In among several perfectly normal sweet potatoes, we came across this rather oddly coloured specimen (see photo). Although all the others were orange, only half of this one had complied, the other half being white. Can anyone explain why this should be and how it happens so perfectly down the length of the vegetable?

Josh Wainwright, Danbury, Essex, UK

Occasionally when reheating broccoli and sweet potato in the microwave, what sounds like violent electrical arcing occurs if the two are in contact with each other. This results in blackened sections. What is going on?

Stephen Plevier, Hadfield, Victoria, Australia