One-seeded Fruits Research Articles

Floral development in the legume tree Colophospermum mopane, Caesalpinioideae: Detarieae

Abstract Floral ontogeny of Colophospermum mopane (Kirk ex Benth.) Kirk ex J. Leonard, an apetalous member of the Crudia group with four sepals and a large number (20–25) of stamens, was studied as part of a larger project on reproductive biology of this much-utilized tree. The flowers have been described as being inserted in the axil of a bract, but lacking lateral bracteoles. Four outer, light cream or white «sepals» are present. The first two sepals are initiated in a lateral position, where the bracteoles, if present, develop in other members of the Caesalpinioideae. The inner sepals arise simultaneously adaxially and abaxially. These four structures, conventionally regarded as sepals, enclose the bud. The outer two «sepals» should be regarded as lateral bracteoles inserted at the apex of the pedicel. The inner structures represent the only two sepals. The large number of stamens arise on a large meristematic surface and different whorls were not observed. The filaments elongate within the bud and after anthesis become exposed outside the flowers. The filaments are of equal length and the large anthers form a suspended cluster. One carpel develops terminally and gives rise to an indehiscent one-seeded fruit.

Reproductive biology of the andromonoecious shrub Trevoa quinquenervia (Rhamnaceae)

Abstract Various aspects of the reproductive biology of the andromonoecious shrub Trevoa quinquenervia Gill. & Hook. were studied in a population located in central Chile. Flowering extends from mid August to the end of December. The small, white, entomophilous flowers are incompletely protandrous and last c . 5 days. A weak, pleasant odour along with nectar and pollen attracts 17 diurnal insect species, seven of which are probable pollinators: these include Diptera (Syrphidae and Bombyliidae), Hymenoptera (Apidae and Colletidae) and Coleoptera (Melyridae). Besides perfect flowers T. quinquenervia individuals possess c . 10% staminate flowers, which are lighter, seem to be shorter-lived, and show a smaller gynoecium with abnormal ovules. Reproduction is exclusively sexual and apparently xenogamous, with pollen transfer depending on insect vectors. Although flower morphology and individual flower phenology do not fully prevent self-pollination (and geitonogamy can easily take place) the level of autogamy is low. Therefore, some self-incompatibility mechanism seems operative in this species. Fruit set of open-pollinated flowers is 6.6%, and ripe fruits contain on average 0.66 viable seeds. Predispersal (maternal) reproductive success (percent ovules becoming viable seeds) is 1.45%. For medium to full-sized individuals this corresponds to c . 2600 to 8600 potential offspring per year. Beyond the production of male flowers, four other aspects of the species» reproductive biology seem directed to enhance pollen export, partly implying increased male allocation: (a) a high pollen:ovule ratio, (b) protection of anthers against pollen-robbing by means of the cucullate petals, (c) secondary pollen presentation in a hairy barrier located above the nectary, and (d) a reduction in female allocation achieved by the regular abortion of two out of the three ovules in each ovary, thus producing a mostly one-seeded fruit provided with a thin, energy-poor pericarp. It is proposed that the advantages of enhanced pollen flow for a self-incompatible organism, which is moreover structured in isolated populations, might explain the increased male effort, including the joint evolution of andromonoecy and one-seededness.

Reproductive biology of the andromonoecious shrubTrevoa quinquenervia(Rhamnaceae)

Various aspects of the reproductive biology of the andromonoecious shrubTrevoa quinquenerviaGill. & Hook. were studied in a population located in central Chile. Flowering extends from mid August to the end of December. The small, white, entomophilous flowers are incompletely protandrous and lastc. 5 days. A weak, pleasant odour along with nectar and pollen attracts 17 diurnal insect species, seven of which are probable pollinators: these include Diptera (Syrphidae and Bombyliidae), Hymenoptera (Apidae and Colletidae) and Coleoptera (Melyridae). Besides perfect flowersT. quinquenerviaindividuals possessc. 10% staminate flowers, which are lighter, seem to be shorter-lived, and show a smaller gynoecium with abnormal ovules. Reproduction is exclusively sexual and apparently xenogamous, with pollen transfer depending on insect vectors. Although flower morphology and individual flower phenology do not fully prevent self-pollination (and geitonogamy can easily take place) the level of autogamy is low. Therefore, some self-incompatibility mechanism seems operative in this species. Fruit set of open-pollinated flowers is 6.6%, and ripe fruits contain on average 0.66 viable seeds. Predispersal (maternal) reproductive success (percent ovules becoming viable seeds) is 1.45%. For medium to full-sized individuals this corresponds toc. 2600 to 8600 potential offspring per year. Beyond the production of male flowers, four other aspects of the species» reproductive biology seem directed to enhance pollen export, partly implying increased male allocation: (a) a high pollen:ovule ratio, (b) protection of anthers against pollen-robbing by means of the cucullate petals, (c) secondary pollen presentation in a hairy barrier located above the nectary, and (d) a reduction in female allocation achieved by the regular abortion of two out of the three ovules in each ovary, thus producing a mostly one-seeded fruit provided with a thin, energy-poor pericarp. It is proposed that the advantages of enhanced pollen flow for a self-incompatible organism, which is moreover structured in isolated populations, might explain the increased male effort, including the joint evolution of andromonoecy and one-seededness.

Ruptiliocarpon (Lepidobotryaceae): A New Arborescent Genus and Tropical American Link to Africa, with a Reconsideration of the Family

A new genus and species of trees from Costa Rica and northern South America, Ruptilio- carpon caracolito, is described and compared to the African Lepidobotrys. It is distinguished from Lepidobotrys primarily by its much shorter fila- ments, basifixed rather than versatile anthers, its lack of styles, its two-rather than three-locular ova- ry, and by its irregularly dehiscent fruits with a woody exocarp and cartilagineous endocarp. In wood anatomy, apart from the presence of vestured pits in Ruptiliocarpon, the two genera are remarkably similar. They match in important floral and fruit characteristics (dioecious; 5 + 5 stamens of unequal length with filaments fused at base; two apical, col- lateral ovules per locule; one-seeded fruit; black seed with a large red aril and no endosperm), and both have unifoliolate leaves with very fugaceous stipules and stipels, and leaf-opposed inflorescences. The familial placement of Lepidobotrys has been con- troversial: the genus was placed first in the Linaceae by Engler, then in the Oxalidaceae by Hallier, then in its own family (between Linaceae and Erythrox- ylaceae) by Leonard, and then again in the Oxali- daceae by Cronquist. Reviewing evidence, old and new, we maintain Ruptiliocarpon and Lepidobo- trys (only) in the Lepidobotryaceae and suggest that they relate more to Sapindales or possibly Euphor- biaceae than to Oxalidaceae.

Seedling Establishment from One- and Two-Seeded Fruits of Cryptantha flava: A Test of Parent-Offspring Conflict

This study uses the relative performance of one- and two-seeded fruits of the semidesert perennial Cryptantha flava to evaluate an earlier hypothesis that the parent plant and its offspring conflict over optimal seed number per fruit (brood size). Under this hypothesis, parents should favor large brood sizes in order to increase offspring number and reduce the amount of pericarp required per seed, whereas each offspring should favor increasing its own mass at the expense of other brood members. The fruits of C. flava, like most multiovulate, indehiscent fruits, commonly mature a single seed, but a few mature more than one. This pattern of seed production has been viewed as evidence that the offspring have won the conflict. The current study shows that in C. flava, a seed (nutlet) initially benefits by being the only one in the fruit. Emergence was greater from seeds of one-seeded fruits than from the smaller seeds of two-seeded fruits, but two-seeded fruits were more likely to yield at least one seedling. On the basis of these data, the parent and offspring have different optimal brood sizes. However, the number of offspring resulting from the multiplicative effects of emergence and survival did not differ for the two fruit types. At one of two sites, higher mortality occurred among individuals growing in pairs than among single individuals. Several reasons are presented, in addition to the possibility of sibling competition, for why the parent could also favor bearing mostly single seeds. Whether a trade-off exists between brood size and number of fruits per plant must be determined before the potential for parent-offspring conflict can be fully evaluated.

Fruchtbiologische Untersuchungen an Heliotropioideae (Boraginaceae).: I. Die Ontogenie der monospermen Früchte von Heliotropium supinum L.

Ontogeny, morphology, and anatomy of the one-seeded fruit of Heliotropium supinum have been investigated by LM and SEM. Prior to anthesis the bicarpellate gynoecium develops symmetrically. Four basal septa build chambers which completely surround the ovules and separate them from each other. After anthesis usually only one ovule from the abaxial carpel develops into a fertile seed. Around this seed the outer wall of the gynoecium and the adjecent basal septa develop into the typical pericarp of a Heliotropium nutlet. The other nutlets crush. The sclerified endocarp is made up by the inner epidermis and additional cell layers originating from the inner subepidermal layer. The mesocarp is parenchymatous and constitutes an apical solid hump by which the stylar base is overtopped. The exocarp is one-layered.

Synchronized dichogamy and dioecy in neotropicalLauraceae

In hermaphrodite neotropicalLauraceae a highly evolved dichogamous system is present which represents a kind of temporal dioecy. This system involves the existence of two flower morphs which are characterized by reciprocal phases of receptivity of the stigmas and pollen release. In some genera (Persea, Cinnamomum), nectar is produced as a reward for the flower visitors, while in other genera (Aniba, Clinostemon, Licaria), nectar is absent and pollen seems to be the only reward. This implies that in this case the flowers in the female stage must be deceptive flowers. In dioecious species of the generaOcotea andNectandra, both the male and female flowers attract the visitors with nectar. The pollen-ovule ratio of theLauraceae is comparatively low. — The type of reproductive system that characterizes theLauraceae, comprising functional dioecy, small, inconspicuously coloured flowers, pollination by small bees, and large, one-seeded fruits dispersed by birds, is quite prominent among trees of various families in the tropical lowland forest. The relationship between the different modes of flowering within theLauraceae and the causes for the correlation of their reproductive traits are discussed.

A New Catostemma (Bombacaceae) from Colombia

A new tree species from Colombia, closely resembling other members of the neotropical genusCatostemma in its large one-seeded fruits, is described and illustrated.Catostemma digitata has palmately compound leaves, previously unknown in mature individuals of this genus.

Seed reserves and seed germination for two seagrasses, Halodule wrightii and Syringodium filiforme, from the western Atlantic

Seeds of Halodule and Syringodium from diverse sites in the western Atlantic showed low rates of germination over extended periods of time. Seeds of Halodule are suited to long-term dormancy, possibly extending over many years, while those of Syringodium are oriented toward short-term dormancy. For Halodule, dormancy involves both seed coats and embryos, but for Syringodium, it probably involves only seed coats. Germination for both seagrasseoccurs in a wide range of salinities: 5–50‰ for Halodule; 20–50‰ for Syringodium. One-seeded fruits of Halodule are produced at rhizome level and remain buried in the sediment until disturbed and constitute a seed reserve estimated at a maximum of ca. 3000 m −2 in both Texas in the U.S. Virgin Islands. Syringodium fruits (one-seeded) are produced on inflorescences elevated above the sediment at a maximum rate of ca. 10 000 m −2, but few reserves in the sediment were recorded. The dormancy of seagrass seeds permits germination over extended periods of time and allows survival in disturbed sites as well as colonization of new habitats.

Seed Predation and Seed Number in Scheelea Palm Fruits

Two Scheelea palm populations in Central America were studied: Scheelea rostrata in Costa Rica and Scheelea zonensis in the Panama Canal Zone. Most of the fruits in both populations contained one seed, but small proportions of the fruits on each tree contained two or three seeds. Compared to single—seeded fruits, seedlings from multiseeded fruits are apparently disadvantaged because of less endosperm and competition among seedlings emerging from the same indehiscent fruit. However, since seed predation of Scheelea is heavy, we hypothesized that differential seed predation may counteract this selection pressure against the production of multiseeded fruits and thus maintain multiseeded fruits in Scheelea populations. At least 61% of the fruits in the Costa Rica population and 81% of the fruits in the Canal Zone population were attacked by seed predators. Beetles (Family: Bruchidae) were the predominant predators in the Costa Rica population (84% of attacked fruits), whereas rodents predominated in the Canal Zone population (78%of attacked fruits). Attack by rodents was independent of seed number, but data from Costa Rica suggested that bruchids concentrated predation slightly on one—seeded fruits. Because seed predators were often restricted to one seed, seed survivorship in attacked fruits was directly related to seed number (0%, 22%, and 41% for attacked 1—, 2—, and 3—seeded fruits, respectively, in the Costa Rica population). As a result of an interaction of these aspects of predation, the proportion of seeds that escaped predation was also directly related to seed number (39%, 54%, and 60% for 1—, 2—, and 3—seeded fruits, respectively, in the Costa Rica population). The major difference in predation between the two populations appeared to be the predominance of bruchid predation in the Costa Rica population, which allowed a greater survivorship in attacked multiseeded fruits (29% survivorship of bruchid attack versus 12% survivorship of rodent attack). This apparent stronger selection pressure for producing multiseeded fruits coincided with a significantly greater proportion of multiseeded fruits in the Costa Rica population (27%) compared to the Canal Zone population (6%). These findings support the hypothesis that seed predation is a significant factor in maintaining multiseeded fruits in Scheelea populations.

Heat-treatment dependent dormancy in seeds ofPsoralea corylifolia Linn.

The intact seeds ofPsoralea corylifolia which are actieually one-seeded fruit, presents a unique problem of dormancy. Germinability of these dormant seeds is not enhanced as a result of a number of treatments: 1) Dry-storage of 44 months under moderate conditions of the laboratory. 2) Periodic germination in different months of the year. 3) Immersion in ethylalcohol (70% and 100%), hydrogen-peroxide, nitric acid, acetone, ether solvent and hydrochloric acid. 4) Removal of pericarp.

Heat-treatment dependent dormancy in seeds ofPsoralea corylifolia Linn.

The intact seeds ofPsoralea corylifolia which are actieually one-seeded fruit, presents a unique problem of dormancy. Germinability of these dormant seeds is not enhanced as a result of a number of treatments: 1) Dry-storage of 44 months under moderate conditions of the laboratory. 2) Periodic germination in different months of the year. 3) Immersion in ethylalcohol (70% and 100%), hydrogen-peroxide, nitric acid, acetone, ether solvent and hydrochloric acid. 4) Removal of pericarp. Four distinct methods have also been evolved which effectively overcome the dormancy of the seeds: 1) Mechanical puncturing of seedcoverings. 2) Sulphuric acid treatment. 3) High temperature treatment. 4) Weathering of seeds. Germination-behaviour of the latter 4 lots of seeds is compared and ecological significance of the reported dormancy mechanism is discussed.

Morphological and Physiological Studies on Subterranean Fructuation of Legume Crops : II Occurrence of one-seeded fruit induced by fertilization failure in peanut : III Fertilization and fruit formation performed by underground flower of peanut

One-seeded fruit of peanut (Fig. 2) is induced by the abortion of one of two ovules due to fertilization failure (Fig. 3). So far as the varieties used in this investigation are concerned, the abortion exceeded slightly at the upper ovule over that at the lower one and was about 8∼10% in sum in the case of normal flower, whereas a greater frequent occurrence of abortion was found at the lower ovule and resulted in one-seeded fruit of 15∼20% as total (Table 2, 3) in the case of underground flowers (Fig. 1). Besides the one ovule abortion, the underground flower contains also a tremendously high rate of non-fertilization of two ovules involved, inducing the failure of gynophore formation (Table 5) Such total damage of two ovules was caused by the extreme scarcity of pollen-set on stigma as well as the imperfect elongation of style retaining the stigma within staminai tube (Table 6). The above-mentioned behavior performed by underground flowers may be explained from their special surroundings and the abnormal flower structure.

Seed Frequencies in Cytisus and Peltandra

The seed distribution in a sample of Cytisus scoparius pods was found to be the same as that observed by earlier workers. Similar counts for Peltandra virginica fruits showed the one-seeded fruits to be most numerous, as previously reported, and indicated that there was a larger proportion of fertile fruits in a sample collected in Maryland than in one from Massachusetts.