Microscopy and chemical analyses reveal flavone-based woolly fibres extrude from micron-sized holes in glandular trichomes of Dionysia tapetodes

Abstract

Background Dionysia tapetodes, a small cushion-forming mountainous evergreen in the Primulaceae, possesses a vast surface-covering of long silky fibres forming the characteristic “woolly” farina. This contrasts with some related Primula which instead form a fine powder. Farina is formed by specialized cellular factories, a type of glandular trichome, but the precise composition of the fibres and how it exits the cell is poorly understood. Here, using a combination of cell biology (electron and light microscopy) and analytical chemical techniques, we present the principal chemical components of the wool and its mechanism of exit from the glandular trichome. Results We show the woolly farina consists of micron-diameter fibres formed from a mixture of flavone and substituted flavone derivatives. This contrasts with the powdery farina, consisting almost entirely of flavone. The woolly farina in D. tapetodes is extruded through specific sites at the surface of the trichome’s glandular head cell, characterised by a small complete gap in the plasma membrane, cell wall and cuticle and forming a tight seal between the fibre and hole. The data is consistent with formation and thread elongation occurring from within the cell. Conclusions Our results suggest the composition of the D. tapetodes farina dictates its formation as wool rather than powder, consistent with a model of thread integrity relying on intermolecular H-bonding. Glandular trichomes produce multiple wool fibres by concentrating and maintaining their extrusion at specific sites at the cell cortex of the head cell. As the wool is extensive across the plant, there may be associated selection pressures attributed to living at high altitudes.

Toxicity Mechanisms of Nanoplastics on Crop Growth, Interference of Phyllosphere Microbes, and Evidence for Foliar Penetration and Translocation

“…We also found that blue fluorescence was mainly concentrated in the phloem of the stem, which is direct evidence for the phloem transport of NPs. Trichomes were thought to be possible pathways for engineered nanoparticles to enter into leaves . Interestingly, we also found PS-Eu inside the trichomes of leaves (Figure S23).…”

“…Trichomes were thought to be possible pathways for engineered nanoparticles to enter into leaves. 66 Interestingly, we also found PS-Eu inside the trichomes of leaves (Figure S23). However, whether these NPs were internalized directly by the trichomes or transferred inside the trichomes after internalization by the cuticle remains to be further explored.…”

“…Furthermore, PS-Eu was found inside and outside the tomato stem trichomes, even though they were not directly exposed to PS-Eu (Figure S24). PS-Eu was most likely extruded through interstitial spaces in specific parts of trichomes, 66 which may be the primary mechanism by which plants detoxify through bodily excretion.…”

Flavone From Plants—Uncommonly Common? A Comprehensive Review

“…15 In a vial, dry farinose exudate reassembles into long threads as observed for Primula florindae Ward (see Figure S1), resembling the in vivo observed extrusion from Dionysia glandular hairs. 16…”

An Overview of Cryo-Scanning Electron Microscopy Techniques for Plant Imaging

“…They may also have shiny surface regions (wax, surface crust and reflective hairs) that give glare with epi-illumination. These types of plants have worked very well for cryoSEM, and their habitation in cold, dry climates appears to greatly limit the amount of exogenous (surface) ice that forms during plunge-freezing [35][36][37].…”