Alterações no perfil anatômico, histoquímico e citológico de galhas foliares de Aceria litchii (Keifer) (Eriophyidae) em Litchi chinensis Sonn. (Sapindaceae)

Abstract

Litchi chinensis Sonn. is a plant native to China that is affected by galls induced by Aceria litchii (Keifer), which feed on the young leaves, leading to the emergence of trichomes, named erineae, which protect the eggs and nymphae. They also lead to the folding and bulging of the leaf, and more severe infestations greatly compromise sales. We hypothesized that the erinosis is indeed a complex gall and, as such, traced the anatomical, histochemical, and cytometric profiles of non-galled L. chinensis leaves and A. litchii leaf galls to map the cecidogenetic field and its effect on host plant fitness. Samples were collected at the Federal University of Viçosa (UFV), and fresh leaves were photographed, cross-sections were made for anatomical and histochemical analyses, gall height and width, mesophyll and epidermis thickness, and epidermal cell width were measured and subjected to statistical analysis, and transmission electron microscopy was performed on the abaxial epidermis. Young galls are characterized by the bulging or folding of the leaf blade due to hypertrophy and hyperplasia processes; maturation starts with the emergence of erinea and a meristem-like layer caused by cell dedifferentiation and redifferentiation of abaxial epidermis cells; on senescence, erineae oxidize. Histochemical analyses revealed the relocation of resources to the gall site. Morphometric results attest that the erinosis significantly affects the leaf blade (p < 0.001). Cytological analyses revealed a progressive overtaxing of cell machinery as the gall matures, leading to nucleus depletion and organelle degeneration. These results help explain how the gall impacts the plant metabolism, compromising host plant fitness, and add to the argument that erinosis is indeed a complex gall.