Plant cells
Plant cells have a distinct set of features and characteristics. They are different to the cells of organisms from other kingdoms of life.
The cells of plants are eukaryotic. A eukaryotic cell is any cell with a ‘true’ nucleus and organelles. This immediately separates plant cells from the cells of bacteria and archaea.
Animals and fungi also have eukaryotic cells. Plant cells have a unique set of organelles that distinguishes them from the cells of animals and fungi. The presence of organelles called chloroplasts, vacuoles and a cell wall are three key features of the cells of plants.
Plant cells are relatively large and can differ considerably within a plant. There is a large diversity of different types of cells found through stems, leaves and roots.
Different types of plant cells
There is a wide range of cells found in plants. Within the leaves alone there is a variety of cells that perform different functions such as providing protection, photosynthesizing or transporting water. They same level of variety occurs in stems, roots and flowers. Here I describe only a few of the different types of cells from different parts of a plant.
Cells of vascular tissue
Vascular tissue in plants consists of the xylem and phloem. The xylem is responsible for transporting water through a plant. Xylem cells are dead, hollow tubes to allow water to move through plants as efficiently as possible.
The phloem is in charge of transporting sugars and other substances from leaves to roots. The cells of the phloem are also tubes but they are living cells. Phloem cells often have large pores to allow substances to move from one phloem cell to another.
Leaf cells
Leaves are designed for photosynthesis. Many leaf cells are packed full of green organelles called chloroplasts. Chloroplasts are responsible for the production of sugars using the sun’s energy and carbon dioxide.
Another structure that is extremely important for leaves and photosynthesis are stomata. Stomata are holes on the surface of leaves that can open and close to allow carbon dioxide into the leaf to be used in photosynthesis. Each stomata is made from two crescent-shaped cells that form a donut shape on the exterior of a leaf’s skin.
Leaves also contain xylem and phloem cells which deliver water to leaves and take sugars away.
Cells of stems and roots
The majority of stem cells are a relatively featureless type of cell called a ‘parenchyma’ cell. Vascular tissues are bunched together into bundles with xylem cells and phloem cells sitting next to each other. Fiber cells, with thick cell walls, are not uncommon and are important for providing structural strength to plant stems.
Roots have many of the same cells as stems. Parenchyma cells are common and vascular cells once again form into bundles.
Structure of plant cells
Plant cells have a general structure composed of several organelles, a nucleus and a cell wall. Animal cells also have a nucleus and organelles but lack a cell wall and have a different set of organelles.
Nucleus
The nucleus is where DNA is housed in the cells of plants. A nucleus consists of the cell’s DNA and a nucleolus which are surrounded by a double membrane.
The double membrane that surrounds the nucleus is called the nuclear envelope. The nucleolus is the largest structure in the nucleus and is responsible for the production of ribosomes.
Plasma membrane
All plant cells have a plasma membrane. This is a membrane that surrounds the inner contents of the cell and determines what substances move in and out of a cell.
Cell wall
In plant cells the plasma membrane is surrounded by a cell wall. The cell wall maintains the shape of a plant cell and provides protection. It is mostly made from a carbohydrate called ‘cellulose’. Cellulose is a major component of dietary fiber in the diets of animals. Cell walls have channels that connect through to the inside of plant cells called ‘plasmodesmata’.
Cytoplasm
The cytoplasm is the internal space of a cell that is not filled by a nucleus or organelle. The cytoplasm consists of a gel-like substance called ‘cytosol’.
Endoplasmic reticulum (ER)
The endoplasmic reticulum is a network of membranes that are connected to the nucleus of a cell. The ER is split into smooth ER and rough ER depending on whether ribosomes are found in the membrane. Smooth ER does not have ribosomes through its membranes whereas rough ER does. The endoplasmic reticulum is important for a number of cellular processes such as modifying and transporting proteins.
Golgi apparatus
Like the ER, the golgi apparatus is a network of membranes. It plays important roles in modifying proteins and lipids and moving substances out of the plant cell.
Chloroplasts
Chloroplasts are a key feature of plant cells. It is chloroplasts that are able to use the sun’s energy to convert carbon dioxide into sugars i.e. the well-known process of photosynthesis. Chloroplasts are green and are the reason why plants are typically green.
Mitochondria
Mitochondria are important organelles found in eukaryotic cells. They are the main site of cellular respiration – a process that converts the energy of sugars and other compounds into energy that cells are able to use. Sugars produced by photosynthesis in chloroplasts are converted into usable cellular energy inside mitochondria.
Ribosomes
Ribosomes are small structures that are responsible for building new proteins.They can be embedded in the endoplasmic reticulum to form the rough ER or they can be floating in the cytoplasm of a cell. Ribosomes are one of the few structures found in both eukaryotic and prokaryotic cells.
Vacuoles
Vacuoles are another key feature of plant cells because they are not found in animal cells. A vacuole is a large organelle that is mostly used for the storage and breakdown of different substances. Plant growth is often the result of increases in the size of vacuoles in plant cells.
Peroxisomes
Peroxisomes are small organelles that perform a range of functions. They are known to produce hydrogen peroxide (commonly used as bleach) and convert it to water.
Differences between plant and animal cells
The cells of plants and animals have some key differences. Firstly, animals aren’t able to photosynthesize whereas plants can. This is because plant cells contain chloroplasts but animal cells do not.
Plant cells also have a cell wall surrounding the plasma membrane and vacuoles inside. Animal cells don’t contain either of these structures. On the other hand, plant cells lack centrosomes, lysosomes and flagella which can all be found in animal cells.
Last edited: 9 March 2016
