The development and distribution of chlorophyll in roots of flowering plants grown in the light

Abstract

Seedlings of sixteen different species were used in this experiment. The seeds were germinated and the seedlings allowed to grow in darkness for about two days (except for a few of the species which were 'earth-grown') and than planted out with, their roots passing through holes in a sheet of cork, the cork being supported by four thin glass rods on the rim of a beaker, which was filled with water. The beakers containing the various seedlings were then arranged around a 200 c.p, lamp, in a deep white sink. The electric bulb was suspended in a large glass jar, which was weighted down with lead. and the sink was filled with water until the water was almost on a level with the rims of the beakers. This arrangement werved both to prevent the temperature from becoming too high and to render the illumination as intense and uniform as possible. The roots were kept well aerated by means of a stream of water passing into each beaker from the tap by way of a piece of rubber tubing, from which the water dripped into a small funnel fixed through the centre of the sheet of cork carrying the seedlings.. An overflow from the sink was arranged to prevent the water level becoming too high and so swamping the seedlings. By such means it was possible to keep the seedlings growing in a healthy condition and free from algae for six weeks, if required. Controls were grown in the dark. Experimental Results After about a fortnight's growth in the light, transverse sections were made of the roots of all the species and 13 out of the 16 species were found to have developed chlorophyll. The distribution of the chlorophyll in the roots, as given below. was constant for any given species.