Cellular and biophysical implications forbm gene mutations affecting plant epicuticular wax
Abstract
Thirty-three chemically-induced mutant isolines were divided into 14 epicuticular wax (EW) classes based on altered EW morphology as viewed using scanning electron microscopy. Filamentous EW was secreted from conical papillae above apical-periclinal cork cell walls. This is the first report of papillae-mediated EW secretion by plants. Cell wall or cuticle microchannels for EW transport were not visible, however, a preferred pathway for EW diffusion to the surface at the sides of papillae is suspected. The effects of bm mutations on ultrastructural changes normally occurring during EW induction were used to associate bm genes with cellular function. Possible roles for ER, Golgi apparatus, osmiophilic globules, vesicles, and the novel cell wall apical cap structures in EW secretion processes are presented. A bm mutation in two different genetic backgrounds altered the ultrastructure of the cuticle proper and increased plant conductance to water vapor and fungal disease(Exserohilum turcicum) susceptibility. This is the first report of a gene mutation affecting the plant cuticle. The influence of EW filaments on scattering of ultraviolet-B (UVB) and photosynthetically active radiation (PAR) was examined. Angular backscattering of UVB and PAR was always higher from the N-15 canopy bearing stalk EW filaments than bm-15 lacking structural stalk EW, except at preflowering when both were the same. The effect of canopy development and changing EW load/density on canopy angular reflectance of UBV and PAR was examined. The presence or absence of filamentous EW on Sorghum bicolor stalks did not influence the canopy extinction of radiation.
Degree
Ph.D.
Advisors
Ashworth, Purdue University.
Subject Area
Botany|Agronomy
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