Plant Tissue Types and Stomata 🌿

As promised, today I will be going cover some basic information on the different plant tissue types and stomata. Let me cover stomata first since that was the last thing we explored.

Think of stomata as mouths for plant leaves. They can open and close to breathe in carbon dioxide, which is used for photosynthesis, and breathe out oxygen it produces. Guard cells form the lips that can open and close the opening, they occur in pairs. The reason it needs to close is so it can stop water from evaporating via these openings.

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Back when I was studying I had drawn and taken a photo of plant stomata I had seen through a microscope. Hopefully you can read the labelling I had written. This was a transverse section of a leaf. The larger image is the middle part of the leaf where the vein bends out. From that we can see the vascular bundle, as we had previously explored, and also chollenchyma cells.

Chollenchyma is a type of ‘simple tissue’ or ‘ground tissue’. Their role is to give support to the plant, especially for younger plants that have not yet fully developed their wall structure. They are usually found at the corners or edge of the plant.

Looking at the hand drawn corner image, that is my drawing of the photo on the right (first image). We can see the opening of the stomata and the guard cells controlling the opening. It is located on the lower epidermis.

Epidermis is a ‘surface tissue’; its role is to protect the plant by forming a protective outer covering of the plant body. It is usually one cell thick and has large vacuoles (storage). They secrete a waxy, water resistant cuticle (stains red) to protect the plant from dehydration. It also helps protect the plant from invasions by parasites and fungi. As we have already seen, it may have hairs, spines or glands along the epidermis, upper or/and lower.

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A quick view of the other types of plant tissues

Meristematic Tissue:

Its role is for growth. It consists of undifferentiated cells (not mature) , they are embryonic cells, so they are always dividing for growth and development.

Surface Tissue:

Epidermis & Periderm. Periderm role is also to protect. It defers from epidermis by having a corky outer bark and the cells are dead. It is also waterproof via the production of suberin (also stains red)

Simple Tissues/Ground Tissues:

There are three types. Chollenchyma, which we already explored, the other two are parenchyma and sclerenchyma.

Sclerenchyma role is for strength and support, they are fibres and mostly dead at maturity. They have very thick, uniform cell walls with a hardening agent, lignin & cellulose, which stains red. They can form shells of fruits, seed or fibres. We have seen this around some of the vascular bundles we’ve seen to date. They make up the fibre caps around the vascular bundle.

Parenchyma role is for repair and storage. It makes up most of the plant’s body. They have large vacuoles to store glucose and you will find most chloroplasts in this tissue. If granules are found inside, they are starch grains. Here is a cool picture I had taken of it back in school. See the purple coloured granules, they are starch grains. You can also see a thicker layer of cuticle too.

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Vascular Tissue:

Yup you guessed it, Xylem and Phloem also make up another type of plant tissue. Xylem transport upwards only. It transports water and dissolved substances and lives for one year.

This is why ringing of a tree is illegal. By cutting a ring only so deep around a tree, you will cut off all supply required for the tree to live.

Phloem transports both upwards and down. It transports nutrients/organic materials.

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Now armed with a little more information, we can keep any eye out for these cells/structures when we look at future samples.

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All images belong to @supersoju

References and further reading:
School notes
What Is the Function of Plant Stomata?
Stomata
Plant Tissues and Organs
Plant Tissues
Plant Tissue