# Shared Flashcard Set

## Details

Quiz #2
Crop Phenology and the Crop Growth Curve
30
Agriculture
10/01/2015

Term
 Explain the PAR portion of the yield equation
Definition
 Photosynthetically Active Radiation   MJm2d-1   Only accounts for visible radiation   Can change PAR by changing location and planting date
Term
 Explain the alpha c component of the yield equation
Definition
 Caopy absorption of radiation   Fraction of light that is actually absorbed by the plant   Shows the relationship between leaf position and radiation
Term
 Explain the RUE component of the yield equation
Definition
 Radiation Use Efficiency    g per MJ1   How efficiently solar radiation is converted into biomass   Impacted by temperature (how much biomass is made per unit of radiation absorbed)
Term
 What is LAI?
Definition
 Leaf Area Index   This is the single sided leaf area per unit ground area   As more leaf area is accumulated, each leaf intercepts less
Term
 What is the Central Dogma of Crop Physiology?
Definition
 The yield equation
Term
 Explain what HI is as part of the yield equation
Definition
 Harvest Index   proportion of total crop dry matter that is allocated to the harvested portion of the crop
Term
 What is the major determinant of total season crop growth?
Definition
 PAR
Term
 What does PAR absorbed by the canopy depend on?
Definition
 incident of PAR and LAI
Term
 What is RUE composed of?
Definition
 Any factor that effects crop growth but doesn't alter radiation absorption
Term
 Why should seasonal values of PAR not be used?
Definition
 Better to use PAR values integrated over time
Term
 How does variety maturity impact the yield equation?
Definition
 Short Season Variety - if you choose a short variety in a long season, there will be early maturity - Thus, total time for dry matter accumulation (PAR, ac and RUE) is less   Long Variety in Early Frost - If frost occurs before the grain filling stage, HI will be lower than normal
Term
 How does planting density impact the yield equation?
Definition
 Low Planting Density - reduces plant stand, hence PAR is limited - Not a lot of leaf area will develop, so alpha c is limited too   High Planting Density - HI will be low - Too much vegetative growth and not enough resources used to establish seed and grain filling
Term
 How does Drought Stress impact the yield equation?
Definition
 Reduces rate of leaf area expansion (alpha c decreaed)   Stomatal closure, so CO2 availability is limited (photosynthetic rate is dropped, so RUE is impacted)
Term
 Explain the shape of the Seed Imbition curve
Definition
 1. Rapid water uptake - Most physiological transitions occur - See cell electrolyte loss because membrane is "leaky"   2. Lag Phase - Rate of water uptake has slowed down   3. Final phase - Seed axis becomes hydrated again to lead to germination
Term
 Uptake of water is a _____ process
Definition
 physical
Term
 What kind of anaerobic stress inhibits seed germination?
Definition
 Drought, as oxygen is needed for seed germination
Term
 What is the difference between Hypogeal and Epigeal emergers?
Definition
 Hypogeal - cotyledons are below ground - All monocots   Epigeal - cotyledons are above ground - too much mechanical impedence can be bad (hypocotyl hook has to pull) - Not all dicots
Term
 Imbition chilling impacts what?
Definition
 Phase 1 of seed imbition graph. Water doesn't get taken up as well.
Term
 Why is proper soil temperture important?
Definition
 Important for strong seed emergence (enzymatic activity is better in warm soil conditions, which leads to better germination)
Term
 What is cold stratification?
Definition
 Exposing seeds to cold temperatures to break seed dormancy
Term
 Is oxygen required for seed germination?
Definition
 Yes   rate of respiration increases dramatically. It is needed to mobilize energy reserves from the seed   High CO2 levels inhibit seed germination
Term
 Does light exposure impact germination?
Definition
 Some yes.   Seeds that are POSITIVELY PHOTOBLASTIC need light expsure or else they will not germinate
Term
 Why is Phytochrome important?
Definition
 It is a pigment that changes red light to far-red   far red to red over night, but can be changed back to red quickly if a flash of far red goes off   far red promotes germination
Term
 What transition occurs after germination?
Definition
 Heterotrophic growth (energy is suppled by seed storage reserves) to autotrophic growth (energy provided by photosynthesis)   During grain filling, energy reserves are stored in endosperm. As the seed dries, these reserves run out   Critical period because once seed reserves are depleted, total seedling energy reserves can get very low if leaves cannot develop for photosynthesis
Term
 What if the vascular system is poorly developed between H to A transition?
Definition
 if water and nutrients cannot be moved easily through the plant, seedling's ability to respond to stress is impacted
Term
 Explain the 3 stages of the Crop Growth Curve
Definition
 1. Exponential Growth - Accelerated Vegetative growth - Photosynthetic machinery developed here - Leaf area is expanding (but law of diminishing returns) - Slow initially because no leaf growth   2. Linear Growth - Rate of dry matter accumulation is constant    3. Senescence - Photosyntheic capacity of leaves declines (RUE decreasing) because no new leaves are made -
Term
Definition
 Finger-like leaves   Makes light more diffused (evenly spread throughout the canopy)   Photosynthesis is higher
Term
 What is the slope of the Crop Growth Rate Curve?
Definition
 g per m2 per day
Term
 What happens between phase 1 and 2 of the CGC?
Definition
 Enough leaf area has developed to maximize interception
Term
 Why is there a levelling off phase in the CGC?
Definition
 RUE is decreasing   Canopy uses the intercepted light less efficiently because upper leaves are losing photosynthetic capacity
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