The Ecology of Mezzettia leptopoda (Hk. f. et Thoms.) Oliv. (Annonaceae) Seeds as Viewed from a Mechanical Perspective

• Published in: Functional ecology 1991-01, Vol.5 (4), p.545-553
• Main Authors: Lucas, P. W., Lowrey, T. K., Pereira, B. P., Sarafis, V., Kuhn, W.
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Annonaceae; Beetles; Biological and medical sciences; Cotyledons; Fracture mechanics; Fracture strength; Fruits; Fundamental and applied biological sciences. Psychology; Germination; Plants; Predators; Seeds; Turgor pressure
• ISSN: 0269-8463; 1365-2435
• DOI: 10.2307/2389637

Mechanical factors relevant to the germination and predation of Mezzettia leptopoda (Hk. f. et Thoms.) Oliv. (Annonaceae) seeds are described. The seed shell is composed of two types of sclerenchyma. Intertwining fibres predominate but roughly isodiametric cells are found in a narrow band encircling the seed. At one end of the band is a woody plug partially separated from the shell. The cotyledons of the mature seed are in the same plane as the band and are apparently saturated with water. An analysis based on fracture mechanics suggests that the band and plug probably act to allow a clam-like shell opening in germination due to turgor pressure of the cotyledons while minimizing the chance of predation on the seed. A circular channel intervening between the cotyledons and band acts as a crack-stopper to prevent the embryo from peeling away from the endosperm. The complexity of shell structure is most plausibly a defence against those megafaunal (mammalian) predators that crack the shell rather than microfauna which abrade it and for whom the shell probably presents a more homogeneous obstacle.