Linking abiotic stress to
horticultural performance of tree
fruit in Washington State
Lee Kalcsits, Assistant Professor
Department of Horticulture
Washington State University
Tree Fruit Research and Extension Center
Wenatchee, WA
What is abiotic stress?
• An non-living external force
that negatively affects the
growth, productivity and
health of a plant (light,
heat, water, nutrient, cold,
etc.)
Light
Air Pollution
Heat
Mechanical
Injury
Water
Salinity
Cold
Plant Responses to Abiotic Stress
Summer Growing Season in
the Pacific North-West (East of
the Cascades)
• Average daily maximum temperature in
July and August (91 F)
• High light intensity (>2000 umol m-2 s-1
PAR)
• We live in a desert
• Water restrictions are forcing the use of
wells
• Sudden cold periods
Plant Responses to Abiotic Stress
How stress interacts with the tree
• Sudden changes in temperature or irrigation failure
• Heat or cold
• Duration
• How long the stress event lasts for, -20 F for one hour or below -10 F for 1 week?
• Time with water stress
• Number of exposures
• How frequent stress events are? Can the plant recover between events
• Combination of stresses
• Water stress with salinity?
• Cold with biotic stress
• Heat with light in the summer
Plant Responses to Abiotic Stress
What affects how a plant responds?
• Affected location of the plant
• Roots are less cold hardy than stems which are less cold hardy than buds
• Fruit is more susceptible to sunburn than leaves
• The developmental stage
• Each stress affects the plants differently at different stages
• Genetic differences
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Each scion/rootstock shows different responses to abiotic stress.
Some are more drought tolerant/cold tolerant
Some are less susceptible to sunburn
Some rootstocks are more cold hardy
Plant Responses to Abiotic Stress
How does a plant respond?
• Tolerance – The stress affects the plant but it does not lead to death
• Resistance – The plant has mechanisms in place to limit damage
caused by stress
• Increased Susceptibility to Pests and Disease – Damage caused by
abiotic stress can increase the risk of insect and disease attack
• Death
Brunner et al. 2015. Frontiers in Plant Sciences
Plant Response - Stress Sensing
Reactive Oxygen Species (ROS)
• Chemically reactive molecules containing oxygen. Examples
include H2O2, O2-, OH-, and O-.
• These are fine at normal rates but increase under stress and can
cause damage.
• Plants respond by scavenging ROS throughout the plant
• Antioxidants
• Secondary metabolites
Hormonal Responses
• Absiscic Acid – ABA
• ABA-mediated signaling also plays an important part in plant responses to
environmental stress
• ABA concentration increases under stress that affects molecular, metabolic
and developmental processes.
• Jasmonic Acid – JA
• The major function of JA and its various metabolites is regulating plant
responses to abiotic and biotic stresses as well as plant growth and
development.
• Changes in plant development with JA include growth
inhibition, senescence, flower development and leaf abscission.
• Ethylene
• Increased levels of ethylene under environmental stresses
• Often unable to grow and proliferate to any great extent, at least until the
stress is removed and the ethylene level is lowered.
Morphological and Developmental Responses
Horticultural Responses
• Manipulation of growth
• Manipulation of flowering
• Crop load/size
• Postharvest quality/storability