Botany – Roots
I. Monocotyledonae
(_______________________________)
vs Dicotyledonae (_______________________________) – These are old names for the
two classes of flowering plants. The names are still used today. However, the divisions
are now referred to as _______________________________.
All flowering plants belong to the Phylum _______________________________.
The dicots belong to Class _______________________________ and the monocots
belong to Class _______________________________.
Root image source: Original image on wikispaces.com by Darkstarz777 licensed CC-BY-SA.
What is a cotyledon? A cotyledon is stored “baby food” in a seed that helps the embryonic (“baby”) plant germinate (sprout) after the seed is planted in the soil. Because the “baby plant” can’t photosynthesize yet, the mother plant has to store all the food required to sprout and grow true leaves in the seed. This makes seeds very nutritious for people.
photo source:
https://www.britannica.com/science/radicle via @britannica ©Merriam-Webster,
Inc.
A. Monocots (Fibrous roots are also found in seedless vascular plants e.g. ferns)
1. Seed has only _______________________________
2. Roots are _______________________________ – many similar-sized,
small & short roots
3. Examples of monocots
a)
Grain crops –
b) Grasses –
c) Flower garden plants –
d) House plants –
e)
B. Dicots
1. Seed has _______________________________
2. Roots are _______________________________
3. Examples of dicots
a) Most of the fruits and vegetables you buy in the grocery store
(except corn, pineapples, onions, & a few others) –
b) Flower garden plants –
c) House plants –
d) Fruit & hardwood trees –
II. Root Development
A. The root originates from the _______________________________
(a part of the embryo of the seed).
B. Longitudinally (or lengthwise, from the root tip), roots have …
1. A root cap
a. _______________________________ is a slimy
polysaccharide that lubricates the passage of
roots through soil produced by the outer cells of the rootcap.
2. Region of cell division
3. Region of elongation, and
4. Region of maturation.
Root
Anatomy – Longitudinal Section
Image modified from: http://tudbotany.blogspot.com/2010/07/lab-2.html
C. _______________________________- composed of thimble-shaped
parenchyma cells produced by the apical meristem.
1. Protects the apical meristem from damage as the root pushes forward
through the soil.
2. Cells seem to have gravity perception (_________________________)
a. _______________________________ (leucoplasts containing
starch grains), are involved in gravity perception.
3. Distribution of growth hormones is influenced by physical stimulation
of the smooth ER causing Ca2+ release.
a. Physical stimulation is caused by the heavy starch grains
tumbling toward gravity.
D. _______________________________- apical meristem
1. Most of the cell divisions occur in a cup-shaped zone just behind the
actual meristem, adjacent to the root cap
a. Cells divide here every _______________________________,
while the actual meristem cells divide every 200-500 hours.
b. Cell division are usually rhythmic, peaking twice a day at about
_______________________________ &
_______________________________.
2. Cells are usually _______________________________with large
central _______________________________ and few
_______________________________
3. The meristem divides into three primary meristematic tissues:
a. _______________________________- outermost, forms
epidermis
b. _______________________________- inside protoderm, forms
parenchyma of the cortex
c. _______________________________- forms solid cylinder in
center of root, forms primary xylem, phloem, and pith.
E. _______________________________- directly adjacent and behind the apical
meristem
1. Cells grow to several times larger than their original length and become
a little wider
2. Small vacuoles within each cell merge to become a single vacuole
3. Except for secondary growth in girth in some plants, no further growth
occurs except in the _______________________________and
_______________________________.
4. The rest of the root remains _______________________________for the
rest of the plant’s life
F. _______________________________- also called region of differentiation or
root hair zone
1. Some epidermal cells form elongated extensions called
_______________________________.
a. Root hairs greatly increase the surface area of the root, thus
aiding _______________________________&
_______________________________absorption without the
necessity of the root growing longer.
b. Typical root may have _______________________________root
hairs/cm2
2. The epidermal cells secrete a thin _______________________________.
a. It is thin enough to allow __________________ to be absorbed.
b. It is thick enough to protect the root from __________________
and __________________ invasion.
3. Other cells differentiate and assume their functional forms
III. Root Structure (considered in cross section from the outer surface to the center)
A. From the outer surface to the __________________ (Greek for “pillar”, this is
the central cylinder of a root or stem, which is surrounded by the cortex.)
1. _______________________________- protective cells
a. Covered by a thin cuticle
b. Forms root hairs which increase the available surface area for the
intake of water
2. _______________________________- loosely packed parenchyma cells
for food and water storage
a. Surrounds the stele.
B. Within the stele…
1. _______________________________—specialized parenchyma cells
that have a waxy _______________________________
between cells called the _______________________________
a. Cell membranes of endodermal cells are fused to the Casparian
strip to regulate _______________________________ flow in/out
of the root
b. Inner walls of endodermal cells become increasingly thickened
by layers of wax and suberin over time
c. Some endodermal cells, called
_______________________________, remain thin-walled
for a longer period of time
2. _______________________________- the tissue of the root inside the
endodermis. Within the vascular cylinder, you find…
a. _______________________________—single layer of
parenchyma surrounding the xylem and phloem
1) Capable of undergoing cell division to produce
_______________________________
2) Gives rise to the _______________________________of
dicot roots
b. Many dicots and a few monocots develop a
_______________________________ from the pericycle
1)
Vascular cambium produces _______________________
to
the inside, and _______________________________
to the outside
2) Primary tissues become crushed or sloughed off and are
replaced by secondary tissues
c. In woody plants, the _______________________________also
arises from the pericycle, and produces suberized cork cells to the
outside.
1)
2) Most monocots have no secondary growth (they are
usually ______________________________)
C. The vascular tissues of the stele look different in dicots vs. monocots
1. In dicot roots
a. Primary xylem core, often _______________________________
b. _______________________________ in between the points of
_______________________________
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Examples of Dicot Root Xylem Cores |
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2. In monocot roots
a. _______________________________- loosely packed
parenchyma cells in the root’s center
b. _______________________________- forms a ring around the
pith
c. _______________________________- forms a broken ring
around the xylem
Root
Anatomy – Cross Section
D.______________________________________________________________of
roots can occur when roots of adjacent plants come into contact.
1. The exact mechanism is unknown, but it occurs through secondary
growth.
2. This can also allow _______________________________ to spread
3. from one plant to another.
IV. Root Function and
Specialized roots
A. Food Storage Roots
1. Extra cambial cells in the xylem produce many large parenchyma cells
for
carbohydrate storage: __________________________________
___________________________________________________________
2. Some storage roots are actually a combination of modified root and
stem: _____________________________________________
________________________________________________
3. Many are _______________________________ (they complete their life
cycle in two years)
4. Important food crops
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B. Water Storage roots 1. Found mainly in _______________________________ family 2. Similar to food storage roots but store water for when the environment is dry a. Some may reach 30 kg or more Photo source: https://www.installitdirect.com/learn/how-to-grow-halloween-pumpkins/ |
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C. Adventitious Roots 1. Roots that grow from places other than the ____________________________or _______________________________ 2. Usually _______________________________ roots that can be removed from the plant and grown normally |
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D. _______________________________ 1. Spongy roots found in plants that grow with their roots in water 2. They rise above the surface and facilitate gas exchange with the submerged portions of the roots Pneumatophores are “snorkels” that let submerged roots get oxygen to make ATP. Yes! Plants can drown. Photo
Credit: Doug Moyer Location: Mangrove Lagoon Wildlife Sanctuary;
Marine Reserve, St. Thomas, US Virgin Islands License
type: Royalty-free |
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E. _______________________________ 1. Usually used for support 2. Most are adventitious 3. Ivies have adventitious roots that attach them to surfaces. |
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4. _______________ have valem roots that attach them to other plants. 5. Some orchids have photosynthetic roots. |
Photo source: smartgardenguide.com |
6. Corn and Banyan trees have ______________ for support and to collect additional soil. |
Photo source: 10 Things You Need to Know About Banyan Trees by Mike Shanahan |
F. _______________________________roots
1. Pull plants deeper into soil
2. Parenchyma cells thicken and decrease in length, causing xylem
elements to become spiraled
a.
e.g. _______________________________
b.
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G. Buttress roots 1. angular roots produced at the bases of trunks of trees |
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H. Parasitic roots
1. Invade the tissues of other plants
2. Not true roots, but are root-like adventitious appendages called
_______________________________
a. Found in _______________________________,
_______________________________, and
_______________________________ which are
nonphotosynthetic (entirely parasitic, can’t live without host)
WATCH THIS VIDEO OF DODDERS: https://youtu.be/5gPuXtmrP0E
3. Also found in photosynthetic plants like
_______________________________ and
_______________________________
WATCH THIS VIDEO OF MISTLETOE & THE BIRDS THAT SPREAD THEM: https://youtu.be/Y84WuSnlbRs
1. Fungal filaments associated with plant roots
2. About 75% of seed plants have a _______________________________
relationship with fungi
a. Up to _______________________________ of the food made by
a plant is used to feed its associated fungi.
3. The fungi help the roots absorb _______________________________
and other nutrients
4. The fungi receive _______________________________ from the plant
J. _______________________________
1. Swollen areas of the roots that contain nitrogen-fixing bacteria…this is
also mutualistic
K. Root knots
1. Swollen areas in response to invasion of parasitic
_______________________________
V. What Makes Soil?
An interaction of:
1.
2.
3.
4.
5.
6.