Development of Peltate Glandular Trichomes of Peppermint

Abstract

Cryofixation and conventional chemical fixation methods were employed to examine the ultrastructure of developing peltate glandular trichomes of peppermint (Mentha ϫ piperita). Our results are discussed in relation to monoterpene production and the mechanism of essential oil secretion. Peltate glands arise as epidermal protuberances (initials) that divide asymmetrically to produce a vacuolate basal cell, a stalk cell, and a cytoplasmically dense apical cell. Further divisions of the apical cell produce a peltate trichome with one basal cell, one stalk cell, and eight glandular (secretory) disc cells. Presecretory gland cells resemble meristematic cells because they contain proplastids, small vacuoles, and large nuclei. The secretory phase coincides with the separation and filling of the sub-cuticular oil storage space, the maturation of glandular disc cell leucoplasts in which monoterpene biosynthesis is known to be initiated, and the formation of extensive smooth endoplasmic reticulum at which hydroxylation steps of the monoterpene biosynthetic pathway occur. The smooth endoplasmic reticulum of the secretory cells appears to form associations with both the leucoplasts and the plasma membrane bordering the sub-cuticular oil storage cavity, often contains densely staining material, and may be involved with the transport of the monoterpene-rich secretion product. Associated changes in the ultrastructure of the secretory stage stalk cell are also described, as is the ultrastructure of the fragile post-secretory gland for which cryofixation methods are particularly well suited for the preservation of organizational integrity.

Mathematical Modeling-Guided Evaluation of Biochemical, Developmental, Environmental, and Genotypic Determinants of Essential Oil Composition and Yield in Peppermint Leaves

“…4F). A gradient of glandular trichome sizes is generally regarded as an indicator of specific stages of leaf development (Turner et al, 2000). Thus, our results indicate that the architecture of peppermint glandular trichomes is a fixed parameter, whereas the program controlling trichome development is flexible.…”

“…The distribution of glandular trichomes on peppermint leaves was evaluated using the method described by Turner et al (2000) with minor modifications. Briefly, leaves were cut along their blade, and each half was divided into three sampling zones (basal, middle, and apical).…”

“…Glandular trichome counting was performed in five grids per zone and on five different leaves. The total leaf area and the diameters of individual glandular trichomes were calculated based on digitized images of leaves (ImageJ, an open source software developed by the National Institutes of Health) using previously described methods (Turner et al, 2000). The calculations of essential oil volume per trichome were performed as described in Supplemental Data S1.…”

Anatomy Features of Lavandula Angustifolia Mill. and Lavandula Hybrida Rev. Plants in Vitro

“…Glandular trichomes were also described on leaf surface in Mentha piperita regenerants (Santoro et al, 2013). Glandular hairs are formed from epidermal outgrowths that divide asymmetrically to produce basal cells (Turner et al, 2000).…”

Process-based modelling of biogenic monoterpene emissions combining production and release from storage

“…Unlike isoprene, monoterpenes and other less volatile compounds can be stored in leaves, either as nonspecific storage in cellular liquid or as specific storage in storage organs, such as glandular trichomes (e.g. Gershenzon et al, 1989;Turner et al, 2000), resin canals, or resin ducts (e.g. Franceschi et al, 2005).…”