Ultrastructural Alterations in Cells of Sunflower Linear Glandular Trichomes during Maturation.

Evelyn Amrehn,Otmar Spring

doi:10.3390/plants10081515

Abstract

Sunflower and related taxa are known to possess a characteristic type of multicellular uniseriate trichome which produces sesquiterpenes and flavonoids of yet unknown function for this plant. Contrary to the metabolic profile, the cytological development and ultrastructural rearrangements during the biosynthetic activity of the trichome have not been studied in detail so far. Light, fluorescence and transmission electron microscopy were employed to investigate the functional structure of different trichome cells and their subcellular compartmentation in the pre-secretory, secretory and post-secretory phase. It was shown that the trichome was composed of four cell types, forming the trichome basis with a basal and a stalk cell, a variable number (mostly from five to eight) of barrel-shaped glandular cells and the tip consisting of a dome-shaped apical cell. Metabolic activity started at the trichome tip sometimes accompanied by the formation of small subcuticular cavities at the apical cell. Subsequently, metabolic activity progressed downwards in the upper glandular cells. Cells involved in the secretory process showed disintegration of the subcellular compartments and lost vitality in parallel to deposition of fluorescent and brownish metabolites. The subcuticular cavities usually collapsed in the early secretory stage, whereas the colored depositions remained in cells of senescent hairs.

Highlights

Plant trichomes are highly essential structures of the epidermis which have numerous physical and physiological functions in various developmental stages of the plant’s life cycle [1,2]
Sunflower and many closely related species of the Helianthinae are known to possess at least two types of multicellular glandular trichomes: the biseriate capitate glandular trichomes (CGTs) and the uniseriate linear glandular trichomes (LGTs) [7]. Both types occur on the leaf blade of the common sunflower Helianthus annuus L., but LGTs are located on petioles, stems and flower parts, with the highest density on the abaxial surface of phyllaries [8]
LGTs located on stems (Figure 1a,b), leaf blades (Figure 1c,d), petioles or phyllaries showed very similar architecture

Summary

Introduction

Plant trichomes are highly essential structures of the epidermis which have numerous physical and physiological functions in various developmental stages of the plant’s life cycle [1,2]. Sunflower and many closely related species of the Helianthinae are known to possess at least two types of multicellular glandular trichomes: the biseriate capitate glandular trichomes (CGTs) and the uniseriate linear glandular trichomes (LGTs) [7]. Both types occur on the leaf blade of the common sunflower Helianthus annuus L., but LGTs are located on petioles, stems and flower parts, with the highest density on the abaxial surface of phyllaries [8]. The data of this report will present details on the cytological development of LGTs from the pre-biosynthetic to the senescent stage using light and fluorescence microscopy (LM/FM) as well as transmission electron microscopy (TEM)

Methods

Results

Conclusion