Feeding and Other Gall Facets: Patterns and Determinants in Gall Structure

Galls are neoformed structures induced by specific animals, fungi, bacteria, virus or some parasitic plants on their host plant organs. Developmental processes are well known in Agrobacterium tumefasciens galls, but the animal-induced galls have a striking anatomical diversity, concerning several patterns, which were reunited herein. Anatomical traits observed in animal-induced galls involve manipulation of plant morphogenesis in convergent ways. Nematode, mite and insect galls usually contain homogeneous storage parenchyma and develop due to hyperplasia and cell hypertrophy. The development of typical nutritive tissues, giant cells, or hypertrophied vascular bundles may occur. Some other anatomical features may be usually restricted to galls induced by specific taxa, but they may eventually be related to the developmental potentialities of the host plants. The combination of distinct morphogenetic peculiarities in each gall system culminates in extant gall structural diversity. Convergent anatomical traits are observed according to the feeding mode of the gall inducers, representing potentiation or inhibition of similar events of host plant morphogenesis and cell redifferentiation, independent of gall-inducing taxa.