Abstract
We studied the reproductive system of Capparis jacobinae Moric ex Eichler (Brassicaceae), based on controlled hand-pollination and observation of pollen tube growth made in a fluorescence microscope. Of 105 self-pollinated flowers only one produced fruits (success = 0.95%), all the other flowers abscised at the same time, between the eighth and tenth day after anthesis. Nevertheless, self- and cross-pollinated pollen tubes reached the micropyle. The rate of penetrated ovules in self-pollinated flowers was lower during the first 24 h after pollination; thereafter this rate was similar between self- and cross-pollinated flowers for treatments of 48 h, 72 h and 96 h after pollination. In addition, we carried out two indirect estimates of the reproductive system, based on pollen/ovule and seed/ovule ratios, which resulted in typical features of xenogamous species. We concluded that C. jacobinae has a late-acting self-incompatibility system. This is the third record of this mechanism for the genus and the first for a species of Capparis endemic to the Caatinga. We suggest that this self-incompatibility system may occur in other species of the same genus and family.
Highlights
The Caatinga covers an area of about 1,000,000 km2 mainly located in northeastern Brazil
Observations on pollen tube growth in this genus were carried out for only two species: C. pittieri Standl. (Seavey & Bawa 1986) and C. retusa Grisenb. (Bianchi & Gibbs 2000), showing that the pollen tubes formed through selfpollination penetrated the ovule’s micropyle. Most of these ovules did not produce seeds, what was interpreted as a recognition-rejection of pollen tubes coming from selfpollination only when they were already inside the ovules. Species with this mechanism have a reproductive system with late-acting self-incompatibility (LSI)
This system, like conventional ones, such as sporophytic and gametophytic, may be distributed among species from phylogenetically related groups, such as genera or families (Gibbs & Bianchi 1999). Taking into account this feature discussed by Gibbs & Bianchi (1999) and the two preceding occurrences of LSI in the genus, the present study aims to describe the reproductive system of C. jacobinae Moric. ex Eichler and to determine the nature of the incompatibility system through analysis of pollen-tube growth
Summary
The Caatinga covers an area of about 1,000,000 km mainly located in northeastern Brazil. Most of these ovules did not produce seeds, what was interpreted as a recognition-rejection of pollen tubes coming from selfpollination only when they were already inside the ovules Species with this mechanism have a reproductive system with late-acting self-incompatibility (LSI) (sensu Seavey & Bawa 1986). This system, like conventional ones, such as sporophytic and gametophytic (where inhibition occurs in the stigma and style, respectively), may be distributed among species from phylogenetically related groups, such as genera or families (Gibbs & Bianchi 1999). Primo & Machado: A new case of late-acting self-incompatibility in Capparis (Brassicaceae): C. jacobinae Moric. 765
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