title: Leaf-derived cecidomyiid galls are sinks in Machilus thunbergii (Lauraceae) leaves.
abstract: Three relevant hypotheses - nutrition, environment and the enemies hypothesis - often invoked to explore source and sink relationships between galls and their host plants are still under dispute. In this research, chlorophyll fluorescence, gas exchange capacity, stomatal conductance, total carbon and nitrogen, total soluble sugars and starches, and scanning and transmission electron microscopy of two types of galls were used to investigate source-sink relationships. Compared with host leaves, these galls demonstrated slightly lower chlorophyll fluorescence; however, gas exchange capacity and stomatal conductance were not detected at all. Scanning electron micrographs demonstrated that the abaxial epidermis of host leaves contain normal amounts of stomata, whereas no stomata were observed on the exterior and interior surfaces of both types of galls. In addition, gall inner surfaces were covered with many kinds of fungal hyphae. Gall total carbon (C) and nitrogen (N) levels were lower but the C/N ratio was higher in galls than host leaves. Both types of galls accumulated higher total soluble sugars and starches than host leaves. Transmission electron micrographs also revealed that both types of galls contain plastoglobuli and giant starch granules during gall development. Results strongly indicate that leaf-derived cecidomyiid galls are sinks in Machilus thunbergii leaves. However, it is perplexing how larvae cycle and balance CO(2) and O(2) in gall growth chambers without stomata.
authors.affiliation: Biodiversity Research Center, Academia Sinica, Nankang, Taipei, 115, Taiwan.
authors.forename: Meng-Yuan
authors.initials: MY
authors.lastname: Huang
authors.forename: Wen-Dar
authors.initials: WD
authors.lastname: Huang
authors.forename: Hsueh-Mei
authors.initials: HM
authors.lastname: Chou
authors.forename: Kuan-Hung
authors.initials: KH
authors.lastname: Lin
authors.forename: Chang-Chang
authors.initials: CC
authors.lastname: Chen
authors.forename: Pei-Ju
authors.initials: PJ
authors.lastname: Chen
authors.forename: Yung-Ta
authors.initials: YT
authors.lastname: Chang
authors.forename: Chi-Ming
authors.initials: CM
authors.lastname: Yang
mesh_terms: D000818:Animals; D001692:Biological Transport; D002244:Carbon / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism / Q000648:ultrastructure; D004175:Diptera / Q000502:physiology*; D006790:Host-Parasite Interactions; D019770:Lauraceae / Q000378:metabolism* / Q000469:parasitology / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D009584:Nitrogen / Q000378:metabolism*; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism / Q000469:parasitology / Q000648:ultrastructure; D018526:Plant Transpiration; D010941:Plant Tumors / Q000469:parasitology*
chemical_list: D002244:Carbon; D009584:Nitrogen