In addition to animals, vascular plants are the only living beings that present tissues, which they have acquired independently during their evolutionary history, which is why both types of tissues, animals, and plants, present differences between them. despite their homology.
We want to explain what they are, the general characteristics and types of existing plant tissues, in addition to their respective functions. It is also intended to highlight the differences between plant tissues and those of animal origin.
Vegetable tissues: what they are and their characteristics
Tissues are organized conglomerates of cells that share a common function, nature, and embryonic origin. Plants have several differentiated cell types that unite to form various tissues, whether simple or complex, depending on whether they have one or more cell types. Each plant tissue has a function and, in conjunction with other tissues, they can create organs such as leaves, flowers, roots, and stems. The different types of plant tissues are grouped into meristematic tissues and permanent or definitive tissues (these seconds differ, in turn, into simple and complex)
Types of plant tissues and their functions
Once we have determined what plant tissues are and their characteristics, we will cite the types of existing plant tissues and their functions. The different types of existing plant tissues, apart from being simple or complex, are classified into three systems: protective, fundamental, and vascular.
It is made up of the epidermis, which is a tissue made up of a single layer of cells that covers the roots, stem, leaves, and flowers of the plant. It protects the plant from water loss, regulates the exchange of carbon dioxide and oxygen, and, in the roots, absorbs water and nutrients from the substrate. The epidermis on the stem and leaves has pores called stomata, through which they diffuse carbon dioxide, water vapor, and oxygen. Epidermal cells are covered by a cuticle that mainly contains a waxy substance that protects them from water loss called cutin. Plants in deserts and other arid regions often have thick cuticles to aid in water conservation.
Composed of the parenchyma, collenchyma, and sclerenchyma.
- Parenchymal cells form the so-called primary cell wall of plants and their functions include photosynthetic activity, the healing and repair of tissue damage, and the storage of nutrients.
- Collenchyma is a supportive tissue (provides resistance and flexibility) that is preferably found in growing organs (young petioles, stem, leaves, fruits, etc.) or immature organs of herbaceous plants. It is made up of living cells with chloroplasts. Collenchyma is classified according to the way in which its cell walls increase in thickness: annular (homogeneous thickening that gives a circular cell light), angular (thickening marked at the angles, giving a polygonal cell light), lagoon (thickening mainly in cell walls that delimit the intercellular spaces) and laminar (thickening only in the periclinal walls but not in the radial ones, giving an appearance of sheets of collenchyma).
- Sclerenchyma is the supporting tissue of adult organs that have already stopped growing and their development is controlled by phytohormones. It is made up of cells that, together with the primary cellulose wall, create a very thick and hard secondary wall due to the lignin deposit, thus offering even greater resistance than collenchyma. Scelrrenchyma is divided into two large groups: short cells (also known as sclereids or stone cells) and very elongated cells called sclerenchyma fibers.
Formed by phloem and xylem. Vascular tissues transport substances between the different parts of the plant.
- Phloem carries organic compounds that the plant uses for food, especially sucrose. The xylem carries water and soluble nutrients. Vascular tissues are long and thin and form cylinders through which nutrients are transported. Vascular tissue is also involved with two types of os, which are tissues that contain undifferentiated cells that function during plant growth. The meristems that accompany the vascular tissue are the cambium cork and the vascular cambium. These meristems are associated with the growth of vascular tissues.
- The xylem or log is a conductive tissue that is responsible for the transport of sap (water and mineral salts and organic compounds) from the root, through the entire plant, and also serves as a support for the plant and mechanical resistance. It is a complex tissue because it is composed of different types of elements: conductors (tracheae and tracheids), parenchymal, secretory (resiniferous, laticiferous) and xillary fibers (libriform, fibrotracheid, septate fibers and mucilaginous fibers).
Differences between plant tissues and animal tissues
The differences between plant tissues and animal tissues lie in their constitutive cells because, despite the fact that both types are eukaryotic, they present a series of distinctions between them:
- Plant cells are immobile, while those of animal organisms can move.
- Plant cells have pigments such as chlorophyll, which animals lack.
- Plant cells have autotrophic metabolism, unlike animal cells, which are heterotrophic.
- Plant cells show unlimited growth in contrast to animals, which do have limitation in their growth.
- Plant cells, in addition to the plasma membrane (also present in animal cells), have a cell wall that provides rigidity.
- All plant cells have vacuoles, which are compartments limited by the plasma membrane that contain substances such as water, enzymes and sugars and that are only present in some animal cells.
- Plant cells usually lack the centrosome, a cellular organelle that is present in animal cells.
- The plants that make up plant tissues are generally capable of differentiation from one tissue to another, but animal cells lack this ability.
- Plant cells make up tissues with a structural function and animal cells make up tissues with a locomotion function.