Here is something interesting... The Maya had food forests in which grew everything except corn, squash, and beans. So they obviously grew one of the most light loving plants I know of.. tomatoes. These food forests were known as pet - kot, because of the loose wall of stones around them. These stones I believe were used to increase light levels. For one thing they were not mortared, just stacked on top of each other, in a circle. As well they were only 2 - 3 feet tall. Not tall enough to keep anything out of the garden. And, if it were to mark land why not make the wall smaller? Or even Mortared. Circles are great for reflecting light back on things. Furthermore, the most common stone in the Yucatan Peninsula used by the Maya is Limestone. Limestone is not only white, but it also sometimes contains shiny crystals. The perfect stone for reflecting light back on to the under story, and in the perfect arrangement to receive light and reflect it back at the "under story." Plus the Mayas didn't worship any crops or consider pet - kot sacred, like they thought corn was. So, to me the only logical explanation for the wall of loose stones surrounding their forest gardens was to increase light levels within their food forests, or pet - kot. (pet - kot actually means, wall of loose stones, and they referred to their food forests as "pet - kot".)