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4.2: Introduction

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  • Plant cells can be classified into three major categories based on their cell wall structure. Most plant cells are parenchyma cells (par- meaning equal), with an evenly-thickened primary cell wall. Some areas of a plant, particularly in young shoots, will require more flexibility, allowing them to bend without breaking. In these regions, you will often find collenchyma cells (coll- meaning glue), cells with strange, unevenly-thickened primary walls. Both of these cell types are alive at maturity. A third cell type, sclerenchyma cells (scler- meaning hard), develops a rigid secondary wall that is composed of lignin. This secondary wall provides structural support, but it also cuts off the exchange of water and other molecules permitted by the plasma membrane. Ultimately, this results in the death of the cell at maturity and loss of internal cell components.

    Figure \(\PageIndex{1}\): Collenchyma cell

    Parenchyma Collenchyma Sclerenchyma

    Plant cells performing a similar function can be assembled into tissues. This lab will introduce you to the three primary cell types found in plants, the tissues where you can find these cell types, and specialized cells that they can differentiate into. Specialized cells covered in this lab will be either parenchyma, collenchyma, or sclerenchyma (referred to as the “cell type”) and will have evolved for a specific function, such as conducting water. At the end of the lab, you will complete a table with the cell types, specialized cells, and functions of the major tissues within a leaf.

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