Unit 3: Roots (A) Flashcards
Vegetative organs, such as (3), help plants make and use food, obtain water and minerals, and store resources, like food and water.
2 types
roots
stems
leaves
monocots (herbaceous)
dicots (woody)
functions of roots
- Absorption
- Anchorage
- Conduction
- Reproduction
- Food storage
- Photosynthesis
Characteristics of Roots
- Cylindrical in form
- Colorless or with drab colors
- Lack nodes and internodes
- Lack buds, leaves and flowers
- Generally branching
root systems
- diffuse or fibrous roots
- taproot or primary root system
- fleshy root system
- fascicled root system
- adventitious root
carrot
taproot
blazing star
taproot
sunflower
taproot
oat
fibrous root
poison ivy
adventitious root
________ (primary) and ________ (Diffuse) Root Systems
Both arise from radicle
taproot (primary)
fibrous (diffuse)
have several or many main roots, usually slender and about the same size and length, with numerous smaller root branches.
Diffuse or Fibrous roots
distinguished by the presence of a primary or main root which is the first root to develop during seed germination and which penetrates deep into the soil.
taproot or Primary Root System
a taproot system wherein the main root has considerably enlarged in size
Fleshy Root System
have swollen bulb-like parts in the roots.
Fascicled Root System
- roots that arise from anything other than the radicle
- can arise in the stems, or other parts of the plant
adventitious root
2 types of seedsq
dicot and monocot seed
external anatomy or Root Structure: Four Regions (Longitudinal section, L-S)
- Root cap
- Region of Cell division or Meristematic region
- Region of Elongation
- Region of Differentiation or Maturation
- Thimble-shaped mass of parenchyma cells at the tip of each root (protects the root from injury)
** the interior cells are meristematic - _____________ release a mucilaginous lubricant called mucigel. It also favors the growth of beneficial commensal bacteria.
- _____________ on the sides of the root cap cells contain starch which act as gravity sensors
ROOT CAP
dictyosomes
amyloplasts
- Region in which new cells are formed via mitosis
- Cells in this area are small, nearly cube-like, with thin cell walls and very distinct nucleus
REGION OF CELL DIVISION OR MERISTEMATIC REGION
- _____________: group of cells known as growth initiating cells
- _____________: consist of group of actively dividing cells directly beneath the root cap; these cells make up the primary meristem
- _____________: consist of cells that have begun to show differentiation
- _____________: group of cells where no cell division takes place
– function as a cellular reserve (a source of replacement to the apical initials)
REGION OF CELL DIVISION OR MERISTEMATIC REGION
- apical initials (in the apical region)
- growing point
- primary meristem
- quiescent center
- Area of cell enlargement
- The cells in this region increase in cell length (up to 10x their original length)
- Cells are mature and columnar in shape
- The cells of this region make up the embryonic tissues /generative tissues (procambium, ground meristem and the protoderm)
3 TYPES OF TISSUES
REGION OF ELONGATION
protoderm/dermatogen
ground meristem/periblem
procambium/phlerome
- Embryonic/Generative tissues:
- ____________ or _____________: produces the epidermis
- ___________ or _____________: produces the cortex and pericycle (ground tissue)
- ____________ or _____________: produces the vascular tissues and the pith
REGION OF ELONGATION
protoderm or dermatogem
ground meristem or periblem
procambium or phlerome
- Region above the elongation region where the cells differentiate into specific vascular tissues (_____ & _____)
- The youngest part of the region is called the ____________
- ____________: outgrowths and elongations of the epidermal cells
REGION OF MATURATION OR DIFFERENTIATION
- xylem & phloem
- root hair zone
- root hairs
- In this region, the embryonic tissues undergo modification and maturation:
____________: -> epidermis
- Ground meristem cortical cells (_________ & ___________)
____________: -> vascular tissues (xylem and phloem) and pith
REGION OF MATURATION OR DIFFERENTIATION
- protoderm
- cortex and pericycle
- procambium
- the region between the epidermis and the pericycle
- stores food
cortex
- region lying between the
endodermis and the conducting bundles (xylem/phloem) - The cells here continue to divide
even after maturation and form the lateral branch roots and part of the vascular cambium
pericycle
undergo modification and maturation
embryonic tissue
- the “youngest” part of the region; root hair is evident in this area
- Root hair-like extensions of the epidermal cells that adhere tightly to soil particles and increase the absorptive surface of the root.
root hair zone
Internal Anatomy of the Root
3 main parts
EPIDERMIS
CORTEX
STELE
- one-cell thick that covers the root except the root cap
- absorbs water and dissolved material from the soil
epidermis
- formed by the ground meristem
- occupies the largest cross-section area of the root
3 LAYERS
CORTEX
hypodermis
parenchyma cells
endodermis
- the outermost layer with suberin
- fxn: slows down the outward flow of water and nutrients
hypodermis