Editing Gall (section)

== Anatomy ==

=== Shape and size ===

Galls develop on various plant organs, providing nutrition and shelter to inducing insects.  Galls display vast variation in [[Morphology (biology)|morphology]], size, and wall composition. The size of insect galls can range significantly, from approximately two inches in diameter to less than one-sixteenth of an inch. Some galls are so small that they are merely slightly thickened patches on leaves.<ref name="IPWD">{{cite web |title=TPWD: Plant Galls -- Young Naturalist |url=https://tpwd.texas.gov/publications/nonpwdpubs/young_naturalist/plants/plant_galls/ |access-date=2024-05-09 |website=tpwd.texas.gov}}</ref> Their shape can range from spherical to bursiform, bullet-shaped, flower-shaped, cylindrical, or diamond-like. Factors influencing gall morphology include plant species, tissue type, gall-inducing agent, and environmental conditions.<ref name="Krikorian 1988">{{Cite journal |last=Krikorian |first=A. D. |date=June 1988 |title=''Plant Galls and Gall Inducers''. Jean Meyer , S. Cheskin |url=http://dx.doi.org/10.1086/415876 |journal=The Quarterly Review of Biology |volume=63 |issue=2 |pages=225–226 |doi=10.1086/415876 |issn=0033-5770|url-access=subscription }}</ref><ref name="Barnes 1993">{{Cite journal |last=Barnes |first=Jeffrey K. |date=1993-01-01 |title=Biology of Insect-Induced Galls |url=http://dx.doi.org/10.1093/aesa/86.1.122 |journal=Annals of the Entomological Society of America |volume=86 |issue=1 |pages=122–123 |doi=10.1093/aesa/86.1.122|url-access=subscription }}</ref><ref>{{Cite journal |last1=Crespi |first1=Bernard |last2=Worobey |first2=Michael |date=December 1998 |title=Comparative Analysis of Gall Morphology in Australian Gall Thrips: The Evolution of Extended Phenotypes |url=http://dx.doi.org/10.1111/j.1558-5646.1998.tb02248.x |journal=Evolution |volume=52 |issue=6 |pages=1686–1696 |doi=10.1111/j.1558-5646.1998.tb02248.x |pmid=28565317}}</ref><ref>{{Cite journal |last1=Heard |first1=Stephen B. |last2=Buchanan |first2=Corinne K. |date=October 1998 |title=Larval Performance and Association Within and Between Two Species of Hackberry Nipple Gall Insects, Pachypsylla spp. (Homoptera: Psyllidae) |url=http://dx.doi.org/10.1674/0003-0031(1998)140[0351:lpaawa]2.0.co;2 |journal=The American Midland Naturalist |volume=140 |issue=2 |pages=351–357 |doi=10.1674/0003-0031(1998)140[0351:lpaawa]2.0.co;2|url-access=subscription }}</ref><ref>{{Cite journal |last1=Florentine |first1=S. K. |last2=Raman |first2=A. |last3=Dhileepan |first3=K. |date=October 2005 |title=Effects of Gall Induction by Epiblema Strenuana on Gas Exchange, Nutrients, and Energetics in Parthenium Hysterophorus |url=http://dx.doi.org/10.1007/s10526-004-5525-3 |journal=Biocontrol |volume=50 |issue=5 |pages=787–801 |doi=10.1007/s10526-004-5525-3 |hdl=1959.17/64564}}</ref> They typically exhibit symmetrical forms, although their end shapes vary due to differences in the physical actions and chemical stimuli of different insects. Around 90% of galls occur on the leaves of [[Dicotyledon|dicotyledons]].<ref name="Raman 2011">{{Cite journal |last=Raman |first=Anantanarayanan |date=2011-06-01 |title=Morphogenesis of insect-induced plant galls: facts and questions |url=https://www.sciencedirect.com/science/article/pii/S036725301100003X |journal=Flora - Morphology, Distribution, Functional Ecology of Plants |volume=206 |issue=6 |pages=517–533 |doi=10.1016/j.flora.2010.08.004|url-access=subscription }}</ref> Galls can develop on various parts of the host plant, such as roots, leaf bases, branches, or leaflets. Internally, galls also exhibit diverse structures. Some are simple, comprising only outgrown and curved leaf tissues, while others feature complex, hierarchical arrangements with multiple chambers containing different types of tissues, including [[Ground tissue|collenchyma]], [[Ground tissue|parenchyma]], physalides-parenchyma, and a nutritive cellular layer.<ref>{{Cite journal |last1=Arduin |first1=M. |last2=Kraus |first2=J.E. |date=1995-06-25 |title=Anatomia e Ontogenia de Galhas Foliares de Piptadenia gonoacantha (Fabales, Mimosaceae) |journal=Boletim de Botânica |volume=14 |pages=109 |doi=10.11606/issn.2316-9052.v14i0p109-130 |doi-access=free }}</ref><ref>{{Cite journal |last1=Kraus |first1=Jane E. |last2=Arduin |first2=Marcos |last3=Venturelli |first3=Margarida |date=December 2002 |title=Anatomy and ontogenesis of hymenopteran leaf galls of Struthanthus vulgaris Mart. (Loranthaceae) |url=http://dx.doi.org/10.1590/s0100-84042002012000009 |journal=Revista Brasileira de Botânica |volume=25 |issue=4 |pages=449–458 |doi=10.1590/s0100-84042002012000009}}</ref><ref>{{Citation |last1=Maresquelle |first1=H. J. |title=Physiologie et morphogenèse des galles d'origine animale (zoocécidies) |date=1965 |work=Differenzierung und Entwicklung / Differentiation and Development |pages=1927–1976 |url=http://dx.doi.org/10.1007/978-3-642-50088-6_49 |access-date=2024-05-08 |place=Berlin, Heidelberg |publisher=Springer Berlin Heidelberg |isbn=978-3-642-50090-9 |last2=Meyer |first2=J. |doi=10.1007/978-3-642-50088-6_49 |url-access=subscription }}</ref>

=== Structure ===

In a general [[gall wasp]] gall, the outermost layer is the epidermis followed by outer cortex and then inner cortex. In some galls these two cortex layers are separated by a lignified layer. The innermost part of a gall is the larval chamber. The nutritive layer is situated between the larval chamber and the inner cortex. There is a nutritional gradient (high to low) from inside to outside of the gall while defense gradient to the opposite direction.<ref name="Schultz 2022">{{Cite journal |last1=Schultz |first1=Jack C. |last2=Stone |first2=Graham N. |date=June 2022 |title=A tale of two tissues: Probing gene expression in a complex insect-induced gall |journal=Molecular Ecology |language=en |volume=31 |issue=11 |pages=3031–3034 |doi=10.1111/mec.16482 |pmc=9321127 |pmid=35466464}}</ref><ref name="Williams 1994">{{Cite book |editor-last=Williams |editor-first=Michele A. J. |url=https://academic.oup.com/book/53725 |title=Plant Galls: Organisms, Interactions, Populations |date=1994-10-06 |publisher=Oxford University PressOxford |isbn=978-0-19-857769-0 |doi=10.1093/oso/9780198577690.001.0001}}</ref>

=== Morphogenesis ===

Gall [[morphogenesis]] involves the regulation of the organ on which the gall occurs while maintaining differentiation freedom. Gall development begins from a single or group of metaplasied cells and progresses through promoter-mediated cell expansion, cell multiplication, programmed differentiation, and control of symmetry.<ref name="Raman 2011" />

Plant response involves the establishment of metaplasied cells and localized metabolic changes to repair the wound and neutralize stress. [[Osmosis|Osmotic]] stress leads to the development of metaplasied cells, characterized by increased quantities of osmotically active material. The rejection response by the plant triggers the synthesis of defense compounds and [[enzyme]]s.<ref>{{Citation |last=Carmen |first=Cogălniceanu Gina |title=Electrical Control of Plant Morphogenesis |work=Plant Tissue Culture Engineering |pages=397–415 |url=http://dx.doi.org/10.1007/1-4020-3694-9_21 |access-date=2024-05-09 |place=Berlin/Heidelberg |publisher=Springer-Verlag |doi=10.1007/1-4020-3694-9_21 |doi-broken-date=1 November 2024 |isbn=1-4020-3594-2|url-access=subscription }}</ref><ref>{{cite book |last=Sinnott |first=Edmund W. |url=http://dx.doi.org/10.5962/bhl.title.4649 |title=Plant morphogenesis |date=1960 |publisher=McGraw-Hill |location=New York|doi=10.5962/bhl.title.4649 }}</ref>

=== Differentiation ===

* Development of novel cell types: Galls exhibit unique cell types such as abnormally thick-walled dead cells (e.g., xylary elements and sclereids) and thin-walled living cells. These cells differentiate in specific patterns, contributing to the structure of the gall.<ref name="Gasson 2000">{{cite journal |last=Gasson |first=P |date=September 2000 |title=Fink S. 1999.Pathological and regenerative plant anatomy. Encyclopedia of plant anatomy XIV. 1095 pp. Berlin, Stuttgart: Gebrüder Borntraeger. |url=http://dx.doi.org/10.1006/anbo.2000.1242 |journal=Annals of Botany |volume=86 |issue=3 |pages=707–708 |doi=10.1006/anbo.2000.1242 }}</ref><ref>{{cite book |last1=Maresquelle |first1=H. J. |title=Physiologie et morphogenèse des galles d'origine animale (zoocécidies) |date=1965 |work=Differenzierung und Entwicklung / Differentiation and Development |pages=1927–1976 |url=http://dx.doi.org/10.1007/978-3-642-50088-6_49 |access-date=2024-05-09 |place=Berlin, Heidelberg |publisher=Springer Berlin Heidelberg |isbn=978-3-642-50090-9 |last2=Meyer |first2=J.|doi=10.1007/978-3-642-50088-6_49 }}</ref><ref name=":Rohfritsch 1982">{{cite journal |last1=Rohfritsch |first1=O. |title=Insect Galls |date=1982 |journal=Molecular Biology of Plant Tumors |pages=131–152 |url=http://dx.doi.org/10.1016/b978-0-12-394380-4.50011-6 |access-date=2024-05-09 |publisher=Elsevier |isbn=978-0-12-394380-4 |last2=Shorthouse |first2=J.D.|doi=10.1016/b978-0-12-394380-4.50011-6 |url-access=subscription }}</ref>
* Nutritive tissue: Most galls contain specialized nutritive tissue that provides nutrition to the inducing arthropod and sometimes to their progeny. The structure of this tissue varies depending on the insect species inducing the gall and their feeding behaviors. Nutritive tissue differentiation is influenced by the length and nature of the insect's mouthparts.<ref>{{cite journal |last1=Bronner |first1=R. |last2=Westphal |first2=E. |last3=Dreger |first3=F. |date=February 1989 |title=Chitosan, a component of the compatible interaction between Solanum dulcamara L. and the gall mite Eriophyes cladophthirus Nal |url=http://dx.doi.org/10.1016/0885-5765(89)90020-9 |journal=Physiological and Molecular Plant Pathology |volume=34 |issue=2 |pages=117–130 |doi=10.1016/0885-5765(89)90020-9|url-access=subscription }}</ref>
* Characteristics of nutritive cells: Nutritive cells exhibit dynamic features such as enriched cytoplasm, fragmented vacuoles, hypertrophied nucleus and nucleolus, and abundant cell [[organelle]]s. They contain elevated levels of carbohydrates, lipids, soluble sugars, and proteins, along with intense phosphatase activity.<ref name="Gasson 2000"/>
* Changes in nutritive tissue: The activity of the nutritive tissue is maintained as long as the inhabiting larva continues to feed. However, when feeding ceases, the dynamic profile of the tissue gradually diminishes, and it is eventually replaced by inactive parenchyma. Removal or death of the [[larva]] leads to rapid changes in the distribution of carbohydrates and lipids within the tissue.<ref>{{cite journal |last=Schwartz |first=W. |date=1966 |title=M. S. Mani, Ecology of Plant Galls (Monogr. Biol. Vol. XII). 434 u. XII S., 164 Abb., 9 Taf. The Hague 1964: Dr. W. Junk Publishers. 40.-hfl |url=http://dx.doi.org/10.1002/jobm.3630060116 |journal=Zeitschrift für allgemeine Mikrobiologie |volume=6 |issue=1 |pages=91 |doi=10.1002/jobm.3630060116 |doi-broken-date=2 December 2024|url-access=subscription }}</ref>
* Accumulation of [[Phenolic acid|phenolic]] substances: Cells lining the larval chamber in mature-old galls accumulate phenolic substances, indicating changes in gall tissue composition over time.<ref>{{cite journal |last=Jensen |first=P. Boysen |date=January 1948 |title=Formation of Galls by Mikiola fagi |url=http://dx.doi.org/10.1111/j.1399-3054.1948.tb07113.x |journal=Physiologia Plantarum |volume=1 |issue=1 |pages=95–108 |doi=10.1111/j.1399-3054.1948.tb07113.x |issn=0031-9317|url-access=subscription }}</ref>
* Mineral content: Gall tissues contain elevated levels of various minerals, which may play a role in gall development and function.<ref name=":7">{{cite encyclopedia |last=Mapes |first=Carol C. |title=Gall Formation |date=2005 |encyclopedia=Encyclopedia of Entomology |pages=942–944 |url=https://doi.org/10.1007/0-306-48380-7_1732 |access-date=2024-05-09 |place=Dordrecht |publisher=Springer Netherlands |doi=10.1007/0-306-48380-7_1732 |isbn=978-0-306-48380-6|url-access=subscription }}</ref><ref name="Barnes 1993" />

=== Types ===

There are two primary categories of galls: closed and open.<ref name="IPWD" /> Insects such as wasps, moths, and flies, possessing chewing mouthparts during their adult or larval stages, typically inhabit completely enclosed galls. Upon reaching maturity, the adult exits either by chewing its way out or utilizing an opening created by the larval stage. Conversely, insects with sucking mouthparts rely on partially open galls or those that naturally open to facilitate emergence. An example of the latter type is the aphid, which forms marble-sized galls on the leaf stems of cottonwood trees. While these galls have thin walls, they harbor entire colonies of aphids within. When the time is right, a slit appears on one side of the gall, allowing the aphids to escape as the slit's lips unfold.<ref name="Krikorian 1988" /><ref name=":Rohfritsch 1982"/>