Thin wall, living, storage, wound healing and regeneration
what are the least specialized cells?
parenchyma
These cells have a lot of intercellular space, are usually stuffed with plastids and are found in the pith of shoots, storage tissue of fruits, seeds and roots and the mesophyll of leaves
parenchyma
cells that can perform a wide variety of functions, including photosynthesis
parenchyma
Collenchyma
thickening walls, living, support
Where is collenchyma found?
near the surface of the cortex in stems, along the veins of leaves, petiole (stalk) of leaves
cells starting to develop a secondary cell wall
collenchyma
these cells can revert to a parenchyma state
collenchyma
These cells are found most often in areas that are growing rapidly and need to be strengthened
collenchyma
celery strands
collenchyma
Two types of sclerenchyma?
Fibers (needle-shaped, mechanical strength for stems, high load-bearing capacity)
and Sclereids (variable in shape, can be grouped in bundles, single cells or small groups of cells within parenchyma tissues)
Where can sclereid tissue be found?
Pears
Hard outer shell of seeds and nuts
Stones of drupes
These have the thickest cell walls
sclerenchyma
when the apical meristem is removed from a shoot, what happens?
B. axillary or lateral buds will grow
The hollow stem of a grass plant is called
D. culm
Stem that holds a corn ear
shank
It supports and arranges leaves to intercept light, supports flowers and fruits, transports water and nutrients, stores plant food, helps with plant propogation and photosynthesis (succulents)
Stem
what plant hormone is involved in apical dominance?
auxin
shoot
stem plus leaves and other structures
stalk
solid stem of grass
examples of a woody stem
walnut tree
example of a herbaceous stem
tomato
what do grass plants have instead of petioles?
sheaths
what are the axillary branches called on grass plants?
tillers
To produce certified disease-free plants, which portion of a plant is typically propogated via tissue culture?
C. apical meristem
This type of plastid stores starch
C. amyloplast
These living cells have sieve tube elements and companion cells, while they do not have vacuoles or nuclei
A. phloem
T/F Stems have vascular bundles of xylem and phloem for water and carbohydrate transport
True
Is xylem living at maturity?
No, it loses cytoplasm at maturity so it's a non-living tissue
Features of a monocot stem
epidermis
parenchyma inside
scattered vascular bundles
no cambium
vascular bundles surrounded by sclerenchyma or other thick-walled cells
Features of a dicot stem
epidermis
cortex in woody dicots is between epidermis and ring of vascular bundles
vascular bundles in circle (circle grows together with age in woody stme)
vascular cambium
pith in center of stem for food storage
T/F Dicot stems have pith in the center for food storage
True
T/F Grasses usually have compound leaves
False
T/F Excess nitrogen can cause weaker plant stems
True
T/F Grasses have intercalary meristems, while dicot plants do not
True
T/F The stem that holds an ear of corn is known as a cob
False (it's a shank)
Lodging is the ability of a plant to produce tiny plants at the margins of their leaves - T/F
False
Low light intensity promotes
etiolation
longer internodes, less lignin (strong fiber in cell walls), lodging
Plants transport photosynthates from leaves to sites of active growth, called
the mark left on a twig where the leaf petiole was attached
the main site of photosynthesis
leaves
also responsible for transpiration, respiration, carb storage and transport and gas exchange
monocot leaves
blade or lamina
sheath
collar (where sheath and blade join)
parallel veins
dicot leaves - two types?
simple (one blade per leaf)
compound (two or more leaflets or blades per leaf)
where are leaves attached?
nodes
where the petiole of leaf attaches to the stem
leaf axil
types of veins
net
pinnate (feather-like)
palmate (finger/hand-like)
Radicle
first root from a seed
develops into primary root
If the primary root continues to grow and develop, what type of root does it become?
tap root
advantages of taproot system?
can grow deeply into soil
some are harvested for food
how do you know if you're looking at a cross section of a dicot root?
it has a cross in the middle
if the primary root doesn't develop much, but there are lots of little roots shooting out, what type of system?
fibrous root system
advantages of a fibrous root system?
more thoroughly distributed and abosorb more water and nutrients within the root zone
allows greater contact within the rooting zone (common in grass crops)
Secondary roots
branch out from first degree roots or arise from plant stem tissue
tertiary roots
arise from second degree roots
adventitious roots
arise from stem or other non-root meristems
usually originate at a node
types of adventitious roots
brace and prop roots
loosely packed parenchyma cells inside the epidermis of a root, which store food and nutrients for the root are called the
D. cortex
the band of water-proof material that forces water to enter the vascular system via cells outside of it is called
E. casparian strip
20-30 percent of photosynthetic energy is spent on what?
root production
How much of plant mass is apical meristem?
less than 1%
where do roots come from?
meristems near the tip of roots
features of a monocot root system?
fibrous root system
root system develops from adventitious roots
scattered vascular system around the perimiter (vascular bundles around the outer part)
features of a dicot root?
taproot system
1st degree root persists, produces branches and continues as main root of plant
vascular system is a cross in the center of the stele
where is the apical meristem?
above the root cap
cells divide fairly rapidly here
above the meristem is
zone of elongation (1 to 10mm long)
this is where new-formed cells take on water and elongate to mature size, its primary function is to increase root length
located above the zone of elongation is
differentiation zone or zone of maturation
Root hairs develop from where?
epidermal cells
once epidermal cells cease elongation, they produce tiny extensions into the soil area
up to 200 root hairs per mm2 of root
these are essential for rapid absorption of water and nutrients
root hairs
in typical soil, water is mostly a thin film surrounding every microscopic soil particle. how does it get absorbed?
by root hairs
water diffuses molecule by molecule, trhough the root hair's cell membrane, toward the main roots and then enters the xylem
Root anatomy: the cortex
under the epidermis
loosely packed cells, can be several layers thick
conduct water and nutrients to vascular bundle
stores food and nutrients for the root
Root anatomy: epidermis
outermost cells
single layer of cells on the root surface
absorb water and nutrients
root anatomy: endodermis
single layer of cells that separates the vascular bundle from the cortex
regulates types of absorbed nutrients allowed to enter vascular cylinder
Two pathways of water in roots
symplast (living portion of cells)
apoplast (moves between the spaces between the cells)
endodermis barrier is
casparian strip
T/F A typical tree has hundreds of miles of roots with hundreds of thousands of root tips
True
T/F Taproots can grow deeper into the soil than fibrous roots, but fibrous roots absorb more water and nutrients than taproots
True
T/F soughing and root secretions are high energy processes, and a plant uses 2 to 5% of its photosynthetic energy to grow new roots
False
T/F Cells in a root's zone of elongation are newly-formed cells that take on water and elongate to their mature size
True
T/F Root hairs are an extension of epidermal cells
True
T/F Roots are able to detect the presence of water in the soil and grow toward the water
False
T/F When water enters a root and moves inside a cell, and then travels from cell to cell on its way to the vascular system, this pathway is known as the apoplast
False (it's the symplast)
Pericycle
separates xylem and phloem
layer of meristematic cells where branch roots develop
vascular cylinder tissue
Stele
vascular cylinder tissue, the stele is the root center tissues including the pericycle, phloem and xylem
stele diameter is larger in monocots than dicots
vascular system
very center of the root
made up of phloem and xylem
pith
found in the center of a monocot
cambium
found only in dicots
cells can divide to produce 2nd degree growth in perennial plants
80% of nutrient and water uptake occurs where in the soil?
the top 18 inches
once water enters the root, it moves through the cortex to where?
the endodermis, through the endodermis to pericycle and then to the xylem
water has entered the xylem. now what?
it moves rapidly upward in plant to stems and leaves, carrying nutrients with it
most carbohydrates transported to the root do what?
they're used for active root growth, but some crops will sore carbohydrates in their roots for later growth or regrowth
stored carbohydrates allow plants to produce new shoot growth
Rhizobium
nitrogen-fixing bacteria
symbiotic relationship with legumes
n-fixing enzyme nitrogenase
converts atmospheric n into ammonia
gives N to Plant
plant gives food to bacteria
Azospirillum
Nitrogen-fixing genus of bacteria in many grasses including grain crops
bacteria secretes auxins which stimulate growth of root hairs
Frankia
Nitrogen
Defense
Increase number of root hairs
mineral and water uptake
transport of hormones through roots
mycorrhizae
A mycorrhizae is a mutualistic symbiosis between plant and fungus
localized in a root in which energy (carbon compounds) move primarily from plant to fungus and inorganic resources (principally phosphate) move from fungus to plant.
root dry weight is usually how much of the total plant dry weight
1/3 to 1/4
Root surface area
at least 20 to 30 times greater than leaf and stem surface area
symbiosis
a mutually beneficial relationship between different species of organisms
The Rhizobium genus of nitrogen-fixing microbes is in this classification
Bacterial
Frankia microbes enter into a mutually beneficial relationship with
Woody trees and shrubs
flavinoids
plant secretes, attracts rhizobium
myco refers to
fungal
the ideal soil has these characteristics
20-25% air space
25% water
45% minerals
5% organic matter
geotropism
roots grown downward with gravity
phototropism
roots grow away from light
thermotropism
roots grow better in certain temperatures
tropism
when growth responds to external stimuli
hydrotropism
roots grow more favorably in moisture environment
T/F Roots can grow only where root pressure is greater than the physical pressures exerted against the roots
true
T/F Wetter soils warm up more slowly and cool more slowly than drier soils
True
T/F Dihydrous oxygen should be banned from drinking water
False
T/F Soil texture is determined by the amount of sand, silt and clay in the ground
True
T/F Adhesion is the attraction between molecules that are not alike, for example, a clay particle and a water molecule
True
T/F Field capacity is the water available for plant uptake a short while after a heavy rain or irrigation (after gravitational water is gone)
True
What percentage of plants are water?
90%
Soil is a water reservoir. Inputs?
Rain, irrigation
Soil is a water reservoir. Outputs?
plant uptake
evaporation
leaching
adhesion
attraction between unlike molecules
cohesion
attraction between like molecules
soil moisture tension
soil particles have an attraction on soil water to keep it near particles
water also has an attraction for itself
water in large pores held with less tension than water in smaller pores (easier for roots to get water from larger pores)
saturation
all soil pores are filled with water
gravitational water (free water)
water in saturated soil that will quickly drain once the source of water input is gone
field capacity
when gravitational water is gone
water held in pore spaces that is available for plant uptake
unavailable water
as soil dries, it reaches a point where plants can no longer extract water from soil although there is still water tightly held in small pore spaces
wilting point
name for soil when the remaining water is unavailable for plant uptake
what pulls water through the plant to the highest leaves?
transpiration
how is the pull of transpiration created?
when water evaporates from stomata
active transport
use energy to make protein move or change shape to allow ion inside membrane (takes energy to transport ions)
where is water stored?
vacuole
turgor pressure
high water volume inside cells creates turgor pressure
gives plants rigidity
organic matter that has decomposed as far as will happen and is considered a stable product is called
D. humus
This is the conversion of organic forms of a nutrient to an inorganic form that plants can absorb
E. mineralization
The A horizon of the soil is
D. answers a and b are both true
T/F Most of the organic matter is found in the top 2 feet of the soil
False - it's the top 12 inches
T/F High rainfall increases the rate at which new organic matter is formed and high temperature increases the rate of organic matter decomposition
True
T/F Litter is crop residue that has not started to decay yet and individual components are still recognizable
True
T/F The higher a soil's CEC, the harder it is for plant roots to obtain nutrients from the soil
False
T/F Negatively charged ions are called cations
False - they're anions
T/F clay and organic matter have a large number of negatively charged sites on their surfaces
True
List some soil inhabitants that become organic matter
roots
fungi
bacteria
microbes
worms
burrowing animals
Soil structure
arrangement of soil particles into stable aggregates or granules
natural and cultural factors can improve or reduce structure
how much of the world's topsoil has been lost to erosion or carried away by water?
1/2
Carbon nitrogen ratio recommended for compost?
30:1
(carbon is brown, nitrogen is green)
sandy soil
well drained
easier to till
warms quickly
low fertility
probably need water more
loams
balanced mix of sand, silt, clay
relatively fertile
clay
poor drainage
so tightly packed, holds onto water
warms slowly
imrove soil structure
add compost, organic matter
facilitate growth of earth worms
the amount of organic matter in soil depends on
precipitation, temperature and cultural practices
increased temp increases rate of OM decomp
increased rainfall increases rate of OM formed
tillage increases decomp
most organic matter is found where?
top 12 inches
Litter
Crop residue - can still recognize what it was originally
Duff
Partially decomposed
can still recognize what it was originally
Humus
Stable OM, broken down as much as it's going to
Mineralization
OM can't be taken up by plants, so it's turned into inorganic matter plants can absorb
Soil air is essential for
root and microbe growth
poor aeration slows microbial decomposition and causes more anaerobic organisms to grow
2 main factors that affect soil nutrient status and availability of nutrients for plant uptake
pH
CED (Cation Exchange Capacity)
CEC of a soil determines
how well it can hold nutrients
Cation nutrients
K, Ca, Mg
Can be held by soil for plant root uptake
Anion Nutrients
Not held by soil and can wash down with gravitational water
Nitrates
Soil pH
measure of acidity or alkalinity of a soil
measures 0-14
Soil pH less than 7
Acid
Soil pH greater than 7
alkaline
Soil pH of 7
neutral
Most horticultural crops prefer a pH of
6.0-7.3
How would you raise pH
add lime, limestone
How would you lower pH
add sulfur or peat moss, pine needles, orange peels (maybe)
T/F Soil pH usually goes down over time
True - alkaline products leach below the root zone
A Horizon
Top soil, top layer
Highest in OM
Main region of plant growth
can wash away
could be 1", 12-18" ideal, or several feet deep
B Horizon
More clay
Less OM than A
Sometimes called subsoil
Can be several feet thick
Can be totally exposed
C Horizon
between B and bedrock
Least amount of chemical changes over time
in certain places, including Ozarks, may not have any or have v. little
On average, how often should you test your soil?
every three years, unless you have a problem or have low CEC soil
salinity
excessive nutrients
symptoms of salinity?
plants wilting even when soil is wet
salt crusting on soil surface
halophytes
can tolerate increased salt conditions
may have roots that exclude uptake, excrete excess salt thru glands, store in vacuoles
Sodic soil
excess sodium
What are saline soils?
C. soils with too many soluble salts
What materials may be added to soil to lower its pH?
B. peat moss and sulfur
A plant will not grow and develop properly if any one nutrient is deficient even if it is a nutrient that the plant needs in very small quantity
law of the minimum
term used to describe a nutrient deficiency that causes leaves or other plant parts to turn yellow
chlorosis
t/f tilling when the soil is wet can destroy soil surface
true
t/f if a nutrient is mobile within a plant, deficiency symptoms will first appear on the youngest, newest tissue
false
list the three macronutrients
Potassium
Phosphorus
Nitrogen
List essential micronutrients
B
Cl
Cu
Fe
Mn
Mo
Zn
Atomospheric Nutrients come from the atmosphere. what are these?
Carbon, Hydrogen and Oxygen
Macronutrients, taken up from the soil
N, P, K
Macronutrients used in the greatest quantity
S, Ca, Mg
Chlorosis
yellowing
interveinal chlorosis
yellowing of areas between veins on leaves
necrosis
browning
marginal necrosis
browning of margins of leaves
gypsum
form of lime, raises pH
Is nitrogen mobile in plants?
Yes
Deficiency symptoms of nitrogen
uniform chlorosis, then necrosis, older leaves first, stunted growth
Nitrogen is a component of
plant proteins, DNA, enzymes, more
Nitrogen exists as
in nature, as gas
inorganic compounds NH4 and NO3
organic compounds
unavailable forms of nitrogen are made available to plants through a series of chemical reactions called
the nitrogen cycle
can lightning during thunderstorms add nitrogen
yes, about 10 pounds per acre per year
luxury consumption
plants absorb with their roots more of a particular element than they need
the manufacturing of ammonia for fertilizer is known as the
haber-Bosch Process
converts N2 to NH3
Urea has how much nitrogen
46%
NO4
Ammonium
NO3
Nitrate
Plants take up nitrogen in what form?
Ammonium (NH4) or Nitrate (NO3)
This element is an essential component of cell walls and has an important role in cell division
Calcium
Which essential mineral may build up in excessive amounts in the soil if you fertilize often with animal wastes?
Phosphorus
A deficiency of this element may result in a purple or reddish color on leaves, especially on the undersides.
Phosphorus
What is phosphorus good for?
component of ATP, DNA, Cell membranes, proteins, enzymes
Required for synthesis of carbohydrates and proteins in the plant
concentrated in regions of active plant growth and flowers and fruit
Most of plant P (Phosphorus) is used in what stages of growth?
the first stage
Is phosphorus (P) mobile or immobile?
mobile
deficiency symptoms of phosphorus
purplish coloring of older leaves
stunted growth
poor root growth
what symbiotic relation helps plants take up P (phosphorus) and can be used as part of a fertility program?
mycorrhiza
can absorb P from soil and carry back to plant in exchange for carbs
T/F If you apply an organic mulch such as wood chips around your plants, you need to add extra nitrogen to the soil so that the microbes and the plants hae adequate nitrogen nutrition
True
T/F Most plants have a vascular/pipe system to move oxygen from the canopy down to the root system
False
T/F Mycorrhizae are more likely to be found in heavily-fertilized soils than in soils of moderately good fertility
False
What is mineralization?
the conversion of an element from an organic form to an inorganic state as a result of microbial decomposition
In a fertilizer analysis of 6-24-16, the 16 tells you that the fertilizer contains
16% potassium by weight as K2O
How much nitrogen would be in a 50-lb bag of 5-10-5?
2.5 pounds
How much potassium would be in a 100-pound of 20-5-10 when the conversion factor to arrive at K = 0.82?
8.2 pounds
What is the ratio of a bag of 20-10-20 fertilizer?
2-1-2
What is a complete fertilizer?
only guaranteed to contain N P and K
Potassium (K)
highly mobile in plant
plants take up more K than N but K is less likely to be deficient
Plants may actually take up more K than they need
Is K prone to leaching?
No - has cation charge which allows it to adsorb to soil particles
Deficiency symptoms of K
marginal necrosis of leaves
curling leaves
weak stems (lodging or falling over of plant parts)
luxury consumption of K can reduce uptake of other essential nutrients, especially
Mg
Essential for cell wall formation and cell division
calcium
it's relatively immobile in soil due to cation charge ++
seldom deficient
Iron
most commonly deficient of micronutrients
immobile
deficiency symptom is yello to white interveinal chlorosis on new growth
Soil nutrient balance: inputs
fertilization
atmopsheric deposition
organic residues
Soil nutrient balance: outputs
plant removal
gaseous loss
conversion to unavailable forms
Leaching loss
Light: quantity is
intensity
measured in foot candles (how much light would give off a foot away)
Light quality is
wavelengths
wavelengths that have the most effect on plant growth are red and blue
blue wavelength
germination
red wavelengths
promote flowering
photoperiod
length of light in a 24 hour day
photoperiodism
response of plants to changes in photoperiod
phytochrome
hormone that controls floral initiation
occurs in two forms - phytochrome red and phytochrome far red
Forcing
tricking a plant into doing something at a time earlier that usual
light quality refers to
light wavelength or color
freezing injury
causes formation of razor-sharp ice crystals
occurs at temps less than 32 F
is a common occurence for crops native to temperate climate
the risk of frost is greatest during the hours just before sunlight on a clear spring night
you are growing a variety of chrysanthemum (a short day plant) whose critical photoperiod is 12.5 hours. when would the crop flower?
when it gets 12.5 hours or more of uniterrupted darkness
which of these adaptations do not help plants tolerate drought?
B. shallow root systems that are quick to take advantage of any rain or irrigation that seeps into the soil
the pigment that controls flower initiation is called