Mechanical Resistance of the Seed Coat and Endosperm during Germination of <i>Capsicum annuum</i> at Low Temperature

Abstract

Decoated pepper (Capsicum annuum L. cv Early Calwonder) seeds germinated earlier at 25 degrees C, but not at 15 degrees C, compared to coated seeds. The seed coat did not appear to impose a mechanical restriction on pepper seed germination. Scarification of the endosperm material directly in front of the radicle reduced the time to germination at both 15 degrees C and 25 degrees C.The amount of mechanical resistance imposed by the endosperm on radicle emergence before germination was measured using the Instron Universal Testing Machine. Endosperm strength decreased as imbibition time increased. The puncture force decreased faster when seeds were imbibed at 25 degrees C than at 15 degrees C. The reduction in puncture force corresponded with the ability of pepper seeds to germinate. Most radicle emergence occurred at 15 degrees C and 25 degrees C after the puncture force was reduced to between 0.3 and 0.4 newtons.Application of gibberellic acid(4+7) (100 microliters per liter) resulted in earlier germination at 15 degrees C and 25 degrees C and decreased endosperm strength sooner than in untreated seeds. Similarly, high O(2) concentrations had similar effects on germination earliness and endosperm strength decline as did gibberellic acid(4+7), but only at 25 degrees C. At 15 degrees C, high O(2) concentrations slowed germination and endosperm strength decline.