Mechanical Resistance of the Seed Coat and Endosperm during Germination of Capsicum annuum at Low Temperature

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Abstract
Decoated pepper (C. annuum L. cv. Early Calwonder) seeds germinated earlier at 25.degree. C, but not at 15.degree. 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.degree. and 25.degree. 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.degree. than at 15.degree. C. The reduction in puncture force corresponded with the ability of pepper seeds to germinate. Most radicle emergence occurred at 15.degree. and 25.degree. C after the puncture force was reduced to 0.3-0.4 N. Application of GA4+7 (100 .mu.l/l) resulted in earlier germination at 15.degree. and 25.degree. C and decreased endosperm strength sooner than in untreated seeds. High O2 concentrations had similar effects on germination earliness and endoserpm strength decline as did GA4+7, but only at 25.degree. C. At 15.degree. C, high O2 concentrations slowed germination and endosperm strength decline.