Can someone identify this plant?

Can someone identify this plant?

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Can someone identify this plant? It was growing under my 2 year old's climbing wall / play house thing. I live in West Virginia, USA and it's currently June 3rd (if that helps from a climate standpoint).

I know there are some potentially dangerous invasive plants like the giant hogweed. I hope someone here can help me identify this and give me any tips on what to do about it if it is in fact hogweed.

As @dd3 stated, it's a spiny (or prickly) sow thistle. It's an annual common in most of the US.

The leaf itself does not have a stem, and if you break the central stalk, it should be hollow and there should be a milky exudate. The plant spreads by fluffy seeds produced from a small dandelion-like flower.

If you pick it while young, it won't hurt (as much); if you prevent it from flowering, it should not spread, although unsprouted seeds can sprout still for a few years (it can come in on the wind as well.)

Prickly Sowthistle

What Do You Call a Scientist Who Studies Plants?

A scientist who studies plants is called a botanist. Also called plant biologists, botanists study diverse plant life ranging from small microorganisms to giant trees. As experts in the field of botany, botanists are well-versed in the identification and classification of plant life, the biochemical functions and processes of plants and the various plant diseases and cures.

The work of botanists include the following:

  • Investigate, discover and classify different plant species and their habitat.
  • Conduct studies, research and experiments on plant growth and their role in the ecosystem.
  • Study the molecular biology and structure of plants.
  • Oversee the care of plants in parks, botanical gardens and protected forests.

Apart from botanical gardens and parks, botanists also work for museums, arboretums, herbariums, zoos and medicinal plant laboratories. Biotechnological firms, pharmaceutical companies and the government may also employ botanists. Academic institutions often hire botanists either as educators or researchers.

To become a botanist, one needs to have a degree in botany or any degrees related to plant science. Aspiring botanists should take up English, mathematics, chemistry, physics and biological sciences. In high school, it will be helpful to take college preparatory classes in biology, mathematics and geography. As with any other degree, graduate and post-graduate studies are required to become a professor in a university.

Phylogenetic System of Plant Classification | Botany

List of six eminent botanists who contributed to the phylogenetic system of plant classification:- 1. Adolf Engler (1844-1930) 2. John Hutchinson (1884-1972) 3. Armen Takhtajan (1911) 4. Arthur Cronquist (1919-1992) 5. Rolf Dahlgren (1932-1987) 6. Robert F. Thorne (1920).

Botanist # 1. Adolf Engler (1844-1930):

The best known and widely accepted phylo­genetic system is that by Adolf Engler, Professor of Botany, University of Berlin. In 1892, he pub­lished a system of classification mainly based on August Wilhelm Eichler in the book ‘Syllabus der Vorlesungen’ as a guide to study the plants avai­lable in the Breslau Botanic Garden.

During 1887-1915, Engler and his associate Karl Prantl made a monographic work, the “Die naturlichen Pflanzenfamilien” in 20 volumes, including all the known genera of plants from algae to the phanerogams along with key to identify the plants.

Engler, in collaboration with Gilg, and later with Diels, published the works in a single volume ‘Syllabus der Pflanzenfamilien’. After his death , the book was revised by followers in several editions and the latest (12th) one in 2 volumes in 1954 and 1964.

The system of Engler has been widely used in the American and Europian continents. Engler divided the plant kingdom into thir­teen (13) Divisions.

The thirteenth (13) Division is the Embryo­phyta Siphonogama (the seed-bearing plants i.e., Spermatophyta). It is divided into two Sub­divisions, Gymnospermae and Angiospermae. The Angiospermae is divided into two Classes — Monocotyledonae and Dicotyledonae. The Class Monocotyledonae is divided directly into 11 Orders.

On the other hand, the Class Dicotyledonae is divided into two Subclasses — Archichlamydeae i.e., lower dicotyledons, and Metachlamydeae or Sympetalae i.e., higher dicotyledons. The Archichlamydeae is further divided into 33 Orders, and Metachlamydeae into 11 Orders. The Orders are divided into Suborders, Families, Genera and finally into Species.

In this system, the Plant Kingdom contains 309 families. The Class Monocotyledonae starts with the family Typhaceae and ends in Orchidaceae, while the class Dicotyledonae starts with the family Casuarinaceae and ends in Compositae.

In this system, Engler considered that in Embryophyta Siphonogama the flower without perianth is the primitive one. Thus, plants like Oak, Willow etc., with woody stem and uni­sexual apetalous flowers (Amentiferae), are treated as primitive Dicotyledons.

The main distinctive features of Engler’s sys­tem that separate it from that of Bentham and Hooker’s system are:

1. The Polypetalae and Monochlamydeae of Bentham and Hooker are amalgama­ted and placed into a single group (Subclasses) Archichlamydeae.

2. The families of the flowering plants are arranged in ascending order with the increasing complexity of the flowers (mainly on floral envelope).

3. Monocotyledons are placed before Dicotyledons.

4. The term Natural order has been replaced by Family.

5. The term Series or Cohort has been replaced by Order.

Merits and Demerits:

1. The entire Plant Kingdom was broadly treated with excellent illustrations, and phylogenetic arrangement of many groups of plants was made.

2. The amalgamation of Polypetalae and Monochlamydeae into Archichlamy­deae is justified.

3. Consideration and placing of Orchidaceae at the end of Monocotyledons and Compositae at the end of Dicoty­ledons are justified — since they are most highly evolved.

4. Juncaceae, Amaryllidaceae and Iridaceae are placed judiciously nearer to Liliaceae.

1. The placement of Amentiferae and Centrospermae almost at the beginning of Dicotyledones, even before Ranales, are not justified.

2. The assemblage of all sympetalous mem­bers under Metachlamydeae increased the distance of closely related orders.

3. The placing of Monocotyledons before Dicotyledons is not appropriate, because it is generally agreed that monocots have arisen from dicoty­ledons by reduction.

4. The placing of the order Helobiae between the advanced orders Pandanales and Glumiflorae is questionable. Araceae was placed much earlier than Liliaceae, from which it has been derived.

5. Fossil evidences gave little support to this system.

Botanist # 2. John Hutchinson (1884-1972):

John Hutchinson was a British botanist asso­ciated with Royal Botanic Gardens, Kew, England. He developed and proposed his system based on Bentham and Hooker and also on Bessey. His phylogenetic system first appeared as “The Families of Flowering Plants” in two volumes.

The first volume contains Dicotyledons (published in 1926) and second volume contains Monocotyledons (published in 1934). He made several revisions in different years. The final revi­sion of “The Families of Flowering Plants” was made just before his death on 2nd September 1972 and the 3rd i.e., the final edition, was pub­lished in 1973.

The following principles were adopted by Hutchinson to classify the flowering plants:

1. Evolution takes place in both upward and downward direction.

2. During evolution all organs do not evolve at the same time.

3. Generally, evolution has been consistent.

4. Trees and shrubs are more primitive than herbs in a group like genus or family.

5. Trees and shrubs are primitive than climbers.

6. Perennials are older than annuals and biennials.

7. Terrestrial angiosperms are primitive than aquatic angiosperms.

8. Dicotyledonous plants are primitive than monocotyledonous plants.

9. Spiral arrangement of vegetative and floral members are primitive than cyclic arrange­ments.

10. Normally, simple leaves are more primitive than compound leaves.

11. Bisexual plants are primitive than unisexual plants and monoecious plants are primitive than dioecious plants.

12. Solitary flowers are primitive than flowers on inflorescence.

13. Types of aestivation gradually evolved from contorted to imbricate to valvate.

14. Polymerous flowers precede oligomerous flowers.

15. Polypetalous flowers are more primitive than gamopetalous flowers.

16. Flowers with petals are more primitive than apetalous flowers.

17. Actinomorphic flowers are more primitive than zygomorphic flowers.

18. Hypogyny is considered as more primitive from which perigyny and epigyny gradually evolved.

19. Apocarpous pistil is more primitive than syncarpous pistil.

20. Polycarpy is more primitive than gynoecium with few carpels.

21. Flowers with many stamens are primitive than flowers with few stamens.

22. Flowers with separate anthers are primitive than flowers with fused anthers and/fila­ments.

23. Endospermic seeds with small embryo is primitive than non-endospermic one with a large embryo.

24. Single fruits are primitive than aggregate fruits.

He divided the Phylum Angiospermae into two Subphyla Dicotyledones and Monocotyledones. The Dicotyledones are further divided into two divisions — Lignosae (arboreal) and Herbaceae (herbaceous).

The Lignosae includes, fundamentally, the woody representatives derived from Magnoliales and Herbaceae includes most of the predominantly herba­ceous families derived from Ranales. The subphylum Monocotyledones are divided into three divisions — Calyciferae, Corolliferae and Glumiflorae.

1. The division Lignosae was further divided into 54 orders beginning with Magnoliales and ending in Verbenales.

2. The division Herbaceae was divided into 28 orders beginning with Ranales and ending in Lamiales.

3. The division Calyciferae was divided into 12 orders beginning with Butamales and ending in Zingiberales.

4. The division Corolliferae was divided into 14 orders beginning with Liliales and ending in Orchidales.

5. The division Glumiflorae was divided into 3 orders beginning with Juncales and ending in Graminales.

So in the latest system of Hutchinson, the Dicotyledones consists of 83 orders and 349 families and Monocotyledones consists of 29 orders and 69 families.

Merits and Demerits Merits:

1. Hutchinson proposed the monophyletic origin of angiosperms from some hypo­thetical Proangiosperms having Bennettitalean characteristics.

2. He made a valuable contribution in phylogenetic classification by his care­ful and critical studies.

3. Monocots have been derived from Dicots.

4. According to him, the definitions of orders and families are mostly precise, particularly in case of subphylum Monocotyledones.

1. There is undue fragmentation of fami­lies.

2. Too much emphasis is laid on habit and habitat. Thus, creation of Lignosae and Herbaceae is thought to be a defect reflecting the Aristotelean view.

3. The origin of angiosperms from Bennettitalean-like ancestor is criticised by many, because the anatomical struc­tures of the early dicotyledons are not tenable with such ancestry.

Botanist # 3. Armen Takhtajan (1911):

Takhtajan was a reputed palaeobotanist of Komarov Botanical Institute of Leningrad, U.S.S.R. (now in Russia). He also made great contributions in the field of angiosperm taxo­nomy. In 1942, he proposed preliminary phylo­genetic arrangement of the orders of higher plants, based on the structural types of gynoecium and placentation.

After 12 years i.e., in 1954, the actual system of classification was published in “The Origin of Angiospermous Plants” in Russian language. It was translated in English in 1958. Later on, in 1964, he proposed a new sys­tem in Russian language. To trace the evolution of angiosperm, he was particularly inspired by Hallier’s attempt to develop a synthetic evolu­tionary classification of flowering plants based on Darwinian philosophy.

The classification was published in ‘Flowering Plants: Origin and Dispersal’ (1969) in English language. Later on, in 1980, a new revision of his system was pub­lished in “Botanical Review”.

Takhtajan (1980) included the angiospermic plants under the Division Magnoliophyta. The Magnoliophyta is divided into two classes Magnoliopsida (Dicotyledons) and Liliopsida (Monocotyledons). The class Magnoliopsida consists of 7 subclasses, 20 superorders, 71 orders and 333 families.

On the other hand, Liliopsida comprises of 3 subclasses, 8 super- orders, 21 orders and 77 families. The class Magnoliopsida starts with the order Magnoliales and ends in Asterales and the class Liliopsida begins with Alismatales and ends in Arales.

The class Magnoliopsida is considered to be monophyletic in origin, probably derived from Bennettitales-like ancestors or stocks ancestral to them. On the other hand, the Liliopsida have been considered to be originated from the stocks ancestral to Nymphaeales. He considered Magnoliopsida more primitive than the Liliopsida. The principles as adopted by Takhtajan (1980) for interpreting the evolutionary lineages in higher plants are mentioned in Table 4.2.

1. The classification of Takhtajan is more phylogenetic than that of earlier sys­tems.

2. This classification is in a general agree­ment with the major contemporary systems of Cronquist, Dahlgren, Thorne, and others. Both phylogenetic and phenetic informations were adopted for delimination of orders and families.

3. Due to the abolition of several artificial groups like Polypetalae, Gamopetalae, Lignosae, Herbaceae, many natural taxa came close together, viz. Lamiaceae (earlier placed under Herbaceae) and Verbenaceae (placed under Lignosae) are brought together under the order Lamiales.

4. Nomenclature adopted in this system is in accordance with the ICBN, even at the level of division.

5. The treatment of Magnoliidae as a primitive group and the placement of Dicotyledons before Monocotyledons are in agreement with the other con­temporary systems.

6. The derivation of monocots from the extinct terrestrial hypothetical group of Magnoliidae is found to be logical.

1. In this system, more weightage is given to cladistic information in comparison to phenetic information.

2. This system provides classification only up to the family level, thus it is not suitable for identification and for adop­tion in Herbaria. In addition, no key has been provided for identification of taxa.

3. Takhtajan recognised angiosperms as division which actually deserve a class rank like that of the systems of Dahlgren (1983) and Throne (2003).

4. Numerous monotypic families have been created in 1997 due to the further splitting and increase in the number of families to 592 (533 in 1987), resulting into a very narrow circumscription.

5. Takhtajan incorrectly suggested that smaller families are more “natural”.

6. Although the families Winteraceae and Canellaceae showed their 99-100% relationship by multigene analyses, Takhtajan placed these two families in two separate orders.

Botanist # 4. Arthur Cronquist (1919-1992):

Arthur Cronquist was the Senior Curator of New York Botanic Garden and Adjunct Professor of Columbia University. He presented an elabo­rate interpretation of his concept of classification in “The Evolution and Classification of Flowering Plants”(1968). The further edition of his classi­fication was published in “An Integrated System of Classification of Flowering Plants” (1981).

The latest revision was published in the 2nd edition in 1988 in “The Evolution and Classification of Flowering Plants”. He discussed a wide range of characteristics important to phylogenetic system. He also provided synoptic keys designed to bring the taxa in an appropriate alignment.

He also represented his classification in charts to show the relationships of the orders within the various subclasses. His system is more or less parallel to Takhtajan’s system, but differs in details.

He considered that the Pteridosperms i.e., the seed ferns as probable ancestors of angiosperm.

The following principles were adopted by Cronquist (1981) to classify the flowering plants:

1. The earliest angiosperms were shrubs rather than trees.

2. The simple leaf is primitive than compound leaf.

3. Reticulate venation is primitive than parallel venation.

4. Paracytic stomata is primitive than the other types.

5. Slender, elongated, long tracheids with numerous scalariform pits are primitive. Further specialisation leads to shorter broad vessels with somewhat thinner walls and transverse end walls with few larger perfo­rations. Later on, the perforation becomes single and large.

6. Long and slender sieve elements with very oblique end walls where the sieve areas scattered along the longitudinal wall with groups of minute pores are primitive. Whereas, the phloem with short sieve tube elements where end walls having a single transverse sieve plate with large openings is a derived condition.

7. The area and activity of cambium and also the length of fusiform initial is more in primitive form which gradually becomes reduced in advanced one.

8. Plants with vascular bundles arranged in a ring are primitive rather than scattered vas­cular bundle as found in monocots.

9. Plants with large and terminal flowers are primitive, those may arrange in monochasia or dichasia and the other type of inflores­cences have been derived from these types.

10. Flowers with many large, free and spirally arranged petals many linear and spirally arranged stamens and free carpels as found in Magnoliaceae are primitive, and other types got evolved through gradual reduc­tion, aggregation, elaboration and differenti­ation of floral members.

11. Plants with unisexual flowers are evolved from bisexual floral ancestors.

12. The large and indefinite number of floral members are primitive than the small and definite numbers.

13. Androecium with many stamens is primitive than the reduced numbers.

14. Linear stamens with embedded pollen sacs as found in some Magnolian genera are considered more primitive than the others.

15. Uniaperturate pollen grains are considered as primitive and the triaperturate type are derived from it.

16. Insect pollinated plants are considered as primitive from which wind pollinated plants got evolved.

17. The gynoecium comprising of many carpels arranged spirally on a more or less elonga­ted receptacle is considered as primitive. Further evolution leads to the reduction of the number of carpels which are arranged in a single whorl and then undergo further fusion.

18. Axial placentation is primitive from which other types have been evolved.

19. Anatropous ovule is primitive from which other types have been evolved.

20. Ovule with two integuments (bitegmic) is primitive and, either by fusion or abortion, unitegmic condition has been evolved.

21. Embryo-sac with 8-nuclei (Polygonum-type) is primitive from which embryo-sac with 4- nuclei (Oenothera-type) has been derived through reduction.

22. Monocotyledons have been developed from dicotyledons through abortion of one cotyledon.

23. The follicle (fruit) is considered as primitive. Further, dry and dehiscent fruit is more primitive than fleshy and indehiscent fruit.

According to him “many of the evolutionary trends bear little apparent relation to survival value and that there are some reversals”.

In 1981, he divided the Division Magnoliophyta (Angiosperms) into two classes Magnoliatae (Dicotyledons) and Liliatae (Monocotyledons). He divided Magnoliatae into 6 subclasses and 55 orders, of which magnoliales is the primitive and Asterales is the advanced taxa.

On the other hand, the class Liliatae has been divided into 4 subclasses and 18 orders, of which Alismatales is the primitive and Orchidales is the advanced taxa. The class Magnoliatae consists of 291 families and Liliatae with 61 families.

Merits and Demerits:

1. There is general agreement of Cronquist’s system with that of other contemporary systems like Takhtajan, Dahlgren and Thorne.

2. Detailed information on anatomy, ultra- structure phytochemistry and chromo­some — besides morphology — was presented in the revision of the classi­fication in 1981 and 1988.

3. The system is highly phylogenetic.

4. Nomenclature is in accordance with the ICBN.

5. The family Asteraceae in Dicotyledons and Orchidaceae in Monocotyledons are generally regarded as advanced and are rightly placed towards the end of respective groups.

6. The relationships of different groups have been described with diagrams which provide valuable information on relative advancement and size of the various subclasses.

7. The family Winteraceae (vessel-less wood present similar to Pteridosperms) placed at the beginning of dicotyledons is favoured by many authors.

8. The subclass Magnoliidae is considered as the most primitive group of Dicotyledons. The placement of Dicotyledons before Monocotyledons finds general agreements with modern authors.

9. As the text is in English, the system has been readily adopted in different books.

1. Though highly phylogenetic and popu­lar in U.S.A., this system is not very use­ful for identification and adoption in Herbaria since Indented keys for genera are not provided.

2. Dahlgren (1983, 89) and Thorne (1980, 83) treated angiosperms in the rank of a class and not that of a division.

3. Superorder as a rank above order has not been recognised here, though it is present in other contemporary classifi­cations like Takhtajan, Thorne and Dahlgren.

4. The subclass Asteridae represents a loose assemblage of several diverse sympetalous families.

5. Ehrendorfer (1983) pointed out that the subclass Hamamelidae does not represent an ancient side branch of the subclass Magnoliidae, but is remnant of a transition from Magnoliidae to Dilleniidae, Rosidae, and Asteridae.

6. There is a difference in opinion with other authors regarding the systematic position of some orders like Typhales, Arales, Urticales etc.

Botanist # 5. Rolf Dahlgren (1932-1987):

Rolf Dahlgren, working at the Botanical Museum in the University of Copenhagen, Denmark, published a new method in Danish in 1974 to illustrate an angiosperm system in a text book of angiosperm taxonomy. Later on in 1975 he published “A System of Classification of Angiosperms to be Used to Demonstrate the Distribution of Characteristics” in Botanische Notiser in English.

The revised and improved version of his system gradually appeared in the subsequent years:

i. In 1980 in “Botanical Journal of the Linnean Society”.

ii. In 1981, in “Phytochemistry and angio­sperm Phytogeny” (Edited by Young and Siegier).

iii. In 1983, in “Nordiac Journal of Botany”.

In his system he included the information at different levels as much as possible. In his classi­fication he extensively used the chemical cha­racteristics. He considered the following mor­phological and chemical characteristics in his classification.

1. Morphological characteristics:

i. Chloripetalae and Sympetalae.

ii. Apocarpous, syncarpous and monocarpellate condition.

iii. Types of microsporogenesis.

iv. Bi- and trinucleate pollen grain.

v. Tenuinucellate, pseudocrassinucellate and crassinucellate.

vi. Bi- or unitegmic ovules etc.

2. Chemical characteristics:

i. Benzylisoquinoline alkaloids.

ii. Pyrrolisidine alkaloids.

v. Ellagic acid and ellagitannins

vi. Various groups of flavonoids etc.

He did not consider angiosperms to be originated polyphyletically from different gymno­sperms, but believed that the combination of different characteristics like 8-nucleate embryo sac, secondary endosperm etc. would hardly have evolved independently from different groups of gymnosperms.

According to Dahlgren (1980), the class Magnoliopsida (Angiosperms) has been divided into two subclasses, Magnoliidae and Liliidae. The Magnoliidae includes 24 Superorders, those start with Magnoliiflorae and end in Lamiflorae 80 orders, those start with Annonales and end in Lamiales and 346 families.

On the other hand, the subclass Liliidae includes 7 Superorders, those start with Alismatiflorae and end in Areciflorae 26 orders, those start with Hydrocharitales and end in Pandanales and 92 families.

Merits and Demerits:

1. Detailed information on morphology, phytochemistry and embryology was presented in the classification of Dahlgren.

2. This system is highly phylogenetic where angiosperms are ranked as a class like other recent systems.

3. The arrangement of taxa in the form of a bubble diagram gives an idea about the relationship of superorders, orders and even families.

4. The use of superorders and the suffixanae are in accordance with the other modern systems like those of Takhtajan, Thorne, etc.

1. This system provides classification of angiosperms only up to the family level, thus it is not suitable for identification and for adaptation in Herbaria.

2. Dahlgren classified angiosperms into dicots and monocots, which shows inconformity with the recent classifica­tion of APG II (2003) and Throne (2003).

3. Dahlgren placed monocots in-between dicots, while in modern classification monocots are placed in-between primi­tive angiosperms and the eudicots.

4. Although the families Winteraceae and Canellaceae showed their 99-100% relationship by multigene analysis, yet Dahlgren placed these two families in two separate orders.

Botanist # 6. Robert F. Thorne (1920- ):

Robert F. Thorne, an American taxonomist, associated with the Rancho Santa Ana Botanic Garden, California, U.S.A., initially published the principles of his classification in 1958 and 1963. Later, in 1968, he published “Synopsis of a putatively phylogenetic classification of the flow­ering plants” in Aliso. The subsequent revisions were published in 1974, 1976, 1981, 1983, 1992 and 2000. The electronic version of his classification was published in 1999 which was finally revised in 2003.

Thorne gave much emphasis on phytochemical approach. In addition to the above, many other different aspects were also considered by him.

6. Host-parasite relationship.

He believed that the Angiospermae are monophyletic.

In 1983, he divided the Class Angiospermae (Annonopsida) into two subclasses Dicotyledoneae (Annonidae) and Monocotyledoneae (Liliidae). The Dicotyledoneae is further divided into 19 superorder’s which start with Annoniflorae and ends in Asteriflorae 41 orders, which start with Annonales and ends in Asterales and 297 families.

On the other hand, Monocotyledoneae is further divided into 9 superorders, which start with Liliiflorae and end in Commeliniflorae 12 orders, which start with Liliales and ends in Zingiberales.

Thus, he preferred the name Annonopsida for angiosperms, Annonidae for dicots, replacing Magnoliflorae by Annoniflorae and Magnoliales by Annonales. He, however, abandoned these nomenclatures and adopted the conventional names Magnoliopsida, Magnoliidae and Magnoliales since 1992.

Robert F. Thorne (1992) revised his classi­fication (“Classification and Geography of Flowering Plants”) and published it in Botanical Review. He followed the arrangements of different taxa in descending order such as subclasses (-idae), superorders (-anae), orders (-ales), sub­orders (-inae), families (-aceae), subfamilies (-oideae), and tribes (-ineae). He treated the flow­ering plants as Class with an initial bifurcation into two Subclasses, Magnoliidae (Dicots) and Liliidae (Monocots).

The subclass Magnoliidae has been divided into 19 superorders, 52 orders and the subclass Liliidae has been divided into 9 super- orders, 24 orders. The Magnoliidae starts with the order Magnoliales and ends in Lamiales, whereas the Liliidae starts with Triuridales and ends in Restionales.

1. Detailed information on molecular systematics and chemotaxonomy was presen­ted in the classification of Throne.

2. This system is highly phylogenetic where angiosperms are ranked as a class like those of other recent systems.

3. The traditional groups, dicots and mono­cots have been abolished and angio­sperms are divided into 10 subclasses which are in conformity with the recent phylogenetic thinking.

4. Several closely related taxa are placed nearer to one another, viz. the orders Malvales, Urticales, Rhamnales and Euphorbiales have been included under the superorder Malviflorae.

1. This system has no practical utility for identification and for adoption in Herbaria, because identification keys for genera are not provided.

2. The systematic position of the five genera — namely Emblingia, Guametela, Haptanthus, Heteranthia and Pteleocarpa — ha not been mentioned.

3. The placement of Asteridae before Lamiidae is not justified.

4. Segregation of Grewiaceae from Tiliaceae is highly questionable, as in the recent APG classification all the members of Tiliaceae, Bombacaceae and Sterculiaceae are placed under Malvaceae.


Symbiosis spans a wide variety of possible relationships between organisms, differing in their permanence and their effects on the two parties. If one of the partners in an association is much larger than the other, it is generally known as the host. [1] In parasitism, the parasite benefits at the host's expense. [2] In commensalism, the two live together without harming each other, [3] while in mutualism, both parties benefit. [4]

Most parasites are only parasitic for part of their life cycle. By comparing parasites with their closest free-living relatives, parasitism has been shown to have evolved on at least 233 separate occasions. Some organisms live in close association with a host and only become parasitic when environmental conditions deteriorate. [5]

A parasite may have a long-term relationship with its host, as is the case with all endoparasites. The guest seeks out the host and obtains food or another service from it, but does not usually kill it. [6] In contrast, a parasitoid spends a large part of its life within or on a single host, ultimately causing the host's death, with some of the strategies involved verging on predation. Generally, the host is kept alive until the parasitoid is fully grown and ready to pass on to its next life stage. [7] A guest's relationship with its host may be intermittent or temporary, perhaps associated with multiple hosts, making the relationship equivalent to the herbivory of a wild-living animal. Another possibility is that the host–guest relationship may have no permanent physical contact, as in the brood parasitism of the cuckoo. [6]

Parasites follow a wide variety of evolutionary strategies, placing their hosts in an equally wide range of relationships. [2] Parasitism implies host–parasite coevolution, including the maintenance of gene polymorphisms in the host, where there is a trade-off between the advantage of resistance to a parasite and a cost such as disease caused by the gene. [8]

Types of hosts Edit

  • Definitive or primary host - an organism in which the parasite reaches the adult stage and reproduces sexually, if possible. This is the final host.
  • Secondary or intermediate host - an organism that harbors the sexually immature parasite and is required by the parasite to undergo development and complete its life cycle. It often acts as a vector of the parasite to reach its definitive host. For example, Dirofilaria immitis, the heartworm of dogs, uses the mosquito as its intermediate host until it matures into the infective L3 larval stage.

It is not always easy or even possible to identify which host is definitive and which secondary. As the life cycles of many parasites are not well understood, sometimes the subjectively more important organism is arbitrarily labelled as definitive, and this designation may continue even after it is found to be incorrect. For example, sludge worms are sometimes considered "intermediate hosts" for salmonid whirling disease, even though the myxosporean parasite reproduces sexually inside them. [9] In trichinosis, a disease caused by roundworms, the host has reproductive adults in its digestive tract and immature juveniles in its muscles, and is therefore both an intermediate and a definitive host. [10]

  • Paratenic host - an organism that harbors the sexually immature parasite but is not necessary for the parasite's development cycle to progress. Paratenic hosts serve as "dumps" for non-mature stages of a parasite in which they can accumulate in high numbers. The trematode Alaria americana may serve as an example: the so-called mesocercarial stages of this parasite reside in tadpoles, which are rarely eaten by the definitive canine host. The tadpoles are more frequently preyed on by snakes, in which the mesocercariae may not undergo further development. However, the parasites may accumulate in the snake paratenic host and infect the definitive host once the snake is consumed by a canid. [11] The nematode Skrjabingylus nasicola is another example, with slugs as the intermediate hosts, shrews and rodents as the paratenic hosts, and mustelids as the definitive hosts. [12]
  • Dead-end , incidental , or accidental host - an organism that generally does not allow transmission to the definitive host, thereby preventing the parasite from completing its development. For example, humans and horses are dead-end hosts for West Nile virus, whose life cycle is normally between culicinemosquitoes and birds. [13] People and horses can become infected, but the level of virus in their blood does not become high enough to pass on the infection to mosquitoes that bite them. [13] - an organism that harbors a pathogen but suffers no ill effects. However, it serves as a source of infection to other species that are susceptible, with important implications for disease control. A single reservoir host may be reinfected several times. [14]

Plant hosts of micropredators Edit

Micropredation is an evolutionarily stable strategy within parasitism, in which a small predator lives parasitically on a much larger host plant, eating parts of it. [2]

The range of plants on which a herbivorous insect feeds is known as its host range. This can be wide or narrow, but it never includes all plants. A small number of insects are monophagous, feeding on a single plant. The silkworm larva is one of these, with mulberry leaves being the only food consumed. More often, an insect with a limited host range is oligophagous, being restricted to a few closely related species, usually in the same plant family. [15] The diamondback moth is an example of this, feeding exclusively on brassicas, [16] and the larva of the potato tuber moth feeds on potatoes, tomatoes and tobacco, all members of the same plant family, Solanaceae. [17] Herbivorous insects with a wide range of hosts in various different plant families are known as polyphagous. One example is the buff ermine moth whose larvae feed on alder, mint, plantain, oak, rhubarb, currant, blackberry, dock, ragwort, nettle and honeysuckle. [18]

Plants often produce toxic or unpalatable secondary metabolites to deter herbivores from feeding on them. Monophagous insects have developed specific adaptations to overcome those in their specialist hosts, giving them an advantage over polyphagous species. However, this puts them at greater risk of extinction if their chosen hosts suffer setbacks. Monophagous species are able to feed on the tender young foliage with high concentrations of damaging chemicals on which polyphagous species cannot feed, having to make do with older leaves. There is a trade off between offspring quality and quantity the specialist maximises the chances of its young thriving by paying great attention to the choice of host, while the generalist produces larger numbers of eggs in sub-optimal conditions. [19]

Some insect micropredators migrate regularly from one host to another. The hawthorn-carrot aphid overwinters on its primary host, a hawthorn tree, and migrates during the summer to its secondary host, a plant in the carrot family. [20]

Host range Edit

The host range is the set of hosts that a parasite can use as a partner. In the case of human parasites, the host range influences the epidemiology of the parasitism or disease. For instance, the production of antigenic shifts in Influenza A virus can result from pigs being infected with the virus from several different hosts (such as human and bird). This co-infection provides an opportunity for mixing of the viral genes between existing strains, thereby producing a new viral strain. An influenza vaccine produced against an existing viral strain might not be effective against this new strain, which then requires a new influenza vaccine to be prepared for the protection of the human population. [21]

Mutualistic hosts Edit

Some hosts participate in fully mutualistic interactions with both organisms being completely dependent on the other. For example, termites are hosts to the protozoa that live in their gut and which digest cellulose, [22] and the human gut flora is essential for efficient digestion. [23] Many corals and other marine invertebrates house zooxanthellae, single-celled algae, in their tissues. The host provides a protected environment in a well-lit position for the algae, while benefiting itself from the nutrients produced by photosynthesis which supplement its diet. [24] Lamellibrachia luymesi, a deep sea giant tubeworm, has an obligate mutualistic association with internal, sulfide-oxidizing, bacterial symbionts. The tubeworm extracts the chemicals that the bacteria need from the sediment, and the bacteria supply the tubeworm, which has no mouth, with nutrients. [25] Some hermit crabs place pieces of sponge on the shell in which they are living. These grow over and eventually dissolve away the mollusc shell the crab may not ever need to replace its abode again and is well-camouflaged by the overgrowth of sponge. [26]

An important hosting relationship is mycorrhiza, a symbiotic association between a fungus and the roots of a vascular host plant. The fungus receives carbohydrates, the products of photosynthesis, while the plant receives phosphates and nitrogenous compounds acquired by the fungus from the soil. Over 95% of plant families have been shown to have mycorrhizal associations. [27] Another such relationship is between leguminous plants and certain nitrogen-fixing bacteria called rhizobia that form nodules on the roots of the plant. The host supplies the bacteria with the energy needed for nitrogen fixation and the bacteria provide much of the nitrogen needed by the host. Such crops as beans, peas, chickpeas and alfalfa are able to fix nitrogen in this way, [28] and mixing clover with grasses increases the yield of pastures. [29]

Neurotransmitter tyramine produced by commensal Providencia bacteria, which colonize the gut of the nematode Caenorhabditis elegans, bypasses the requirement for its host to biosynthesise tyramine. This product is then probably converted to octopamine by the host enzyme tyramine β-hydroxylase and manipulates a host sensory decision. [30]

Hosts in cleaning symbiosis Edit

Hosts of many species are involved in cleaning symbiosis, both in the sea and on land, making use of smaller animals to clean them of parasites. Cleaners include fish, shrimps and birds hosts or clients include a much wider range of fish, marine reptiles including turtles and iguanas, octopus, whales, and terrestrial mammals. [4] The host appears to benefit from the interaction, but biologists have disputed whether this is a truly mutualistic relationship or something closer to parasitism by the cleaner. [31] [32]

Commensal hosts Edit

Remoras (also called suckerfish) can swim freely but have evolved suckers that enable them to adhere to smooth surfaces, gaining a free ride (phoresis), and they spend most of their lives clinging to a host animal such as a whale, turtle or shark. [3] However, the relationship may be mutualistic, as remoras, though not generally considered to be cleaner fish, often consume parasitic copepods: for example, these are found in the stomach contents of 70% of the common remora. [33] Many molluscs, barnacles and polychaete worms attach themselves to the carapace of the Atlantic horseshoe crab for some this is a convenient arrangement, but for others it is an obligate form of commensalism and they live nowhere else. [22]

The first host to be noticed in ancient times was human: human parasites such as hookworm are recorded from ancient Egypt from 3000 BC onwards, while in ancient Greece, the Hippocratic Corpus describes human bladder worm. [34] The medieval Persian physician Avicenna recorded human and animal parasites including roundworms, threadworms, the Guinea worm and tapeworms. [34] In Early Modern times, Francesco Redi recorded animal parasites, while the microscopist Antonie van Leeuwenhoek observed and illustrated the protozoan Giardia lamblia from "his own loose stools". [34]

Hosts to mutualistic symbionts were recognised more recently, when in 1877 Albert Bernhard Frank described the mutualistic relationship between a fungus and an alga in lichens. [35]

Comparison Chart

Feature Fungi Plants
Major cell wall component Chitin (N-acetylglucosamine) Cellulose (glucose)
Has chlorophyll for photosynthesis? No Yes
Digests food before uptake? Yes No
Has roots, stems and leaves? No, has filaments Yes
Can make their own food? No, heterotrophic Yes, autotrophic
Types of gametes Spores Seeds and pollen
Trophic level Decomposers Producers
Food storage form Glycogen Starch

One difference between plants and fungi is in the main substance that makes up their cell walls. The image above shows how N-acetylglucosamine polymerizes into chitin (in fungi cell walls) and how glucose polymerizes into cellulose (in plant cell walls).

Dandelion and cat’s ear

For our plant comparison we are going to look at dandelion (which most people know) and cat’s ear (a similar looking plant). Beginning with this image of a lush dandelion (Taraxacum officinale), we can see lots of flower heads and a number of new heads forming, along with some closed heads which bloomed recently. The dandelion could almost be an evergreen plant as it seems to grow year-round — at least whenever the temperature stays above freezing. Let’s go through the dandelion’s life cycle and then check out the cat’s ear similarities and differences.

The dandelion’s flower head begins developing low in the center of the rosette of leaves.

Gradually, the stem supporting the new flower head elongates until it rises well above the basal rosette.

The dandelion’s hollow stem exudes a milky white substance (a type of latex) when broken. After the flower head has blossomed, it closes in on itself . . .

. . . converts those fertilized ovaries to seeds with wings . . .

. . . and re-opens to create the familiar seed head which, once again, rises high above the basal rosette of leaves.

Note the fleshy stem supporting the seed head. Here’s a closer view of that head with its symmetrical arrangement of the winged seeds.

After all the seeds have dispersed, what remains is the head’s receptacle. It, too, has a lovely pattern.

Here is a final view of a dandelion plant. You can see that most of its flowers have converted to seeds and/or have sent the new seeds on their way — to the irritation of people who want perfect lawns — and to the delight of herbalists and wild food foragers.

Cat’s ear (Hypochoeris radicata) looks, on first glance, very much like the dandelion — especially when you see an area full of the plants.

Let’s look more closely at this plant. Here is its flower head . . .

. . . which, in isolation, looks like a dandelion flower head. However, note its more wiry stem in the photo above and the next photo.

You can see a developing flower head in the background of the above photo. This flower head looks similar to — and yet, different from — the dandelion flower head. The difference is subtle.

As we stand back and look at the entire cat’s ear plant, we can see its flower heads rise on stems above the basal rosette of leaves.

Although frequently a single flower head grows on a single stem (like the dandelion), it is just as likely the cat’s ear flower heads will appear on a branched stem. In contrast, the dandelion’s single flower head will only appear by itself on an unbranched stem. Along with the branched stems, this next photo shows the wiriness of the stems and the different looking unopened flower heads.

After the flower heads have bloomed and become seeds, the heads re-open and spread their winged seeds — just like the dandelion.

Here’s a view of the basal rosette of a cat’s ear plant.

And this is where we can finally see some distinguishing characteristics between dandelion and cat’s ear. The cat’s ear leaves are quite hairy while the dandelion leaves are smooth. When you look closely at the shape of the leaves — by placing them side by side — you can see the dandelion is definitely sharply toothed, with its teeth pointing back toward the center of the plant.

Those softly hairy leaves probably account for the common name given to cat’s ear.

  1. Isolation and Identification of Desired DNA/Genes
  2. Cloning and Production of Identical Copies of Isolated DNA Segment
  3. Introduction of Cloned DNA into Plant Cells and its Integration with Plant DNA
  4. Expression of Introduced Genes in the Plants

Genetic Engineering: Step # 1. Isolation and Identification of Desired DNA/Gene:

Two types of DNA can be isolated:

(ii) Complementary DNA (cDNA).

Total DNA isolated from the cells is called genomic DNA. It is isolated by breaking the walls of the cells by physical or biochemical methods. Finally the DNA is separated by ultracentrifugation.

(ii) Complementary DNA (cDNA):

In this case first the mRNA is isolated and then DNA is synthesized on mRNA template by the process of reverse transcription. The base sequence of this DNA is complementary to mRNA base sequence. Hence, it is known as complementary or cDNA.

Genetic Engineering: Step # 2. Cloning and Production of Identical Copies of Isolated DNA Segment:

Fragment of DNA (genes) from any source can be multiplied or amplified more than million fold. This is known as gene cloning. It may be genomic DNA cloning or cDNA cloning. In this technique, DNA to be cloned is first inserted into a plasmid (cloning). Plasmids are small circular DNA found in bacterial cells apart from genomic DNA.

Plasmids can replicate independently. During gene cloning the plasmids are first isolated from bacterial cells. They are purified. They are then cut open with restriction endonuclease. The DNA to be cloned is then joined to plasmid DNA by another enzyme known as DNA ligase. The hybrid or chimeric or recombinant plasmid is thus produced. This plasmid is then reintroduced into bacterial cells.

The transformed bacterial cells are then grown on culture medium. As the bacteria divide, the plasmids containing foreign DNA also divide and thus large number of copies of recombinant DNA is produced.

This is referred to as gene cloning and it is one step of genetic engineering. After cloning various genes of a particular species can be stored to form gene/DNA libraries.

Genetic Engineering: Step # 3. Introduction of Cloned DNA into Plant Cell and its Integration with Plant DNA:

Transfer of cloned DNA into plants can be done by use of another vector called gene transfer vector. It is different from cloning vector because cloning vector is used for gene cloning but gene transfer vector is used for gene transfer.

In dicotyledonous plants, the soil borne pathogen, bacterium, Agrobacterium tumefaciens is used as gene transfer vector. The bacterium causes crown gall disease in many species of dicotyledonous plants. The bacterium enters the plants through wound and after infection a callus or tumour is formed near the wounded area at the juncture of root and stem.

This bacterium contains, apart from its genomic DNA, a large plasmid called Ti plasmid (Tumour inducing plasmid). The plasmid contains tumour inducing genes. When the bacterium infects plant cells, a part of the Ti Plasmid with recombinant DN A gets incorporated into DN A of the plant cell. Thus, the foreign DNA becomes part of plant DNA and is called transfer or T DNA (Fig. 24.14).

The desirable donor gene/DNA after cloning is first incorporated into Ti Plasmid of Agrobacterium. This DNA is called transfer DNA, or T DNA or recombinant DNA. The bacterium is then introduced into the plant at cut end. Bacteria enter the plant tissue and a part of its plasmid having T DNA gets integrated into plant DNA.

The cells of callus thus contain foreign DNA from donor species. These cells are known as transformed or transgenic cells. Through tissue culture technique plants can be generated from the callus containing transgenic cells (Fig. 24.15). These plants will now contain additional DNA from donor species. These plants are called transformed plants or genetically modified (GM) plants or transgenic plants.

Various Uses of 'Plant-Based'

However, over the several decades that plant-based has been in use, it has come to mean different things to different people. Some use it synonymously with the adjectival form of vegan, others think it is closer to vegetarian (insofar as something plant-based may contain animal products, such as dairy or eggs, although no flesh), while others still employ the word in a self-explanatory fashion, reasoning that any food or product which is largely based on plants deserves this label.

Our earliest records of plant-based, beginning in the mid-1970s, seem to indicate that it was often intended to have a meaning close to vegan, as plant-based diets were seen as distinct from those that contained dairy or eggs.

His book is the usual attack on meat-eating, but a new argument is added: the ecological and economic necessities for giving up breeding, slaughtering and eating animals, and for turning to an exclusively plant-based diet.
Medical History (London, Eng.), 1 Jul. 1976

“Plant-based diets supplemented with milk or with milk and eggs tend to be nutritionally similar to diets vmntaining (sic) meats.
Call and Post (Cleveland, OH), 4 Nov. 1978

The best advice for preventing osteoporosis would probably stress a shift toward a plant-based diet (sound advice from many points of view), rather than the increased intake of dairy foods emphasized by Mrs. Brody.
— Michelle Marder Kamhi (letter to Ed.), The New York Times, 22 Oct. 1980

In subsequent decades plant-based has come to be employed in a looser fashion by many people. In many instances it can be difficult to say why speakers choose to distinguish between vegan and plant-based possible reasons include a perceived animus toward vegans, or the desire to be semantically precise.

Rather than use the term “vegan” and “vegetarian,” EarthSave promotes “plant-based diets.” Instead of promoting a distinct and sharp dividing line between meat-eaters and vegetarians, EarthSave advocates prefer the idea that all people are eating more or less plant-based diets.
— Donna J. Maurer, The Vegetarian Movement in North America (PhD diss.), 1997

Still, the Gippsland speed demon insists he's no vegan pin-up. "I like to say I'm more a plant-based diet rather than vegan I do play a sport that uses leather and that type of thing," he said.
— Eliza Sewell Melbourne, The Advertiser (Adelaide, Aus.), 26 Dec. 2013

In spite of the fact that we are still figuring out what exactly plant-based means, the word is moving steadily in the direction of being entered in our dictionary. After all, we have repeatedly demonstrated that we are able to use and understand words which have a number of closely-related-yet-distinct meanings.

"The response in Atlanta continues to underscore the growing consumer demand for high-quality, delicious plant-based meats," said Ethan Brown, Beyond Meat CEO and founder, in the release. "Together with KFC's team, we have created a plant-based chicken that looks, tastes and pulls apart like a chicken breast.”
— Kelly Tyko, USA Today (online), 29 Jan. 2020

One of the more common uses of plant-based is to describe a type of meat. This is a word which may be defined as “animal tissue considered especially as food,” “the edible part of a nut, fruit, or egg,” or simply “solid food as distinguished from drink.” Plant-based may end up having a single meaning, or it may end up like meat, and contain multitudes.

Words We're Watching talks about words we are increasingly seeing in use but that have not yet met our criteria for entry.

The Two Parts of Photosynthesis

Photosynthesis takes place in two stages: the light-dependent reactions and the Calvin cycle. In the light-dependent reactions, which take place at the thylakoid membrane, chlorophyll absorbs energy from sunlight and then converts it into chemical energy with the use of water. The light-dependent reactions release oxygen from the hydrolysis of water as a byproduct. In the Calvin cycle, which takes place in the stroma, the chemical energy derived from the light-dependent reactions drives both the capture of carbon in carbon dioxide molecules and the subsequent assembly of sugar molecules. The two reactions use carrier molecules to transport the energy from one to the other. The carriers that move energy from the light-dependent reactions to the Calvin cycle reactions can be thought of as “full” because they bring energy. After the energy is released, the “empty” energy carriers return to the light-dependent reactions to obtain more energy.

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