1. Catalase activity in corn.


a. The catalase activity of leaf tissue of various chloroplast pigment deficient types of corn seedlings growing in a greenhouse was determined by the "catalase tube" method of Knott. The catalase activity of albino seedlings averaged 1.54 ml. of O2 in five‑minute interval, that of yellow seedlings 2.83 ml. and that of green seedlings 10.14 ml.


b. The same chloroplast pigment‑deficient types of corn seedlings grown in the dark showed a catalase activity which was surprisingly high in all cases and which was approximately the same for all of the three types.


c. When the dark‑grown seedlings were exposed to light, there was a rapid photo‑oxidation of catalase, so that catalase values approached that of similar aged light (greenhouse) grown albinos, yellow seedlings and green seedlings, respectively.


d. A series of hybrid strains of corn arranged from darkest green to lightest green showed progressively less catalase activity.


e. Catalase in leaves of corn seedlings was destroyed by temeratures at or above 55C.


f. A comparison of the temperature effects on etiolated and green seedlings of approximately the same age showed the catalase in green ones to be slightly the more heat‑labile or destructible.


g. There seems to be a common thermal effect on catalase, starch synthesis enzyme, and chlorophyll synthesis enzyme. 55 is the critical temperature above which all three enzymes are destroyed. A plausible explanation for this enzymatic destruction is that these enzymes are proteinaceous and are subject to identical thermal denaturation.


h. The catalase activity was found to be quite high in chlorotic corn seedlings grown in greenhouse at 1OC, but did increase somewhat in ones transferred to 25C.