12. Tryptophane, niacin, indoleacetic acid in sugary and starchy.


Interrelationships of tryptophane, indoleacetic acid, and niacin reported in various plants prompted extending assays for these substances to developmental stages of the corn kernel and determining carbohydrates in the same samples for more direct comparison.


In the first series of tests, starchy kernels were obtained from an inbred line KYS and sugary kernels from a closely related sugary KYS conversion having an average of 15/16ths of its germ plasm from KYS.


As work proceeded, irregularities in the results were suspected to be due to differences in the "physiological age" of the kernels from the two types of plants. Differences could be due both to individual plant variation, and to systematic differences between kernels produced on starchy and sugary parent plants. Since starchy and sugary seeds cannat be distinguished until about maturity neither of these sources of error could be eliminated by taking samples from ordinary segregating ears. However, yellow and white seeds can be classified on segregating ears by about the 16th day from pollination. By use of an R4 conversion of translocation 4‑6a carrying su and y the two types of seeds were separated on the basis of endosperm color with only about 4.5 per cent error due to crossing over.


Carbohydrate patterns were essentially similar in the two series, although KYS apparently as a later maturing line attained peaks of the various components from four‑eight days later than the R4. Reducing sugars were higher in sugary than starchy and were highest in both genotypes at 20 and 28 days, the [sic] dropped more rapidly in starchy than in sugary; sucrose was consistently higher in sugary then starchy and decreased sharply after 24 and 32 days; water soluble polysaccharides accumulated rapidly in sugary from 18 to 32 or 34 days, then decreased slightly at maturity; very little water soluble polysaccharide was found in starchy samples at any stage. Carhohydrate patterns are thus in general agreement with published ones.


Niacin increased considerably in starchy between 18 and 24 days, then decreased toward maturity. In sugary it increased somewhat more rapidly to a higher peak at 28 and 32 days and decreased less than starchy at later dates. Indoleacetic acid was also higher in sugary than starchy, although in the KYS series there were points of overlap. Highest indoleacetic acid levels were at 28 and 32 days. At maturity the values were almost identical in starch and sugary for both series. Tryptophane levels were irrgeular in KYS and overlapped. In the R4 series tryptophane was higher for sugary from 20 days through maturity.


These data are consistent with a catalytic role for niacin in carbohydrate metabolism. However, they provide no proof for such a role. The amounts of tryptophane are sufficiently high previous to the rise of niacin and indoleacetic acid levels to account for the quantities of the latter two substances by tryptophane conversion.


H. Teas, Anna Newton, J. W. Cameron, and E. G. Anderson