Sink Status and Photosynthetic Rate of the Leaflet Galls Induced by Bystracoccus mataybae (Eriococcidae) on Matayba guianensis (Sapindaceae)

Abstract

The galling insect Bystracoccus mataybae (Eriococcidae) induces green and intralaminar galls on leaflets of Matayba guianensis (Sapindaceae), and promotes a high oxidative stress in host plant tissues. This biotic stress is assumed by the histochemical detection of hydrogen peroxide, a reactive oxygen species (ROS), whose production alters gall physiology. Thus, we hypothesize that high levels of nutrients are accumulated during gall development in response to a local maintenance of photosynthesis and to the galling insect activity. Moreover, the maintenance of low levels of photosynthesis may guarantee O2 production and CO2 consumption, as well as may avoid hypoxia and hypercarbia in gall tissues. To access the photosynthesis performance, the distribution of chlorophyllous tissues and the photochemical and carboxylation rates in gall tissues were analyzed. In addition, histochemical tests for hydrogen peroxide and phenolic derivatives were performed to confirm the biotic stress, and set the possible sites where stress dissipation occurs. The contents of sugars and nitrogen were evaluated to quantify the gall sink. Currently, we assume that the homeostasis in gall tissues is ruptured by the oxidative stress promoted by the galling insect activity. Thus, to supply the demands of gall metabolism, the levels of water-soluble polysaccharides and starch increase in gall tissues. The low values of maximum quantum efficiency of PSII (Fv/Fm) indicate a low photosynthetic performance in gall tissues. In addition, the decrease of PSII operating efficiency, (F’m–F’)/F’m, and Rfd (instantaneous fluorescence decline ratio in light, to measure tissue vitality) demonstrate that the tissues of B. mataybae galls are more susceptible to damage caused by stressors than the non-galled tissues. Thus, the high oxidative stress in gall developmental sites is dissipated not only by the accumulation of phenolic derivatives in the protoplast, but also of lignins in the walls of neoformed sclereids.

Structural, histochemical and photosynthetic profiles of galls induced by Eugeniamyia dispar (Diptera, Cecidomyiidae) on the leaves of Eugenia uniflora (Myrtaceae)

“…Reactive oxygen species (ROS) were detected around the larval chamber in association with primary metabolites, especially proteins, which is indicative of biotic stress (Schönrogge, Harper, & , 2000). Stress was also detected in gall tissues by chlorophyll a fluorescence, which demonstrates that galls retain a low-level photosynthetic capacity, as observed in other Neotropical gall systems (Castro Oliveira, Moreira, Lemos-Filho, & Isaias, 2012;Oliveira et al, 2017). Associated with low photosynthetic activity, many intercellular spaces may facilitate gas diffusion, as has been previously proposed for other gall systems (Pincebourde & Casas, 2016).…”

“…Carotenoids and NPQ are responsible for energy dissipation during the xanthophyll cycle and, consequently, prevent damage to the photosynthetic apparatus during stress (Demmig-Adams & Adams, 1996). Contrary to expectations, there was a decrease in carotenoid content in gall tissues compared to non-galled leaves of E. uniflora, an indication that the gall tissue may invest in different mechanisms for stress dissipation and maintenance of tissue homeostasis Oliveira et al, 2017); we also detected a decrease of NPQ levels in galls induced by E. dispar on leaves of E. uniflora.…”

“…Despite the formation of compact tissues in different gall systems, the galls induced by E. dispar on leaves of E. uniflora have large intercellular spaces in the outer layers. These intercellular spaces may help to maintain gas diffusion and, consequently, avoid hypoxia and hypercarbia in gall tissues (Pincebourde & Casas, 2016;Oliveira et al, 2017).…”

“…Cecidomyiid galls, for example, possess a histochemical gradient associated with a large accumulation of certain primary metabolites near the larval chamber, thereby forming nutritive tissue, while others (such as starch) accumulate more distant from the larval chamber and are known as reserve tissues (Bronner, 1992;Ferreira, Álvarez, Avritzer, & Isaias, 2017). In addition to nutritive tissue formation, structural and physiological alterations, such as decreases in the amount of chlorophyllous tissues, pigment content, gas exchange, and photosynthetic rates, have been detected in gall tissues (Florentine, Raman, & Dhileepan, 2005;Oliveira et al, 2011b;Oliveira, Moreira, Isaias, Martini, & Rezende, 2017). Nonetheless, green galls should maintain their photosynthetic activity in spite of the oxidative stress and structural changes caused by the gall-inducing organism.…”

“…Nonetheless, green galls should maintain their photosynthetic activity in spite of the oxidative stress and structural changes caused by the gall-inducing organism. This maintenance of photosynthetic activity would have interesting implications for the oxygen and carbon dioxide cycle of galls by reducing hypoxia and hypercarbia (Castro, Oliveira, Moreira, Lemos-Filho, & Isaias, 2012;Haiden, Hoffmann, & Cramer, 2012;Oliveira et al, 2017).…”