Giant Pumpkins (Cucurbita maxima) have developed a unique vascular transport system. Instead of supplying the carbohydrates made through photosynthesis in the leaves to cells, the phloem vessels of Giant Pumpkins store carbohydrates. This adaptation is what allows these pumpkins to grow so large (the world’s heaviest pumpkin weighed in at over 2,300 pounds!). The change to Giant Pumpkins’ vascular transport system is thought to be due to selective breeding.