Cell – Division of labor in plants

Division of labor in plants

• A multicellular organism has a division of labor and specialization.
• For maximum efficiency, work is broken down into small, specific tasks.
• The ability to handle multiple tasks simultaneously and efficiently is a great benefit.

Tissues in Multicellular Organisms (Eukaryotes)

We know that a cell membrane is also called a plasma or cytoplasmic membrane. It is a biological membrane that protects internal organelles from its outside atmosphere. The main function of a plasma membrane is to protect the cell. It consists of a phospholipid bilayer with proteins enclosed in it. The cell membrane is selectively permeable to ions and some organic molecules. Therefore, the cell membrane is very accommodating to permit certain molecules or cells, such as red blood cells and white blood cells, to pass through it.

Multicellular (Eukaryote) Organisms

Plant parts

As a plant grows, it has three main parts: roots, leaves, and stems. Each part has a set of tasks to complete to keep it healthy. The roots absorb water and minerals from the soil and anchor the plant. The leaves are what attract sunlight and provide nourishment to the plant. Finally, the stem supports the plant above ground and carries water and minerals to the leaves.

A tree’s trunk (or bole) is the stem and main wooden axis of a tree, which is an important feature in tree identification. In addition, the trunk is the most important part of the tree for timber production.

Tree branches help transport materials from the trunk to the leaves of the tree. They grow from the main trunk of the tree.

Twigs are thin terminal branches of woody plants. They show abscission scars where the leaves have fallen, an important diagnostic characteristic.

Plant roots form the biggest underground part of the plant, which is collectively referred to as its root system. They anchor the plant firmly to the ground.

Stems form the basis of the shoot system and bear leaves, fruit, and flowers. They are the part of the plant that grows above ground. The stems of trees have brown bark, while young stems are green. The region where the leaves arise is known as the node, and the region between the nodes is known as the internode. The stem provides support to the plant. It also protects it and aids in reproduction. Some underground stems are modified to store food, like potatoes and ginger.

The leaf is the most important part of the plant, containing chlorophyll which helps the plant prepare food by converting sunlight, carbon dioxide, and water into carbohydrates. The leaf consists of three parts, petiole, basal leaf, and lamina. Flowers produce fruit as the matured ovary develops after fertilization. Some fruits develop without fertilization and are known as parthenocarpy fruits. Their process is called parthenocarpy.

Types of plant tissues:

Plant tissues are of two types—meristematic tissues and permanent tissues.

Meristematic tissue: Cells divide actively at the tip. These are broadly categorized into three types.

1. The apical meristem produces the primary tissues, including the dermis, vascular tissue, and ground tissues.
2. The intercalary meristem: – Usually, monocotyledonous plants have intercalary meristems at the bases of their leaves, where they help lengthen the internode. Intercalary meristems can divide cells. They allow for rapid growth and regrowth of many monocots.
3. The lateral meristem produces secondary tissues, including cambium.

Permanent Tissue

Permanent tissue stops dividing after attaining its specialized structure and function, which occurs when the cells don’t divide further after attaining their specialized structure and function. These are further divided into simple permanent tissue and complex permanent tissue. Simple permanent tissues are composed of only one type of cells and have the same structure and function, while complex permanent tissues are composed of multiple types of cells cooperating with one another.

a. Simple Permanent Tissue

i. Parenchyma

Parenchyma is a type of simple permanent tissue that contributes to ground tissues in plants. It is composed of simple, living, and undifferentiated cells.

ii. Collenchyma

It is also found in mature herbaceous plants, including those with very little secondary growth, in stems and leaves. In addition, Collenchyma provides support for growing organs in herbaceous and woody plants.

iii. Sclerenchyma

Sclerenchyma cells are of many shapes and sizes, although they do not have a specific shape. But two main types occur— fibers and sclereids.

• Dicots have bean-shaped guard cells that contain chloroplasts
• Grasses have dumb-bell shaped guard cells
• Root hairs are unicellular
• Trichomes are multicellular

The ground tissue system

They form the major bulk of tissues between epidermal and vascular tissues, e.g., cortex, pericycle, and pith. In addition, it contains simple tissues of chloroplasts called mesophyll.

b. Complex Tissue

i. Xylem

Xylem guides water and nutrients from a plant’s soil interface to its stems and leaves while supporting and storing its mechanical energy. The xylem is one of the characteristics that distinguishes vascular plants from herbaceous plants.

ii. Phloem

The phloem is the vascular tissue responsible for transporting and distributing organic nutrients. It is also a signaling pathway to molecules and has a structural function in the phloem.

Protective tissues

These provide fortification to the plant. They include the cork and epidermis.

Epidermal Tissue System

The stomata are perforations in the epidermis that allow water and gas to escape from the plant. They assist the plant in losing water. The epidermis is composed of the outer covering of the plant, such as the epidermis, cuticle, stomata, epidermal extensions, as well as trichrome that forms on the stem and root hairs. Through transpiration, stomata regulate gaseous exchange and water loss.

Cork – In mature stems and roots, cork cells replace epidermal cells. Cork cells lack intercellular gaps, are lifeless, and are impervious to gas and water molecules. An extensive layer of cork is produced by the cork cambium to protect the delicate cambium of the vascular system and secondary phloem from mechanical damage, predation, and desiccation.