Plant plasticity and adaptation
Romy Steenkamer
Plant ecophysiology aims to provide mechanistic explanations for ecological
questions relating to survival, distribution, abundance, interactions of plants with
other organisms and the organization of communities and the function of
ecosystems.
Plant species in different environments are known to have different morphological
features. (Small thick leaves of dessert plants minimize the heat load).
Not only physiological responses to abiotic environments are important,
physiological interactions with other organisms are important as well.
Ecophysiology offers chances to develop less stress sensitive crops, by studying the
mechanisms of environmental stress responses.
Lecture 1 What are plant plasticity, adaptation and acclimation?
Plasticity is the ability of an organism to change its phenotype in response to
changes in the environment.
Acclimation is the process of physiological, biochemical or anatomical
modifications occurring within the lifetime of an individual organism that result
from exposure to a naturally occurring environmental challenge. Acclimation helps
an individual organism to survive unfavourable changes in the environment. Does
not involve genetic change and is reversible.
Adaptation is an anatomical structure, physiological process or behavioural trait
that has evolved of a period of time by (natural) selection and increases the fitness
of the genotype. An adaptation is thus a heritable characteristic.
Stress is an environmental factor that reduces the rate of some physiological
processes (growth/ photosynthesis) below the maximum rate that the plant could
otherwise sustain.
Varying rates between individuals and ecotypes make it difficult to quantify stress.
Stresses are only stresses for species that evolved in its absence.
Stress can also be defined as adverse factors that inhibit ‘normal physiology’. For
examples: climatic, biotic factors, factors related to phenological stages and crop
management. Reduced growth, lower survival can be consequences of stress.
Plants need to adapt to stresses because of their sessile lifestyle, they cannot run
away. Plants respond to stresses as individual cells and as whole organisms; stress
induced signals are then transmitted throughout the plant and to neighbours,
making other plants more ready to resist the stress.
,The severity of a stress response depends on the rate of change and the magnitude
of stress and extremes. Possible responses depend on the nature of the stress and
the affected physiological processes. Responses include:
• Resistance: ranging from
- avoidance (deep roots in low rainfall area)
- tolerance (Mediterranean species can cope with low water content)
• Adapt
• Die
Stress can act on any life cycle stage and can limit the distribution of a species
through effects on one or more of the following:
• Survival
• Reproduction
• Development young organisms
• Interactions other organisms (competition, predation, parasitism, disease)
Different time scales of plant responses to stresses can be distinguished:
1. The immediate response Generally occurs over seconds to days, resulting in
a decline in performance of the affected process (resistance; avoidance,
(tolerance)).
2. Acclimation: within the lifetime of an individual organism
3. Adaptation: requires genetic changes
Acclimation mechanisms are often the result of adaptation.
Requirements to evolve adaptations
• Differences in the trait cause differences in fitness
• Differences in the trait are heritable: genetic variation
• Fitness depends on the environment (not the same in all environments)
,Certain adaptations come at a cost: adaptations to prevalent conditions may reduce
fitness in alternative conditions.
Adaptation can be studied by common garden experiments: multiple genotypes are
sown in different environments:
Honsei lacks acclimation but shows huge genetic adaptation to the middle
environment.
Filters determine whether a certain species live at a particular site are:
-historical: does it arrive?
- physiological: can it germinate, grow, survive and produce?
- biotic: does it successfully compete and defend itself?
Ecological amplitude < physiological amplitude
Biotic interactions decrease the actual distribution of a species (its realized niche)
below the range of conditions where it can grow and reproduce (its fundamental
niche).
As filters are constantly changing and interacting, species composition is not static.
A given species is most common under suboptimal conditions because biotic
interactions prevent most species from occupying the most favourable habitats.
, Biomass production of 2 species (x and y) as a function of resource supply. Physiological amplitude defines in the
upper panels the range of conditions over which each species can grow. Top left = different max Biomass/ Top centre
= different resource response curve/ Top right= different physiological amplitude. The narrower range of conditions,
constrained by other species, in the lower panels shows competition.
Adaptation types
• Structural adaptations
- Brightly coloured flowers with nectar to attract pollinators
- Specific root growth
- Specific seed dispersal (practical M1)
• Behavioural adaptations
- Phototropism: plants grow towards the sun (Lecture 6)
- Gravitropism: roots grow down into soil.
Ecotypes (also called accessions) are the results of local adaptation through
divergent natural selection of traits that have high fitness in the environmental
conditions specific to a population. E.g. population of sunflowers around the Great
Salt Lake are highly salt tolerant there, but not elsewhere.
Adaptations to specific stresses
• Drought stress can be tolerated by means of:
- an improved water uptake by roots
- a reduce of water loss by stomatal closing, reduction of cuticular
respiration, reduction of LAI
- storing water
Xerophytes are plants capable of living in dry areas. Most have the above
adaptations.
Romy Steenkamer
Plant ecophysiology aims to provide mechanistic explanations for ecological
questions relating to survival, distribution, abundance, interactions of plants with
other organisms and the organization of communities and the function of
ecosystems.
Plant species in different environments are known to have different morphological
features. (Small thick leaves of dessert plants minimize the heat load).
Not only physiological responses to abiotic environments are important,
physiological interactions with other organisms are important as well.
Ecophysiology offers chances to develop less stress sensitive crops, by studying the
mechanisms of environmental stress responses.
Lecture 1 What are plant plasticity, adaptation and acclimation?
Plasticity is the ability of an organism to change its phenotype in response to
changes in the environment.
Acclimation is the process of physiological, biochemical or anatomical
modifications occurring within the lifetime of an individual organism that result
from exposure to a naturally occurring environmental challenge. Acclimation helps
an individual organism to survive unfavourable changes in the environment. Does
not involve genetic change and is reversible.
Adaptation is an anatomical structure, physiological process or behavioural trait
that has evolved of a period of time by (natural) selection and increases the fitness
of the genotype. An adaptation is thus a heritable characteristic.
Stress is an environmental factor that reduces the rate of some physiological
processes (growth/ photosynthesis) below the maximum rate that the plant could
otherwise sustain.
Varying rates between individuals and ecotypes make it difficult to quantify stress.
Stresses are only stresses for species that evolved in its absence.
Stress can also be defined as adverse factors that inhibit ‘normal physiology’. For
examples: climatic, biotic factors, factors related to phenological stages and crop
management. Reduced growth, lower survival can be consequences of stress.
Plants need to adapt to stresses because of their sessile lifestyle, they cannot run
away. Plants respond to stresses as individual cells and as whole organisms; stress
induced signals are then transmitted throughout the plant and to neighbours,
making other plants more ready to resist the stress.
,The severity of a stress response depends on the rate of change and the magnitude
of stress and extremes. Possible responses depend on the nature of the stress and
the affected physiological processes. Responses include:
• Resistance: ranging from
- avoidance (deep roots in low rainfall area)
- tolerance (Mediterranean species can cope with low water content)
• Adapt
• Die
Stress can act on any life cycle stage and can limit the distribution of a species
through effects on one or more of the following:
• Survival
• Reproduction
• Development young organisms
• Interactions other organisms (competition, predation, parasitism, disease)
Different time scales of plant responses to stresses can be distinguished:
1. The immediate response Generally occurs over seconds to days, resulting in
a decline in performance of the affected process (resistance; avoidance,
(tolerance)).
2. Acclimation: within the lifetime of an individual organism
3. Adaptation: requires genetic changes
Acclimation mechanisms are often the result of adaptation.
Requirements to evolve adaptations
• Differences in the trait cause differences in fitness
• Differences in the trait are heritable: genetic variation
• Fitness depends on the environment (not the same in all environments)
,Certain adaptations come at a cost: adaptations to prevalent conditions may reduce
fitness in alternative conditions.
Adaptation can be studied by common garden experiments: multiple genotypes are
sown in different environments:
Honsei lacks acclimation but shows huge genetic adaptation to the middle
environment.
Filters determine whether a certain species live at a particular site are:
-historical: does it arrive?
- physiological: can it germinate, grow, survive and produce?
- biotic: does it successfully compete and defend itself?
Ecological amplitude < physiological amplitude
Biotic interactions decrease the actual distribution of a species (its realized niche)
below the range of conditions where it can grow and reproduce (its fundamental
niche).
As filters are constantly changing and interacting, species composition is not static.
A given species is most common under suboptimal conditions because biotic
interactions prevent most species from occupying the most favourable habitats.
, Biomass production of 2 species (x and y) as a function of resource supply. Physiological amplitude defines in the
upper panels the range of conditions over which each species can grow. Top left = different max Biomass/ Top centre
= different resource response curve/ Top right= different physiological amplitude. The narrower range of conditions,
constrained by other species, in the lower panels shows competition.
Adaptation types
• Structural adaptations
- Brightly coloured flowers with nectar to attract pollinators
- Specific root growth
- Specific seed dispersal (practical M1)
• Behavioural adaptations
- Phototropism: plants grow towards the sun (Lecture 6)
- Gravitropism: roots grow down into soil.
Ecotypes (also called accessions) are the results of local adaptation through
divergent natural selection of traits that have high fitness in the environmental
conditions specific to a population. E.g. population of sunflowers around the Great
Salt Lake are highly salt tolerant there, but not elsewhere.
Adaptations to specific stresses
• Drought stress can be tolerated by means of:
- an improved water uptake by roots
- a reduce of water loss by stomatal closing, reduction of cuticular
respiration, reduction of LAI
- storing water
Xerophytes are plants capable of living in dry areas. Most have the above
adaptations.
