Lemon zest cell (Citrus limon), scanning electron micrograph (SEM). The outer lemon rind (lemon peel) contains 'zest' cells that are specialized epidermal cells known as trichomes. Shown here is a cross section through a lemon peel revealing a zest cell as a round, concave structure (highlighted in a different colour). These trichomes are glandular trichomes that secret an oil that gives the lemon peel its tangy flavour. The oil obtained from the peel is used extensively in the perfume industry. Lemons are a rich source of Vitamin C and the fruit juice is used for culinary and non-culinary purposes throughout the world. Lemons are used as commercial source of citric acid and ascorbic acid. Magnification: x35 when shortest axis printed at 25 millimetres.