关键词：
Plants
Germination
Pollen
Anthers
Corolla
Fruits
Seeds
Calyx
Flowering
摘要：
The reproductive biology of two closely related Ajuga (Lamiaceae) species, Ajuga iva (L.) Schreber and Ajuga chamaepitys (L.) Schreber, was compared. Ajuga iva is a perennial, cleistogamous species that occurs relatively frequently in the southwest of the Iberian Peninsula, while A. chamaepitys is an annual, chasmogamous species that is rarely encountered in the same region. Flowers from the two species are homogamous and self-compatible. However, they exhibit substantial differences in their reproductive behavior. Ajuga iva produces two types of flowers: cleistogamous (CL) flowers that are obligately selfed, and chasmogamous (CH) flowers that are potentially outcrossed. CH flowers are produced in small numbers relative to CL flowers. Ajuga chamaepitys produces chasmogamous flowers only. However, if the flowers are not visited by insects within 1-2 d after anthesis, some changes in the relative disposition of the anthers and stigma lead to self-pollination, a rare occurrence in the Lamiaceae. The fruits produced by the two species are morphologically almost identical and are dispersed by ants. However, they differ significantly in germination, characteristics. Ajuga chamaepitys nutlets germinate under a wide range of conditions and in high proportions; A. iva nutlets, however, only germinate under highly restrictive conditions and at a very low percentage. There are no differences in nutlet dispersion or viability between the two species. These differences in germination characteristics may account for the qualitative and quantitative differences observed between populations of the two species in the southwest Iberian Peninsula.
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