![Sample our Environment & Agriculture journals, sign in here to start your access, latest two full volumes FREE to you for 14 days]({"type":"image" , "src" : "/sda/5934/TOC-Subject-Sample-2021-Environment-Agriculture.jpg"})
Abstract
Multicellular long-stalked glandular hairs of the outer involucral bracts of Sigesbeckia jorullensis Kunth were investigated with transmission electron micros-copy. The apical layer of head cells was characterized by many irregular leucoplasts, a well developed and in the secretory phase mostly agranular endoplasmic reticu-lum, few dictyosomes, and one calcium oxalate crystal per cell. The prevalent part of the secretion seems to originate from leucoplasts of apical head cells and is secreted into a subcuticular space after crossing cytoplasm and the plasma membrane. The sheath of this sub-cuticular space was formed exclusively by a thin cuticle, which was detached from the cell wall in the secretory phase. Some small wall protuberances were found between the sub-apical and apical cell layer. Whether the three to six layers of sub-apical head cells, containing many chloroplasts, contribute to the biogenesis of the lipophilic secretion or not, remains unclear. Light microscopy demonstrated that there was a small girdle bordering the subcuticular space, where the cuticle was firmly fixed to the cell wall. Analysis with EM did not reveal alterations in cell wall ultrastructure, which might cause the firm attachment of the cuticle to the cell wall along a girdle.