Introduction of Aphid Crescent‐Shaped (Marginal) and Pea‐Shaped Galls in Pistacia vera: Their Morpho‐Anatomical and Histochemical Characteristics

Galling organisms induce redifferentiation of plant tissues to provide shelter, nutrition, and protection for gallicolous organisms. For the first time, the present work describes morphological, anatomical, and histochemical characteristics of two aphid galls of Pistacia vera during development. Intact (control) mesophyll was homogenous, composed of palisade cells; epidermal layers were uniseriate, and vascular bundles, surrounded by bundle sheath, were apposite collateral in the midvein and single in lateral sides. The identified galls were the crescent‐shaped at leaflet edges and small pea‐shaped at leaflet midvein apex. In both galls, the adaxial epidermis was the origin of the epidermis inside the gall, and the abaxial epidermis was the origin of the epidermis outside the gall. Pea‐shaped galls showed both opposite and single vascular bundles, whereas crescent‐shaped galls had only single bundles. They showed the following features compared with control: multilayer epidermis‐lumen (a kind of hyperplasia), increasing total cell layers of gall wall, replacement of palisade cells with shorter cells, increasing the size of phloem system and schizogenous ducts (a kind of hypertrophy, only in crescent‐shaped gall), xylem low stainability, and the absence of bundle sheath. Some primary and secondary metabolites were present in both types of galls as well as non‐galled leaflets. All the mentioned features are developed to feed aphids or protect them against biotic and abiotic stresses.