Transfer cells in trichomatous nectary in Adenocalymma magnificum (Bignoniaceae).

THÁLIA S.S. GAMA,DIEGO DEMARCO,ANA CRISTINA A. DE AGUIAR-DIAS

doi:10.1590/0001-3765201620140606

THÁLIA S.S. GAMA, DIEGO DEMARCO + Show 1 more

Open Access

https://doi.org/10.1590/0001-3765201620140606

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Abstract

Transfer cells are specialized cells that play an important role where there are high energy costs due to facilitation of transmembrane flow of solutes. This study aimed to investigate the ontogenesis, histochemistry and ultrastructure of glandular trichomes focusing on stalk cells and their possible transfer function. Samples of prophylls of axillary buds, calyces of flowers in anthesis, and flower buds in different stages of development were collected, fixed and processed according to the common methods of microscopy. The glandular trichomes are composed of a secretory head with its cells in columnar format. The stalk is formed by two layers of cells, with the upper layer composed of cuboidal cells where the wall starts to thicken at the beginning of the pre-secretory phase. The secretion is heterogeneous, releasing glucose, other carbohydrates, lipids and phenolic compounds, with two types of release - eccrine and granulocrine. These trichomes are functionally termed as nectaries. The stalk cells appear as transfer cells since they have a thicker anticlinal wall with irregular ingrowths. The presence of transfer cells in the nectaries suggests a high specialization because it improves transport capacity of nectar and compensation in the high energy expenditure for its production and release.

Highlights

Transfer cells are highly specialized cells and occur in vegetative and reproductive organs, especially in places where the demand for an intensive transport of solutes through the membrane, is high (Gunning and Pate 1974).For most cells, the primary wall is deposited uniformly over all faces of the cell during expansion (Carpita and Gibeaut 1993)
For the anatomical analysis over light microscopy, samples were fixed in 50% FAA and neutral buffered formalin for 24 and 48 h, respectively, dehydrated in a butyl series, and embedded in Paraplast (Leica Microsystems Inc., Heidelberg, Germany)
In A. magnificum different events occur simultaneously, which were understood by the manner in which a heterogeneous secretion was released in the presence of chemical substances produced by various metabolic pathways, unique to secretory structures

Summary

Introduction

Transfer cells are highly specialized cells and occur in vegetative and reproductive organs, especially in places where the demand for an intensive transport of solutes through the membrane, is high (Gunning and Pate 1974).For most cells, the primary wall is deposited uniformly over all faces of the cell during expansion (Carpita and Gibeaut 1993). The deposition of these wall ingrowths amplifies the surface area of the plasma membrane, which hypothetically facilitates the transmembrane flow and exchange of solutions between apoplast and symplast (Pate and Gunning 1972). Because of this specialization, transfer cells are found in various organs, such as gametophytic cells (Diboll and Larson 1966, Cass 1972, Wilms 1981, Bohdanowicz and Turała-Szybowska 1985, 1987) and vascular tissues, in the parenchyma. DE AGUIAR-DIAS and DIEGO DEMARCO cells of the xylem and companion cells of the phloem (Pate and Gunning 1969, Gunning et al 1970, Talbot et al 2002)

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