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Greenhouse systems > Quiz #2 > Flashcards

Quiz #2 Flashcards

1
Q

why does the earth have longer winter nights and shorter summer days?

A

Because of the Axial tilt of the earth.

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2
Q

photosynthesis is…

A

converting light energy to chemical energy

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3
Q

what are the two kinds of pigments?

A

Primary: Chlorophyll A
Accessory: Chlorophyll B, Caratinoids.

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4
Q

What is PAR?

A

Photosynthetically active radiation… What we can see!

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5
Q

What is PPFD?

A

The amount of light particles that hit a surface (plant leaves) in one second. We measure light in ppfd, (Photosynthetic photon flux density)

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6
Q

What is DLI?

A

Daily light integral. Total amount of PAR in a day.

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7
Q

Does climate change effect PAR>

A

Yes, climate change is changing the atmosphere so the light is struggling to get through. It does not change daylight.

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8
Q

What are the two types of light?

A
  1. Direct (from the sun)
  2. Diffuse (scattered direct light)
    And plants cannot tell the different.
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9
Q

What are some things that happen to light ?

A

Reflection, Absorption, Transmittance (what’s coming through), Emissivity (ability to emit energy which it has absorbed; heat that has been radiated back out)

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10
Q

There can be a lot between the light and the plant… name a few

A

structural barriers, shade cloths, supplemental lighting. these can reduce useable light for plants 40%-50%.

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11
Q

What is glazing?

A

A material that lets light in.

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12
Q

1% light increase in light = ?

A

1% increase in plant production

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13
Q

at what angle is light most effective when it hits the glazing material?

A

90 degrees… although it rarely ever happens

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14
Q

What are the most common glazing materials for greenhouse production?

A

glass, laminated glass, diffused glass, tempered glass, rigid plastics and plastic films

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15
Q

Glass: glazing material

A

highest light transmittance, lasts the longest 30+ years, and is the most expensive.

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16
Q

Laminated glass; glazing material

A

Constructed of two layers of bonded glass with some kind of gas between the layers. When they break, it looks like a spiderweb and is often required in garden centers for this reason.

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17
Q

Diffused glass; glazing material

A

scatters light on its way in giving better light distribution, and is preferred for veggie growers because it provides a better surface area of light.

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18
Q

Tempered glass

A

is chemically or heat treated, breaks into bits.

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19
Q

Rigid plastics; glazing material

A

made of polycarbonate and acrylic, has lifespan of about 15 years. Is less expensive, and has a reduced transmittance of light over time.

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20
Q

Plastic films; glazing material

A

Made of polyethylene, has a lifespan of 4-5 years, has two layers and reduces heat loss by 40%. This is the material used for the hoophouses at the FIC.

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21
Q

what are some common glazing material add ons?

A
  1. Ultra violet protection
  2. Infrared Radiation blockers
  3. Anti-condensate surface treatments
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22
Q

what are the three types of bulbs used in supplemental lighting?

A
  1. T-5s
  2. HIID- High intensity Discharge.
  3. Light emitting diodes (LEDs): in grow room at FIC
23
Q

T-5 lighting

A

Full spectrum fluorescent light.

24
Q

HIID- High intensity discharge

A

Is currently the most cost effective, can get too hot and intense.

25
Q

LEDs

A

An electrical current passes through a microchip and illuminates a diode. can cut energy usage up to 75%, is typically low maintenance and doesn’t get too hot. LEDs are the most efficient.

26
Q

How do we use lights to influence plant growth?

A

Photoperiodism and Phototropism

27
Q

Define Photoperiodism

A

Photoperiodism is how plants respond to daylight. It is a developmental response that synchronizes flowering, fruiting, germination and growth.

28
Q

Define Phototropism

A

Tropisms are directional plant responses to stimuli. Positive = grow towards. Negative = grow away from.

29
Q

How do plants sense light?

A

Plants sense light with photoreceptors that absorb photons.

30
Q

What are the two types of Photoreceptors?

A
  1. Phytochrome
  2. Cryptochromes
31
Q

Phytochrome

A

Red and far red light, good for germination, stem elongation and flowering.

32
Q

Cryptochrome

A

Blue light, good for plant height, effects flowering time and morphological patterns.

33
Q

Shade escape aka Shadow avoidance

A

Plants can tell the difference between the shade from a rock, and the shade from a plant.

34
Q

The amount of continuous (?) influences flower formation in most plants

A

Darkness

35
Q

Short day plants

A

Short day plants need more than 12 hours of darkness every day, they flower in the spring and fall. Plants like poinsettias and Christmas cactus are short day plants.

36
Q

How do you create short days?

A

Using blackout cloths. This can cause a lot of heating up in the summer, so you’ll want to use them later in the day.

37
Q

Long day plants

A

Long day plants need less than 12 hours of darkness a day. Many garden veggies are long day plants.

38
Q

How do you create long days?

A

Supplemental lighting. for example, if the sunrise is at 7:51, and the sunset at 6:01, run the supplemental lighting until you reach 12 hours of light for that day. Night interruption is also a way to create long days.

39
Q

Growing degree days (GGD)

A

GGD measures heat accumulation over time. Organisms have set temperature accumulation for development. We usually use a Base 50 to determine GGD

40
Q

Base 50

A

Base 50 is a temperature used to determine Growing degree days. The threshold, or base temperature, is the temperature under which no significant crop development is expected. Also known as Maximum temperature threshold.

41
Q

what is the growing degree days formula?

A

High temp + low temp/ 2 = average temp.
GGDx= average temp - X
X = 50 (normally)

42
Q

What does temperature regulate when it comes to greenhouse growing?

A

Growth, water use, germination rates, flowering, ripening.

43
Q

Greenhouse edge effects, what are some things around the edges of the greenhouse that can potentially alter the environment?

A

Heat, light, water, air flow, humidity, space, pests, people..

44
Q

How does heat loss work?

A

Heat is lost through three different ways.
1. Conduction
2. Convection
3. Radiation

45
Q

Conduction

A

Heat loss/transfer through touch. Floor heating systems.

46
Q

Convection

A

Air circulation. Cold air displaces warm air and warm air rises, fans help!

47
Q

Radiation

A

Something giving off heat.

48
Q

What are some common hot water heating systems used in the greenhouse?

A

Finned pipe systems, floor slabbed systems, bench top systems, geothermal heating.

49
Q

Geothermal heating

A

Geothermal energy is heat that is generated within the Earth. It is a renewable resource that can be harvested for human use.

50
Q

BTU

A

British thermal unit = amount of energy it takes to heat one pound of water

51
Q

BTUH

A

Number of BTUs transferred in one hour

52
Q

U value

A

ability of a material to transfer heat

53
Q

Air temperature is not the only thing to worry about, you also need to manage the temperature of the (?)

A

Media! plants exist in two unique environments, above and below the soil. both need to be managed

54
Q

What is a photon

A

A light particle.

Greenhouse systems (3 decks)

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