SECRETARY’S REPORT 109 
of their protochlorophyllide synthesizing ability. Adding certain 
carbohydrates at optimal concentration or leaving one cotyledon 
attached prevented the loss of synthesizing ability. When sucrose was 
supplied as a substrate, the determination of carbohydrates within the 
leaves revealed a marked increase in reducing sugars and starch, indi- 
cating a rapid utilization of the products of phosphorolysis of sucrose. 
Determination of the specificity of carbohydrates causing a stimula- 
tion of pigment synthesis and of their rates of metabolic utilization re- 
vealed that, of a dozen or more sugars varying from 38 to 18 carbon 
atoms, glucose at a concentration of 0.20 to 0.25 mole was most effective. 
This was found both through direct measurement of protochlorophyl- 
lide synthesis and by manometric measurements of respiration on tis- 
sues supplied with various carbohydrates. Technics are being 
developed for the isolation of proplastids and the measurement of 
their subsequent photomorphogenic development into mature 
chloroplasts. 
During the course of our investigation of light-induced develop- 
mental changes in plants, one of our reported observations was that 
the lag phase in chlorophyll synthesis in etiolated bean leaf tissue could 
be eliminated by pretreating the leaves with low irradiances of mono- 
chromatic red or blue energy. The study of the lag phase of chloro- 
phyll synthesis has been continued, and it has been demonstrated that 
X-irradiation of 5-10 kiloroentgens can increase the lag phase in 
etiolated bean leaves. Subsequent exposure to 10 minutes of white 
light initiated recovery of the chlorophyll synthesizing mechanism. 
Iixperiments are in progress to ascertain whether the recovery is a red- 
or blue-sensitive reaction and whether nonionizing radiation can coun- 
teract the effect of ionizing radiation in chlorophyll synthesis. 
Radiant energy in the spectral region of 710 to 820 my significantly 
increases the frequency of chromosomal aberrations when used as a 
supplement to X-irradiation. Biochemical studies are being pursued 
to investigate the mechanism of the eflect of far-red (710-820 mp) on 
the rejoining of chromosomes. 
Three new members of the research staff of the Division are: Dr. 
Edward C. Sisler, biochemist; Dr. Walter A. Shropshire, Jr., bio- 
physicist; and Dr. Maurice M. Margulies, biochemist. Dr. Sisler 
comes to the Smithsonian Institution from Brookhaven National Lab- 
oratory where he was engaged in photosynthesis studies. Dr. Shrop- 
shire returns to the Division from the California Institute of Tech- 
nology, where he worked on action and transmission spectra. Dr. 
Margulies was formerly at Johns Hopkins University, where he was 
investigating photosynthesis and the biochemistry of micro- 
organisms. 
