Substances essential for a red, far-red light reversible attachment of mung bean root tips to glass.

In a recent publication (5), I reported that several substances are necessary for barley root tips to show a rapid photoreversible attachment to wet glass surfaces. These substances are: 3-indoleacetic acid (IAA), adenosine-5'-triphosphate l(ATP), L-ascorbic acid (AA), Mnn2+, Mg2+, and K+. Since mung bean root tips also show a tendency to adhere to wet glass surfaces, their requirement for these factors was investigated in red and in far-red light. All these substances plus Ca 2 were found to be necessary for the rapid photoreversible attachment of mung bean root tips. After soaking for 8 hr in deionized water, mung bean seeds (Phaseolus aureus L, var. Oklahoma 612) were germinated and grown in darkness at 230 as described in the previous paper (5). Three days later, the seedlings were exposed to dim white light for at least 1 hr before excision of root tips. Ten 1-mm tip sections were cut off and placed in a glass beaker containing 10 ml of solution of the following composition: Na. ATP, 4 X 10-6 M; IAA, 10-10 M; AA (ascorbic acid), 1,0-6 M; MnCl1, 2 X 10-6 M MgCl], 10-4 M; KClI 1,04 M; CaCl, 10-4 M; and HCl, 7 X 10-5 M. Adhesion of tips to the beaker bottom was scored as described previously (5) using the same 2 light source during 1-min irradiation. Some typical results showing the necessity of each substance for photoreversibility are presented in table I. The first number under each column for a cycle shows the number of tips adhering in red light, and the second the number of tips adhering in far-red light. Good photoreversibility of attachment for several cycles is shown in the complete solution. The tips adhere in red light and detach in far-red