Editing Gall (section)

== Physiology ==

Insects induce the formation of galls on plants from which they receive various services, such as a source of nutrition and a place to lay eggs, develop, and be provided protection from the environment and enemies. The gall producers are specific to specific plants, thus inducing galls with unique appearances (such as balls, knobs, lumps, and warts) and a range of colors (red, green, yellow, and black). Different taxonomic groups of gall inducers vary in the complexity and diversity of gall formation and organization, with insect induced galls generally being more complex and diverse.<ref name="Gatjens-Boniche 1359–1382">{{Cite journal |last=Gatjens-Boniche |first=Omar |date=2019-12-01 |title=The mechanism of plant gall induction by insects: revealing clues, facts, and consequences in a cross-kingdom complex interaction |url=https://revistas.ucr.ac.cr/index.php/rbt/article/view/33984 |journal=Revista de Biología Tropical  |volume=67 |issue=6 |pages=1359–1382 |doi=10.15517/rbt.v67i6.33984 |doi-access=free}}</ref> Additionally, gall frequency varies based on factors such as weather, plant susceptibility, and pest populations.

=== Gall formation ===

There are four stages of gall development: initiation, growth and differentiation, maturation, and dehiscence. Gall tissues are nutritive and present high concentrations of lipids, proteins, nitrogen, and other nutrients.

The formation of galls, called induction, begins with insect saliva. Insect saliva contains various chemicals that induce shock and osmotic changes in the host plant cell.<ref name="Raman 2011"/> The severity of injury to the plant from the feeding activities of the insect varies depending on the insect. The [[Osmosis|osmotic]] changes that occur as a result are characterized by increased quantities of osmotically active material, leading to cell [[metaplasia]] and formation of a gall.

Gall growth occurs gradually over time, with the length, breadth, and height of galls increasing proportionally. The growth rate is greatest during the insect's early developmental stages and slows as it approaches adulthood. [[Plant hormone]]s like [[auxin]]s play a crucial role in gall growth. The presence of stress and insect secretions stimulates the synthesis of growth-promoting substances, possibly involving a combination thereof, such as auxins and [[kinin]]s. Gall growth involves both cell enlargement and division, but the specific factors triggering cell enlargement remain unclear.<ref name="Stone 2003"/><ref name="Larson 1991"/>

The earliest impact from the insect leads to metaplasia in the affected cells, during which they undergo changes in structure and function. However, when the chemical shock is of high intensity, metaplasia does not occur. Instead, the plant cells surrounding the shock site die, thereby rejecting the insect and defending the plant tissue. Enzymes like [[invertase]]s are involved in gall growth, with greater activity correlating with stronger gall development. Gall-inducing insect performance is influenced by plant vigor and module size, with larger, fast-growing plant modules resulting in larger galls. Conversely, galls are easily induced on smaller plant modules.<ref name="Barnes 1993"/><ref name="Raman 2011"/><ref name="Williams 1994"/><ref name=":7"/>