HCS 2204 Midterm

It is what it is.

What are the three parts of Sustainability and their components?

Sustainability is the idea that we must conserve the resources we have now for the sake of the future and each individual circle is an aspect greatly impacts the goals of sustainability.

Economy (Blue) - employment of farmers and productivity

Society (Green) - livability and accessibility

Environment (Teal) - Pollution and weather change

What us a dicotyledon?

A flowering plant that has an embryo with 2 cotyledons (seed leaves) (4 to 5 petal flowers) (branched)

• Monocotyledons - have an entire/ complete seed like grasses (3 to 6 petal flowers) (Parallel)

Polyploids in Plants (benefits)

Three or more complete sets of chromosomes

• They are larger in cell size and plant size 

• Less tolerant to environmental stress

• less subject to the effect of mutation and greater genetic diversity when they sexually reproduce.

• Increased vigor

What is the center of origin?

The geographical region from which a species originated

• They preserve genetic diversity (germplasm) of crops and their wild relatives

Grafting

A horticultural technique what joins two or more plants together so that they grow as one.

Accession

A distinctly, uniquely identified sample of seeds, that is maintained as a part of a germplasm collection

Germplasm

Genetic resources such as seeds, tissues, and DNA sequences that are maintained for the purpose of animals and plant breeding, conservation efforts, agriculture, and other research.

What are the key phenotypic traits in domestication?

1. Elimination/ reduction of natural seed dispersal (non-shattering) (most important domestication trait)

2. Reduction in seed dispersal aids 

3. Trends towards increasing seed/fruit size 

4. Loss of germination inhibition 

5. Synchronous tillering

6. More compact growth habit

What is the importance of selection in plant breeding?

Selection exploits genetic variation to create distinct plants  

• It is primarily based on phenotype (plant appearance) and increasingly quantitative measurements are required.

What are some hybridization breeding systems?

Different kinds of pollination systems result in different species changing.

• Open pollination - 5-50 elite parents are crossed this occurs with help from wind and pollinators

• Self pollination - most common for annual species with limited access to insects (soybeans)

• Hand pollination (human intervention) - breeder approach to ensuring that precise crosses of specific plants. good for achieving crosses from self pollinated plants

Back-cross breeding hybridization

Where the initial F1 generation is not crossed with itself but with another parent to produce progeny more related to one parent than another.  

• Double cross hybrids in corn requires inbred parent lines, male sterile lines, and hybridization (within species) 

• Heterosis (hybrid vigor)

Inbreeding to create a larger crop offspring. Pollen from one plant to pollinate another. They stop the pollination of one plant so that they can cross breed it with another (detasseling - genetically modifying it to be sterile). 

Heterosis

the tendency of a crossbred individual to show qualities superior to those of both parents. 

• occurs when crossing two genetically unrelated inbred parents to create a hybrid. 

• contributes greatly to the high productivity in maize

Inter-species breeding systems

Breeding Between different species

Intra-species hybrid

Breeding between the same species

Inbreeding Depression

reduced phenotypic expression (lost yield) resulting from homozygosity

Hybrid Vigor

Increased phenotypic expression (increased yield) resulting from heterosis

GMO Mechanisms

Roundup Ready (RR) - transgenic plants that include a gene (extracted from bacteria) that confers resistance to glyphosate. Blanket-sprayed glyphosate to RR crop to kill of susceptible weeds but not the crop 

Bt - transgenic plants that include a gene (extracted from bacteria) that produces a  enzyme that digests caterpillar gut wall. Predominantly used for corn and cotton (reduced insectide use by 30%)

What are the pros and cons or GMO in plants

Pros

• yield protection (prevent yield loss due to weeds and insects but do not increase yield)

• Improved nutritional value 

• Longer shelf life

• Weather resistant

Cons 

• Lack of public awareness 

• additional expense 

• resistant weeds

• loss of biodiversity

Crop evolution of wheat

1. The ancestral wheat is a diploid 2n=14 

2. become hybridized with goat grass and became tetraploid 

3. Goat grass is hybridization with another species creating a triploid 

4. Finally, further chromosome doubling produced the hexaploidy Triticum aestivum (6n=42) 

In what way might humans have contributed to the evolution of crop plants? What are characteristics (or traits) of domesticated crops that differ from their wild relatives?

Humans have contributed to the evolution of plant through artificial selection favoring more desirable traits like large fruit/ grain size, uniform ripening, and increased yield. Domestication. non-shattering.

Plant Variety Rights and their significance in plant systems

A form of intellectual property protection for new plant varieties, granting breeders exclusive right sto control commercial use of their creations such as sale and reproduction.

• This encourages innovation and investment because it incentivizes the development of improved plants overall.

Plant Taxonomy and their significance in plant systems 

The identification, description, classification, and naming of plants

• important for organizing and keeping track of plant knowledge. accuracy and communication become easier with a standard system

Growing degree days equation and importance in agricultural science

Used to provide a metric for tracking crop development, predicting harvesting times and optimizing resource application which reduces variable cost

GGD = growing degree days

s = Start date of measurements

n = End date of measurements

Td = base temperature for each day

base = base temp for the crop in question

The importance of light for plant systems

1. light is a key determinant of seasonality 

2. cloudiness 

3. canopy management (avoid shade, optimize planting density and breed for short plants) 

4. Greenhouse lighting - reduced energy costs LED and different wavelengths like red and blue lights

Evapotranspiration (ET)

water is lost by leaves because the stomata opens during photosynthesis. as CO2 enters the leaf, H2O leaves the leaf

• ET = plant transpiration (surface evaporation) and soil evaporation

• primary way of plant cooling

What are some management options to reduce water use?

1. Low vs high volume irrigation - drip rather than flood

2. Mulch - eliminates soil evaporation

3. Species selection - high water efficiency crops and plants

4. canopy management - weed removal and dense canopy

What is the composition of air?

Nitrogen - 78%, Oxygen - 21%, Carbon Dioxide - 0.04%

How do plants benefit from shelter (from wind)?

• Reduced wind speeds (mechanical abrasion)

• Conserve water loss (lower ET)

• Can promote wild life (both birds and small rodents)

What is the plant boundary layer?

A micro-layer of static air that surrounds all stationary objects

• Can slow down the movement of water vapor out the leaf and result in warming on a cool day.

• Heat absorption can also lead to differences in leaf temp and air temp.

In what ways does wind affect plants?

1) Air movement affects plant temp and water loss. Increase air movement = more water loss.

2) Mechanical Disturbance caused by wind moving over plants which slow stem elongation

3) Wind reduces Plant boundary layer

4) Low air flow (and high humidity) can promote the development of fungal and bacterial diseases.

5) Wind Erosion cause cause losses of top soil and make soil more sandy and dry.