A scanning electron microscopic examination of radiation-induced structural changes in potato tubers.

Abstract

Both chemical and scanning electron microscopic (SEM) analyses were done on potato tubers ("Superior" variety) before and after a sprout inhibiting dose (10 Krad) of radiation. The chemical analyses were run to detect any changes in the reducing and nonreducing sugar content as well as any changes in the starch concentration. A colorimetric method using 3,5-dinitrosalicylic acid was chosen to estimate the change in sugar and starch content. The results obtained indicate that radiation caused an increase in the reducing and nonreducing sugar (sucrose) content and a decrease in the amount of starch.

SEM analyses of the number and size of the starch granules within tuber cells showed that radiation caused a significant decrease in both values. There did not appear to be a significant difference in either value when comparing the samples 3 days and 1 week after irradiation. Observation of isolated starch granules from a blended tuber did not show any obvious change in granule surface or size. Irradiated sprout samples did not show a significant decrease in the number or size of the starch granules.

Microscopic examination of the wound periderm did show a decrease in formed cells as a probable result of irradiation. The surface of the irradiated periderm appeared to be smooth and flattened compared to the unirradiated periderm.

SEM analysis of the membrane surrounding the starch granules did not prove to be worthwhile. Transmitting electron microscopic examination of this fraction would be a more useful technique since it will show more detail about the internal structure.