Complex sentence: In many local markets, the demand for hydroponically grown watercress exceeds supply, partly because cress leaves are unsuitable for distribution in dried form, and can only be stored fresh for a short period.
Split into simpler sentences: In many local markets, the demand for hydroponically grown watercress exceeds supply. This is because, in part, cress leaves are unsuitable for distribution in dried form, and can only be stored for a short period.