Proline, which increases proportionately faster than other amino acids in plants under water stress, has been suggested as an evaluating parameter for irrigation scheduling and for selecting drought-resistant varieties. The necessity to analyze numerous samples from multiple replications of field grown materials prompted the development of a simple, rapid colorimetric determination of proline. The method detected proline in the 0.1 to 36.0 ~moles/g range of fresh weight leaf material.Cooperative investigations of D e p a r t m e n t of Grain Science a n d I n d u s t r y , C o n t r i b u t i o n no. 796, a n d E v a p o t r a n s p i r a t i o n L a b o r a t o r y , D e p a r t m e n t of Agronomy, C o n t r i b u t i o n no. 1306, K a n s a s Agricultural E x p e r i m e n t Station, M a n h a t t a n , K a n s a s 66506.

Preliminary tests have shown that the endosperms of maize seeds homozygous for the opaque-2 mutant gene have a higher lysine content than normal kernels. As a critical test, a backcross progeny was divided into opaque-2 and normal kernels, the endosperms separated, and the amino acids determined. The opaque-2 endosperms had a different amino acid pattern and 69 percent more lysine than the normal seeds. The major reason for these changes is the synthesis of proteins with a greater content of basic amino acids in the acid-soluble fraction of the mutant endosperm. This is accompanied by a reduction in the ratio of zein to glutelin.

The mutant floury-2 results in the production of maize endosperm proteins with an altered amino acid pattern. The lysine concentration is high, eapproximately equal to that in mutant opaque-2, and the methionine concentration is higher than in any other stock tested. Other mutants of similar phenotype!, opaque-1, floury-1, and soft-starch do not cause major changes in amino acid Pattern.

Six weanling male rats were fed a diet containing 90 percent opaque-2 maize for 28 days. The average gain in weight was 97 grams. In control rats fed on a standard hybrid maize the average gain was 27 grams. This confirms results of a previous feeding test on rats and demonstrates the superior quality of the proteins in opaque-2 mutant endosperm.

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