Apical Pattern of Fruit Production in the Racemes of Ceratonia Siliqua (Leguminosae :C Aesalpinioideae): Role of POLLINATORS1 (original) (raw)
Related papers
American Journal of Botany, 1999
Fruit production and arrangement within the raceme were studied in two dioecious populations of Ceratonia siliqua (Leguminosae: Caesalpinioideae), an arboreal species that produces caulogenous racemes (emerging only from the old branches) with numerous flowers. Fruit production per raceme was low and similar between years and populations and even between individuals. During flowering, there were considerable flower losses from predation and lack of pollination. A mean of nine flowers per raceme began the transformation into fruits, of which 77% aborted. The final fruit production per raceme increased significantly following hand pollination, but was always very much lower than the availability of flowers in the raceme. The results suggest that fruit production of each raceme is limited by both availability of resources and a deficient pollination. In racemes setting fruit arrangement follows a definite pattern that remains constant between years and populations: fruit production was significantly higher in the apical zone of the raceme and lower in the basal zone. The pollinators of C. siliqua (flies and wasps) showed a clear preference for beginning their visits at the apex of a raceme. As a result, the pollen load deposited on the stigmas decreased from apex to base of the raceme. In most of the flowers situated in the central and basal zone of the raceme, the number of pollen grains deposited on their stigmas was lower than the number of their ovules. The high number of seeds in developed fruits suggests that the plant selectively aborts flowers that receive a smaller pollen load. The results indicate that the final pattern of fruit arrangement within the raceme is a direct result of pollinator activity.
Horticultural Science and Technology
Hylocereus polyrhizus, commonly known as red-fleshed dragon fruit, is an exotic fruit crop whose commercial fruit production depends to a great extent on fruit weight, often with the grower's intervention for optimal fruit production. The purpose of this study was to characterize the floral structure, the morphology of pollen and stigma, and the reproductive process involving pollen-stigma interaction and pollen tube growth in red-fleshed dragon fruit plant grown in an open field using light, scanning electron, and fluorescence microscopy. Flowers of H. polyrhizus typified the floral traits of Cactaceae, in which large and white-coloured flowers with nocturnal anthesis are accompanied by strong floral emission. The extension of floral anthesis also indicated mixed pollination syndromes of nocturnal and diurnal pollinators. Self-incompatibility of the plant is evidenced by spatial segregation of the sexual organs with approach herkogamy and dry-type stigma. Numerous stigma lobes positioned above the anthers create a large area that enhances a large amount of pollen deposition. The highly ornamented, echinate sculpture of the pollen plays crucial roles in the attachment and adhesion of pollen grains on the stigma, and the presence of pellicles on papillae surfaces are specialized adaptations for pollen tube growth in dry-type stigma. The pollen germinated two hours after pollination with pollen tube elongation underneath the papillae tissues. Infertile pollen grains or incompatible pollination can be observed at 1 day after pollination (DAP), as indicated by the collapsed or dehydrated pollen grains, whereas compatible pollen grains travelling downward through the style transmitting tissues were observed at 2 DAP. After pollination, most of the pollen tube took approximately 4 days to reach the ovary cavity and fertilized the ovules leading to eventual fruit set.
Oikos, 2010
Pollination syndromes involve convergent evolution towards phenotypes composed of specifi c scents, colours or fl oral morphologies that attract or restrict pollinator access to reward. How these traits might infl uence the distributions of plant species in interaction with pollinators has rarely been investigated. We sampled 870 vegetation plots in the western Swiss Alps and classifi ed the plant species into seven blossom types according to their fl oral morphology (wind, disk, funnel, tube, bilabiate, head or brush). We investigated the environmental features of plots with functional diversity (FD) lower than expected by chance alone to detect potential pollination fi ltering and related the proportions of the seven blossom types to a combination of environmental descriptors. From these results, we inferred the potential eff ect of the pollinator on the spatial distribution of plant species. Th e vegetation plots with signifi cantly lower FD of blossom types than expected by chance were found at higher altitudes, and the proportions of blossom types were strongly patterned along the same gradient. Th ese results support a biotic fi ltering eff ect on plant species assemblages through pollination: disk blossoms became dominant at higher altitudes, resulting in a lower FD. In harsh conditions at high altitudes, pollinators usually decrease in activity, and the openness of the disk blossom grants access to any available pollinator. Inversely, bilabiate blossoms, which are mostly pollinated by bees, were more abundant at lower elevations, which are characterised by greater abundance and diversity of bees. Generalisation through openness of the blossom could be advantageous at high elevations, while specialisation could be a successful alternative strategy at lower elevations. Th e approach used in this study is purely correlative, and further investigations should be conducted to infer the nature of the causal relationship between plant and pollinator distributions.
European Journal of Agronomy, 2016
Pear and apple are among the main fruit crops worldwide. These species can be planted in mixed orchards, and they both depend on insect pollination for fruit set. As pollinating insects are attracted by the floral resources, we investigated nectar and pollen production and chemical composition in four pear ('Concorde', 'Conférence', 'Doyenné du Comice', 'Triomphe de Vienne') and five apple ('Braeburn', 'Golden Reinders', 'Jonagored', 'Pinova', 'Wellant') cultivars commonly grown in Belgium. We also investigated whether insect flower visitation rate and pollination efficiency are linked to floral resource quantity and quality. The pear cultivars flowered one week before the apple cultivars in early spring, and their flowers were about six times less visited by insects. The visitors foraged more on the pollen of the pear trees and the nectar of the apple trees. Pear flowers produced higher volumes of nectar than apple flowers (1.3-3.2 l vs. 0.4-0.6 l), but with lower sugar concentration (9.6%-10.8% vs. 28.3%-36.4%). Pear flowers also produced fewer pollen grains per anther than apple flowers (2425-4937 vs. 3284-7919), but these had higher polypeptide (346-362 g/mg vs. 216-303 g/mg), amino-acid (40-77 g/mg vs. 12-18 g/mg) and phytosterol (21-47 g/mg vs. 15-43 g/mg) concentrations. The foraging behavior of the insects is thus better explained by nectar and pollen quality rather than quantity. Despite the differences in flower visitation rates, pollination of both species resulted in valuable fruit production.
2000
This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically those of translation, reprinting, re-use of illustrations, broadcasting, reproduction by photocopying machines or similar means, and storage in data banks.
Austral Ecology, 2009
ABSTRACT Spatial patterns of fruit set within inflorescences may be controlled by pollination, nutrient allocation, or inflorescence architecture. Generally, flowers that have spatial and/or temporal precedence are more likely to set fruits. We sought to separate these factors by comparing patterns of fruit set on inflorescences of two species of Telopea (Proteaceae); one that flowers from the tip to the base of the rachis, the other from base to tip. In both species, most fruits were set at the top of the inflorescence (the last flowers to open for T. speciosissima) and this was extreme for T. mongaensis, where the top flowers open first. Fruit set was not generally limited by inadequate pollination for either T. mongaensis or T. speciosissima, as hand pollinations did not increase fruit set and many abscised flowers contained pollen tubes. In T. speciosissima, we tested whether removal of developing topmost fruits would ‘release’ those that had initiated but not yet aborted lower down. There was no significant effect. Plant hormones can increase the degree to which a developing fruit is a sink for nutrients, so we applied cytokinin to the developing lower fruits on some inflorescences. There was no significant effect of the hormone treatment. We conclude that temporal precedence may contribute to the skewed pattern of fruit set in T. mongaensis, because there was an extreme concentration of fruit set on the distal part of the inflorescences, but it cannot explain this pattern of fruit set in T. speciosissima, where the distal flowers are the last to open. Some other process must therefore constrain fruit set to the topmost flowers in an inflorescence. While cytokinin application had no significant effect, the power of this experiment was low and we consider that the hypothesis of hormonal control is worth further exploration.