts cannot do. The plant vascular system is made up of two tubular networks: xylem, which consists of dead hollow cells known as tracheids, and phloem, which consists of living cells known as sieve-tube members. While the xylem is assigned the task of transporting water from the roots to the various parts of the plant, the phloem is assigned the task of transporting nutrients and products of photosynthesis to various parts of the plant. The two systems work in coordination to ensure that the plant growth is not affected at any stage.
This group of plants includes various species ranging from ferns and club-moss to conifers and flowering plants inhabiting the planet. The diversity in this class of plants can be determined from the fact that these plants range from sweet asylum, which seldom grows beyond 30 cm, to Giant Sequoia, which attains a height of 80 meters at full growth. Irrespective of whether they are annuals, biennials, or perennials, all flowering plants are vascular in nature. Some examples of vascular ferns are horsetails, club-mosses, ferns, quill-wort, etc. As far as trees are concerned, all coniferous trees fall in this group. Similarly, certain types of grass, including bamboo, Kentucky blue grass, quack grass, western wheat grass, etc., are also vascular.
Fossil records suggest that the first species of vascular plants probably came into existence somewhere around 350 - 400 million years ago. Before that the Earth's vegetation was dominated by mosses and algae, which were not able to grow to a considerable size because of the absence of a proper vascular system to carry water and nutrients throughout the plant. That being said, these plants have come a long way to become the most abundant plants of the planet, and their evolution has surely been one of the most crucial attributes of the development of Earth's ecosystem.