2006 Volume 75 Issue 4 Pages 518-525
The viability of the seed-in-shell of groundnut is longer in small-seeded cultivars, and the role of the shell in the viability of the seed of groundnut was examined. Exocarp, mesocarp with vascular bundles, and endocarp were observed in the shell of immature pod. The thickness of exocarp plus mesocarp in very small-seeded cv. Chico was about 60% of that in large-seeded cv. Nakateyutaka, but no marked difference was observed between the two cultivars in the number of cell layers. In mature pods, the mesocarp occupied most of the shell, and a markedly developed sclerenchyma was observed in the innermost layer and around the vascular bundle in mesocarp. The large lysigenous aerenchyma-like space that developed between vascular bundle rows was suggested to play a role in moisture and gas exchange. In the medium—large-seeded cultivar group (22 cvs.), the pod weight, seed weight/pod, volume of seeds/pod, volume of ovarial cavity, pod surface-area, shell weight, volume of shell, and volume of inner space of ovarial cavity of dried mature pod were about twice as large as those in the small-seeded cultivar group (18 cvs.). However, the difference between the two cultivar groups was small in shell thickness, and negligible in shell density. Further studies on the effects of difference in structure and physical characteristics of shell on moisture and gas exchange of the seed are necessary.
