LINKING ABIOTIC STRESS TO HORTICULTURAL PERFORMANCE OF TREE
FRUIT IN WASHINGTON STATE
Kalcsits, L
[email protected]
Department of Horticulture, Washington State University, Wenatchee, USA
Tree Fruit Research and Extension Center, Wenatchee, USA
KEYWORDS
Abiotic stress, light, temperature, water, salinity, cold, physiological responses,
avoidance, tolerance.
ABSTRACT
In Washington State, abiotic stress such as heat, light, salinity, drought, cold and
flooding stress can affect tree fruit orchards at some point during their productive life.
Abiotic stress can be defined as a non-living factor that negatively affects plant growth,
survival and its ability to reproduce. Abiotic stress causes changes in the soil-plantatmosphere continuum and can lead to reduced yields and decreased plant
performance. These stresses are sensed in the plant and plants can either respond by
increasing their tolerance to or using physiological avoidance to survive these events.
These strategies lead to physiological and developmental changes that affect the
productivity and growth of the tree. The severity, duration, frequency of exposure and
combination with other stresses and its location of effect on the plant shape the type of
response from the plant (Figure 1).
Figure 2. Plant response scenarios to abiotic stress
Plants have the ability to sense the environment around them. They have signalling
networks that quickly respond to changes in environment and, in turn, adjust protein
activation, gene expression and cellular balance to tolerate or avoid abiotic stresses
(Figure 2). Many abiotic stresses affect similar physiological pathways in plants and
often similar mechanisms exist to tolerate abiotic stress, whether it is drought, cold,
salinity or other stresses. Physiological responses include both immediate and longterm adjustments that include osmotic adjustment, cell wall permeability, protein
adjustments, production of antioxidants and hormonal changes (Figure 2). For example,
when water supply cannot meet the water demand by the plant, the plant is able to
sense changes in water availability through ionic imbalance that lead to ion transport
and concentration regulation which affect protein activity and gene expression. These
biochemical changes shape how the plant acts and responds and ultimately affects the
long-term productivity of the tree.
Figure 3. Sensing external environmental changes in plants
Although stress is defined as negatively affecting plant growth, productivity and survival,
when properly managed, it can be used as a tool to manipulate growth and flower
induction in horticultural crops. Timely water limitation or nutrient restrictions can induce
responses that allow a grower to manipulate vegetative growth, dormancy induction,
flower induction. However, there are other abiotic and biotic stresses that have negative
effects on plant growth and performance. Here, the strategies of trees to survive abiotic
stress events will be described in addition to the effects that these stresses have on tree
performance, health and productivity.
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
•
•
•
•
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