Plant Cells and Tissues Overview

Study Notes

Plant cells are identifiable by their cell walls and large central vacuole.
Plant cells have many types of cells adapted for specific purposes.
Parenchyma Cells
- Storage
- Photosynthesis
- Gas exchange
- Protection
- Tissue repair and replacement
Collenchyma Cells
- Support for surrounding tissues
- Provides flexibility for plant
- Tissue repair and replacement
Sclerenchyma Cells
- Support
- Transport of materials

A tissue is a group of cells that work together to perform a function.
A plant tissue can be composed of one or many types of cells.
There are four different tissue types found in plants:
- Meristematic
- Dermal
- Vascular
- Ground

Xylem: water carrying vascular tissue, composed of specialized cells called vessel elements & tracheid.
- Vessel elements: tubular cells stacked end to end, lack end walls, allowing free movement of water from one element to the next.
- Tracheid: tubular cells with pitted ends and end walls, less efficient at moving water than vessel elements.
Phloem: main food-carrying tissue in vascular plants.
- Contains two types of cells:
  - Sieve tube members: Contain cytoplasm but lack nuclei and ribosomes when mature.
  - Companion cells: Occur next to sieve tube cells and have a nucleus.

The tip of a root is covered by the root cap.
The root cap consists of parenchyma cells to help protect root tissues as the root grows.
Between the epidermis and vascular tissue is the cortex.
Next to the endodermis, towards the center of the root, is the pericycle, which produces lateral roots.

Herbaceous stems: soft, flexible, and capable of photosynthesis.
Woody stems: rigid and fibrous.
Main function: support of leaves and reproductive structures.
Stem Types & Functions:
- Tuber: food storage
- Rhizome: food storage, asexual reproduction.
- Runner: asexual reproduction.
- Bulb: food storage
- Corm: food storage

Structure:
- Water travels from the roots up through the stems and into the leaves, replacing water used in photosynthesis and lost from the plant by evaporation.
- Water evaporates from the inside of a leaf to the outside through stomata in a process called transpiration, which helps pull the water column upward.
Function:
- The main function of leaves is photosynthesis, with many adaptations to optimize this purpose.
- Most plants have a flattened portion called the blade with a large surface area.
- The blade is attached to the stem by a stalk called a petiole