Exam 3 Flashcards
Phytohormones are chemical messengers that have an ____ and ____ site. Nutrient supply affects both the _______ and ______ site.
Active and synthesis (for both)
Where are auxins produced and what plant organ do they affect?
Auxins are produced in the shoots and affect, or act on, the roots
Where are cytokinins produced and what plant organ do they affect?
Cytokinins are produced in the roots and affect, or act on, the shoots
How do high nutrient levels affect auxin and cytokinin production and action?
High nutrient levels result in a decrease in auxin levels and an increase in cytokinin levels. This results in increased shoot growth and decreased root growth.
How do low nutrient levels affect auxin and cytokinin production and action?
Low nutrient levels cause an increase in auxin levels and a decrease in cytokinin levels. This results in decreased shoot growth and increased root growth.
Define root:shoot ratio and functional equilibrium. How does the root:shoot ratio relate to the carbohydrate partitioning in a plant?
This ratio is equal to the amount of root dry weight divided by the amount of shoot dry weight. Functional equilibrium is the balance of the function of the shoot system to the function of the root system. The root:shoot ratio qualities how the plant is distributing the products of photosynthesis between the shoot and the root. This gives quantitative data we can run statistics on.
Why is targeting a functional equilibrium in plant growth a good goal for a fertilizer program?
Do you need to supply them with high amount of nutrient to push a lot of shoot growth? If you don’t want to push a lot of growth, you will need to make sure you are not supplying such high amounts of nutrients. Targeting a functional equilibrium may result in similar root and shoot growth. This would be important for the living wall example since there is not much room for deep root systems and you would not want large plants coming off the wall.
What factors impact a plant’s root:shoot ratio?
Light
Water
Nutrient levels (the levels of N,P, and Mg have the greatest impact)
What plant nutrition function do the cotyledons serve the germinating and developing seedling?
All nutrients, sugars, phytohormones (everything the plant needs) are in the seed. Root emerges and cotyledon emerges. Until true leaf emerges, the plant doesn’t photosynthesize. Everything the plant needs until true leaf will be contained in the cotyledons. Without a true leaf, the movement within the seeding is through the phloem from the cotyledons into the xylem. The phloem can go down to the root system but xylem only goes upward.
Under adequate nutrient supply, where do most of the water and nutrients transported in the xylem go in a plant?
The sources are the photosynthesizing leaves. The sinks are the root system, the top of every branch (apical meristem), and the fruit. Water and nutrients are transported through the xylem up from the roots to the leaves.
Under adequate nutrient supply, where does most of the photosynthate and nutrients transported in the phloem go in a plant?
If this is a mature plant that is flowering and has fruit similar to what we discussed in lecture, the photosynthates and nutrient transported through the phloem can go up or down to reach the fruit.
Why is challenging for a plant to move nutrients into fruits?
Transpiration pulls nutrients strongly into newest leaves through xylem making it hard to get nutrients into fruit. Fruit doesn’t transpire. There is nothing pulling nutrients and water into the fruit through the xylem. The only movement of water and nutrients into fruit is through the phloem.
Define labiality
Nutrients are labial in the plant, meaning they can translocate out of leaves to storage organs and vice versa.
What are the 3 critical periods of sink development that may be impacted by nutrient availbility?
Flower induction
Pollination
Tuber initiation and growth
How does the biomass composition of an herbaceous plant differ from that of a woody plant?
Herbaceous plants have higher water content when compared to dry matter content than woody plants do. In herbaceous plants, biomass composition is about 90% water and 10% dry matter. In woody plants, biomass composition s about 50% water and 50% dry matter.
What factors affect yield?
Light
CO2
Genetics
Water
Nutrients
Why do nutrient rate and ratio needs differ for woody and annual plants?
Annual plants can be produced in greenhouses, have much faster growth rate, grown in quicker cycle of turnover. In general, they need a higher concentration of nutrients. Woody plants can store more nutrients and have slower growth rate.
How should nutrient rate by directed by goal for growth?
You need to change how you fertilize so that is tailored to the goal of the plant in the production system that you are growing it in and the stage of development of that plant.
What are the goals for supplying the nutrient needs of the plant?
Once you have determined the needs of the plant, you want to consider the expense of the fertilizer, waste of nutrient resources, environmental pollution, and excessive growth. You want to minimize each of these things while supplying the nutrient needs of the plant
Describe the deficiency range, adequate range, and toxicity range of the traditional biomass/nutrient response curve.
Deficiency range: this is where the growth rate increases with increasing nutrient supply. As the growth rate increases in the deficiency range, it is nearing the adequate range. Being in the deficiency range does not necessarily mean there will be visual symptoms.
Adequate range: Range between deficiency and toxic. This is where growth rate reaches a maximum and remains unaffected by nutrient supply.
Toxicity range: in this range, the growth rate is falling with increasing nutrient supply. This is beyond the adequate range.
Define the critical concentration of the biomass/nutrient response curve. Why is this the point of diminishing return on increasing supply of nutrients?
This is the nutrient concentration in the tissue needed for maximum growth. Fertilizer applied in excess of what is needed to meet this critical concentration may not be needed. Once you have reached maximum growth, further fertilization will likely just be a waste of money or harmful to the environment.
Define/describe growth in phases I,II,III,IV,V, and VI in Fig. 12.3. What does the dashed line a Phase I represent? Define: critical deficiency concentration, critical toxicity concentration, adequate range, and luxury range.
Phase I and II: where growth sharply increases without increase in nutrient content. Think of this as germinating the seed. there is rapid growth, but nutrients are not being taken up from the soil yet, the plant can get everything it needs from the seed/cotyledons. Not a lot of reason to fertilize here since growth response is not driven by nutrient uptake.
Phase III: increases in growth and increases in nutrient content are very closely related to each other.
Phase IV-V: growth is not nutrient limited but nutrient content increases. You have reached the potential of that plant in its production system. Excessive nutrient content causes toxicity and a corresponding decrease in growth
Dashed line in Phase 1: nutrient content of a nutrient deficient plant decreases when supplied with the deficient nutrient due to increased growth and water content
Critical deficiency concentration: the point at which deficiency symptoms begin to show/to be seen
Adequate range: region of growth is maximal meaning it is up to its genetic potential within the environment it is growing in. In this range, the growth is not being limited by nutrients.
Luxury range: the plant is storing nutrients and the nutrient content in the plant is high enough to sustain the plant even if it is not able to take up more nutrients or if the growth rate is very high.
Why is 90-95 of maximal growth usually targeted in developing fertilizer application rates? Why is foliar analysis used in describing plant nutrient needs for achieving desired growth instead on fertilizer rates in Fig. 12.3?
When we design fertilizer program, we generally design one to target 90-95% of optimal growth. We done try to achieve maximum growth because the cost difference and increase in environmental damage between 90% and maximal growth is not worth it. The small increase in growth would not be worth the amount of money and damage.
(no answer for part 2)
Define symplasm, apoplasm, adsorption, and absorption.
Symplasm: living space within a cell and plant, meaning this is where metabolism is happening. There is a cytoplasmic connection between the symplasm of every cell and the cell next to it. Once nutrient ion is in symplasm, it can easily move to the next cell symplasm through the plasmodesmata. Symplasm includes cytoplasm, phloem, and all organelles except the vacuole.
Apoplasm: non-living space within a cell and plant, meaning no metabolism is occurring. Apoplasm includes cell walls, vacuole, and xylem.
Adsorption: electrical binding of ions to charged soil particles or to fixed charges in the apoplasm (cell walls have CEC)
Absorption: movement into or across the plasma membrane (toward the cell cytoplasm); “uptake”
What are the three primary destinations for nutrients in a cell?
1) Adsorption in cell wall
2) Absorption/uptake into cytoplasm
3) Storage in vacuole
Where does metabolism occur in the cell?
Symplasm
What are the ionic forms absorbed, stored, and storage location for N?
Absorbed as: ammonium (NH4+) and nitrate (NO3-)
Stored as: organic compounds (amino acids, amides) and nitrate
Stored in: vacuole and cytoplasm
What are the ionic forms absorbed, stored, and storage location for P?
Absorbed as: H2PO4- and HPO42-
Stored as: inorganic Pi (most common) and organic P (C-O-P)
Stored in: vacuole (more H2PO4-) and cytoplasm (equal H2PO4- and HPO42-)
What are the ionic forms absorbed, stored, and storage location for K?
Absorbed as: K+
Stored as: K+
Stored in: cytoplasm
What are the ionic forms absorbed, stored, and storage location for Ca?
Absorbed as: Ca2+
Stored as: Ca2+
Stored in: cell walls, membranes, vacuole
What are the ionic forms absorbed, stored, and storage location for Mg?
Absorbed as: Mg2+
Stored as: Mg2+ and Mg-
Stored in: cytoplasm (Mg- containing compounds) and vacuole (Mg2+)
What are the ionic forms absorbed, stored, and storage location for S?
Absorbed as: sulfate (SO42-)
Stored as: sulfite (SO3-)
Stored in: the plant as sulfite or amino acids (it is immobile as sulfite)
Why must NH4 be assimilated quickly?
It is toxic within the cytoplasm
Why is inorganic P (Pi) stored in the vacuole and not in the cytoplasm?
Vacuole has lower pH so it has inorganic P (Pi) in the single negative form. The pH of the cytoplasm is higher, less acidic
What are the ionic forms of the micronutrients taken up most commonly by plants?
Boron: H3BO4
Iron: Fe2+
Manganese: Mn2+
Zinc: Zn2+
Copper: Cu2+
Chlorine: Cl-
Nickel: Ni2+
Molybdenum: MoO4-
What are the mobile nutrients? Where in the plant do deficiency symptoms of mobile nutrients first appear?
The mobile nutrients are N, P, K, Mg, Ni, and Cl. Deficiency symptoms first appear in the older leaves, or lower part of the plant. Although Ni and Cl are also mobile, seldom see a deficiency in these.
