Last month, as Fujitsu began selling lettuce from the Aizu-Wakamatsu plant, Toshiba Corp. said it would begin growing vegetables inside a floppy disk factory near Tokyo that hasn’t been used for two decades. Later this year, Panasonic Corp. will start selling computer-program controlled greenhouses to grow spinach and other vegetables. And Sharp Corp. last year began laboratory tests to grow strawberries at an indoor site in Dubai using its lighting and air-purifying technologies.