A quantitative and structural comparison of Citrus pollen tube development in cross-compatible and self-incompatible gynoecia

Abstract

Pollen tube development in Orlando tangelo (Citrus paradisi Macf. × C. reticulata Blanco.) was compared within and between cross-compatible pollinations of Orlando pollen on Dancy tangerine (C. reticulata Blanco.) stigmas and self-incompatible pollinations on Orlando tangelo stigmas. Orlando and Dancy gynoecia were morphologically similar but differed slightly in stigma, style, and ovary lengths. Orlando pollen tube development was studied 1, 3, 6, 9, and 12 days after both cross- and self-pollination to record the number of pollen tubes at each of five levels: stigma surface, upper style, lower style, ovary, and entrance into ovules. In the incompatible cross (self-pollinated Orlando), the stigma was the primary region of pollen tube arrest. In the compatible cross (Orlando pollen on Dancy), some pollen tubes penetrated ovules between 9 and 12 days after cross pollination; however, other pollen tubes were arrested in the stigma. Pollen tubes that successfully penetrated ovules in the compatible cross differed morphologically from pollen tubes arrested in both the compatible and incompatible situations. Successful compatible pollen tubes were straight with thin-walled tips and regularly spaced callose plugs behind the growing tips. Many pollen tube abnormalities associated with the self-incompatible pollination of Orlando were also present among arrested pollen tubes from the compatible cross.

Pollen–pistil interactions and early fruiting in parthenocarpic citrus

“…A reduction in the number of pollen tubes has been reported previously in other Citrus species (Kahn and DeMason, 1986). Similarly, a reduction in the number of pollen tubes travelling along the style has been recorded in compatible pollinations in a number of unrelated species (Cruzan and Barrett, 1996;Herrero and Hormaza, 1996), and it is especially noticeable in species where the number of germinating pollen grains is higher than the number of ovules available for fertilization (Hormaza and Herrero, 1994).…”

Cytology of 2N pollen formation and pollen morphology in diploid lotus tenuis (fabaceae)

“…Branched pollen tubes have been reported in different genera; radish, Raphanus raphanistrum L. (Hill and Lord, 1987); Citrus spp . (Kahn and DeMason, 1986); Rhododendron spp. (Williams, Knox, and Rouse, 1982); spinach, Spinacia oleracea L. (Wilms, 1974); Pinus spp.…”

Critical studies on the sexuality of southern Argentinian Ericaceae

“…Pollen germination and the growth of pollen tubes strongly suggest that self-compatibility is the rule, which would be consistent with its classification in a self-compatible family (Fryxell 1957). The fact that these pollen tubes show anomalous growth (coiling and spiralling) within the style and in the ovary loculus instead of following a straight downward course, however, would suggest some kind of self-incompatibility (Williams et al 1982;Kahn and DeMason 1986). It is curious that in this species female sterility does not reside in modification of the stigma but rather in the absence or abortion of ovules.…”