Final Flashcards
1
Q
What are the functions of leaves?
A
- Photosynthesis
- Transpiration
- Respiration
- Storage
2
Q
Describe Transpiration in the leaf.
A
- It is the movement of water from inside the leafs to the atmosphere outside the leaf.
- More than 97%-99.5% of water which a plant takes up is lost through transpiration
- To collect CO2 for photosynthesis, the stomata remains open, thus losing a lot of water.
- It cools the plant, changes osmotic pressure, and enables movement of nutrients from the roots
3
Q
Describe Respiration within the leaves.
A
- Respiration only occurs at night
- Oxygen that is needed for respiration is gathered during the day through the open stomata.
4
Q
Describe storage within the leaves.
A
In some plants, the leaves store food.
- Ex. Spinach, Lettuce
In some plants those same leaves are stored underground
- Ex. Onion, Garlic
In some dicots, the petiole becomes enlarged and stores food
- Ex. Rhubarb
5
Q
What do dicot leaves consist of?
A
The blade
And sometime a petiole
6
Q
What are the types of venation on dicot leaves?
A
Branched (like a tree, one big trunk and branches coming off)
Netted (sorta like a feather, with a few extra branches)
7
Q
What is a stipule?
A
Leaf like appendages, the are found where the petiole and stem join.
They are common in legume plants
8
Q
What do monocot leaves consist of?
A
- Blade
- Sheath
- Ligules
- Auricles
9
Q
Describe the blade of a monocot leaf.
A
Generally long and narrow
Veins are always parallel
10
Q
Describe the sheath of a monocot leaf
A
The structure that surrounds the stem
Attaches the blade to the stem.
11
Q
Describe the ligule of a monocot leaf.
A
Thin, filamentous appendage on the inside between the stem and top of sheath.
Shape of ligule can determine the species.
12
Q
Describe the auricles of a monocot leaf.
A
Little arms that extend out form the top of the sheath and clasp the stem, like a hug
13
Q
What leaf arrangement do monocots usually have, and describe it.
A
Alternating, one league per node and they alternate which side the grow from.
14
Q
What is the final leaf in monocots?
A
The final leaf to emerge, may be shaped differently from the rest.
15
Q
What are three kinds of leaf arrangement?
A
Alternate
Opposite
Whorled
16
Q
Describe alternate leaf arrangement in dicots.
A
One leaf per node, and they alternate the side they grow from.
17
Q
Describe opposite leaf arrangement in dicot plants.
A
Two leaves grow from each node.
18
Q
Describe whorled leaf arrangement in dicot plants
A
Several leaves coming from one node.
19
Q
What are the leaf types of dicot leaves?
A
Simple leaf - the one blade is the leaf.
Compound leaf - has two or more leaflets coming from the petiole
20
Q
What are the kinds of simple leafs in dicot plants?
A
Simple pinnate - just a regular ass leaf
Simple palmate - veins radiate from a central point
21
Q
What are the kinds of compound leaves in dicot plants?
A
Compound pinnate - a main branch (rachis) in which multiple leaflets emerge from
Compound palmate - leaflets radiate from a central point at the end of the rachis
22
Q
What is trifoliate arrangement?
A
A special arrangement of a compound leaf where 3 leaflets emerge from the same point on petiole.
23
Q
What are plant stresses?
A
Anything that prevents a plant from growing to its full potential
24
Q
What are the abiotic plant stresses?
A
- Cold
- Heat
- Nutrients
25
Describe stresses caused by Salts
Salts in soil deprive plants of water and dissolved nutrients in that water.
26
Describe low temperature stress on a plant
- Lower then optimal temp for a plant will result in slower growth speeds
- when the plant freezes, the water in a cell freezes and melts, leaking the cells contents out and killing it
- perennial species will undergo change to become dormant for winter, but can still be damaged by low temps
27
What is winter burn?
winter burn is primarily a problem of evergreens and results when these 3 situations occur: low soil moisture, freezing temperatures, blowing wind. With these 3 factors in place, evergreens lose moisture through transpiration faster than their roots can replace it from the frozen ground.
28
Describe high temp stress on plants
High temperature coagulates the proteins of the plant cells, causing the plant to die.
29
What is wilting stress on a plant?
- During warm weather, if plants cannot take up enough moisture they will die because the respiration exceeds the photosynthesis
- to cope with the loss of moisture, the stomata close preventing the plant from performing photosynthesis
30
What are the stomata responsible for?
- Allows for the movement of gasses
- Vaporized water leaves, and CO2 enters through the stomata
- open during the day, and closed at night.
31
Describe the order of the structures of a leaf
Cuticle on the outside
Then upper epidermis
Middle fillings (with xylem and phloem)
Lower epidermis
And some stomata within the lower epidermis
32
What are Trichomes? Describe them.
- Little hairs on the outside of some leaves. They prevent wind sucking water out of the stomata
- they can reflect solar radiation to keep the plant cooler, some release compounds to prevent herbivory
33
Describe the biotic stress, weeds.
- A weed is defined as any plant that is growing in a place that is not wanted
- an example is Purple Lustrife
34
Describe the biotic stress, contamination.
- Contamination is when weed seeds are inseparable from the crop seed, lowering the grade and value of the grain.
- Cab make the grain unsuitable for certain uses
35
What are some toxic weeds?
Death Camas - all parts of the plants are poisonous
Water Hemlock - concentrated in the stems but all other parts have toxins too
36
Why are weeds a problem?
- They’re hard to control because they’re adapted to their environment.
- they have vigorous growth habits, very competitive, adapted to a wide range of environments
- they have a quick life cycle, and effective dormancy mechanisms
37
What are Rhizomes?
Horizontal underground stems
- Serve as a over-wintering organs and a method of vegetative propagation
- These stems produce shoots and roots at nodes that grow into a new plant
- Ex. Canada Thistle
38
What allows for weeds to grow so abundantly?
Their seed distribution is very effective, for example dandelions and wind dispersion.
39
What are ways for weed seeds to be distributed
Can be distributed by:
Wind - winged fruits, parachute fruit, or entire plants meant to move with wind
Water - designed to be carried in water (coconut)
Animals - attach to animals and move to new sure by the use of barbs
40
Describe the biotic stress, Infectious Plant Diseases.
- Spread through pathogens. Majority of infections are extremely infectious and difficult to control
41
Describe the disease cycle in plants.
1. Inoculation - period when the pathogen transfered from a source to a host plant
2. Incubation - Tim period from when the pathogen reaches the plant until it begins to effect the plants function.
3. Infection - Multiplication of the pathogen and the appearance of the characteristics of the disease
42
When is the best time to implement control methods?
Before inoculation, step 1.
The best disease management is to prevent or limit infection
43
What are some causes of infectious diseases?
Caused by microorganisms attacking susceptible plants.
- environments and conditions like wet weather, injured/stressed plant, ect, it makes it easier for the plant to be infected.
**The most plant disease causing organism in western Canada is Fungi**
44
How does fungi reproduce, and grow?
- Fungi reproduces through spores
- spores spread through wind, water, machinery(combine), animals, insects, contaminated seed, ect.
- when moisture is present, spores in plant tissue germinate and grow and penetrate the plant through stomata or a wound.
45
How do plants react to Disease?
Plant disease will cause Yield Loss
Symptoms can include:
- death of part/all of the plant
- lesions on stem hindering photosynthetic area
- changes in colour
-reduced/stunting growth
-ect
46
Describe the biological stress, Insects.
There are actually two groups of insects:
- Beneficial
- Harmful
47
Describe Beneficial Insects
Perform duties advantageous to humans:
- Pollinating insects
- Parasitic insects (wasps - lay eggs in aphids and other larva)
- Flies recycle Nutrients
48
Describe Harmful Insects
- Damage to crops, food, buildings, ect.
- Ongoing battle to control insects
- can become resistant to insecticides
49
What does insect injury do to plants?
- Insects can pass on disease
- They directly damage the plant by feeding on it
Ex. Sucking plant juices from leaves, chewing leaves/flowering parts
The greater the population the the more damage would be done to the plant.
50
What is Integrated Pest Management (IPM)
A process used to solve pest problems by minimizing risk to people and the environment. It focuses on long term prevention.
51
What things are crucial for effective IPM
Monitoring and correct pest identification are crucial. IPM programs use multiple approaches for greater effectiveness
52
What are the five major components of all IPM programs?
1. Preventing pest problems
2. Pest identification
3. Monitoring and assessing pest numbers and damage
4. Guidelines for when management action is needed.
**5. Using a combination of biological, cultural, physical/mechanical and chemical management tools**
53
What are the five ways weeds can be managed?
1. Physical Damage
2. Plant competition
3. Pesticides
4. Rotation
5. Insects
54
Describe how physical damage can prevent weeds
Tillage uproots weeds and prevents them from properly growing.
55
Describe how plant competition can prevent weed growth.
Plants that compete well with weeds steal the nutrients so that the weeds cannot grow properly and eventually die out.
56
Describe how herbicides can be used to prevent weed growth.
Herbicides are a type of pesticide used to control weeds.
- herbicides kill weeds specifically, and don’t effect the crop.
- Different herbicides kill different weeds, so you need to know which is which
57
Describe how crop rotation prevents the growth of weeds.
Rotation occurs because:
- some crops compete with weeds better
- A certain range of herbicides safe for one crop may not be effective against the weed, so the crop should be rotated to allow for use of other herbicide
58
Describe how biological control prevents the growth of weeds.
It’s taking control of weeds natural predators, Insects or disease are used to control weeds.
59
What are the advantages and disadvantages of Biological Control?
Advantages: selectivity, effective in inaccessible areas, negligible environmental impacts, can be less expensive.
Disadvantages: Lacks immediacy, as it takes time to control and it is difficult to find control agents for all weeds
60
What are some other methods to control weeds?
- The management of fertilizers or irrigation to ensure they are being used by the crop and not (as much) by the weeds.
- Alternating seeding dates to increase competition.
- animals to control weeds
61
What are 5 ways Disease can be managed?
1. Resistant Plants
2. Healthy seed and good growing conditions
3. Cultural practices
4. Pesticides
5. Biological Control
62
How does plant resistance manage Disease?
Some plant variety’s are resistant to disease. Plant variety is the most economical method of disease control.
63
How does healthy seed and good conditions help control disease?
Seeds free of disease are important, along with good quality seed that isn’t damaged. Good growing conditions help defend against disease.
64
How do cultural practices help control disease?
Early Seeding:
- If the crops are already grown, they defend against disease much easier then a newer plant.
Crop Rotation:
- Crop rotation can prevent against the build up of disease.
Removal of Diseased Crop:
- By tilling or burning.
65
How do fungicides prevent disease?
Most fungicides must be applied prior to any symptoms occurring.
They’re applied on practically everything
66
How can insects be managed?
1. Resistant plants
2. Pesticides
3. Cultural Practices
4. Biological Control
67
How do resistant Varieties defend against insects?
- The plant may produce a substance which has effects on insects
- the plant has a trait which makes the plant undesirable for food, shelter, egg laying, ect.
68
How do cultural practices defend against Insects?
- Early/Late seeding to avoid insect damage
- Changing tillage method
- ensure plants are healthy to recover
- provide habitats for beneficial insects
- crop rotation
69
How can biological control help defend against Insects?
There are fungi that can infect and control an insect. There are also fungi that are straight up poisonous to insects when consumed
70
What is the definition of agronomy?
The science of soil management and the production of field crops.
71
What is plant ecology?
studies the distribution and abundance of plants, the effects of environmental factors upon the abundance of plants, and the interactions among plants and between plants and other organisms
72
What is autecology?
The biology of a species and how it interacts with the environment.
73
What is population ecology?
Drivers of species abundance, spacial pattern and population growth
74
What is community ecology?
Relationships among species, species abundance in relation to other species, consumptive, competitive, and facilitative interactions
75
What is ecosystem ecology?
Relationships between species and the abiotic environment; how species respond to and influence biographical cycling
76
What are the stages of plant growth?
Germination - The emergence of the seedling
Vegetative State - growing as many leaves as possible
Floral Initiation - growing the flower parts
Flowering - “blooming”
Pollination and Zygote Formation
Fruit and Seed Maturity
Senescence - deterioration due to age.
77
What is the definition of the zygote?
The beginning of a new plant.
Formed by fertilization of the ovule by pollen
78
What are the requirements for germination?
1. Suitable Water
2. Suitable Temperature
3. Adequate Oxygen
79
Describe the First requirement of Germination.
Imbibition - The absorption of water. May cause the testa to rupture.
- Water activates enzymes (in the aleurone layer), break down food, increases respiration, activates cell division in meristems.
- Imbibition is influenced by Soil firmness and soil water content.
80
What does the Rate of Imbibition rely on?
Composition of the seed: What it’s made of.
- proteins absorb more water then starches. More protein, more al water.
Seed coat: Testa
- some seed coats have impermeable testas.
81
What is the second requirement for germination?
Each plant has an optimal temp, for example:
Cereal crops will germinate just above freezing and 37 C. The ideal temp is 15 C
82
What is the third requirement for Germination?
Oxygen is required for the seed to respire, use the food it has stored.
- If plants are too deep/ waterlogged, there may be oxygen shortages
83
What happens if a seed sits too long without germinating?
Microorganisms begin feeding on it, in what is called **Seed Decay**
84
Is light needed for Germination?
Some but not all plants need light. Some seeds Need to be in the light, and some need complete darkness. Then some just don’t care
85
What is embryo growth and development like?
The radicle and plumule begin to grow.
Food is transported to the growing parts
The testa rupture
The embryo is called a seedling as soon as it begins to perform photosynthesis
86
Describe what happens in monocot germination?
the plumule, coleoptile, cotyledon, and radicle make up the embryo of the seed.
The plumule is protected by the coleoptile
The cotyledon remains below ground.
87
What are the two types of Dicot germination?
- Eigeal
- Hypogeal
88
Describe epigeal germination?
The hypocotyl (the stem below the cotyledons) pushes the cotyledons above ground.
- the cotyledons function as leaves until the true leaves emerge
**Canola :3**
89
Describe Hypogeal Germination.
The cotyledons remain below the ground.
The epicotyl (true stem, stem above the cotyledons) grows and raises the plumule out of the soil.
90
What conditions promote Good germination?
Seed Viability - (is it alive? Have any impediments?)
Seed depth - (the deeper the seed the more food it needs to reach the surface)
91
What is dormancy?
A survival mechanism which allows plants to survive until favourable time/conditions are met. Also allows for staggered germination.
92
What are the two(?) types of dormancy called?
Exogenous (something outside prevents germination)
Endogenous (something inside prevents germination)
Double Dormancy (a combination of both)
93
Describe Exogenous Dormancy
Due to physical constraints
- The hard testa prevents water and oxygen from entering.
- in nature, natural weathering would open the testa.
- in a lab they’d use scarification, essentially scratching the seed.
Legumes are very hard
94
What is heat treatment?
Some plants need their exogenous dormancy broken by high temperatures for short periods of time.
Ex Jack Pine 49 C
95
Describe Endogenous Dormancy
Embryonic/Physiological dormancy.
Ways to overcome it:
Stratification - Seed won’t germinate till they’ve had long term exposure to low temps with oxygen and water - *Cherry tree*
Chemical Block - Adequate moisture will leach out chemical blocks (salts, Cyanide, ammonia)
96
What is the dormancy like in cultivated crops?
Dormancy has been lost
Beneficial: because dormancy can interfere with the production of the crop.
Negatives: the germination happens so fast, it may happen too soon.
97
What is the viability of a seed?
The ability to germinate if suitable conditions are met.
Loss of viability usually occurs gradually.
98
What is the longevity of a seed?
The length of time a seed can remain dormant and still be viable
- Longevity depends on:
• Plant Species
• Growing conditions
• Storage conditions
Russian scientists germinated 32,000 yo seeds
99
What can decrease longevity?
- Immature seed (let go of seed too soon due to frost)
- Low food reserves (usually from drought)
- Disease
- Physical Dmage
100
What are the function of roots?
- Absorption
- Anchorage
- storage
- nitrogen Fixation
101
Describe the necessities and qualities of Absorption within roots.
Roots must have extensive contact with soil particles
- Roots absorb water & Dissolved nutrience
Roots absorb NPKS (Nitrogen, Phosphorus, Potassium, Sulfur)
102
Describe the necessities and qualities of Anchorage within roots.
Roots provide support
Poor roots are susceptible to lodging (being uprooted)
Adventitious Roots - roots formed from stem tissue rather then root tissue
(Corn develops Prop Roots - arise from stem just above soil)
103
Describe the necessities and properties of storage within roots.
For biennial, perennial, and winter annual plants, root storage is very important.
- Food is stored in roots to last the winter, and have food for the next year.
Plants like carrots and turnips store food in the roots. These are biennial
104
What is the importance of the sugar beat?
Grown for its sugar in southeastern Alberta
- Harvested in fall in the year their planted. Tops feed animals, bottoms are crushed and juice is extracted and refunded to make sugar.
105
Describe nitrogen fixation.
It occurs in Legumes, due to the Rhizobium on them. Rhizobium live in the roots in nodules, and take nitrogen from the air and fix it to the plant in a symbiotic relationship. **Rhizobium is a bacteria**
106
How do roots develop?
The original root, called the radicle, emerges first.
Dicots: the radicle forms the tap root (major central root). Secondary roots grow from tap root. Ex. Canola, Alfalfa.
Monocot: the radicle is *replaced* by the SRS (secondary root system) early on. The SRS develops from the crown (just below the soil surface).
107
Describe the functions and structure of the general root.
Tip of the root is covered by root cap. (Covers apical maristem). Right behind the Apical maristem is the area of cell enlargement. Cells are made and grown to push root through soil. Behind that is where cells mature into specialized cells.
108
What are root hairs? what’s their importance?
Crucial for absorption. Not very long, but there are so so many of them. Root hairs increase surface area of the roots. They take up water through osmosis. The **Xylem** brings the water to the shoot and rest of the plant.
109
What are the primary functions of the stem?
- Support
- Translocation
- Photosynthesis
- Storage
110
Describe the function of support within the stem.
The stems basic function is to support green tissue (leafs)
- Erect is holding itself up
- Twinging is climbing up something
- Prostrate is growing along the ground
111
Describe the function of translocation within the stem
Stems contain Vascular bundles (xylem and phloem) that are responsible for the movement of
Xylem: Water and nutrients
Phloem: Food (**Ph**ood)
112
Describe the function of photosynthesis within the stems
In some plants photosynthesis can occur in the green stem. And in some it’s the primary photosynthesis are. Ex cactus, Wheat, corn
113
Describe the function of storage with the stem
Stems can be modified for storage. Ex, sugar cane.
Some are harvested early so the food in the stem is not used up. Ex, asparagus
114
Describe the function of storage with the stem
Stems can be modified for storage. Ex, sugar cane.
Some are harvested early so the food in the stem is not used up. Ex, asparagus
115
How do stems grow?
Through meristem regions which develop all organs and structures for plants.
116
Describe dicot stems.
Dicots have vascular bundles in a circle around a central pith. They grow their width through lateral meristens and vascular cambium. In dicots, nodes are placed of growth for one or more leaves as well as buds, which can also grow into branches.
117
Describe monocot stems.
Monocots have vascular bundles scattered through the outer layer of pith. Stems are hollow in many monocots.
Internodes are hollow, nodes are usually solid
The Intercalary meristem is at base of leaf
118
What is tillering in monocots (grasses)?
Tillering is producing a side shoot from the Intercalary meristem. The ability to produce tillers is controlled by genetics and environmental conditions.
For example, 2 row barley will produce more tillers than 6 row types.
119
What controls Branching(dicot) and tillering(monocot)?
They are controlled by mostly environmental conditions. If they’re in their own, they’ll grow more and farther spread out due to increased light availability.
120
What is apical dominance in monocots?
Hormones are located in the very top stem of the plant, controlling the formation of branches from buds along the tree. If their apex branch is removed the tree may grow un inhibited.
121
What are 3 Plant-Microbial relationships?
- Legume Rhizobium symbiosis (N fixation)
- Mycorrhizal Symbiosis
- Plant growth promoting rhizoorganisms
- Pathogen protection, improved crop nutrition
122
Describe Legume-Rhizobium symbiosis
- Allows for atmospheric N2 to ammonia (NH3), a form usable by plants
- Plant provide photosynthetically-derived carbon, and rhizobium provides usable nitrogen.
123
Describe how Rhizobium infects and grows on legume roots.
Occurs in Nodules. Legume roots release flavonoids when N-starved. The Flavonoids induce modulation genes in rhizobia, which produces a chemical response called Nod factor. Mod factor initiates the development of nodules.
124
Describe Mycorrhizal symbiosis.
Mycorrhizal fungi is very old, evolved over 450y. Over 90% of plants associate. They don’t infect Brassica (canola, mustard, broccoli, ect)
125
Describe Mycorrhizal symbiosis.
Mycorrhizal fungi is very old, evolved over 450y. Over 90% of plants associate. They don’t infect Brassica (canola, mustard, broccoli, ect)
126
What are the two types of Mycorrhiza?
Arbuscular Mycorrhizal Fungi (AMF) - important to agr systems. They get into the cell.
Ectomycorrhizal Fungi - Important in forests. They go between the cells
127
How does Fungi grow to get resources?
Fungi grows microscopic hair-like structures called Hyphae. These form Hyphae networks which extend outside the root to increase surface area enabling greater exploration.
128
What is Plant Growth Promoting Rhizoorganisms? (PGPR)
Molecular mechanisms by which microorganisms that *colonize the rhizosphere* can promote plant performance.
129
What are some examples of PGPR
1. Biological Nitrogen Fixation (free living)
2. Nitrogen Metabolism
3. Phosphorus Solubilization and Mineralization
4. Biocontrol of Pathogens or Weeds.
5. Production of Biochemicals that affect nutrient availability and or plant root growth
130
How can PGPR be exploited to promote plant growth and performance?
1. Use of management practices to promote PGPR population size and interactions with plants.
2. Engineering of the host plant to select PGPR
3. Isolation of PGPR and inoculation onto plant roots
131
What are biologicals in reference to crop production?
Products that contain Microorganisms
- Or biochemical of microbial origin that can be used in cropping systems to enhance plant growth.
Biostimulants is a buzz word with no def
132
What Inoculants?
Additives that contain a single or multiple species of microorganisms added to soil or plant seed for the improvement of plant growth
Both bacterial and fungal inoculants are possible
133
Can Rhizobium be used in any plants?
No, Only specific Rhizobium species work for specific crops.
134
Are there AMF inoculants? What do they do?
Arbuscular Mycorrhizal Fungi inoculants do exist, and they enhance P, Micronutrient and water intake.
135
What is Penicillium Bilaiae (P. bilaii)
A fungus, but not an AMF. Solubilizes phosphate minerals by producing organic acids, making P a usable form for the plant
136
What is soil fertility?
The ability of the soul to supply essential nutrients to support plant growth and reproduction
137
What makes an element essential for plants?
1. Element is necessary for plant to complete vegetative/reproductive stage if life
2. Deficiencies of the element are specific to that element; nothing can replace that element
3. Element is directly involved in growth or metabolism
138
Where do essential elements come from?
Majority are from mineral and organic fractions of soil
Exception - C, H and O are from CO2 and H2O
139
What are the four primary essential nutrients?
N P K S
140
What is the function of nitrogen and usable forms of it?
NO3-, NH 4+
Combines with carbs to form amino acids and proteins involved in enzymatic processes; Component of nucleic acid.
141
What is the function of Phosphorus in plants and the usable forms of it?
H2PO4-, HPO42-, PO 43-
Energy transfer - main factor of ATP (adenosine tri**phosphate**)
142
What is the function of potassium and what are the usable forms?
K+
Activates cellular enzymes; regulates osmotic potentials
143
What is the function of sulphur and what are its usable forms
SO 42-
Essential component of some amino acids, important in synthesis of oils.
144
What are the uptake methods of roots, and which nutrients do they effect?
Diffusion - Conc gradient drives diffusion
- Huge for K
Mass Flow - Mass movement of nutrients in water through transpiration
- huge for Ca, Mg, NO 3-
Root Interception
- Important for P (Relatively small contribution to uptake)
145
What is Liebig’s law of the minimum?
Crop growth is dictated by the most limiting factor.
146
What are symptoms of nitrogen deficiencies?
Yellowing of leaves
Stunted growth
Less Tillering in cereals
147
What are symptoms of a phosphorus deficiency?
- Stunted growth
- Limited root development
- Purplish colouration of stems and leaves
148
What are some symptoms of a potassium deficiency?
- Dull green leaves
- Yellowing of leaves (on edge, rather then the whole leaf)
149
What is nutrient cycling?
Movement of elements within and between biotic and abiotic parts of an ecosystem.
Driven by photosynthesis
150
Describe some facts about Nitrogen Management
- Often the most limiting nutrient
- N fert. Is one of highest input costs for farming
- Hard to manage due to complex N cycle
151
What is so significant about nitrogen fixation?
Requires large amount of energy to break the triple bond of N2
152
What are three types of N fixation?
- Lightning (3% of total N fixed)
- Biological (67% of total N fixed)
- Industrial (30% of total N fixed)
153
If 99% of soil N is in organic matter, how do plants access it?
- Microorganisms decompose organic matter releasing simpler forms or organic N
- Soil microorganisms transform simple forms or organic N into inorganic N through mineralization
154
What is immobilization?
The process of microorganisms converting inorganic N into Organic N
155
What is Nitrification?
Ammonium (NH4+) being oxidized in a two step process to produce Nitrate (NO3-)
- Nitrification occurs in soils that are well aerated
156
What is **Denitrification**?
Gaseous Losses - a multi step process performed by bacteria to convert NO 3- to N2 gas under anaerobic conditions
- Necessary to complete the N cycle; returns N2 to the atmosphere.
157
What is **Volatilization**?
Gaseous Losses - Ammonia in soil become ammonia in air.
(The more OH (alkaline), the more volatilization occurs)
158
What is **Leaching**?
Nitrate leaching down the soil profile into groundwater.
Nitrate is more mobile then ammonia cause clay and nitrate are negatively charged, their not binding.
159
Briefly describe the P cycle
Soil Phosphorus originates from weathering of primary minerals
- it doesn’t cycle through the atmosphere like N
160
What are some problems with Phosphorus?
Next to N, phosphorus is the most limiting nutrient.
- 0.1% if soil is P
- Majority of P in soil is not available. Not more than 0.01% of total p is available for use
161
What is P fixation?
The chemical process that renders P unavailable to plants.
Processes leading to fixation include:
- Precipitation reactions
- Absorption to Al and age oxide surfaces.
162
Describe the mineralization of organic P
Organic P is mineralized into inorganic P by microorganisms, and can also me immobilized for use by microorganisms too.
163
What are some Losses of P?
Leaching to groundwater isn’t huge.
Lost mostly through erosion and runoff which can lead to eutrophication.
164
Briefly describe the K cycle
Inputs:
- weathering of primary material
- fertalizer
Losses:
- Leaching, runoff, soil erosion
- Export of K important in HAY crops
165
What are some problems with potassium?
The third most limiting nutrient.
- Does not go into the atmosphere
- K losses don’t cause off site environmental issues (like N and P do)
