Sexual Systems in Prunus

Transactions of the Linnean Society of London: Botany. Second ser, 1: 338, 362(1875)
On the self-fertilization of plants
Rev. Henslow
Lastly, Prunus spinosa and Padus, as well as Crataegus oxycantha, are proterogynous.
p. 362:
ROSACEAE.—"Our three species of Prunus," writes Sir John Lubbock (l.c. p. 90), "differ somewhat in the relations of the anthers to the stigma. In P. Cerasus (the Cherry) both mature at the same time, while in P. spinosa (the Black Thorn) and P. Padus (the Bird Cherry) the stigma reaches maturity before the anthers; though, as it retains the capability of fertilisation after the anthers have opened, the flowers are doubtless often self-fertilised, which, from the position of the anthers, probably happens more frequently in the Bird Cherry than in the Black Thorn."

The case of Prunus is an interesting one, for it is opposed to the rule that proterogynous flowers are inconspicuous and usually unattractive to insects. The cause of the species of this genus maturing the pistil early is probably in consequence of their flowering early in spring; the temperature not being high, there is no special tendency to stimulate the staminal and coronal whorls, or possibly the glands. It has been elsewhere shown that flowers, usually perhaps intercrossed, will become self-fertilizing in cold weather; so that what takes place abnormally with proterandrous flower becomes normal in the case of Prunus. The same remarks apply to the Apple and Hawthorn, which are proterogynous.

Heideman: Sexual Affinities of Prunus americana (1895)
We know this from the fact that distinct species will sometimes cross, but not freely, in a reciprocal direction. I have myself, within the past ten years, produced hybrids between P. angustifolia and P. Americana; between P. domestica and P. Americana; between P. Besseyi, Bailey (P. pumila Lin.) and P. hortulana, B.; between Cerasus avium var. and P. Besseyi, B. I made several hundred crosses to produce hybrids between our sand cherry (P. Besseyi) and horticultural varieties of Cerasus avium. Pollen of C. avium var. on P. Besseyi invariably proved sterile; reciprocal crosses set fruit, but they failed to germinate, the seed containing only a trace of the aborted ovule. When I finally used the pollen of a proterandrous form of P. Besseyi on a short-styled form of C. avium fertilization was effected and developed a normal fruit, the seed of which germinated and produced an undoubted hybrid. The reciprocal crosses of the same varieties failed to fertilize a single ovule out of over fifty crosses made. I had applied the same principle in the production of hybrids between P. hortulana and P. Besseyi with fair success.

Pollination in Plums (Aug 1896)
F. A. Waugh
According to my own observations the proterogynous forms are relatively common in the Western wild plum, the typical Prunus Americana, and its varieties. Proterandrous forms are infrequent and not pronounced, though Professor Sargent, who makes Prunus nigra separate from P. Americana, mentions proterandry as characteristic of that species. Long-styled forms are rather frequent, but I have not seen the short-styled forms outside Prunus Virginiana and P. serotina.
    The gynodioecious form I have never seen, nor any pronounced suggestion of it; though the andromonoecious form is very common both in Prunus Americana and P. Chicasa. It is only less common among varieties of the Wild Goose group, and may be found among the Japanese varieties, or even among the varieties of Prunus domestica, where it is most unusual. The Marianna plum is also often andromonoecious. A very large proportion of blossoms rated in the succeeding tables as having defective pistils, belong to this class.

USDA Experiment Station Record 63: 139 (1930)
Maintaining the productivity of cherry trees, V. R. GARDNER (Michigan Sta. Spec. Bul. 195 (1930), pp. 27, figs. 11). — Supported by data on fruit bud, fruit spur, and lateral shoot production on different length shoots, on the fruiting performance and growth under different systems of culture and pruning, and on growth response to fertilizers, the author presents a comprehensive discussion on the growth and fruiting habits of the sour cherry from the time of planting to full production.
    The vigorously growing young sour cherry tree forms fruit buds freely, mainly on spurs in some varieties and mainly through lateral fruit buds on shoots in others. In the Montmorency cherry, fruit is formed on both shoots and spurs, and, although this habit may be modified by pruning, yields are thereby reduced and such pruning is therefore undesirable. The general effect of pruning on the sour cherry was to reduce bearing area and yields, despite increasing the vigor of the remaining shoots and branches. Pruning weakened the fruit spurs. Diseases, such as leaf spot, which cause premature defoliation, result in shorter and weaker shoots and less productive spurs. Yields can be maintained by cultural practices which tend to produce shoots averaging 5 to 7 in. in length. Nitrogen fertilizers applied to healthy trees tended to promote shoot growth, enlarge the bearing area, and increase yields. Sod culture was not found desirable, as it tended to slow down growth.

Polish Agricultural Annual. Series A - Plant Production 105(4): 23-40 (1984)
Investigations on morphology of the cherry flower and its androecium biology [cultivars variation; pollen productivity; effect on pollination and yield] [1983]
Wocior, S.; Miculska, A. (Akademia Rolnicza, Lublin (Poland). Inst. Produkcji Ogrodniczej);
Observations on the morphology of flowers of 7 cherry cultivars have proved that the pistil length as well as mutual arrangement of pistil and anther stigmata, flower diameter and inclination of stamina in relation to pistil should be regarded as varietal features. The heterostyly phenomenon occurrence in cherry cultivars has been found. Under field conditions the bursting of cherry anther covers occurred, depending on temperature and relative humidity of air, within 3-12 hours from opening of the flower petals. Anther cover movements and swelling of pollen cause a loosening of pollen mass in anthers, considerably improving their dusting after casual rainfalls and nocturnal dew. Biological phenomena observed affect the flower pollination through the pollen amount regulation in cherry orchard

Biological Journal of the Linnean Society, 50(1): 65-84 (Sept 1993)
Pollination biology of Prunus mahaleb L.: deferred consequences of gender variation for fecundity and seed size
Pedro Jordano
Abstract
This study describes the reproductive biology of Prunus mahaleb, a rosaceous treelet, in a southeastern Spanish population. The species is gynodioecious with 55.4% of the plants being male-fertile and 44.6% presenting non-functional, shrunken anthers with no pollen, and behaving as functional females.

Acta Phytotaxonomica et Geobotanica 52(1): 115-124 (2001)
Dimorphic Nature in Stigma-Anther Separation of Prunus nipponica (Rosaceae)
Satoko Hirata, Takashi Sugawara
Abstract
Stigma height, anther height and stigma-anther separation were studied to examine their dimorphic nature in two populations of Prunus nipponica occurring in sub-alpine zone of Mts. Norikura and Utsukushigahara, central Honshu of Japan. The stigma and anther heights considerably varied among the plants and each of the characters showed normal frequency distributions within populations. However, stigma-anther separation showed a bimodal distribution. Based on this floral character the populations concerned were tentatively divided into two discrete floral morphs: long (L)-styled morph and homo (H)-styled morph. Each of the two morphs was highly constant within a plant and did not change its floral nature for over two years. Artificial pollination experiments indicated that the two morphs were strongly self-incompatible and crosses between the same morphs (HxH or LxL) produced seeds in higher percentage. These results suggest that the dimorphic nature in P. nipponica does not exhibit an ordinary heterostyly but may be regarded as an example of herkogamous polymorphism. We briefly discuss on the possible adaptive significance of dimorphic natures of the flowers exhibited by P. nipponica.

Plant, Cell & Environment 26 : 1673-1680 (2003)
The effect of temperature on stigmatic receptivity in sweet cherry (Prunus avium L.).
Hedhly, A., J. I. Hormaza, and M. Herrero
Plant reproduction is highly vulnerable to environmental conditions such as temperature and, consequently, planet warming may have significant consequences on the reproductive phase with serious implication in agricultural crops. Although pollen tube growth is clearly affected by temperature, little information is available on its effect on the female side and on flower receptivity. In this work, the effect of temperature has been evaluated on stigmatic receptivity of sweet cherry in vivo, in the laboratory, and in planta, in the field. Results herein show that temperature has a clear effect on the duration of stigmatic receptivity. Thus, whereas high temperature reduced stigmatic receptivity, low temperature enlarged it. The stigma lost the capacity to offer support first for pollen penetration, second for pollen germination and, finally, for pollen adhesion. The effect of temperature was more pronounced on pollen germination and penetration than on pollen adhesion. High temperature reduced the germination capacity of the pollen as early as the first day after anthesis, a time when no apparent signs of stigma degeneration are apparent. This clear effect of temperature on stigmatic receptivity and pollen performance may have clear implication in crop performance and in establishing screening criteria of best-adapted genotypes.

Mol Ecol. 14(6): 1821-30. (May 2005)
Mating patterns, pollen dispersal, and the ecological maternal neighbourhood in a Prunus mahaleb L. population.
C. García, J. M. Arroyo, J. A. Godoy, P. Jordano
Abstract
Gender polymorphism, plant-animal interactions, and environmental heterogeneity are the three important sources of variation in mating system and pollen dispersal patterns. We used progeny arrays and paternity analysis to assess the effects of gender type and density level on variation in mating patterns within a highly isolated population of Prunus mahaleb, a gynodioecious species. All the adult trees in the population were sampled and located. The direct estimate of long-distance insect-mediated pollination events was low (< 10%). Gender expression deeply influenced the mating system, decreasing the outcrossing rates (t(m)) and the pollen pool diversity in hermaphrodite trees. Long intermate distances (> 250 m) were significantly more frequent among female mother trees. Variation in local tree density also affected pollen pool diversity and intermate distance, with a higher effective number of fathers (k(e)) and longer intermate distances for female trees in low-density patches. A canonical correlation analysis showed significant correlations between mating variables and the maternal ecological neighbourhood. Only the first canonical variable was significant and explained 78% of variation. Outcrossing rates tended to decrease, and the relatedness among the fathers tended to increase, when mother trees grew in dense patches with high cover of other woody species and taller vegetation away from the pine forest edge. We highlight the relevance of considering maternal ecological neighbourhood effects on mating system and gene flow studies as maternal trees act simultaneously as receptors of pollen and as sources of the seeds to be dispersed.

Botany, 95(9): 913-922 (2017)
Sex morphs and invasiveness of a fleshy-fruited tree in natural grasslands from Argentina
M. R. Amodeo, S. M. Zalba
Abstract
Invasiveness has usually been studied as a species-level attribute; nevertheless, phenotypic differences between individuals in a population can lead to significant variations in colonization ability. In this paper, we analyse the potential effects of sex morphs of Prunus mahaleb L., a gynodioecius fleshy-fruited tree, on its invasiveness in natural grasslands in the southern Argentine Pampas. We assessed the abundance of both hermaphrodite and female plants, and compared their fecundity, propagule size, and germination response. We found that the females were less abundant in the invasive populations studied, apparently since the beginning of the colonization. However, our results demonstrated that at the present time, females do not show any fecundity reduction, which clearly shows that P. mahaleb has established an effective interaction with generalist pollinators that compensates for the apparently disadvantaged females. Fruit set showed a wider range of variability over time in the females than in the hermaphrodites, which could be the consequence of greater susceptibility to changes in the activity of pollinators. We found no evidence of a female benefit due to reallocation of resources or better outcrossed progeny when considering propagule size and germination. We discuss the relative importance of sex morphs and interactions at different stages of the invasion process.

Wikipedia
Prunus geniculata — The species is andromonoecious, with individuals bearing both bisexual and male-only flowers.


proterogynous/protogynous — Having the pistil come to maturity before the stamens.

proterandrous/protandrous — Having the stamens come to maturity before the pistil.

Heterostyly is a unique form of polymorphism and herkogamy in flowers. In a heterostylous species, two or three morphological types of flowers, termed "morphs", exist in the population. On each individual plant, all flowers share the same morph. The flower morphs differ in the lengths of the pistil and stamens, and these traits are not continuous. The morph phenotype is genetically linked to genes responsible for a unique system of self-incompatibility, termed heteromorphic self-incompatibility, that is, the pollen from a flower on one morph cannot fertilize another flower of the same morph.

geitonogamy — fertilization of a flower by pollen from another flower on the same (or a genetically identical) plant.


Fragaria

USDA Experiment Station Record 63: 139 (1930)
Fruit-bud development in strawberry varieties and species, G. F. WALDO (Jour. Agr. Research [U.S.], 40 (1930), No. 5, pp. 393-407, figs. 12). — Of a large number of strawberry varieties and species examined at the United States Plant Field Station, Glenn Dale, Md., only one, Fragaria nilgerrensis, native of northern India, failed to differentiate fruit buds in September and early October. This species did not develop buds until November and is considered potentially valuable for breeding new varieties with adaptability to a wider range of environments than is possessed by existing varieties. Indications of the onset of fruit bud differentiation were observed over a considerable period before actual differentiation could be established. Duration of the period of differentiation varied with varieties, and the rapidity and uniformity of subsequent development were also found to vary considerably. Although no absolute correlation was established between early differentiation of fruit buds and early blooming and ripening and conversely between late development and late blooming and ripening, these correlations did exist in many cases.

USDA Experiment Station Record 63: 139-140 (1930)
Fruit-bud formation in everbearing strawberries, G. F. WALDO (Jour. Agr. Research [U.S.], 40 (1930), No. 5, pp. 409-416, figs. 6). — A companion paper to the above, in which it was found that in everbearing strawberries the fruit that ripens in May and early June apparently develops from fruit buds differentiated the preceding autumn, while that which ripens in July and later develops from buds differentiated during the same season. Instead of continuing runner production throughout the summer, everbearing varieties developed flowering stalks from the leaf axil or more often produced short branches the growing point of which differentiates a fruit bud. This process continues until checked by winter cold. A break in flower stalk production for three or four weeks following the spring crop and favorable environment are suggested as causes for the unusual activity of everbearing varieties in producing runners, new branches, and fruit buds at this season.