Water as a Limiting Factor Part 1 Flashcards

1
Q

First three important principle of water requirements?

A
  1. Know the symptoms on the vine of water stress
  2. Know the physiological stages when a lack of water will affect the size and quality of the crop
  3. Know the depth and size of the root system
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2
Q

Last two important principles of water requirements?

A
  1. Know the soil in order to know what the storage capacity of the soil is for water
  2. Know how much water to apply
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3
Q

3 indicators of plant water stress:

A
  1. Leaf water potential (pressure machine)
  2. Leaf stomatal conductance
  3. Soil water potential
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4
Q

What does stomatal conductance describe?

A

It describes gas diffusion through plant stomata.
- Plants regulate stomatal aperture in response to environmental conditions

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5
Q

Do stomata control leaf water loss?

A

When we look at the the transpiration flux vs stomatal aperature we can see that on windy days there is a higher transpirational flux at lower aperatures.

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6
Q

Why do we have slow transpiration under still air?

A

Because the boundary layer is higher

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7
Q

Boundary layer conductance relies on three things:

A
  1. Wind speed
  2. Leaf size
  3. Diffusing gas
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8
Q

What can we see when we look at a graph showing mid-day leaf water potential (bars) vs. Stomatal Conductance?

A

Here we can see that there is a positive linear relationship, in that when there is more negative leaf water potential, we have less stomatal conductance

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9
Q

What does soil water potential define when looking at water stress?

A

Defines the supply part of the supply/demand function of water stress

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10
Q

When looking at the graph showing when to irrigate we can see that…

A

Silt and Loam have the highest amount of available water

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11
Q

What are the 6 critical physiological stages for water stress?

A
  1. Prior to bud break in dry regions without winter rainfall (Dormant phase)
  2. Bud Break before flowering
  3. Flowering a fruitset up to pea size
  4. Pear size to berry softening
  5. Ripening (berry softening to harvest)
  6. After Harvest
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12
Q

The bleeding phase is positively affected by

A

a good content of water in the soil

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13
Q

Bleeding is a very important stage for two reasons:

A
  1. If we see a drop of water coming out from the pruning cut that means that there is a continuous water transport from the soil to that point
  2. If we have a good bleeding phase, we also have a good transport of auxins to the buds that stimulate bud burst.
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14
Q

What can we see from the graph showing days of bloom vs. Yield loss?

A

We can see that with very early water stress we can have a hugely negative impact on yield. The earlier the stress, the more limitations on final yield

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15
Q

2 Practical methods for evaluating soil moisture and 3 tools

A
  1. Dig a soil pit
  2. Feel the soil

Tools:
1. Tensiometers (Water potential)
2. Resistance blocks (water content)
3. Neutron probe (water content)

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16
Q

The relationship between soil water potential and volumetric water contentdepends on…

Rate of water infiltration depends on…

A
  1. Soil type
  2. Soil type and volume of water applied
17
Q

3 different indicators for when to irrigate. Which is the best?

A
  1. Visual symptoms
  2. Vine water status (the best)
  3. Weather conditions
18
Q

What is ET?

A

Evapotranspiration

19
Q

Two important considerations for deficit irrigation

A
  1. Applied water is less than ET
  2. Water stress is when photosynthesis is down and transpiration is down
20
Q

The purpose of a regulated deficit irrigation is triple:

A
  1. Save water.
  2. Preserve yield because I’m not really going into a severe stress.
  3. Diminish the competition between vegetative structure and bunches, I would increase the quality.
21
Q

What is the main philosophy of RDI?

A

Regulated Deficit Irrigation philosophy is that we never want the vineyard working at the maximum transpiration level, we want to keep our vineyard in a condition of saving water without having big limitations.

22
Q

What is RDI? (3)

A
  1. Again Regulated Deficit Irrigation.
  2. Maintain vine water status within prescribed range of water stress (e.g., -0.5 to -1.0 MPa) for a defined part of the growing season.
  3. Water stress needs to be removed after this period by irrigating >100%ETc.
23
Q

What is PRD? (3)

A
  1. Alternately irrigating two spatially separate parts of the rootzone
  2. Each cycle 5 to 14 days, depending on the site and weather
  3. Deep sandy loam
24
Q

True or false: RDI is a evolution of PRD

A

False PRD is an evolution of RDI

25
Q

What is the main point of utilizing RDI or PRD, why would intentionally induce a water stress?

A

We would do this in order to control vigor, increase berry quality and increase water use efficiency. We do this via reducing vegetative growth

26
Q

Is more stress better?

A

Too much water stress and when it is too late, can be incredibly detrimental

27
Q

Plant water status affects berry size in which way, what are two ways that we can irrigate and how could they affect berry weight or size?

A
  1. Irrigate less before veraison to limit berry size
  2. Irrigate more after veraison to prevent weight loss
28
Q

Discuss the difference between red and white grapes and how RDI and PRD can be used in respect to the different grapes (2)

A
  1. Deficit irrigation/nutrition useful for most red grapes
  2. RDI less suited for white grapes than is PRD
29
Q

The more severe is the water stress, the faster is the ________, the faster is the _________ into the cluster, affecting an higher pH, to low acidity and so on.

A
  1. senescence
  2. recycling of K
30
Q

Too little water before budbreak = (2)

A

delayed budbreak and stunted shoot growth.

31
Q

No bleeding =
Normal bleeding =

A
  1. Bad budbreak
  2. Good budbreak
32
Q

Too much water stress after veraison = (3)

A
  • Berry dehydration
  • Decrease in yield
  • Sunburn
33
Q

Too much water stress after veraison = (2)

A

Yelow leaves
Early defoliation

34
Q

Yelow leaves and Early defoliation =

A

Recycled leaf K+ = undesirable increase in berry k+, increased juice pH

35
Q

Which one is doing better?
Sangio on left, Montepulciano on right?

A

Sangio on the left

36
Q

What is the function of ABA?

A

We know that ABA is the regulator of stomatal closure, it’s produced at the root level, it’s transported by xylem up to the leaves

37
Q

______occurs when the soil moisture is well above field capacity and water drives gases out of the soil pores so that there is insufficient oxygen for proper root function.

A

Waterlogging

38
Q

Depending on the severity of waterlogging this condition is termed?

A

hypoxia or anoxia

39
Q

Which vine rupestris or riparia is better suited to water logging?

A

Riparia is better suited