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Plant Science

Physiology refers to what? The process and activities with the functioning of a living organism.
What are two items that decrease photosynthesis? Water and Nitrogen
Does photosynthetic rate of individual leaves increase or decrease with age? Decrease
Young leaves actively capture sunlight with a peak at about how many weeks of age? 3
When do young leaves become inactive? 4-8 weeks
Should you graze or cut old, non-productive leaves? Yes
Do leaves age more rapidly under warm or cool conditions? Warm
What is growth rate of a pasture related to? The total photosynthesis of the stand
Initially, do all leaves contribute to plant growth? Yes
As leaf number increases, what happens? Shading of lower leaves increases
As leaf mortality increases, what decreases? Net accumulation of green matter
What are the effects of shading? 1. Reduced photosynthesis 2. Increased leave length 3. Reduced leaf width and thickness 4. Bud and grass tiller development and branching of legumes decreases 5. Internode length and plant height increase 6. Legumes show reduced nodulation and N fix
What does the arrangement of leaves affect? The amount of light intercepted and the photosynthetic potential of the sward
What is a sward? Grass-covered soil
Which type of leaf display allows the greatest amount of light absorption? Horizontally displayed
What is an example of a plant that has horizontally displayed leaves? Tall fescue
How is self-shading of horizontal leaves prevented? By grazing the plant
Based on temperature, what are the three groups of warm season perennial grasses? Intolerant to cold (Tifton 85) Relatively cold-hardy (Coastal) Cold Hardy (Switchgrass)
What is the major limiting factor of plant growth? Water
Where is water transpired? Through leaves
What does water carry throughout the plant? minerals, sugars, amino acids
What is the most limiting nutritive factor? Digestible energy
What are some factors affecting forage quality? Species, climate, rain, humidity
What is the greatest effect on forage quality? Maturity
What will consumption of toxic substances or mineral imbalances result in? Reduced productivity, being ill, death
Fescue toxicity is a problem in what type of fescue? Pure stands
What is fescue toxicity? Vasoconstriction of extremities resulting in loss of hooves, ears, tails, etc.
What clovers can cause bloat? Button, White, Persian
What causes Nitrate poisoning? Consumption of pasture or hay containing high levels of Nitrate
Does danger of Nitrate poisoning decrease with time? NO
Is hay containing 2500 PPM Nitrate usually safe? Yes
What are some plants known to have Prussic Acid problems? Johnsongrass, Sorghum, Sudangrass, Wild Cherry
Which plant does NOT produce prussic acid? Pearl Millet
What can cause prussic acid build up? Frost, drought, herbicides, stress in general
How long can the fungus that causes Bermudagrass Staggers stay toxic? Up to two years
What is a young plant in a resting state? A seed
What are the components of a grassland ecosystem? Non-living (water, air, soil), Plants, Herbivores, Decomposers (earthworms, fungi, bacteria)
Pasture yield potential increases as leaf area increases until leaves intercept how much light? 90%
What should the objective of a grazing method be? To manage the pasture and other feed inputs to efficiently produce animal products
Created by: lac043



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