Nothing says summer like a fresh, local, tree-ripened peach. As I was eating one this morning, it broke in two along the pit, exposing the seed inside. This of course is the perfect opportunity for a botany lesson! A peach is a fruit type known botanically as a drupe. Drupes are fleshy with seeds enclosed in hard pits.
My morning snack: peach (Prunus persica, Rosaceae)
In this peach you can easily see all three layers of the fruit wall, known collectively as the pericarp, which develop from the ovary wall of the flower. The outermost layer of the pericarp is the exocarp (also called the epicarp), which you know as the soft, fuzzy skin of the peach. The delicious and very juicy layer in from the exocarp is the mesocarp. The hard, woody pit in the middle is the endocarp (often called the stone in drupes). Inside the endocarp is the seed that is white with a brown seed coat.
In this peach you can also see vascular tissue in the flesh and seed coat (look for the horizontal lines in both) and sap leaking from the broken pit (shiny golden droplets at the right top and bottom of the seed).
It is my understanding that part of the peach pericarp is derived from structures other than the ovary such as the receptacle and sepals(?). Can you clarify which structures form the endo, meso, and epi carp of the peach?
About the seed inside the peach stone . . . it looks a lot like an almond, and I’ve been tempted to eat it whenever I get a peach with the pit broken open, but have never tried.
What does it taste like? Has anyone ever eaten one? Is is poisonous (unlikely)?
A peach is actually entirely derived from ovary tissue, making the entire structure truly a “fruit.” The fuzzy skin of the peach is the exocarp, the fleshy part is the mesocarp, and the bony pit is the endocarp – all of which are derived from the ovary. For an excellently labeled photo of a dissected peach, visit Wayne’s Word at Palomar State University.
Peach seeds, like many other members of the rose family (Rosaceae), contain cyanide and thus eating many of them will result in poisoning (likely only to the point of severe discomfort, but I would not risk it). However, the poisoning risk is probably not why people don’t usually eat peach seeds (since it would require quite a few to do serious damage to your health) – instead, people probably don’t consume them because they are extremely bitter.