BOTANY WITH THE BASICS OF HYDROBOTANY (AQUATIC PLANTS OF UKRAINE) - B.Ye. Yakubenko - 2011

V. CYTOLOGY. CONCEPT OF THE CELL

Structure of the Plant Cell

Vacuoles

Endogenous structures characteristic of plant Eukaryotic Cells. They are separated from the cytoplasmic matrix by an internal cytoplasmic membrane, the tonoplast. The content of vacuoles is referred to as Cell sap. Its main component is Water with dissolved substances. The concentration of dissolved substances is quite high (0,4-0,6 M). Among Mineral Substances, ions of N⁺ , К⁺ , Са²⁺ , Mg²⁺ , СL^-, SO₄ ^-2, РO₄ ^-2 predominate.

Organic compounds are represented by sugars, mucilaginous substances, organic acids, Phenolic Compounds—particularly Flavonoids (anthocyanin, anthochlor) and Tannins. Among the nitrogenous compounds of The Cell sap are Amino Acids, amides, Peptides, Proteins (including Enzymes), and Alkaloids. Vacuoles also contain insoluble substances in the form of Suspensions or crystals (for example, calcium oxalate or protein).

The number and size of vacuoles within a cell change with its age. Thus, young meristematic cells contain numerous small vacuoles, whereas in mature cells, one or several vacuoles may occupy up to 90% of the cell volume.

Water enters the vacuole through the tonoplast via osmosis, driven by the higher concentration of solutes in the cell sap. Substances are transported into the vacuole via Active Transport or in membrane vesicles, which are most frequently derived from the Golgi apparatus.

Vacuoles perform three main Functions in the cell. Firstly, by maintaining the cell in a turgid state, they act together with The Cell wall to provide structural support for plant cells.

Secondly, vacuoles accumulate specific substances. These include nutrient reserves in seed cells, which can undergo certain transformations and return to the Cytoplasm. Such substances may include aleurone protein grains and Other Compounds that attract animals to plants, thereby facilitating flower pollination as well as fruit and seed dispersal. Unpalatable or toxic substances, such as alkaloids or Glycosides, deter animals and protect plants from being eaten.

The third function of vacuoles is associated with the hydrolytic enzymes they contain, which facilitate The breakdown of polymers and complex compounds into monomers or simpler constituents.