Factors affecting the enzymic destruction of carotene in alfalfa.

In these experiments the term “whole alfalfa” is used to indicate the part of the plant which is harvested in the usual hay-making operation. In all cases in which defrosted tissue was used the material wss frozen at 15” and defrosted immediately before use. In part of the experiments, only the leaves were subjected to treatment, while in others whole alfalfa was used. In all experiments, only the leaves were used for carotene determinations. The carotene content of the fresh leaves was also determined in each experiment. All samples were blanched with steam before carotene determinations were made. Carotene was determined by a modification (2) of the method of Moore and Ely (3). Measurements were made with a Beckman spectrophotometer at 4360 A. E$ect of ModiJication of Cell Structure-In this experiment, 5 gm. samples of alfalfa leaves were divided into three series. Each series was incubated at 37”. Series I-The leaf structure was preserved as nearly as possible in its initial condition by incubating fresh leaves over water in desiccators. By this procedure the leaves were held in an atmosphere saturated with water vapor, which greatly retarded wilting and prevented desiccation. Series g-Fresh leaves were permitted to wilt and to desiccate by incubating in open beakers. Series S-Defrosted leaves, in which cell permeability had been increased by freezing (4), were incubated in beakers which were covered with watchglasses to retard the loss of moisture. Samples of each series were removed at intervals up to 24 hours and were analyzed for carotene. The results are presented in Fig. 1.