Plant Tissues | Tissues Part - 1

Biology.

Today we'll be looking at one of the most beautiful topics in biology. The group of the most fundamental unit of life. We at Enlightened Wisdom: Smart Science have created a lot of posts on cells which is yes, is known as the most fundamental unit of life. So, you can check them out. But for now, today's topic focuses on the topic of tissues. Yes, tissues, which are a beautiful group of cells clumped together which work day and night for your survival. Biology is a beautiful aspect of science. And today, we'll be looking at one of its dialect.

Now the question really is, what are plant tissues. Now, Tissues are a group of cells that have similar structure and that function together as a unit. A family of cells, similar in structure and function is called a tissue.

Plants and animals are both complex living organisms. Since plants don't move and are stationary, most plant tissues are involved in providing structural support to the plant body. And on the other side, animals constantly move here and there in search of food and shelter. Thus, most tissues in animals obviously are used to help different body parts to move. 

So, there are two types of tissues. Plant and animal tissues. And in this Part 1, we'll be dealing with Plant tissues.

Plant tissues

In plants, growth usually occurs only at certain sites, like the tips of branches, stems and roots. So, only the tissues present in these growing regions are capable of dividing and giving rise to new cells. 

Based on their capacity to produce new cells, plant tissues are classified into 2 types, Meristematic Tissues And Permanent Tissues. Let's look at both of these types one by one!

1) Meristematic Tissue

The tireless, fearless, ever growing most active tissues found in the growing regions of the plants. They are made up of bunches of small densely packed, thin walled cells that keep on and on dividing to produce new cells.

So, they have a huge nucleus and they lack of the central vacuole. Now this lack, is for a good reason. See, vacuole's function is for the storage of water and support. And meristematic cells lack this central vacuole because they need neither storage nor support.

Now, meristematic tissue has 3 types further, let's see at each one of them quickly.

Type 1: The Apical Meristem: The apical meristem is usually present in the tips of the shoots and the roots and is responsible for unilateral growth.

Primary growth is growth that occurs as a result of cell division in the apical meristems at the tips of stems and roots causing them to elongate. This is how the apical meristem works.

Type 2: Intercalary Meristem: The intercalary meristem is present at the base of the leaves (nodes) and in the internodes. Intercalary meristem allows rapid stem elongation at the nodes. While those present at the base of damaged leaves, allows rapid regrowth of leaves.

Type 3: Lateral Meristem: Now the last chunk of the types of meristematic tissue is the lateral meristem. Lateral meristem is responsible for secondary growth. Secondary growth is the increase in the thickness or girth of the plant. It is caused by the cell division in the lateral meristem. This tissue is present on the sides of stems and branches.

Now, some important things you should know, is that secondary growth is because of the activity of 2 types of lateral meristem - Cork Cambium and Vascular Cambium. The cells of the vascular cambium divide and form wood. And the cells of the cork cambium form the bark of the tree/plant. How unique and amazing!

Apical Meristem increases the length, whereas the lateral meristem increases the thickness!

So, if the tips of the stems and branches are cut off, the apical meristematic tissues in those regions will be destroyed, affecting the growth of the plant.

2) Permanent Tissue

We now know what are meristematic tissues and what are its types. We saw all the things in detail. Now its time for us to move on to the next classification of plant tissues. Yes, the Permanent tissues! Now what happens to meristematic tissues when they mature?

Well, this is what brings to the concept of the permanent tissues! Meristematic tissues become specialized for a particular function and form permanent tissues. Unlike meristematic tissues, central vacuoles are present inside the permanent tissue and can even comprise up to 95% of itself in the permanent tissues.

Once the meristematic tissue cells in a region have finished dividing, no more growth occurs in that region. The meristematic tissue matures and transforms into a tissue with non-dividing cells known as permanent tissues.

The cells of the permanent tissue are modified to perform specific functions in plants. Permanent tissue provides support and protection, and aid in photosynthesis, and conduction of water, minerals and nutrients. 

Now, permanent tissue also has 2 types again. They are the Simple permanent tissue and Complex permanent tissue. Lets look at each one of them.

Type 1: Simple Permanent Tissue: Simple permanent tissue are made of the same kind of cells. Now the thing is, this simple permanent tissue is again of 3 types. Yes! See, biology keeps on dividing and diving. So, yes, the three types of simple permanent tissue are:

1) Parenchyma: Parenchyma are a type of simple permanent tissue which are living and oval shaped cells which provide mechanical support and is a storage house of food. Parenchyma cells have thin cell walls, large central vacuoles and dense cytoplasm.

2) Collenchyma: Collenchyma are another type which are living and elongated cells which provide flexibility to plant parts. Collenchyma have thickened cell wall corners and have very little intercellular space between the cells.

3) Sclerenchyma: Sclerenchyma, the last and the third type of simple permanent tissue, are dead and random/different shaped cells which provide stiffness and hardness to plant parts. They also provide strength to the plant as well! Mind you, sclerenchyma is the only type of simple permanent tissue which is dead, otherwise the other two classifications are living cells. Now, sclerenchyma have thick cell walls deposited with lignin. Lignin is basically a polymer which helps in cell wall formation etc.

Above three types that we just saw were three classifications of simple permanent tissue. Simple permanent tissue are made of the same kind/type of cells.

Now, its time to move to the last leg of the classification of the permanent tissues, the complex permanent tissue. Let's begin!

Type 2: Complex Permanent Tissue: The next classification of the permanent tissue is the complex permanent tissue. Complex permanent tissues are made of different kinds of cells. Thus, the name complex tissue. Now, plants are able to transport different materials with the help of these complex permanent tissues only.

Complex permanent tissues work altogether to transport food, water and nutrients throughout the plant body!

Again, there are 2 types of complex permanent tissues: Xylem And Phloem. Let's delve in deeper.

1) Xylem: Its function is to conduct water and minerals from the root to stems and leaves. It consists of four elements. Namely, Tracheid, Xylem parenchyma, Vessels and Xylem fibers. We'll really look deeply at each one of them in our upcoming posts where we'll discuss on the topic of xylem and phloem.

2) Phloem: Its function is to transport food prepared by the leaves through photosynthesis to all parts of the plant body. It consists of four elements as well. Namely, Sieve tubes, Phloem fibers, Companion cells and Phloem parenchyma.

With this we can conclude with the fact that plants do move, just not very visibly!

In a nutshell we can say that a tissue is defined as a group of cells that are similar in structure and work together to perform a specific function. Once the meristematic tissue stop dividing, they mature into permanent tissue. Plants transport water and nutrients throughout their body using complex permanent tissue.

So, yes we have wrapped up everything about the plant tissues that you needed to know. Now there is another classification of tissues known as animal tissues. Yes, you'll learn about them in the next part coming very soon.

So, I hope you enjoyed today's journey exploring and dividing tissues into different classifications! For more such scientific content and posts, follow us at Enlightened Wisdom: Smart Science. 

Thank you!~