5. Sucrose storage in corn stalks.

Several lines of corn have been investigated during the past year to determine the extent of sucrose storage in the stalk after maturation of the ear. Selfed single ear progenies of C103, Ind. 38‑11‑2A, Ind. 38‑11‑CtS1CtS3, and T1 inbreds were grown and the stalk press‑juice analyzed for reducing sugars and sucrose by the method of Shaffer‑Somogyi. Along with the chemical analyses, the percentage of total solids in the press‑juice was obtained using a Bausch and Lomb hand refractometer. The refractometer readings were compared with the sucrose content and a correlation coefficient of 0.79 calculated. Since there is such a high correlation it is possible to obtain a fairly accurate estimate of sucrose production and storage by using the hand refractometer. By so doing it is possible to analyze many more plants than would be feasible chemically.

The mean refractometer readings found for the lines investigated are given in Table 1.

The results for the C103 plants are not markedly different from the plants analyzed at New Haven (10.8 to 15.3 for 32 plants) and at Yaphank (10.0 � .67 to 15.1 � .29) reported by Singleton in last year's News Letter. Row 640 which was a greenhouse progeny of 610 gave refractometer readings comparable to those of 610.

The chemical analysis of the stalk press‑juice of the T1 line substantiated earlier findings that the sugars present in this line are mainly reducing sugars and not sucrose. An analysis of 20 samples of T1 showed reducing sugars and sucrose contents of 3.5% and 1.4% respectively. This gives a value of 2.5 for the ratio of reducing sugars to sucrose. The chemical analysis of 22 samples of C103 (Row 610) showed reducing sugars and sucrose contents of 1.3% and 6.8% respectively or a ratio value of 0.2. Further studies will be conducted to determine the cause of this pronounced difference.

Other studies concerning sucrose formation and translocation are being planned utilizing C14 as a tracer. One problem of interest concerns the ability of the plant to translocate sucrose from the leaf to the stalk against an apparent concentration gradient.

Table 1. Mean refractometer readings of mature field corn (Su Su) inbreds

Row	Pedigree	No. of plants	Mean refractometer reading % total solids
609	C103	25	8.3 � 0.50
610	C103	25	12.2 � 0.44
640	C103 (progeny of 610)	20	11.3 � 0.84
641	C103	20	12.0 � 1.00
658	C103	23	10.7 � 0.50
692	C103	22	14.0 � 0.58
693	C103	22	15.5 � 1.10
638	Ind. 38‑11‑2A	21	4.9 � 0.59
639	Ind. 38‑11CtS1CtS3	20	4.8 � 0.47
659	T1HP	20	6.9 � 0.51

Robert Van Reen