Inquilines: The Tiny Architects of Plant Galls

Inquilines, small organisms that live inside galls, have a big impact on the structure and chemistry of these plant growths. Galls are abnormal growths on plants, often caused by insects or mites. They can change the plant's anatomy and even its cell walls. Inquilines feed on gall tissues, altering their structure and chemistry. For instance, in globoid leaf galls caused by Neolithus fasciatus on Sapium glandulosum, inquilines keep most of the primary and secondary metabolites in the gall cells. This means they maintain the basic and complex chemicals that the cells need to function. However, they also change the cell walls' structure, making them stronger. This could be due to the physical pressure from the number of inquilines inside the gall. The cell walls have more non-methylesterified homogalacturonans, which are types of pectin that help reinforce the cell walls. This structural change is quite fascinating. It shows how inquilines can manipulate the plant's growth to their advantage. Inquilines also affect the distribution of hemicelluloses, another type of cell wall component. These are found mainly in the inner cortex of galls with inquilines, which might be due to their feeding habits. The presence of certain epitopes, or markers, in the vascular bundles of these galls is another interesting point. These markers, like (1 → 4)-β-D-galactans and (1 → 5)-α-L-arabinans, along with extensins, indicate that the cell walls are flexible and adhesive. This is crucial for supporting the high flow of metabolites, or chemicals, that result from the remobilization of reserves. The impact of inquilines on leaf galls of S. glandulosum is significant. They stimulate the gall tissues, changing their histological patterns and the composition of non-cellulosic compounds in the cell walls. This is a clear example of how small organisms can have a big impact on their environment. It also shows the complexity of plant-insect interactions and how they can shape the natural world.