Methods of preparing flower stem samples for scanning electron microscopy

Poliana Cristina Spricigo,Marcos David Ferreira,Jéssica Prada Trento,Luiz Francisco De Mattêo Ferraz,Viviane Faria Soares,Joana Dias Bresolin

doi:10.14295/rbho.v21i1.771

Abstract

Brazil has great capacity for expansion in the floriculture sector. Studies on postharvest cut flowers contribute to development of the sector, helping to maintain the quality of domestic production. Scanning electron microscopy (SEM) is a powerful tool that allows viewing of flower structures and also microorganisms. The aim of this study was to evaluate methods of preparing flower stem samples for viewing in SEM as a support for studies on postharvest cut flowers. Ways of cutting, fixing, and drying samples were tested. Cutting with a stainless steel blade and through freeze-fracture were tested; fixation was carried out without the use of osmium tetroxide (OsO4); and drying of the samples was performed through freeze-drying and through critical point dryingwithCO2. Cutting with a stainless steel blade proved to be a satisfactory method for stem samples, with low cost and simple application compared to freeze-fracturing. Good fixation and high image contrast were obtained without the use of osmium tetroxide, thus avoiding the use of this toxic compound. Freeze-drying allowed the structure and morphological composition to be viewed, while critical point drying withCO2 preserved the microorganisms present in the samples.

Highlights

In Brazil, floriculture still has great potential for expansion, seeking to assert a more relevant position both in production and in exports (AGRIANUAL, 2014)
The aim of this study is to evaluate methods of preparation of flower stem samples for viewing of images in Scanning electron microscopy (SEM) as a support for postharvest studies of cut flowers
Sampling The samples obtained after fracturing in liquid nitrogen showed excellent preservation of the flower stem cells; they did not allow viewing of the whole sample in a cross section, as a result of damage caused by freezing in liquid nitrogen (Figure 1)

Summary

Introduction

In Brazil, floriculture still has great potential for expansion, seeking to assert a more relevant position both in production and in exports (AGRIANUAL, 2014). The state of São Paulo has 74.5% of domestic production of flowers and ornamental plants (IBRAFLOR, 2013). Studies that involve maintaining the quality of ornamental plants in Brazil may assist in development of the sector. Loss of moisture to the environment without due replacement reduces vase life (KOHL, 1968; BOROCHOV et al, 1982).Flower stems take up water through the transport vessels of the vascular system. Water transport through these vessels is simple and shows little resistance, efficiently allowing displacement of large amounts of water (RASCHKE, 1975). Water imbalance leads to dehydration of flower tissues, which may be linked to occlusion of the transport vessels, making maintenance of the cohesion-tension dynamic in the vessels impossible (AHMAD et al, 2010)

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