Deep capillary impact of a psyllid gall on its host ecophysiology, architecture and performance

Key Message Neolithus fasciatus gall affected the host's efficiency to absorb and use the available light and functioned as a sink source for photoassimilates, water, and nutrients that would be allocated to plant development and reproduction of Sapium glandulatum. Abstract The knowledge on the effects of galls on the redistribution of resources and reproductive performance of the host is fragmentary. We used a combined approach of physiological and biochemical analyses to investigate the impact of galling on host ecophysiology and performance to aid in the bridging of this gap. We determined the frequency of galled hosts on 155 individuals of Sapium glandulatum in the field. The following ecophysiological parameters: oxidative stress, gas exchange, contents of chlorophyll, flavonoids, water, and total carbohydrates were recorded on galled and ungalled individuals. In addition, the impact of galling was recorded through the number of lateral shoots and fruit production. Approximately 75% of the studied host population had at least one galled shoot, and galls were most abundant on younger leaves. While galled and ungalled individuals did not differ in their oxidative stress, galled individuals showed higher stomatal conductance, internal carbon concentration, and flavonoid production, but lower net photosynthetic rate and effective quantum yield of PSII. Total carbohydrate and content of water were higher in galled tissues compared to healthy tissues of galled and ungalled host leaves. Galling induced attacked shoots to produce ca. four lateral shoots while ungalled shoots did not produce any lateral shoots. Last, while ungalled shoots produced an average of six fruits each, galled shoots did not bear any fruits. The presence of Neolithus fasciatus galls affected the host's efficiency to absorb and use the available light and functioned as a sink source for photoassimilates, water, and nutrients that would be allocated to plant development and reproduction. These data support the hypothesis that galling insects are important herbivores and their negative effects on the hosts can spread into several organs and functioning systems of the hosts.