Exam 1 Lectures 5-6

Question 1

What is a seed?

Answer 1

A plant structure consisiting of an embryonic plant, the food supply necessary for germination and a protective coat.

Question 2

What is an Embryo?

Answer 2

The rudimentary (undeveloped) plantlet within a seed

Question 3

What is Germination?

Answer 3

Beginning of growth by an embryo

Question 4

What is a Cotyledon?

Answer 4

1. Leaf that forms part of a seed embryo
2. In the case of a legume the major portion of the two halves of a seed that emerges from the soil
3. In grasses the cotyledon remains in the soil

Question 5

What is an Epicotyl?

Answer 5

The stem of the young seedling above the cotyledon

Question 6

What is a Hypocotyl?

Answer 6

The stem of the young seedling below the cotyledon

Question 7

What is a Radicle?

Answer 7

The part of the seed which at initation of germination becomes the root

Question 8

What is a Coleoptile?

Answer 8

The sheath covering the first leaf of a grass seedling as it emerges from the soil

Question 9

What is a Plumule?

Answer 9

1. Terminal bud of the embryo
2. In grasses it emerges from the coleoptile after the coleoptile emerges from the soil
3. In legumes emerges above the cotyldonary node

Question 10

What is a seedling?

Answer 10

The juvenile stage of a plant grown from seed

Question 11

What is necessary from external conditions in order for germination to occur?

Answer 11

1. Ample moisture
2. Oxygen
3. Suitable temperature
4. Specific light conditions

Question 12

How does the initial processes in germination occur?

Answer 12

1. Seed absorbs water and after about 3 days their mositure concentration may be more than 60%. During this process (called imbibition) the seed coat softens and the seed swells
2. Soluble nutrients in the seed go into solution and are transported to growing sprout
3. Proteins are broken down into amides and amino acids and incorportated into seedling proteins
4. Fats are broken down by lipases and are used to form sugars and fats in the seedling
5. Energy for the germination process is supplied by respiration, the biological oxidation of carbo and hydron into carbon dioxide and water

Question 13

What occurs in grass seedling emergence?

Answer 13

1. Radicles emerges from seed
2. Coleoptile emerges from seed
3. Coleoptile pushed through soil by elongation of growing point below ground
4. Coleoptile merges from soil as a pale tube-like structure that ecnloses true leaf
5. Slit develops at tip of coleoptile & leaf emerges through it.
6. Photosynthesis begins & seedling establishes independence from stored food
7. Cotyledon & apical meristem (growing point) remain underground

Question 14

What is a legume seedling emergence ?

Answer 14

1. Radicle emerges from seed and elongates
2. Hypococtyl elongates, forms an arch, arch is forced through the soil
3. Arch emerges followed by cotyledons
4. Cotyledons open & photosynthesis begins
5. Plumate (true leaves) emerges from between Cotyledons

Question 15

What are the advantages of grass compared to legumes?

Answer 15

1. Grass has pointed colyoptile
2. Keeps gorwing point underground longer

Question 16

When it comes to vegetative propogation what does it consist of?

Answer 16

1. Some plants are sterile and do not produce seeds, while others do not produce uniform offspring from seed
2. A vegetative stem can reproduce itself since its contains:
   * A meristematic tissue exists at the base of the internode-axillary bud (intercalary meristem)
   * Can produce new shoots & roots

Question 17

When it comes to vegetative propogation what does it consist of? (part 2)

Answer 17

3. Vetitative propogation consists of putting nodes in contact with soil in the presence of adequate moisture, temperature, and light, resulting in the production of new shoots and roots
4. The new plant is identical in genetic composition to the plant it was derived from (clone)

Question 18

What does Photosynthesis consist of?

Answer 18

1. Primary mechanism of energy input into the living world
2. Directly or inderictly resposible for all life on earth
3. In essence photosynthesis is a two-phase process:
   * Harvesting energy from light and producing ATP and NADPH
   * Uptake of CO2 from the atmosphere and synthesis of organic acids using the energy from ATP and reducing power of NADPH

Question 19

What is the formula for photosynthesis?

Answer 19

nCO2+H20+light -> (CH2O)n+nO2

Question 19

What pathways make up the carbon dioxide fixation pathways in forage plants?

Answer 19

The Two major pathways are:
* C-3: First product is a three-carbon compound first
* C-4:First product is a four-carbon compound

Question 20

How is the process of carbon fixation?

Answer 20

1. CO2 from atmosphere diffuses through stomata into the leaf
2. In C-3 CO2 enters mesophyll cell and goes to chloroplast encountering Rubisco, a five-carbon compound & oxygen
3. CO2 and Oxygen compete for binding sites in C-3 if CO-2 wins 6 carbon compounds turn into 2 3-carbon compounds. If oxyegn weins photorespiration occurs
4. In C-4, CO2 enters mesophyll and is fixed or added to a 3-carbon compound using PEP carboxylase. (It does not bind with oxygen)

Question 21

What is a generla description of plants represented by each pathway?

Answer 21

1.Almost all grasses of tropical origin and most sedges are C-4
2.Temperate grasses and both temperate and tropical legumes are C-3 plants. Most trees & trees are C-3

Question 22

What is the significance of different pathways?

Answer 22

1. C-4 plants have kranz anatomy
   -Tights rings of mesophyll surrounding a well-defined bundle sheath
   -More structural component in leaf (sclerenchyma fibers & vascular bundles
2. C-3 plants have loosely arranged mesophyll, open spaces between cells, & less structural support & vascular tissue.

Question 23

When it comes to C-4 how come it is much more capable of higher growth rates than C-3 plants?

Answer 23

1. C-4 plants contain enzyme that fixes on carbon dioxide (PEP) does not bind with oxygen
2. Rubisco in C-3 essentially binds with oxygen and CO2
3. Plants produce more dry matter per unit of nitrogen and per unit of water than C-3 making it more efficient
4. C-4 optimum temperature is 90-95 degrees F, in C-3 it is about 65-75 degress F

Question 24

How does one determine forage nutritive value?

Answer 24

1. More structural support & vascular cells in C-4 grass leaves lower digestiblity 2. Tightly packed leaf cells provide less surface area for attachment by bacteria, digestion is lower and less complete. strong structural components slow breakdown of leaf particles. 3. Efficient nitrogen use by C-4 grasses means lower crude protein contentrations than found in C-3 grasses.

Question 25

What is the use of fixed carbon by plants?

Answer 25

1. Growth and maintenance 2. Reserve storage

Question 26

When it comes to prioritization of growth versus reserves what occurs?

Answer 26

1. Growth has priority over storage for carbyohydrate use. (uncontrolled grazing can deplete a plant's reserve & kill it) 2. Storage occurs when leaf area is more than adequate to meet growth demand. 3. Storage is reduced when leaf area cannot supply all needed energy for growth

Question 27

What are the contributions of legumes to forage-livestock systems?

Answer 27

1. Fix atmospheric N2 2. May improve seasonal distribution of frage DM (may be more productive during dry periods) 3. Utilize more of the soil rooting zone ( deep rooted)

Question 28

Why do Legumes fix atmopsheric N2?

Answer 28

1. Legumes produce high crude protein forage 2. Legumes improve soil fertility for subsequent crops

Question 29

What factors make legumes a limited use in Florida?

Answer 29

1. Requires greater managment inputs in fertilizer and control of grazing 2. Difficult/unreliable estblishment (low seedling vigor in some cases, unpredictable weather causes failures in others) 3. Lack of persisten perennials for grazed pasture

Question 30

What would be an overview of nitrogen relationships?

Answer 30

1. In most grassland systems, nitrogen is the most limiting nutrient for plant growth. 2. Occurs despite 79% if the atmosphere is N2 3. N2 is inert, very stable, and a large amount of energy is required to break the triple bond 4. Bacteria can break the N2 bond at room temperature and atmospheric pressure

Question 31

What are the bacteria involved in biological N fixation in forage legumes?

Answer 31

1. Rhizobium - Often associated with temperate legumes 2. Bradyrhizobium - Often associated with tropical legumes

Question 32

What is the nature of the association between rhizobia and legumes?

Answer 32

1. Both parties benefit * Rhizobia use carbohydrates from plant * Plants obtain N compounds from the bacteria

Question 33

How is the nature of symbiosis?

Answer 33

1. Rhizobia traditionally were classified based on their host 2. Some bacterial species are host specific and others will inoculate a large number of hosts

Question 34

How does the establishment of association of infection and nodulation occur?

Answer 34

1. Bacteria is the root zone attach to root hairs 2. Bacteria release a compound that causes the root hairs to curl 3. Rhizobia are trapped in the curled root hair and an opening is formed in the root hair cell wall 4. Rhizobia enters the opening in the root hair cell wall and travel to the root cortex

Question 35

How is the process of nitrogen fixation?

Answer 35

1. Energy demanding 2. Nitrogenase - enzyme complex (two seperate enzymes) that reduces N2 to NH4 3. Pratically field test to determine if nodules are fixing N (cut nodule in half, if actively fixing N, will have burnt red color, gray if not fixing)

Question 36

What factors affect quantity of N fixed? (negative effect)

Answer 36

1. Drought 2. Flooding 3. Very acid soils 4. Low soil fertility 5. N fertilization 6. Shading 7. Extreme temperatures

Question 37

What is the reason for seed inoculation?

Answer 37

1. Maximize growth & N fixation 2. Reduce risk of seedling failure

Question 38

When should legume seeds be inocuulated?

Answer 38

1. Always when planting a legume in a new field 2. Always, as it is cheap insurance to ensure your legumes thrive!

Question 39

What are the requirements for succesful seed inoculation?

Answer 39

1.Use correct inoculant 2.Use viable inoculant (expiration date, storage) 3.Sticker - Used to attach inoculum to seed 4.Plant immediately (heat & UV sensitive)

Question 40

What are forms of inoculant?

Answer 40

1. Peant humus- peat serves as the carrier 2. Granule flowable- put in a granular form to flow through a seeder, often used for large seeded legume 3. Coated seed- seed seller adds a coating to the seed that includes inoculant and coudl also include lime and fertilizer