Learn about plant cell types and organelles types of electricity generation


Plant cells are eukaryotic cells or cells with a membrane-bound nucleus. Unlike prokaryotic cells, the DNA in a plant cell is housed within a nucleus that is enveloped by a membrane. In addition to having a nucleus, plant cells also contain other membrane-bound organelles (tiny cellular structures) that carry out specific functions necessary for normal cellular operation. Organelles have a wide range of responsibilities that include everything from producing hormones and enzymes to providing energy for a plant cell.

Plant cells are similar to animal cells in that they are both eukaryotic cells and have similar organelles. However, there are a number of differences between plant and animal cells. Plant cells are generally larger than animal cells. While animal cells come in various sizes and tend to have irregular shapes, plant cells are more similar in size and are typically rectangular or cube shaped. A plant cell also contains structures not found in an animal cell. Some of these include a cell wall, a large vacuole, and plastids. Plastids, such as chloroplasts, assist in storing and harvesting needed substances for the plant. Animal cells also contain structures such as centrioles, lysosomes, and cilia and flagella that are not typically found in plant cells.

This image shows starch grains (green) in the parenchyma of a Clematis sp. plant. Starch is synthesized from the carbohydrate sucrose, a sugar produced by the plant during photosynthesis, and used as a source of energy. It is stored as grains in structures called amyloplasts (yellow).

Parenchyma cells are usually depicted as the typical plant cell because they are not as specialized as other cells. Parenchyma cells have thin walls and are found in dermal, ground, and vascular tissue systems. These cells help to synthesize and store organic products in the plant. The middle tissue layer of leaves (mesophyll) is composed of parenchyma cells, and it is this layer that contains plant chloroplasts.

Chloroplasts are plant organelles that are responsible for photosynthesis and most of the plant’s metabolism takes place in parenchyma cells. Excess nutrients, often in the form of starch grains, are also stored in these cells. Parenchyma cells are not only found in plant leaves, but in the outer and inner layers of stems and roots as well. They are located between xylem and phloem and assist in the exchange of water, minerals, and nutrients. Parenchyma cells are the main components of plant ground tissue and the soft tissue of fruits.

The center of this stem is filled with large xylem vessels for transporting water and mineral nutrients from the roots to the main body of the plant. Five bundles of phloem tissue (pale green) serve to distribute carbohydrate and plant hormones around the plant.

Water conducting cells of xylem have a support function in plants. Xylem has a hardening agent in the tissue that makes it rigid and capable of functioning in structural support and transportation. The main function of xylem is to transport water throughout the plant. Two types of narrow, elongated cells compose xylem: tracheids and vessel elements. Tracheids have hardened secondary cell walls and function in water conduction. Vessel elements resemble open-ended tubes that are arranged end to end allowing water to flow within the tubes. Gymnosperms and seedless vascular plants contain tracheids, while angiosperms contain both tracheids and vessel members.

Vascular plants also have another type of conducting tissue called phloem. Sieve tube elements are the conducting cells of phloem. They transport organic nutrients, such as glucose, throughout the plant. The cells of sieve tube elements have few organelles allowing for easier passage of nutrients. Since sieve tube elements lack organelles, such as ribosomes and vacuoles, specialized parenchyma cells, called companion cells, must carry out metabolic functions for sieve tube elements. Phloem also contains sclerenchyma cells that provide structural support by increasing rigidity and flexibility.