Biomaterial Database

Chloroplast ultrastructure in leaves of Urtica dioica L. analyzed after high-pressure freezing and freeze-substitution and compared with conventional fixation followed by room temperature dehydration. 2005

Stephan Pfeiffer, and Karin Krupinska

Central Microscopy, Center of Biology, University of Kiel, D-24098 Kiel, Germany. spfeiffer@bio.uni-kiel.de

In this article, we report on the adaptation of high-pressure freezing and freeze-substitution (HPF-FS) for ultrastructural analysis of leaf tissue with special emphasis on chloroplasts. To replace the gas in the intercellular spaces, a mixture of water and methanol (MeOH) was employed. We compared three different supplements for FS--osmiumtetroxide, uranyl acetate, and safranin--with regard to the preservation of the ultrastructure of chloroplasts and other cellular compartments. The results show that (i) replacement of air within intercellular spaces by 8% (v/v) MeOH has no influence on the ultrastructure of the chloroplasts, (ii) undulation of membranes frequently observed after conventional preparation of specimens does not occur during chemical fixation but during room temperature dehydration, and (iii) uranyl acetate or osmium tetroxide employed during FS are not superior over safranin.

UI	MeSH Term	Description	Entries
D002736	Chloroplasts	Plant cell inclusion bodies that contain the photosynthetic pigment CHLOROPHYLL, which is associated with the membrane of THYLAKOIDS. Chloroplasts occur in cells of leaves and young stems of plants. They are also found in some forms of PHYTOPLANKTON such as HAPTOPHYTA; DINOFLAGELLATES; DIATOMS; and CRYPTOPHYTA.	Chloroplast,Etioplasts,Etioplast
D003681	Dehydration	The condition that results from excessive loss of water from a living organism.	Water Stress,Stress, Water
D001274	Atmospheric Pressure	The pressure at any point in an atmosphere due solely to the weight of the atmospheric gases above the point concerned.	Atmospheric Pressures,Pressure, Atmospheric,Pressures, Atmospheric
D013696	Temperature	The property of objects that determines the direction of heat flow when they are placed in direct thermal contact. The temperature is the energy of microscopic motions (vibrational and translational) of the particles of atoms.	Temperatures
D015925	Cryopreservation	Preservation of cells, tissues, organs, or embryos by freezing. In histological preparations, cryopreservation or cryofixation is used to maintain the existing form, structure, and chemical composition of all the constituent elements of the specimens.	Cryofixation,Cryonic Suspension,Cryonic Suspensions,Suspension, Cryonic
D016707	Tissue Fixation	The technique of using FIXATIVES in the preparation of cytologic, histologic, or pathologic specimens for the purpose of maintaining the existing form and structure of all the constituent elements.	Fixation, Tissue
D017110	Freeze Substitution	A modification of the freeze-drying method in which the ice within the frozen tissue is replaced by alcohol or other solvent at a very low temperature.	Substitution, Freeze
D018515	Plant Leaves	Expanded structures, usually green, of vascular plants, characteristically consisting of a bladelike expansion attached to a stem, and functioning as the principal organ of photosynthesis and transpiration. (American Heritage Dictionary, 2d ed)	Plant Leaf,Leaf, Plant,Leave, Plant,Leaves, Plant,Plant Leave
D026982	Urtica dioica	A plant species of the genus Urtica, family URTICACEAE. Roots have been used to treat PROSTATIC HYPERPLASIA. Leaves are edible after the stinging quality is eliminated by brief heating.	Nettle, Stinging,Stinging Nettle,Nettles, Stinging,Stinging Nettles,Urtica dioicas,dioica, Urtica