3: Plant Structure

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Page ID: 27728

Melissa Ha, Maria Morrow, & Kammy Algiers
Yuba College, College of the Redwoods, & Ventura College via ASCCC Open Educational Resources Initiative

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Plants cells are complex structures with several organelles lacking in animal cells. Among these are the cell wall, central vacuole, and plastids (the most familiar of which are chloroplasts). There are three main tissue types, called epidermal, ground, and vascular tissue. Each tissue type consists of specialized cells adapted for unique functions. Plants have two organ systems: the root system and the shoot system (figure \(\PageIndex{a}\)). The root system is typically belowground and consists of roots, which specialized in water and nutrient absorption. The shoot system consists of stems and leaves and is typically aboveground. Stems function in supporting the plant and transporting materials (conduction), and leaves function in photosynthesis. This unit will explore these structure at the macroscopic and microscopic level.

A block of recently germinated grass with a network of roots underneath — Figure \(\PageIndex{1}\): The shoot system consists of the stems and leaves, and the root system is the fibrous mat embedded in the soil. Image by Maria Morrow (CC-BY-NC).

3.1: Cells and Tissues
A cell is the smallest unit of a living thing. Organisms can be unicellular or multicellular. Thus, cells are the basic building blocks of all organisms. Several plant cells of one kind that interconnect with each other and perform a shared function form tissues.
3.2: Roots
Roots are an important plant organ. They anchor the plant, transport water, minerals, and sugars, and store excess nutrients.
3.3: Stems
The stem is an organ of the shoot system that functions in support, conduction, photosynthesis, and storage.
3.4: Leaves
Leaves are the organs of the shoot system adapted for photosynthesis. They often consist of a petiole and a blade. Leaves differ with respect to their arrangement on the venation, and shape. Internally, leaves consist of three main tissues: epidermis, mesophyll, and vascular bundles. Some leaves are modified for other functions such as defense, storage, or attachment.

Thumbnail Image: Cross section of a beach grass leaf from Berkshire Community College Bioscience Image Library (public domain).