Plant Tissues Flashcards
Three Types of Simple Tissues
Parenchyma, Collenchyma and Sclerenchyma
Complex Tissues….
make up the plant’s vascular system and outer covering
Secretory tissues….
Produce and Secrete Materials
Parenchyma
- These are the most common cell type
- Cells are somewhat spherical and elongated with thin flexible walls which is sometimes lignified
- Cells have a large vacuole with many plastids
- Located where light is present (Photosynthesis)
Parenchyma Uses
- Stores starch, oils, water and salt
- Plant growth
- Food production (photosynthesis)
- Resins (sap), hormones, enzymes, and nectar can be secreted by these cells
- Wound healing and regeneration
- Hydrostatic support
Collenchyma
- Cells are strong and flexible and they develop from parenchyma cells
Celery strings are strands of collenchyma
- The cell walls are thickened at the corners (via cellulose) and quite flexible, these walls are composed of alternating layers of pectin and cellulose.
Collenchyma Uses
- Provide mechanical support to a growing plant
- Specialized to support young stems and leaf petioles
- Cells are elongated, often contain chloroplasts, and are living at maturity
Sclerenchyma
- Cells are strongest plant cell type
- Cells are long, narrow cells with thick, pitted cell walls and tapered ends. Sometimes very elastic and can be stretched to a degree, but they will snap back to their original lengths.
- Second cells wall hardened by lignin
- Cells die when they reach maturity
- Used by humans to make linen and rope
Two types of cells: fibers and sclereids
Sclereids
- short cells that vary in shape
- common in shells of nuts or the stones of fruits
eg. gritty texture of pears are sclereids
Fibers
- long tapered cells that occur in groups or clumps
- abundant in the wood, inner bark, and veins of leaves
Vascular System
- Consists of an interconnected network of cells that traverse the entire body of the plant
- All cells of the plant require minerals and water, which are absorbed by the roots and transported by the xylem.
- Sugars are manufactured in the leaves and transported by the phloem.
Xylem
- A complex tissue made up of different kinds of cells that work together to transport water and dissolved minerals.
- The cell types in the xylem are, the water conducting cells- tracheid and vessel members (these join together end to end to make vessels)
- Cell walls are thickened with secondary deposits of cellulose which are usually further strengthened by lignin
- The secondary walls are deposited in spirals and rings and are usually perforated by pits
eg: wood
Primary Xylem
- Formed in the root and shoot apex very early in organ development
-Xylem that forms later in the development of stems and roots is organized in cylindrical patterns and is called secondary xylem
Usually leaves have only primary xylem
Phloem
Tissue that transports sugar through the plant
Primary phloem- occurs in vascular bundles near the primary xylem in young stems and leaves and in the vascular cylinder in roots
Secondary phloem- occurs outside the secondary xylem in older stems and roots, usually in plants that live more than one year
Both sieve tube elements and companion cells are connected by numerous plasmodesmata
Sieve Tubes
Sieve Tube Members- cells that join at their ends, to form long sieve tubes.
Sieve Tubes- are conducting elements of the phloem (a,b) which transport sugars produced by photosynthesis in the leaves to other plant parts.
Companion Cells
- Part of the phloem
- Control the metabolism of the sieve tubes
- Aid in the movement of materials into and out of the sieve tube members
Plant Tissues
- Dermal or Protective
- Ground
- Vascular/Transport
Ground Tissue
- Meristematic
- Parenchyma
- Collenchyma
- Sclerenchyma
Meristematic (Ground Tissue)
- Apical
- Intercalary
- Cambial
Vascular/Transport Tissue
- Xylem
- Phloem (fibers)
Both with associated parenchyma
Dermal Tissue
- aka the Epidermis
- has a protective function
- keeps the internal plant environment separate from the external environment
- covers the surface of leaves, roots and stems
- has flattened cells with their top and bottom surfaces parallel with NO intercellular spaces
- only stomata and lenticels present as pores
eg: upper and lower epidermis
