Dry Fruits

Dry fruits

  • Dehiscent fruits split open to release the mature seeds. These fruits have sutures or weakened seams that break to allow the fruit to open

    • ex: follicles, legumes, capsules

  • Indehiscent fruits do not break open

Dehiscent fruits

  • can have either 1 carpel or many carpels

    • 1 carpel

      • follicle: a simple, dry, dehiscent fruit that splits along one suture (ex: milkweed, magnolia)

      • legume: a simple, dry, dehiscent fruit that splits along 2 sutures

    • 2+ carpels

      • capsule: a compound, dry, dehiscent fruit with 2+ carpels, the fruits typically split open along the sutures, which correspond to the number of carpels, very common fruit type in trees

Indehiscent fruits

  • Indehiscent fruits do not split open at maturity

  • Nut: has an ovary with 2+ carpels, but fruit usually one-seeded with a hard wall; sometimes partially or entirely encased in a husk; small examples include nutlets

  • Samrara: small, one-seeded, with a wing

  • Achene: small, one-seeded, unwinged; includes all members of Asteraceae

  • Caryopsis: very small, seeds inside and do not separate from ovary wall, only found in Poaceae

Fruit dispersal

  1. Water

  2. Gravity

  3. Animals

  4. Wind

Fruit dispersal and evolution

  • Why disperse?

    • evolutionary benefits, as well as costs, to different dispersal mechanisms, some trees have more than one dispersal method

  • Convergent evolution: different organisms with develop mechanisms that function in the same way. So different fruit types may have similar structures that enable them to use the same dispersal method

Gravity dispersal

  • Heavy fruits that fall off the tree—dispersal range in small

  • Advantages?

    • good for trees that develop best near the mother tree. shade tolerant species, good soil present, reduces uncertainty of finding suitable habitat

    • enhanced gravity dispersal: explosively dehiscent fruits

Animal dispersal

  • Animals collect the fruit for food; examples include deer, pigs, squirrels, wood ducks, and humans

    • animal carries off but doesn’t eat (buries or plants it)

    • animal eats and deposits seeds in droppings

      • many seeds that have been through the digestive tract have a higher germination rate!

  • Human dispersal of fruits and invasive species

Wind dispersal

  • Includes many tree species. Requires large seed production to maximize chances of success

  • Fruits can contain wing-liken structures that help carry it on the wind

    • Samaras: ovary wall grows out into a wing

    • Other fruit types have a bract that functions as a wing

    • Cone scales in pines can detach with the seed attached