| Summary: | Experiments were carried out over a period of three years to examine the effects of a sprout inhibitor and storage temperature on the storage and post-harvest physiology of yams Dioscorea alata L. and swedes Brassica napus L. The inhibitor used was isopropyl N-(3-chlorophenyl) carbamate (CIPC or chlorpropham). It was found to be effective at a rate of 450 g/1000 kg in controlling sprout growth in swedes stored under laboratory and farm conditions but the development of rots then became the major factor limiting storage life, especially at temperatures above 10°C. CIPC did not seem to affect the normal chemical changes in stored swedes. Friesian bulls were fed CIPC-preserved swedes supplemented with 50% concentrate ration and gave satisfactory growth compared with similar bulls fed on an all-barley diet. The prospects of using CIPC granules commercially to prolong the storage life of swedes stored in conventional clamps are very slim. This is because one of the essential conditions for effective sprout inhibition by CIPC is restricted ventilation, but this also encourages rot development. Cold storage is suggested as a method which would check both sprout growth and rot development and the implications of this are discussed. In yams, CIPC treatment at both 450 and 900 g/1000 kg was without effect on sprouting at 20° and 25°C. Lower temperatures (15° and 10°C) inhibited sprouting even in the absence of CIPC. Below about 10°C, however, yams are susceptible to chilling injury. Membrane permeability changes are said to be among the causative factors. The effects of storage at chilling temperature on subsequent ion absorption, salt retention capacity and respiration confirmed that membrane damage occurred. Ion absorption and salt retention capacity were adversely affected after storage of the tubers at or below 10°C. However, respiration was markedly stimulated after storage at 10°C and became depressed only after 5°C storage. Thus, whilst respiration measurement can be a useful guide to storage history, the most straightforward and immediate check for the occurrence of chilling injury is to test salt retention or absorption against a control sample. In this way chilling injury can be detected long before visual deterioration sets in. Temperature control offers the best prospects of prolonging yam storage and the techniques used in this investigation offer a rapid method of screening yam cultivars to establish minimum storage temperatures together with those higher maximum temperatures at which satisfactory storage may be achieved; for the higher the maximum temperature the more economic cool storage of yams will be.
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