Plant Tissues and Systems

Cell Specialization in Plants

• Meristems are regions within plants that contain meristematic cells (undifferentiated or partially differentiated cells)

• These regions are critical for plants to grow in height and girth

  • Apical meristem in root and tip for height

  • Lateral meristem in stem for girth

• They will differentiate to form three types of plant tissues

Plant tissues

• Three types:

  • Dermal tissue

  • Ground tissue

  • Vascular tissue

Dermal tissue

• The outermost layer of a plant

• 2 types:

  • Epidermis tissue (leaves and new shoots – non-woody)

  • Periderm tissue (woody parts)

Epidermis

• A single layer of cells surrounding a plant

• Structures found on it include:

  • Stomata (sing. stoma)

  • Trichomes (hairs)

• Typically transparent with NO chloroplasts

Stomata

• Pores on the surface of a leaf

• Regulated by two guard cells

• Stomata open when plants respire and release water vapour and other gases

• Stomata close when plants want to protect themselves from heat and water loss

Functions of dermal tissue

• Protection

• Regulate gas exchange

• Helps with transpiration

• Absorbs water and nutrients (roots)

Ground tissue

• All tissues that are not part of the dermal and vascular tissues

• Found in all parts of plants (for example, space between the epidermis and vascular tissue in stems)

• three types

• structure/hardness of a plant is based on the ground tissue

Functions of ground tissue

• Photosynthesis

• Storage of water and sugars

• Structural support

• And many more…

Vascular tissue

• Responsible for conducting materials in a plant

  • Water

  • Nutrients

  • Minerals

  • Hormones

Xylem and phloem vessels

• Xylem vessels are bigger than phloem

• Xylem vessels mainly for water and minerals

• No barriers on the inside of the xylem vessel

• Phloem vessels mainly carries food such as sugar in a plant

• Phloem vessels can flow in two ways, while xylem vessels can only flow in one way

• The cell wall of the phloem cell is a lot thinner than the walls of the xylem vessels

• Structure and function

Organs and organ systems

• Root system (below ground)

  • Root (organ)

• Shoot system (above ground)

  • Leaf (organ)

  • Stem (organ)

  • Flower (organ in some plants)

  • Fruit (organ in some plants)

Root system

• Functions:

  • Absorbs water and minerals

  • Anchors plants

  • Stores food

• Typically fall under two categories: fibrous root and taproot

Shoot system

• Functions:

  • Photosynthesis

  • Reproduction

  • Transports water and nutrients

• Consists of leaf and the stem (organs); flowers and fruits are also found in some plants

Leaf

• Main site of photosynthesis and transpiration

• Coated by a waxy cuticle (for protection)

• Mesophyll cells with chloroplasts (ground tissue) found under the epidermis

  • Palisade mesophyll (a lot of chloroplasts)

  • Spongy mesophyll (spaces between cells)

Stem

• Called trunk in trees

• Supports the plant, transports water and nutrients, and can even store food (i.e. potatoes) 

Problems with animal organ systems

Problems with the Root system

• Root Rot

  • Fungal infection due to overwatering or poor soil drainage

  • Infectious (soil and pot need to change)

  • Symptoms include yellowing leaves and wilting

Problems with the Shoot system

• Blight

  • A group of diseases that causes withering, yellowing, or lesions on leaves

  • Can be bacterial or fungal infections

  • Results in eventual death of the plant