BIO 102 Chapter 33: Plant Cells and Tissues

• BIO 102 Chapter 33 focuses on the plant body.

Plant Cells

• Plant cells contain chloroplasts for photosynthesis.
• Large vacuoles within plant cells maintain turgid pressure and store minerals and nutrients.
• Cell walls, composed of cellulose offer structural support to plant cells.
• Plasmodesmata connect adjacent plant cells.

Plant Tissues

• Three general types of plant tissues are dermal, ground and vascular.

Dermal Tissue

• Dermal tissue comprises the epidermis and periderm.
• The epidermis consists of closely packed cells that cover and protect underlying tissues, and controls water loss.
• Epidermal cells can secrete a cuticle, which is a waxy substance that protects against water loss and pathogens.
• Epidermal tissues can have hair-like structures, and stomata with guard cells to facilitate CO2/H2O exchange,.
• The periderm is a thick layer of dead cells that grows on the outside of stems and roots due to secondary growth and is part of the bark.
• The periderm protects the plant from pathogens, injury, and excessive water loss.

Ground Tissue

• Ground tissue makes up the majority of the plant.
• It is composed of parenchyma, collenchyma, and sclerenchyma cells.
• Parenchyma cells are the most common and perform photosynthesis to create sugars, and also store energy as starch.
• Collenchyma and sclerenchyma cells provide strong, flexible structure and have thick cell walls made of cellulose/lignin.

Vascular Tissue

• Xylem includes tracheids and vessel elements.
• The xylem cells have a wider diameter.
• Xylem transports materials faster, and allow for faster growth in angiosperms.
• Phloem's sieve tube cells are supported by companion cells in angiosperms, facilitating efficient nutrient transport.

Growth in Plants

• Primary growth results in plants growing upwards (shoot system; in the air) and downward (root system; underground).
• Primary growth is facilitated by apical meristems, with cells that continuously copy/reproduce.
• The root apical meristem has a cap to push through the soil to find water, and the new cells push downwards toward the cap.
• The shoot apical meristem lacks a cap, and produces new cells behind it for upward growth.

Secondary Growth

• Secondary growth is an outward growth where stems and roots get thicker over time, resulting in wooded growth.
• Secondary growth occurs due to the vascular cambium, a thin layer of cells between the xylem and phloem.
• Cells create new xylem to the interior, pushing the vascular cambium outwards.
• Cells also create new phloem to the exterior, pushing the old phloem outwards.

This lesson summarizes plant cells and tissues. Plant cells use chloroplasts for photosynthesis and have cell walls for support. Plant tissues include dermal, ground, and vascular types, each with specific functions.