Double Staining of Mitochondria and Bacteria in Plant Tissues

Milovidov, in Professor Guilliermond's laboratory, has worked out the following technic to stain mitochondria red and bacteria blue in root nodules of legumes.     

Delafield'S Hematoxylin and Safranin for Staining Plant Materials

An improved schedule is suggested for staining plant materials in Delafield's hematoxylin and safranin. Tissues are stained first in Delafield's hematoxylin. A short bath in acidulated water (1 or 2 drops concentrated HCl to 100 cc.) removes objectionable precipitates, and at the same time serves as a destaining agent. The acid bath must be followed quickly by a thoro wash in tap water, or dilute lithium carbonate solution, to restore the original dark blue color (made reddish in the acid bath) of the hematoxylin and to “set” the stain. Once the hematoxylin solution is satisfactory, none of the reagents ordinarily used will remove it—unless they contain acid. Tissues are counterstained in rapid safranin (5 drops analin in 100 cc. of 1% safranin 0 in 50% ethyl alcohol); this materially lessens the time necessary for staining. The safranin is de-stained in 50% ethyl alcohol (which does not affect the hematoxylin) until sharp differentiation is secured. If destaining is too slow, or differentiation poor, a quick rinse in acidulated 50% alcohol usually sharpens contrast of the stains. This must be followed quickly by a wash in 50% alcohol containing lithium carbonate to neutralize the acid. Dehydrate, and mount as usual. This schedule allows each stain to be individually, and independently, controlled at the will of the operator.     

Block Staining of Botanical Materials

Plant materials, including coleus stem tips, Psilotum stems and onion root tips, were stained in iron-mordanted celestine blue and safranin (Gray and Pickle 1956) prior to embedding and sectioning. Mitotic figures as well as general morphological and anatomical features are adequately stained by this procedure. The plant materials, subdivided so that the largest dimension is about 8-10 mm, are stained for 12-48 hr. The time is dependent upon the tissue and dilution of the stain used. Excess stain is washed out and the tissues are dehydrated, embedded, sectioned and mounted on slides in the usual manner. Following removal of the wax by xylene the sections may be counterstained, or a cover slip may be added immediately.     

Staining of plant Materials Cleared in NaOH

Stains are listed which have proved suitable for staining the epidermis, mesophyll, and sclerenchyma and tracheary elements, respectively, of cleared leaf material of Mouriri and Linociera. Too rapid leaching is avoided by overstaining high in the dehydration series, destaining briefly in the same solvent, and moving through to xylene. Twenty to thirty minutes staining time is generally sufficient. Concentrations and solvents can be varied widely. If destained too much, the material can usually be replaced in the dye with no ill effects. A double stain schedule (Bonnett) of five to ten minutes in 1% Bismarck brown Y in 95% alcohol followed by one to two minutes in 1% fast green FCF in 100% alcohol may be advantageous for thin-walled cells in thick material. It may be preferable to treat thinner material with tannic-acid-iron-chloride followed by safranin (Foster). The effects of bleaches and clearing compounds other than NaOH on staining have not been investigated; however, Dr. Bonnett finds that lactic acid used after NaOH improves clearing and also improves the staining of his combination (above). Mordants can doubtless be used to advantage.     

Double Staining of Skeleton Using Microwave Irradiation

The fetal skeleton double staining method is used to reveal developmental abnormalities in the skeletal system. We used alizarin red S and al-cian blue successfully with microwave irradiation for skeletal double staining. The fixation time was reduced from 4-7 days to 2-2.5 min and the staining time was reduced from 4 days to 23 min.     

Double Staining for Comparative Measurements in Squash Preparations

Comparative measurements of nuclei or chromosomes following different treatments are seldom made on squash preparations, since variations which arise during preparation of the slides may easily mask genuine treatment differences. This drawback may be overcome by making use of dyes which, when substituted for basic fuchsin in Schiff's reagent, will give a Feulgen-type reaction with chromatin. By selecting dyes of contrasting colours, it is possible to intermingle cells from different treatments in the same squash preparation, and to perform comparative measurements on adjacent cells.

Suitable dyes which contrast well with basic fuchsin are toluidine blue, or azure A (which stain chromatin blue) and chrysoidin yellow (which stains chromatin yellow). These dyes are made up and used in the same manner as ordinary Feulgen reagent.

Samples of cells from the two treatments to be compared are fixed, washed and hydrolysed in 1 N HCl at 60 C. One sample is stained in regular Feulgen reagent, the other in the contrast dye, then both are macerated and thoroughly mixed on the same slide in a single drop of 45% acetic acid. A coverslip is added, and the preparation flattened to the required amount and made permanent after dry-ice removal of the cover. This technique may also be utilised for comparative grain counts in autoradiography, provided that the contrast dye does not cause chemical fogging of the film.     

Staining Cell Constituents in Diseased Plant Tissues

Tissues of diseased plants, where embryonic cells, with dense cytoplasm, are to be studied cytologically in the same section with vacuolated cells, should best be killed with the Meves or Regaud fluids. The greatest changes in affected cells of diseased tissues are likely to occur in the vacuolar system, the contents of which should be well preserved in the killing process.

Staining with acid fuchsin and decolorizing with light green, makes it possible, in properly killed tissues, to detect the slightest alteration in tissues, and to observe the different parts of the cell, nucleus, mitochondria and plastids, even when excessive vacuolation compresses the cytoplasmic inclusions.     

Aceto-Iron-Haematoxylin for Staining Chromosomes in Squashes of Plant Material

Haematoxylin can be used successfully in the acetic squash technic if adequate mordanting is provided, (a) in the stain—composed of 4% haematoxylin and 1% iron alum in 45% acetic acid—and (b) in a step that combines additional fixation, mordanting and maceration in a 1:1 HCl-alcohol mixture, to which is added chrome alum, iron alum and iodic acid: 0.1 gm of each to 6 ml of HCl-alcohol. The material is usually given a preliminary fixation in 1:3 acetic alcohol, then macerated, fixed and mordanted in the acidified alum-HIO₃ step for 10 min, transferred to Carney's fluid (6:3:1) for 10-20 min, squashed in a drop of stain and gently heated. In some species, the preliminary fixation may be omitted. The method yields intensely and selectively stained chromatin. To secure consistently good results, the stain can be diluted with 45% acetic acid, and the iodic acid omitted for some plant materials.     

Staining Paraffin-Embedded Plant Tissues with Acridine Orange

Stem, leaf, and bud tissue of sweet potato, tomato, and pepper were embedded in paraffin, sectioned, mounted, and stained with 0.01, 0.1 and 1% aqueous and 0.1% alcoholic solutions of acridine orange. Temporary and durable mounts were prepared and irradiated under short and long wave ultraviolet light. Intensity and specificity of the fluorescence imparted to tissues were chiefly affected by type of fixative. Best results were obtained with fixatives containing formalin but not acetic acid. Tests on the effect of pH obtained with McIlvaine's buffer between 4.5 and 8.3, and made only with the aqueous stain, showed 6-8 to be optimal. Aqueous staining 1 hr in 0.1% solution, pH 6-8 is recommended for temporary mounts. Durable mounts in a nonfluorescent resin can be made after differentiation in buffer and dehydration in dioxan solutions.     

Microwave Enhanced Staining for Plant Virus Inclusions

Plant virus inclusion bodies can be stained specifically with established staining methods for light microscopy. The procedure can be augmented by a short microwave treatment to provide better staining intensity and reduced staining time. The method is useful for preliminary sampling prior to collection for electron microscopy and for plant pathologists, plant breeders, and diagnosticians as a rapid means of plant virus characterization.     

An Adaptable Staining Schedule for Plant Tissues

A general schedule for staining meristematic, maturing, and mature plant tissues is described. Treatment with a dilute aqueous solution of Delafield's hematoxylin is followed with staining in 0.1% safranin in 60% alcohol. Destaining of safranin may be partly accomplished in alcohol and completed by counterstaining with dilute fast green FCF in a xylene and alcohol mixture. Various modifications and adaptations are briefly discussed.     

Dissection and Bulk Staining of Wool Follicles from Biopsies of Sheep Skin

Skin biopsies from sheep were fixed 2 hr in Carnoy's fluid, washed well in absolute alcohol and brought to distilled water through descending grades of alcohol. The specimens were then soaked 0.5 hr in M/15 phosphate buffer, pH 7.3, and digested at 33° C, first about 18 hr in 0.15% collagenase dissolved in pH 7.3 phosphate buffer, then washed, and finally in an equal-parts mixture of crude saliva and phosphate buffer (pH 7.3) to which 1 mg/ml ribonuclease was added. Enzymes were obtained from L. Light and Company. Staining of the washed, enzyme-treated tissue in bulk by the periodic acid-Schiff method gave differential staining of the wool follicle papilla, and separation of indvidual follicles by dissection was readily accomplished. Routine handling of large numbers of intact wool follicles is facilitated by this method.     

Differential Staining of Tannin in Sections of Epoxy-Embedded Plant Cells

A staining procedure is described for the light microscopic localization of ergastic tannins in epoxy sections of plant cells embedded for study by transmission electron microscopy. Callus and cell suspensions of Pseudotsuga menziesii and Pinus taeda fixed in glutaraldehyde:acrolein and then OsO₄, followed by epoxy embedding, were sectioned 0.5 μn thick, stained on a glass slide with ethanolic Sudan black B at 60 C as described by Bronner, and then mounted in Karo syrup. Tannin deposits stained brownish-orange and were easily distinguished from lipid bodies of similar size, which stained dark blue to black, and from starch grains, which were unstained. The significance of this differential polychromasia was confirmed by transmission electron microscopy. This staining proadure should prove valuable in the cytoplasmic evaluation of the plant cell ergastics (especially tannins) via light microscopy whether or not electron microscopic examination is intended.     

An Automated Double Staining Procedure for Bone and Cartilage

Differential skeletal staining is an important part of developmental toxicologic studies. Traditionally these studies have required time-consuming differentiation of one or both stains used and careful attention to the maceration step to prevent specimen destruction. We present a fully automated protocol which does not require differentiation of either dye and incorporates a controlled maceration step which is highly reproducible. This has resulted in high quality staining that is reproducible, stable, and can be done in volume with minimal personnel time. The process involves the staining of skinned, eviscerated specimens fixed in 95% ethanol. Using an automated tissue processor, the specimen is stained in alcian blue for 24 hr, macerated in 3% potassium hydroxide for 24 hr and stained with murexide for 24 hr. The specimens are cleared and preserved in glycerol. Within three days specimens have red stained bone and blue stained cartilage. The procedure was developed using 20-day-old Sprague-Dawley rat fetuses to evaluate the feasibility of using the procedure for teratology studies involving the fetal skeleton. Evenly stained specimens can be examined within three days and stored for years without loss of staining.     

A Rapid Safranin-Metal Phthalocyanine Double Staining Technique for Plants

Pure metal 4.4',4',4'-tetxa-substituted, sulfo-, carboxy- and nitrophthalocyanines were synthesized. Mounted, deparaffinized and partially dehydrated sections of plant tissues were stained with 0.5% safranin in 50% alcohol for 5-10 min. Excess safranin was removed with a series of 70%, 95% and absolute alcohol washes. The sections were then stained for 2-3 min using metal 4,4',4',4'-phthalocyanine tetracarboxylic acid (MPTC, 0.5% (V/V) containing a few drops of dilute sodium hydroxide), metal 4,4',4',4'-tetra-sulfophthalocyanine (MPTS, 0.5% (V/V)) or metal tetranitrophthalocyanine (MPTN, 0.5% (V/V) in dimethyl sulfoxide). The sections were washed with 95%, then absolute alcohol; however, the metal tetranitrophthalocyanine section was washed only with absolute alcohol. Stained sections were treated briefly with xylene, then mounted on a coverslip. Bright peacock blue (MPTC and MPTS using Cu, Co or Ni), turquoise blue (MPTN using Cu or Ni) or parrot green (zinc phthalocyanine tetracarboxylic acid-ZnPTC, zinc phthalocyanine tetranitro derivative-ZnPTN) colors were obtained. Lignin-containing cells were stained red by safranin and the remaining cell structures were stained by the metal phthalocyanine complex with color brightness superior to that of fast green. Uniform staining, no color fading after a year, reliability, brief staining times, high color contrast (log ε = 4.0-4.9) and ease of use make this double staining combination ideal for routine use and photomicrography.     

Staining Air Dried Protoplasts for Study of Plant Chromosomes

The air drying technique used in mammalian cytology was applied to isolated plant protoplasts for study of chromosomes. For cultured celery cells, this technique resulted in good spreads of metaphase chromosomes with high resolution. Mitotic chromosomes of Brassica species are relatively small, poorly stained by common stains, and difficult to spread by the squash technique. In this study, however, the chromosomes of B. carinata in callus culture were spread well and stained clearly with Giemsa staining solution. The chromosome preparations by the present techniques should also be amenable to chromosome banding studies in plants.     

Feulgen Staining of Intact Plant Tissues for Confocal Microscopy

A method was developed to prepare plant structures for confocal laser scanning microscopy by combining Feulgen staining with pararosaniline and embedding in LR White_TM. This procedure preserves intact, delicate structures for three-dimensional imaging without loss from sectioning or squashing, and the slides can be viewed several times without serious photobleaching.     

Feulgen Staining of Intact Plant Tissues for Confocal Microscopy

A method was developed to prepare plant structures for confocal laser scanning microscopy by combining Feulgen staining with pararosaniline and embedding in LR White_TM. This procedure preserves intact, delicate structures for three-dimensional imaging without loss from sectioning or squashing, and the slides can be viewed several times without serious photobleaching.