Short answers, pulled from the story.
Lemons most likely originated in northwestern India, with some evidence suggesting the first millennium BC as the period of origin. The fruit is a hybrid of the citron and the bitter orange. From India, lemons spread to Persia, Iraq, Egypt, and eventually across the Mediterranean through Arab agricultural networks between 1000 and 1150 AD.
Lemon juice contains about 5-6% citric acid, which equates to roughly 47 grams per litre. This is slightly more than lime juice, nearly twice the citric acid content of grapefruit juice, and approximately five times that of orange juice.
Lemons arrived in the Americas in 1493, when Christopher Columbus brought lemon seeds to Hispaniola during his voyages. Spanish conquest then spread lemon seeds further across the New World as part of the Columbian exchange of plants.
In 2024, world production of lemons (reported together with limes) was 23 million tonnes. India and Mexico together led production, accounting for 31% of the total, with China and Argentina as secondary producers.
The Eureka is the most common supermarket lemon, also called Four Seasons or Quatre Saisons because it produces fruit and flowers throughout the year. It developed in California in the 19th century from specimens brought during the Gold Rush by immigrants from Naples and Sicily.
In 1747, the English physician James Lind conducted experiments on sailors suffering from scurvy by adding lemon juice to their diets. This was done before vitamin C had been identified as the key dietary component responsible for preventing the disease.