48
Stress Management
Stress Management
Outline
What is stress and how does it affect potato plants?
How does stress impact external tuber quality?
How does stress impact internal tuber quality?
How can you avoid or manage stress?
What is Stress?
Any condition (moisture availability, temperature, fertility, etc.) that is above or below the optimum for plant growth and tuber production
The “ideal” temperature for growing potatoes is 77oF in the day and 54oF at night.
“Therefore, potatoes grown in all regions experience temperature stress every year”
What is Stress?
The impacts of stress tend to be cumulative- 10 days of heat stress is more damaging than 5 days- Two stresses together (ex. heat and water stress) tend to cause more damage than a single stress
Moisture Stress and High Soil Temperatures Combine to Cause Damage
0
20
40
No Stress LowMoisture
LowMoisture +
Hot Soil
Hot Soil
% S
ug
ar E
nd
s
Source: Kleinkopf, 1988
Hot Soil
No Stress
Heat cables increase soil temperature by 6 to 9 F
Environment (uncontrollable) Heat/cold/frost Drought/excess rainfall Hail/lightening Air pollution
Sources of Stress
Management (controllable)
Soil moisture deficits or excesses Nutrient deficits or excesses Poor stand establishment Compaction/root pruning Physical damage to tubers
Sources of Stress
Water Stress
Low moisture availability
High demand (heat, wind, excess N)
Low capacity (poor root system)
Heat and Water Stress Occur Together
As temperatures increase, so does water use by the plant
0
0.1
0.2
0.3
0.4
0.5
50 60 70 80 90 95 100
Average Temperature
ET
Rat
e (i
n/d
ay)
Effect of ET rate on level of soil moisture that can be used before development of stress
0
10
20
30
40
50
60
1 3 5 7 9
Relative ET Rate
% o
f av
aila
ble
so
il m
ois
ture
Low High
Data for a sandy soil in Egypt
Stress–related problems
External
Tuber size Malformation Second growth Chain tubers Growth cracks Greening Enlarged lenticels Heat sprouts
Internal
Hollow heart / Brown centerInternal brown spot (IBS)Sugar endsVascular discolorationBlack heart*Blackspot /shatter bruiseLow starchHigh sugars*Frost*Chilling injuryPressure bruise
*Immediate
From Hiller, WCS 19:169
Stress-related problems
Requirements for Expression
Susceptible variety
+ Stress conditions
Weather or environmentManagement mistakes
Russet Burbank
Common Defects TriggersMalformations Heat, drought
Growth cracks Moisture stress, erratic growth
Sugar ends Heat
Hollow heart Cold soil, low tuber set
Stem end ??
Low solids Heat, early death
Net necrosis PLRV
Outline
What is stress and how does it affect potato plants?
How does stress impact external tuber quality?
How does stress impact internal tuber quality?
How can you avoid or manage stress?
During stress low availability of sugars and the imbalance in top/tuber growth can temporarily stop tuber growth. When growth resumes, it occurs at the site of most active cell growth. The end result is malformed tubers that may have knobs
Around the eyes and bud end is where growth resumes
1. How does stress affect sugar development - Energy production and use
The temperature optimum for Photosynthesis (energy production) is around 65o to 75o F , Respiration (energy use) continues to increase with temperature
0
10
20
30
40
50
60
41 50 59 68 77 86 95
Temperature (F)
Net Ps Rate
cloudy
sl. overcast
sunny
respiration
Source: Winkler, 1961
Plants Continue to Produce Sugars on Hot Days
There is a period during the morning where photosynthesis reaches the optimum, even on very hot days
0
5
10
15
20
25
30
Time of Day
Ph
oto
syn
thes
is R
ate
Temperature (F) 61 82 93 86
“Mid-day depression”
Source: Dwelle, 1983
Dry matter partitioning – two temps
APJ 69:653Harvest Index =
.5 to .7
Harvest Index = .2 to .7
Outline
What is stress and how does it affect potato plants?
How does stress impact external tuber quality?
How does stress impact internal tuber quality?
How can you avoid or manage stress?
During stress there is less sugar available, and the tuber has a harder time converting sugar into starch. The tuber becomes a weaker sink, and the end result is lower specific gravity and more sugar ends
Stems
StarchSugar
Carbohydrate metabolism in potato tubers
During normal tuber growth, metabolism is driven towards the production of starch. Stress (in-season or in-storage) changes enzyme activity and membrane function
Effect of temperature on specific gravity of potatoes
1.101
1.075
1.084
1.050
1.040
1.050
1.060
1.070
1.080
1.090
1.100
1.110
61 86 61 86
Soil Temperature (oF)
Specific Gravity
Air Temperature (oF)
Cool (77/54) Hot (100/82)
Comparison of soil temperatures at Oakes, ND
60
65
70
75
80
85
Date
Soil temp (F)20032004
High sugar ends
Kincaid et al., 1993
“Soil temperature was directly related to percentage of sugar end tubers”
R2 = 0.42 Irrigation Frequency
WE
75.7%
36.6% 50.4%
63.4%
0”
8”
4”
Percentage of 10 Tuber Sample with Sugar Ends
Impact of row orientation on Russet Burbank quality
Row Width Can Influence Sugar Ends
0
5
10
15
20
32" 34" 36"
% S
ug
ar E
nd
s
Source: Shock, 1988
0
50
100
150
200
250
300
Early July Late July October December March May
Date
En
zy
me
ac
tiv
ity
Sugar End
Normal
End of stress Harvest
Storage at 48 F
•The damage that occurs to the starch production system early in the season is permanent – The symptoms usually develop when the tubers are exposed to cold
Source: Sowokinos
Effect of a single water stress event on the incidence of disorders in Russet Burbank
0
10
20
30
40
50
100 75 65 55 45 35
Available Moisture (%)
% S
ug
ar
En
ds
19911992
Source: Shock, OSU
Pattern of hormone changes during tuber growth and storage
Stress event
High or erratic N
availability
Outline
What is stress and how does it affect potato plants?
How does stress impact external tuber quality?
How does stress impact internal tuber quality?
How can you avoid or manage stress?
Principles of Stress Avoidance and Management
Maintain uniform and optimal conditions throughout the plant growth and tuber bulking growth phases
Minimize environmental stress
Avoid added management stress
Plant resistant varieties
Don’t Contribute to Environmental Stress with Management Stress! Poor root development
– Compaction and late cultivation
Poor vine development
– Erratic stands and early stress
Excess vine development
- Too much N
Disease
Plant root systems 21 days after emergence extracted from:
compacted soil (left)uncompacted soil (right)
1 ft
Source: Modified from Weaver (1926)
2 ft
3 ft
By row closure a healthy potato root system extends more than 3 feet down and across the entire furrow
Compact layerRoot
Pruning
How does a stand like this impact row closure and soil temperature?
Excess Nitrogen Fertility Can Lead to an Imbalance in Vine and Root Growth
-200
0
200
400
600
800
20 30 40 50 60 70 80 90 100 110 120 130
Days After Planting
Rel
ativ
e V
ine
and
Ro
ot
Gro
wth
Rat
e
Vines with too much N
Roots with too much N
Stress (water, heat, nutrients, pests) can lead to premature plant death
Impact of Resistance on Stress Management
Intensity of Management Required
Resistance Level Input Level
High Low
Moderate Moderate
Low High
Sugar End Susceptibility by Variety
0
25
50
75
100
Ru
sset
Ran
ger
Sh
epo
dy
Gem
Leg
end
Um
atill
a
% S
ug
ar E
nd
s
Parma, ID - 1994
65
70
75
80
85
Sp
ec
Gra
v
Ab
02
She
02
Ab
03
She
03
Genetic Stability for
Tuber Specific Gravity
R Norkotah
Russet B
Varieties With Stress Resistance
Heat and Drought Stress
Ranger Russet Gem Russet
Russet Norkotah Clearwater Russet
Umatilla Russet
Water Use Efficiency (WUE)
15 cwt/ in of water
18 cwt/ in of water
Varieties With Stress Resistance
Defoliation Stress
Ranger Russet Alturas Gem Russet Bannock Russet Summit Russet Russet Norkotah (affects yield)
Varieties With Stress Resistance
Stresses Conducive to Hollow Heart
Ranger Russet Alturas
Shepody Umatilla Russet
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