Frank P. McWhorter

Plant-Virus Differentiation by Trypan-Blue Reactions within Infected Tissue

Trypan blue has proved effective for demonstrating the presence of certain plant viruses within infected tissues. The amorphous and crystalline inclusions which constitute cytological evidence of viruses stain proportionately. The effects produced by different viruses react differently to the stain and those inclusions which do not absorb trypan blue tend to stain with phloxine. This selective staining is the basis for using trypan blue singly and in combination with phloxine as standardized procedures for demonstrating and differentiating cytological evidence of plant viruses. These tests are very rapid and are especially applicable to temporary mounts of living tissue but permanent mounts can be made from material fixed in formalin.

Possible uses of Dioxan in Botanical Microtechnic

Dioxan has been well established as an advantageous dehydrating agent for plant tissues. It dehydrates equally well after fixatives containing formalin, acetic acid, chromic acid, chromates, mercuric chloride, osmic acid, and alcohol. Better infiltration of paraffin after dehydration may be obtained by passing the material thru (1) a cold bath composed of 30 cc. of dioxan, 5 cc. of xylol and 20 cc. of melted soft paraffin and, (2) a warm bath of 50 cc. of dioxan, 50 cc. of paraffin, and 10 cc. of xylol. Transfer from (2) to soft paraffin. A dioxan fixative consisting of dioxan 50 cc., formalin 6 cc., acetic acid 5 cc., water 50 cc. was devised for delicate subjects. The fixed material is transferred directly into dioxan and mounted in dioxan-diaphane or dioxan-balsam. Very delicate objects require dioxan dilution of the balsam and slow concentration of the mounting medium by evaporation.Entire plant parts or epidermal peelings are fixed in any desired fixative, washed if necessary, transferred to dioxan a...

Chlorazol Fast Pink B And Trypan Blue Tests for Virus and Other Proteinaceous Inclusions

A 1% solution of chlorazol fast pink B in 0.9% NaCl can be used like trypan blue to detect virus inclusions and proteinaceous entities in peelings from leaves or thin sections taken from living plant tissue. Like trypan blue, a solution of the pink dye causes somatic nuclei to swell and thus facilitates observation of their structure. The two dyes combine into a beautiful differential bicolored stain. Mix 5 ml of 0.5% trypan blue stock solution with 35 ml of 1% chlorazol pink B in 0.9% NaCl. Stain fresh tissue 1-2 minutes. The combination stain is superior to either dye alone for differentiating virus entities.

The Examination of Tissues in Living Leaves and Flowers by Means of a High Vacuum Technic

The cells of living leaves and flowers can be prepared for examination in toto by replacing the intercellular air with physiological salt solution. This is done by mounting all or parts of leaves and flowers in salt solution and subjecting the preparation to a vacuum of close to 0.1 μ of mercury. The solution is allowed to boil a few moments, the vacuum is slowly released; then the tissues are ready for examination. Preparations in many ways far superior to chemically cleared mounts can be made in one minute.

Contact Photomicrography in the Ultraviolet on High-Resolution Plates

Ultraviolet photographs of cells can be made without quartz optics by placing the cells on high-resolution plates capable of resolving more than 2000 lines per millimeter and by passing monochromatic radiation of the desired wavelength through them to the emulsion. Prints can be made by enlarging the resulting negative with a microscope to the magnification desired.

Differential Illumination within a Microscope Field for Making a Photomicrograph

Variations in density and/or coloration of stained sections involving distinct tissues often make attractive photographic rendition difficult because a proper filter for the light-colored areas renders dark-colored areas too black in the final print. This happens when the necessary filter is placed at the light source. In many cases the difficulty can be overcome by removing the light-source filter and inserting a perforated gelatin filter between the slide and the upper surface of the condenser lens. The filter is prepared by punching holes in a 1 cm wide strip of gelatin with a sharp needle and then gluing the filter to a piece of cardboard to serve as a handle. To manipulate, the condenser is lowered slightly, the filter inserted under the slide and moved until one of the tiny holes serves as a window and directly illuminates the dense portion of the section; then the condenser is raised to its normal position, thereby holding the filter in place. Thus, depending upon th light value of the filter, the ...

Application of Fine Grain Processing and Condenser Illumination Enlarging to Photomicrography

Photomicrographs involving great resolution are usually made by means of long initial projection. This involves the use of heavy, often cumbersome, apparatus designed to eliminate vibration. This paper evaluates the possibility of using an intermediate projection distance equal to or greater than 160 mm., which is considered the minimum efficient distance, and recording the initial negative image in very fine grain. Then by critical enlarging a positive image is obtained which closely approaches the resolution obtainable by the finest long projection equipment. The initial short projection permits elimination of vibration difficulties attending long exposures so that critical printing at magnifications above 2000 × will give consistently good results, provided fine grain technic is mastered by the operator.