User:Frazie25/sandbox

Introduction
Define heteroblasty and then discuss

Introduction
Define heteroblasty and summery/overview of affect on a plant.

Article Topic and Outline
I have chosen heteroblasty as my article for this project. This is my proposed Outline and additions:

Outline
5. Biogeography
 * 1) Why do plant behave this way?
 * 2) Evolution of Heteroblasty
 * 3) Many hypothesize that heteroblasty is a result of natural selection for species that can best survive in both low and high light environments. As a plant grows in the forest it experiences predictable changes in light intensity. With this in mind a plant that changes its leaf morphology and phyllotaxy to best suit these changes in light intensity could be more competitive than one that has only on leaf form and phyllotaxy. It is also hypothesized that the development of heteroblastic tress preceded the development of divaricating shrub forms which are now very common in New Zealand. It is though that these shrubs are a mutation from the heteroblastic trees and have lost the ability to develop into the adult stage and so are very similar to heteroblastic trees in their juvenile form. It has also been observed that heteroblastic species do not stem from a single point of origin they are found in many different and unrelated species, because of this it is believed that large scale convergence evolution had to have occurred for so many unrelated plants to exhibit similar behavior.
 * 4) Ecolology
 * 5) Heteroblasty can affect all parts of the plant but the leaves are the most common examples and by far the most studied. It's been hypothesized that the heteroblastic changes are due to changes in the plants exposure to sun because many species spend their juvenile years in the understory then grow to maturity were they are apart of the top canopy and so have full exposure to sun. This has not been well studied because the common heteroblastic plants are woody and take so long to grow such as Eucalyptus grandis. The juvenile plants tend to face more competition and must make special adaptations to succeed that are then unnecessary as a mature plant. For example a sampling in a dense forest must grow quickly to succeed at first but once it has established itself most woody plants no longer compete severely with their neighbor and so the adaptations needed as a juvenile plant are no longer necessary. This can lead to a change in growth in maturity as the tree faces new environmental factors. Such as a need to resist new pathogens or parasites.
 * 6) How do they make the switch
 * 7) Internal and external signals
 * 8) Hormones are known to regulate heteroblastic change in plants. One hormone that has been identified is Gibberellin. In a study it was used to spontaneously revert the mature form of an ivy to its juvenile form. After being sprayed with gibberellin acid some of the ivy began to produce aerial roots which is a characteristic of the juvenile form as well as three lobed leaves another characteristic. It is also hypothesized that Auxin and Cytokinin when working together can cause the sudden change in phyllotaxy of heterogenetic plants. The gene ABPH1 has been found to code for cytokinin and when changed in a mutant affected the plants ability to regulate the phyllotaxy of the stem. The hypothosis is based mostly on studies done on nonheteroblastic plants and so it is not certain that these are the cause of the sudden changes in a heteroblastic plant. Dramatic change in leaf size is another example of heteroblastic change in plants and researchers have looked to studies done on non heteroblastic plants for answers about what hormones and genes could regulate these changes. AINTEGUMENTA has been found to be one of these regulatory genes that regulated cell growth. It is believed that many genes are involved in the regulation of leaf size and these genes do not closely interact meaning they are not caused by a master regulator but instead are a part of many different pathways.
 * 9) Genetics
 * 10) The most common model plants are Arabidopsis thaliana, Antirrhinum majus, common name: snapdragon, and Zea mays, common name: corn. None of these are helpful in the study of gene expression in heteroblastic plants because none of them express obvious heteroblastic traits. They can us Arabidopsis to some degree for study as it does undergo change form the juvenile phase to the mature phase but it is not clearly heteroblasty. If we assume the process of change is similar and uses similar regulations we can use Arabidopsis to analyze the causes of the change in the more dramatic heteroblast and so can only be used to analyze heteroblastic changes if we assume the regulation is similarThere for scientists must find other plants to use as model subjects. The problem with this is that most plants that display heteroblastic growth are woody plants. Their life spans are much longer in general and unlike Arabidopsis very little of their genomes are known or mapped. A species that shows promise is Eucalyptus grandis. This tree is grown commonly because of its many uses for teas, oils, and wood. The tree over all is fast growing and widely grown due to its many uses and so is one of the best candiates for genome sequencing, which is being done now so that the tree can be better studied in the future. There is already a complete quantitative trait loci map for the juvenile traits.
 * 11) Examples of plants and how many
 * 12) Lightwood (Acacia implexa) is a fast wood tree found in Australia
 * 13) Spiral Ginger (Costus pulverulentus C.Presl) is an herb found in south america found primarily in Nicaragua and is used as a traditional medicine in teas for pain and inflamation. It is also used to treat cancer.
 * 14) Lance Wood (Pseudopanax crassifolius) is a native of New Zealand
 * 15) pōkākā (Elaeocarpus hookerianus) native to New Zealand
 * 16) Bucket-of-Water tree, of Maple Leaf (Carpodetus serratus) native to New Zealand
 * 17) Concepts related to but not to be confused with Heteroblasty
 * 18) Heteroblasty can be a confusing topic by nature because it is qualitative and is often confused with other like processes.
 * 19) Homoblasty is the first example of this. To understand Heteroblasty you must first understand that homoblasty is different. Homoblastic change is the slight change a plant experiences over a long period of time as it grows to maturity. Examples of this are a plants leaves growing slightly larger over time as it matures or a trees trunk growing in girth.
 * 20) Heterophylly is another term that is often used interchangeably with Heteroblasty. The process of heterophylly refers to specifically changes in leaf morphology that lead to variation in leaf shape or size on a single plant. This type of change is seen when you study the individual leaves and compare them, this is different than homoblasty in which the entire foliage changes dramatically but for the most part uniformly. A heteroblastic plant can have heterophyllic changes but they are not the same.
 * 21) Phenotypic Plasticity changes the structure of plants as well but should not be confused with Heteroblasty. Phenotypic Plasticity is when an individual can use the same genes to create a different phenotype based on environmental signals. Such as when a plant is adapting its immune system to a new pathogen or when a reptile changes it’s sex based on environmental queues. The difference here is that Heteroblasty is not entirely dependent on the environment, though it can be affected by it, and happens throughout the plants maturity instead of at random points because of an environmental change.
 * 1) Phenotypic Plasticity changes the structure of plants as well but should not be confused with Heteroblasty. Phenotypic Plasticity is when an individual can use the same genes to create a different phenotype based on environmental signals. Such as when a plant is adapting its immune system to a new pathogen or when a reptile changes it’s sex based on environmental queues. The difference here is that Heteroblasty is not entirely dependent on the environment, though it can be affected by it, and happens throughout the plants maturity instead of at random points because of an environmental change.

1. New Zealand has a very large population of heteroblastic plants with about 200 tree species and 10% of the woody shrubs species having heteroblastic tendencies.

2. Australia also has heteroblastic species though the exact amount is not known.

3. South America also has a few heteroblastic plants, specifically known in Mexico, and Nicaragua.

6. Why there is so little study

Article
Heteroblasty is a significant and abrupt change in form and function of a plant that occurs between a plants early stage of maturity, called the juvenile stage, and the adult stage so that the adult stage is distinctly different form the juvenile stage. This change is genetically predetermined and not a result of environmental stimuli or mutations. This change is different from a homoblastic change which is a gradual change or little change at all so that there is little differnce between the juvenile and adult stages. Some characteristics affected by heteroblastic change include internode length and stem structure as well as leaf form, size and arrangement. Heteroblasty is found in many different Families as well as different species with in a genus, this random spread of heteroblastic plants across species is beleived to be caused by convergence evolution. Heteroblasty should not be confused with seasonal heterophylly, where early and late growth in a growing season are markedly different.

The term heteroblasty, as well as the term homoblasty, were coined by German botanist Karl Ritter von Goebel. Leonard Cockayne observed that heteroblasty occurred in an unusually high proportion of tree species native to New Zealand.

Evolution
Many hypothesize that heteroblasty is a result of natural selection for species that can best survive in both low and high light environments. As a plant grows in the forest it experiences predictable changes in light intensity. With this in mind a plant that changes its leaf morphology and phyllotaxy to best suit these changes in light intensity could be more competitive than one that has only on leaf form and phyllotaxy. It is also hypothesized that the development of heteroblastic tress preceded the development of divaricating shrub forms which are now very common in New Zealand. It is though that these shrubs are a mutation from the heteroblastic trees and have lost the ability to develop into the adult stage and so are very similar to heteroblastic trees in their juvenile form. It has also been observed that heteroblastic species do not stem from a single point of origin they are found in many different and unrelated species, because of this it is believed that large scale convergence evolution had to have occurred for so many unrelated plants to exhibit similar behavior.

Ecology
Heteroblasty can affect all parts of the plant but the leaves are the most common examples and by far the most studied. It's been hypothesized that the heteroblastic changes are due to changes in the plant's exposure to sun because many species spend their juvenile years in the understory then grow to maturity where they are apart of the top canopy and so have full exposure to the sun. This has not been well studied because the common heteroblastic plants are woody and take so long to grow such as Eucalyptus grandis. The juvenile plants tend to face more competition and must make special adaptations to succeed that are then unnecessary as a mature plant. For example, a sampling in a dense forest must grow quickly to succeed at first but once it has established itself most woody plants no longer compete severely with their neighbor and so the adaptations needed as a juvenile plant are no longer necessary. This can lead to a change in growth in maturity as the tree faces new environmental factors. Such as a need to resist new pathogens or parasites.

Internal and External Signals
Hormones are known to regulate heteroblastic change in plants. One hormone that has been identified is Gibberellin. In a study it was used to spontaneously revert the mature form of an ivy to its juvenile form. After being sprayed with gibberellin acid some of the ivy began to produce aerial roots which is a characteristic of the juvenile form as well as three lobed leaves another characteristic. It is also hypothesized that Auxin and Cytokinin when working together can cause the sudden change in phyllotaxy of heterogenetic plants. The gene ABPH1 has been found to code for cytokinin and when changed in a mutant affected the plants ability to regulate the phyllotaxy of the stem. The hypothosis is based mostly on studies done on nonheteroblastic plants and so it is not certain that these are the cause of the sudden changes in a heteroblastic plant. Dramatic change in leaf size is another example of heteroblastic change in plants and researchers have looked to studies done on non heteroblastic plants for answers about what hormones and genes could regulate these changes. AINTEGUMENTA has been found to be one of these regulatory genes that regulated cell growth. It is believed that many genes are involved in the regulation of leaf size and these genes do not closely interact meaning they are not caused by a master regulator but instead are a part of many different pathways.

Genetics
The most common model plants are Arabidopsis thaliana, Antirrhinum majus, common name: snapdragon, and Zea mays, common name: corn. None of these are helpful in the study of gene expression in heteroblastic plants because none of them express obvious heteroblastic traits. They can us Arabidopsis to some degree for study as it does undergo change form the juvenile phase to the mature phase but it is not clearly heteroblasty. If we assume the process of change is similar and uses similar regulations we can use Arabidopsis to analyze the causes of the change in the more dramatic heteroblast and so can only be used to analyze heteroblastic changes if we assume the regulation is similarThere for scientists must find other plants to use as model subjects. The problem with this is that most plants that display heteroblastic growth are woody plants. Their life spans are much longer in general and unlike Arabidopsis very little of their genomes are known or mapped. A species that shows promise is Eucalyptus grandis. This tree is grown commonly because of its many uses for teas, oils, and wood. The tree over all is fast growing and widely grown due to its many uses and so is one of the best candiates for genome sequencing, which is being done now so that the tree can be better studied in the future. There is already a complete quantitative trait loci map for the juvenile traits.

Examples of Heteroblastic Plants

 * 1) Lightwood (Acacia implexa) is a fast wood tree found in Australia
 * 2) Spiral Ginger (Costus pulverulentus C.Presl) is an herb found in south america found primarily in Nicaragua and is used as a traditional medicine in teas for pain and inflamation. It is also used to treat cancer.
 * 3) Lance Wood (Pseudopanax crassifolius) is a native of New Zealand
 * 4) Pōkākā (Elaeocarpus hookerianus) native to New Zealand
 * 5) Bucket-of-Water tree, of Maple Leaf (Carpodetus serratus) native to New Zealand

Concepts Confused With Heteroblasty

 * 1) Heteroblasty can be a confusing topic by nature because it is qualitative and is often confused with other like processes.
 * 2) Homoblasty is the first example of this. To understand Heteroblasty you must first understand that homoblasty is different. Homoblastic change is the slight change a plant experiences over a long period of time as it grows to maturity. Examples of this are a plants leaves growing slightly larger over time as it matures or a trees trunk growing in girth.
 * 3) Heterophylly is another term that is often used interchangeably with Heteroblasty. The process of heterophylly refers to specifically changes in leaf morphology that lead to variation in leaf shape or size on a single plant. This type of change is seen when you study the individual leaves and compare them, this is different than homoblasty in which the entire foliage changes dramatically but for the most part uniformly. A heteroblastic plant can have heterophyllic changes but they are not the same.
 * 4) Phenotypic Plasticity changes the structure of plants as well but should not be confused with Heteroblasty. Phenotypic Plasticity is when an individual can use the same genes to create a different phenotype based on environmental signals. Such as when a plant is adapting its immune system to a new pathogen or when a reptile changes it’s sex based on environmental queues. The difference here is that Heteroblasty is not entirely dependent on the environment, though it can be affected by it, and happens throughout the plants maturity instead of at random points because of an environmental change.