Cultures of plant cells.

Abstract

It has recently been shown by Robbins 1 that excised seedling root tips about 1 cm. in length, when planted in flasks of sterile liquid or agar media, grow to a limited extent to form organized root tissue with secondary and tertiary root branches. It is interesting to note that no one has observed a tendency for these plant cells to separate as animal cells separate from fragments placed in a nutrient medium. In a recent series of experiments it has been found that the individual plant cells will separate and migrate away from the fragments if the fragments are of a definite size and are cut from a definite part of the plant. This migration is in every way similar to that seen in animal cells.

Squash tissue was used for this study. Seedlings were grown aseptically and fragments of primary meristematic tissue were excised from the root tip for culture. They were planted in a drop about 1 mm. thick of a nutrient salt medium similar to Pfeffer's, with the addition of 0.04 per cent peptone, 2 per cent dextrose and 0.6 per cent agar, and kept in the incubator at 27°C. The reaction of the medium was pH 5.6. The size of the fragments varied in diameter from 0.3 mm. and 2.5 mm. From fragments of this tissue 0.4 to 1.0 mm. in diameter the cells reacted like the cells of higher animals. Pieces of tissue 1 mm. or greater in diameter, on the other hand, grew to form organized root tissue having a length often as much as 8 to 10 mm.

In animal tissue Burrows has shown that the rate of cell migration and growth is related to the size of the fragment, the original cell density of the fragment, and the original blood supply.