Malcolm Rivera
Plants have evolved defence mechanisms against insect herbivory over the course of 350 million years of co-evolution. These defences can be broadly classified into two categories: constitutive defences, which are permanent and present before an attack, and induced defences, which are temporary and activated only when an attack occurs. Constitutive defences include mechanical barriers such as skin and gut walls in animals, while induced defences are activated by environmental stimuli, such as herbivory, and involve the production of toxins and other defensive proteins. Induced defences allow plants to be phenotypically plastic, reducing the chance that insects adapt to their defences. However, they can be costly for plants, reducing their growth and reproductive capacity.
| Characteristics | Values |
|---|---|
| Definition | Constitutive defenses are traits always expressed within a plant. Induced defenses are activated in response to an environmental stimulus, such as herbivory or infection. |
| Timing | Constitutive defenses are present before an attack or infection. Induced defenses are activated only when attacks or infections occur. |
| Examples | Constitutive defenses include mechanical barriers, preformed antimicrobials, and plant toxins. Induced defenses include reactive oxygen species, cytokines, antibodies, antimicrobial peptides, and the hypersensitive response. |
| Costs | Constitutive defenses incur costs even in the absence of disease or enemies. Induced defenses may result in ecological costs due to disruption of symbiotic relationships and reduced fitness. |
| Trade-offs | Constitutive defenses may have trade-offs between different chemical compounds within a plant species. Induced defenses involve a trade-off between resistance and fitness, with resources diverted from growth to defense. |
Explore related products
What You'll Learn
- Constitutive defences are always present, while induced defences are activated in response to stimuli
- Constitutive defences include mechanical barriers, while induced defences include antibodies
- Constitutive defences are permanent, while induced defences are temporary
- Induced defences may reduce the chance insects adapt to plant defences
- Constitutive defences are costly in the absence of disease, while induced defences are costly when used
Constitutive defences are always present, while induced defences are activated in response to stimuli
Plants have evolved defence mechanisms to protect themselves from insect herbivory. These defences can be broadly classified into constitutive defences and induced defences. Constitutive defences are always present in plants, acting as a permanent barrier against herbivores. They include physical barriers such as thorns and chemical barriers such as toxins. For example, N. tabacum plants with a higher constitutive level of nicotine are less susceptible to insect herbivory. However, these plants flower significantly later than plants with lower levels of nicotine.
On the other hand, induced defences are activated in response to stimuli, such as an herbivore attack. They are temporary defences that are rapidly activated when needed. Induced defences can be physical, chemical, or indirect. For instance, plants may produce longer thorns or increase symbiotic ants as a defence mechanism. The activation of induced defences involves changes in gene expression, with genes involved in defence being up-regulated and genes involved in other processes being down-regulated. This allows plants to allocate more resources towards producing proteins that are directly involved in the resistance response.
The presence of constitutive defences before an attack can be beneficial as it provides immediate protection. However, it also incurs costs even in the absence of herbivores, as plants invest resources into defence rather than growth and reproduction. In contrast, induced defences allow plants to avoid these costs when enemies are absent, but there is a delay in mounting the defence response, during which plants may suffer damage. The delay occurs because plants need to sense the nature of the injury and identify the stimulus before activating the appropriate defence mechanism.
The trade-off between constitutive and induced defences has implications for the epidemiology of diseases affecting plants. Constitutive defences may prevent full-blown infection, while induced defences act after infection. High virulence in parasites, for instance, selects for higher induced defences, even if they result in high disease mortality. The defence mechanism employed impacts the spread and prevalence of infectious diseases, influencing the selection for specific defences.
In summary, constitutive defences are always present, providing an immediate but costly protection, while induced defences are activated in response to stimuli, offering a flexible but delayed response. The balance between these defence mechanisms is critical for optimising plant fitness and influencing the epidemiology of diseases.
Constitution and Constitutionalism: Shared Roots and Values
You may want to see also
Constitutive defences include mechanical barriers, while induced defences include antibodies
The defence mechanisms of plants and animals can be classified into constitutive defences and induced defences. Constitutive defences are those traits that are always expressed within a plant or animal, whereas induced defences are activated rapidly in response to an environmental stimulus, such as an infection or herbivory.
Constitutive defences include mechanical barriers, such as the skin and gut walls in animals, and preformed antimicrobials in vertebrates. In plants, constitutive defences are present before an herbivore attack and include chemical defences such as nicotine in tobacco plants, and physical defences such as thorns. Constitutive defences may also include plant toxins that generally act constitutively.
Induced defences, on the other hand, are activated once infection or herbivory has occurred. In vertebrates, induced defences include mechanisms such as reactive oxygen species, cytokines, and antibodies, which are elicited upon infection. Inducible defences allow plants to be phenotypically plastic, which may confer an advantage over constitutive defences as it reduces the chance that attacking insects adapt to the plant's defences. Induced defences in plants include the hypersensitive response, which involves changes in gene expression, with genes directly involved in defences being up-regulated in response to an attack.
The two routes to defence have different implications for individuals and the epidemiology of diseases. Constitutive defences are likely to incur costs even in the absence of disease, while induced defences may suffer considerable damage during the time required to mount a defence response upon infestation. Therefore, a balance between constitutive and induced defences is necessary to optimise defence and diversification.
The Constitution: Still Relevant or Relic?
You may want to see also
Constitutive defences are permanent, while induced defences are temporary
Plants have evolved many defence mechanisms against insect herbivory over the course of the 350 million years in which they have co-evolved. These defences can be broadly classified into two categories: constitutive defences and induced defences. Constitutive defences are permanent and always expressed within a plant, whereas induced defences are temporary and activated in response to an environmental stimulus, such as herbivory or infection.
Constitutive defences are present before an attack occurs and include mechanical barriers, such as the skin and gut walls in animals, and chemical barriers, such as preformed antimicrobials in vertebrates and plant toxins. They are always expressed within a plant, and their traits are always present. For example, N. tabacum plants with a higher constitutive level of nicotine are less susceptible to insect herbivory. However, N. tabacum plants that produce a continually high level of nicotine flower significantly later than plants with lower levels of nicotine.
Induced defences, on the other hand, are activated rapidly in response to an attack or infection. They are typified by mechanisms such as reactive oxygen species, cytokines, and antibodies in vertebrates, antimicrobial peptides in invertebrates, and the hypersensitive response in plants. Induced defences allow plants to be phenotypically plastic, which may confer an advantage over constitutive defences. For example, induced defences cause variations in the defence constituents of a plant, making it a more unpredictable environment for insect herbivores.
The two types of defences have different implications for individual health and the epidemiology of diseases. Constitutive defences may incur costs even in the absence of disease, while induced defences may incur substantial costs when activated in response to infection. Additionally, deficiencies in defence capabilities can result in plant damage, so a balance between growth and defence must be achieved to optimise plant fitness.
In summary, constitutive defences are permanent and always present in a plant, while induced defences are temporary and activated in response to a specific stimulus. Both types of defences play important roles in the plant's ability to defend itself against herbivory or infection, and they work together to optimise the plant's fitness and survival.
Federalizing the National Guard: Constitutional Quandary
You may want to see also
Explore related products
Induced defences may reduce the chance insects adapt to plant defences
Plants have evolved defence mechanisms against insect herbivory over the course of 350 million years of co-evolution. These defences can be broadly classified into two categories: constitutive (permanent) and induced (temporary) defences. Constitutive defences are those traits always expressed within a plant, such as mechanical barriers, preformed antimicrobials, and plant toxins. Induced defences, on the other hand, are activated rapidly in response to environmental stimuli, such as herbivory or infection.
Induced defences may reduce the chance that insects adapt to plant defences. This is because inducible defences allow plants to be phenotypically plastic, creating an unpredictable environment for insect herbivores. When induced, plants may produce proteins and enzymes that are directly involved in plant defence, such as proteinase inhibitors. Additionally, induced defences can cause variations in the defence constituents of a plant. For example, in cultivated tobacco, photosynthetic genes are down-regulated, while genes directly involved in defences are up-regulated in response to insect attack. This allows more resources to be allocated to producing proteins that aid in the resistance response.
The activation of induced defences typically involves plants sensing the nature of an injury, such as wounding from an herbivore attack, through cues such as touch and the detection of salivary enzymes. The induction of defences can result in trade-offs between resistance and fitness, with potential ecological costs due to the disruption of symbiotic relationships with the environment. For example, the use of jasmonic acid to induce defences in tomato plants resulted in plants with fewer but larger fruits, longer ripening times, and reduced ability to attract seed dispersers.
While induced defences offer advantages in terms of adaptability and plasticity, they also come with costs. Plants may suffer damage during the time required to mount an induced defence response upon infestation. Additionally, the implementation of induced defences can impose a substantial demand for resources, potentially reducing growth and decreasing overall energy reserves. Therefore, plants must achieve a balance between growth and defence to optimise their fitness.
In summary, induced defences in plants may reduce the chance of insect adaptation by introducing variability and unpredictability in defence constituents. However, induced defences also come with costs in terms of resource allocation, growth, and ecological impacts, highlighting the importance of a balanced approach to optimise plant fitness.
Founding Principles: The Constitution's Four Pillars
You may want to see also
Constitutive defences are costly in the absence of disease, while induced defences are costly when used
The defence mechanisms of plants against herbivory can be classified into constitutive defences and induced defences. Constitutive defences are those traits that are always expressed within a plant, such as mechanical barriers, preformed antimicrobials, and plant toxins. They are present before an attack occurs and are permanent. On the other hand, induced defences are activated rapidly in response to an environmental stimulus, such as herbivory or infection. They are temporary and typified by mechanisms such as reactive oxygen species, cytokines, and antibodies.
Constitutive defences are costly in the absence of disease or herbivory. This is because the plant must allocate resources towards defence instead of growth and reproduction. For example, N. tabacum plants with a higher constitutive level of nicotine are less susceptible to insect herbivory, but they flower significantly later than plants with lower levels of nicotine. The production of constitutive defences may also reduce the overall pool of energy reserves available to the plant.
Induced defences, on the other hand, allow plants to avoid the costs of implementing defences when there is no threat. This is because induced defences are only activated upon an attack or infection. However, plants may suffer considerable damage during the time required to mount this defence response. The activation of induced defences can also result in a reduced growth rate, delayed reproduction, and a decrease in the overall energy reserves of the plant.
The costs of constitutive and induced defences have important implications for the epidemiology of diseases and the evolution of defence mechanisms. The trade-off between the two types of defences has been cited as a factor contributing to the diversity of defence strategies observed in nature. Additionally, the ability of induced defences to vary the defence constituents of a plant may confer an advantage over constitutive defences by making the plant a more unpredictable environment for herbivores or pathogens.
UK Constitution: Does It Exist?
You may want to see also
Frequently asked questions
Constitutive defenses are those traits that are always expressed within a plant or animal, acting as a permanent defense mechanism. They are present before an attack or infection occurs.
Induced defenses are activated rapidly in response to an environmental stimulus, such as an attack or infection. They are temporary defense mechanisms that are only activated when needed.
Induced defenses can include physical changes, such as longer thorns on plants, or indirect defenses, such as rewards for symbiotic ants. In animals, induced defenses can include the production of antibodies to fight an infection.
