A Squash Technique for Chromosome Morphological Studies

Abstract

ANY different methods of making squash preparations for chro-M mosome studies have been described. These involve the application of various chemical and physical agents for the pretreatment and fixation of the dividing cells. A good technique should permit the chromosomes to become well spread during the squashing, and, at the same time, the fixation should bring out the details of chromosome morphology as distinctly as possible. Well spread chromosomes with a clear morphology are essential for karyotype studies and chromosome measurements. It is much more difficult to make good preparations from some species than from others. The grasses do not belong to the easiest materials in this respect. The root tips are hard and difficult to squash due to the failure of the cells to separate readily from one another, even after prolonged hydrolysis in normal HCI, or repeated heating in the acetic stains (PIENAAR, 1955).During a study of the karyotypes of some species and hybrids of Agropyron a number of different techniques were tried. These experiments involved pre-fixation treatment, methods for fixation and staining, and also the maceration technique to be used in order to make the roots sufficiently soft for squashing. The cytological results of the study on the Agropyron chromosomes are given elsewhere (HENEEN, 1952 b). The present paper is concerned only with the technical aspects of producing the squash preparations. Satisfactory results for chromosome morphology were obtained when we used a technique involving oxyquinoline as the pretreatment agent combined with a new fixative. The Feulgen stain was used and pectinase was employed as the softening agent.The roots are treated with a solution of 8-hydroxy-quinoline before

A Natural Homoploid Hybrid between Centaurea horrida and Centaurea filiformis (Asteraceae) as Revealed by Morphological and Genetic Traits

“…Samples were hydrolyzed in 1N HCl for 12 min at 60°C and stained with Schiff's reagent (Feulgen and Rossenbeck 1924) at room temperature for 30 min. The samples were mounted in a drop of acetocarmine according to Östergren and Haneen (1962). Preparations were made permanent by ethanol-dehydration and mounted in Canada balsam, and observed using a Zeiss microscope.…”

Karyomorphometric analysis of Fritillaria montana group in Greece

“…The cytological study is based on the squash technique and the chromosome counts were made from root tip metaphases (Östergren and Heneen 1962, Kamari 1976). The root tips were pretreated in a mixture of 1:1 8-hydroxyquinoline (0,002% w/v):colchicine (0.3 w/v) for 3 hrs (Kamari 1984a) and fixed in 3:1 (v/v) absolute ethanol:glacial acetic acid for 24 hours at 4 °C.…”

Biosystematic study of 11 plant taxa from Cyprus

“…Vouchers are deposited in UPA. Chromosome counts were obtained from root tip metaphases, using the squash technique (Östergren and Heneen 1962) with some small modifications. Root tips were pretreated for 6 h in an 1:1 mixture of 8-hydroxyquinoline (0.002% w/v):colchicine 0.2% w/v.…”