Variation In Fruit Production Research Articles

Variation in fruit‐ and seed set among and within inflorescences of Melampyrum roseum var. japonicum (Scrophulariaceae)

Abstract Variations in fruit set and seed set among and within inflorescences of the annual herb, Melampyrum roseum var. japonicum, were studied. Under natural conditions, although the mean fruit set was slightly different among inflorescences, the mean seedset was not significantly different among inflorescences within the plants. In constrast, within the inflorescences, the flowers located at a lower position of the inflorescence and which opened earlier showed higher fruit set than those at a higher position and which opened later. However, the seed set of matured capsules were not significantly different from each other, regardless of the position of flowers within the inflorescences. Patterns of the fruit‐ and seed set under open pollination indicated that variation in seed reproduction of M. roseum is due to variation in fruit production. The results of clipping experiments of flowers revealed that there was no functional limitation in seed production among flowers located at various positions within the inflorescence. It seemed that the variation in the fruit set within the inflorescences of M. roseum was not attributable to ‘architectural effects’. Reduction of the number of flowers within the inflorescences resulted in an increase of fruit set and seed weight, indicating that the flowers in an inflorescence compete for resources. This phenomenon supports the ‘resource competition hypothesis’, and variation in fruit set within the inflorescence is attributable to competition among flowers within the inflorescence for limited resources. Consequently, it was concluded that, under natural conditions, the early blooming flowers located at lower positions of the inflorescences obtain more resources and produce more fruits than the late blooming flowers located at higher positions in M. roseum.

The faint promise of a distant market: a survey of Belem’s trade in non-timber forest products

Increased trade in non-timber forest products (NTFPs) has been promoted as one possible means to slow tropical deforestation by increasing the economic value of intact forest. A market survey of NTFPs occurring in the Capim River basin in eastern Amazonia, Brazil demonstrated that the reality for many smallholder communities in frontier and remote regions includes chronic transportation difficulties, high variability in fruit production, perishable products and lack of market expertise. In some communities, declining abundance of NTFPs due to logging and fire has resulted in a lack of forest products to even meet subsistence needs. In areas close to cities where transportation is assured and where forest clearing has eroded the natural occurrence of some valuable native NTFPs, smallholders who manage and successfully market native fruit and medicinal species are overcoming these obstacles. In frontier regions undergoing rapid transformation, however, decline in locally used and regionally marketed NTFPs currently pose detrimental consequences for communities. Findings suggest that an overemphasis on NTFP marketing has diverted attention from local livelihood, resource access and subsistence issues.

Storage and the delayed costs of reproduction in the understorey perennial Lathyrus vernus

Summary A trade‐off between current and future reproduction, often referred to as the cost of reproduction, is a fundamental assumption in life history theory. In long‐lived plants, large absolute differences in size between individuals, storage of resources between reproductive events and organ preformation may make such costs difficult to demonstrate, especially when only natural variation is considered. The long‐lived legume Lathyrus vernus shows large size differences compared with variation in carbon resource allocation, and is known to store resources in below‐ground rhizomes. We therefore followed individual plants over a period of 4 consecutive years. We examined the cost of reproductive investment by comparing the performance of untreated plants that differed in size and herbivore damage. We also compared controls with plants where we experimentally reduced flowering in terms of fitness measured as: survival, growth, flower number, fruit:flower ratio and storage. Natural patterns of flowering and fruiting provided no evidence of a negative relationship between current and future reproduction. Individuals that produced fruits did not experience a lower probability of surviving and producing fruits the following season compared with flowering individuals that failed to produce any fruits, even when differences in above‐ground size and herbivore damage were taken into account. Flower removal in a single season increased the allocation to the rhizome but the size of shoot buds for the next season was not increased. Experimental manipulation of reproductive effort by repeated removal of flowers during 3 consecutive years, however, resulted in a significant increase in vegetative size and the probability of flowering and setting fruit compared with control plants. While long‐term data on natural variation in fruit production and short‐term experimental data provided no evidence of a cost of reproduction, such a cost is still present, although detectable only after repeated flower removal.

Reproductive Phenology of a Tropical Canopy Tree, Spondias mombin1

We studied the reproductive phenology of isolated populations of Spondias mombin to determine the degree of flowering and fruiting synchrony among populations and to examine spatial and temporal variability in fruit production. The study was conducted on six small islands (1.8–3.5 ha) in the Panama Canal. All individuals (10 cm in diameter at breast height (DBH) were marked in 1991 and censused each year through 1994 to record recruits and deaths. All marked trees were censused monthly for flowering and fruiting activity from April 1992 through December 1995. Spondias mombin was seasonal and highly synchronous in flower and fruit production among islands and across years. Proportions of individuals fruiting varied among islands, years, and tree size classes. There was a positive relationship between probability of fruit production and tree size. Synchronous reproductive activity in S. mombin probably was due to responses to proximate environmental cues such as fluctuations in irradiance, but other factors must have been responsible for temporal and spatial variation in reproductive performance. We suggest that this variation may have been due partly to temporal and spatial differences in pollinator abundance.

Fruit production in Sorbus aucuparia L. (Rosaceae) and pre-dispersal seed predation by the apple fruit moth (Argyresthia conjugella Zell.).

Variation in fruit production and pre-dispersal seed predation by Argyresthia conjugella was studied in␣four populations of Sorbus aucuparia in northern Sweden.␣The number of infructescences, fruits per infructescence, consumed seeds and developed unattacked seeds per fruit were scored in marked trees from 1984 to 1990. The results showed that the number of fruits produced in each population determined the number of seed predators occurring in the host population, as the yearly number of seed predators was significantly and positively correlated with yearly number of fruits, in all but one population. The seed predators showed a delay in response to variation in number of fruits produced. This lag in response resulted in a large proportion of fruits being attacked and seeds consumed in a bad fruiting year that followed a good fruiting year, and vice versa. The proportion of fruits attacked and seeds consumed was largest in the population showing the greatest between-year variation in fruit production and lowest in the population showing the lowest between-year variation in fruit production. Furthermore, the individuals within the former population were synchronised, while they were not in the latter population. These results contradict one of the possible explanations of mast-seeding, where large synchronised between-year variation is supposed to reduce pre-dispersal seed predation. Instead, differences in attraction of the seed predator to differences in fruit crop size could explain the observed difference in seed predation between the two populations with opposite fruiting patterns. Within each population, irrespective of year, the proportion of fruits attacked and seeds consumed was independent of a tree's fruiting display. Therefore, trees with high fruit production, despite harbouring the largest number of seed predators, produced the largest number of developed seeds in absolute numbers, compared to trees that produced few fruits.

Buffaloberry [Shepherdia Canadensis (L.) Nutt.] Fruit Production in Fire-Successional Bear Feeding Sites

Buffaloberry [Shepherdia canadensis (L.) Nutt.] fruits are the usual late-summer food for bears (Ursus spp.) in the Front Ranges of Banff National Park, but little is known about the effect of fire or other factors on fruit production. I assessed the association between fruit production (fruits m-2 of buffaloberry shrub) and environmental factors at 76 plots in Banff National Park and found a negative association with forest canopy cover. Forest canopy cover accounted for 70% of the variation in fruit production. Fruit production also decreased from NNE- to SSW- facing slopes, but this effect was small compared to the decrease associated with increasing forest canopy cover. Forty plots were re-established at or near the original 76 sites the following year. A strong negative association between fruit production and forest canopy cover again occurred, but there was no significant association between fruit production and slope aspect. Fruit production began 5 years after fire in 2 recent burns. In sites burned 23 and 25 years ago, fruit production was comparable to the recorded in older-aged burns, and already was low at one site in the 25-year-old burn where regenerating lodgepole pine (Pinus contorta Dougl.) canopy cover measured 72%. Many sites in older burns, however, have remained forest-free due to xeric site conditions, chinook wind, avalanching, or other factors. These open sites were associated with abundant fruit. Managers must consider the prolonged effects of fire when assessing relation ships among fire, forest canopy cover, and buffaloberry fruit production.

Production and characterization of fertile somatic hybrids of eggplant (Solanum melongena L.) with Solanum aethiopicum L.

In order to produce fertile somatic hybrids, mesophyll protoplasts from eggplant were electrofused with those from one of its close related species, Solanum aethiopicum L. Aculeatum group. On the basis of differences in the cultural behavior of the parental and hybrid protoplasts, 35 somatic hybrid plants were recovered from 85 selected calli. When taken to maturity either in the greenhouse or in the field, the hybrid plants were vigorous, all rapidly overtopping parental individuals. The putative hybrids were intermediate with respect to morphological traits, and all of their organs were larger, particularly the leaves and stems. DNA analysis of the hybrids using flow cytometry in combination with cytological analysis showed that 32 were tetraploids, 1 hexaploid and 2 mixoploids. The hybrid nature of the 35 selected plants was confirmed by a comparison of the isoenzyme patterns of isocitrate dehydrogenase (Idh), 6-phosphogluconate dehydrogenase (6-Pgd) and phosphoglucomutase (Pgm). Chloroplast DNA (ctDNA) restriction analysis using Bam HI revealed that among the 27 hybrid plants analyzed, 10 had S. aethiopicum patterns and the 17 remaining hybrids exhibited bands identical with those of eggplant without any changes. All of the somatic hybrid plants flowered. Both parental plants had 94% stainable pollen, while the hybrids varied widely in pollen viability ranging from 30% to 85%. The somatic hybrids showed high significant variation in fruit production. Nevertheless, there was a tendency for low fertility to be associated often with S. aethiopicum chloroplast type and/or with an abnormal ploidy level, while good fertility was mostly associated with the tetraploid level and eggplant chloroplasts. Interestingly, 2 tetraploid somatic hybrid clones were among the most productive, yielding up to 9 kg/plant. As far as the fertility of the F1 sexual counterpart was concerned, only 2 fruits of 50 g were obtained. Hybrid fertility in relation to phylogenetic affinities of the fusion partners is discussed.

Biomass and Fruit Production for the Prickly Pear Cactus, Opuntia ficus-indica

Productivity of irrigated prickly pear cactus [Opuntia ficus-indica (L.) Miller] was studied over 3 years in central Chile using two planting densities. A low-density planting (0.25 plants/m2), traditionally favored for fruit production, had maximal fruit productivity in the 2nd year (6 Mg dry weight/ha per year). A high-density planting (24 plants/m2), which assured almost full interception of incident solar radiation, led to an extremely high shoot dry-weight productivity (50 Mg·ha-1·year-1) in the 2nd year and maximal fruit productivity (6 Mg·ha-1·year-1) in the 3rd year. Cladode dry weight tended to increase with cladode surface area. However, fruit production did not occur until the dry weight per cladode exceeded the minimum dry weight for a particular cladode surface area by at least 33 g. The year-to-year variation in fruit production apparently reflected variations in such excess dry weight and, hence, in the storage reserves of individual cladodes.

Selective Flower Removal Increases Cranberry Fruit Set

Selective flower removal was used in 1987 and 1988 to evaluate intraplant competition or inhibition within flowering uprights of `Searles' cranberry (Vaccinium macrocarpon Ait.). The lowest two flowers were removed from uprights at various stages of plant development in 1987. With one or both of the two earliest, i.e., lowest, flowers developing `into fruit, 25% of the remaining flowers matured into fruit. Removal of the earliest two flowers at preblossom or late blossom resulted in ≈ 46% fruit set for the remaining flowers. Slightly fewer upper flowers set (36%) when the earliest flowers and fruit were removed at early fruit development. In 1988, the lowest two flowers were removed at preblossom and natural insect pollination was supplemented by hand pollination. Hand-pollinated (upper) flowers set 58% when the lowest two flowers were removed, compared to 17% for the unthinned control. Yield and fruit numbers were lowered slightly as a result of flower thinning in both years. A significant amount of variation in fruit production was explained by the number of flowering uprights per unit of production area in both years.

Seasonal Variation of Nutrient Concentrations in a Semi-Arid Savanna Ecosystem in Botswana

(1) Seasonal changes of nutrient concentrations in the leaves of the main tree and grass species of a semi-arid savanna in Botswana have been analysed. (2) The nitrogen concentration in the leaves of shallow-rooted Acacia species is higher than in deep-rooted ones. The higher nitrogen status of the shallow-rooted Acacia species could be the cause for their encroachment into overgrazed areas. (3) Substantial quantities of nitrogen and phosphorus are translocated from the deciduous leaves to perennial organs long before leaf abscission; sodium, calcium and iron are accumulated in older leaves. (4) A comparison of the nutrient budgets of inflorescences and infructescences in trees shows a strong nutrient demand for the developing infructescence. It is suggested that the high variability in fruit production between and within trees is caused by the high phosphorus demand of the developing fruit.

Interpopulational Variation in Fruit Production: The Role of Pollination-Limitation in the Olympic Mountains

Interpopulational Variation in Fruit Production: The Role of Pollination-Limitation in the Olympic Mountains

Migrant Birds Are the Main Seed Dispersers of Blackberries in Southern Spain

Between-habitat variation in fruit production and bird attributes enhancing seed ingestion and removal were studied to describe the avian seed-dispersal system of blackberries (Rubus ulmifolius, Rosaceae) in southern Spain. Migrant birds were largely responsible for seed dispersal. Among 20 passerine species recorded feeding on fruits, five removed the bulk of seeds: Sylvia atricapilla (29.6% of 897 visits recorded), Erithacus rubecula (15.2%), S. born (14.7%), S. melanocephala (10.1%) and Turdus merula (7.7%). During an average day 32400 seeds left a parent clone through the activity of these species. Seed production was density-dependent, being maximum in high-density situations. Seed removal (i.e., fruit consumption) from individual clones was dependent on crop size, habitat occupied and ripening phonology. Clones ripening a small crop later in the season and/or in low-density habitats had a lower fraction of the crop consumed than did those producing huge crops in high density habitats and/or synchronously with autumn bird migration. The small, passerine birds presumably contributed to the bulk of seed dispersal because they (1) feed on Rubus fruits extensively, (2) showed high visit rates and removed a very high fraction of the seed crop from parent clones, (3) did not damage the seeds nor drop them beneath the parent clone and (4) performed species-specific flights to apparently safe sites for the plant, thus enhancing its colonizing ability.

Determinants of fruit set in Yucca whipplei: Reproductive expenditure vs. pollinator availability.

The number of flowers produced by inflorescences of Yucca whipplei (Agavaceae) consistently exceeds the number of fruits produced by about one order of magnitude. To determine the factors responsible for low fruit set, the relation between pollinator availability, the amount of resources spent on reproduction (as indicated by inflorescence size), and the number of fruits matured was studied during 1978 and 1979 at 18 locations in chaparral, coastal sage scrub, and desert scrub communities of southern California.The following results support the conclusion that pollinators do not usually limit fruit production in Yucca whipplei. Rather, fruit production is limited by the amount of resources available to support developing fruits. (1) Fruit production is positively correlated with inflorescence size both within and between populations. The average size of inflorescence for a population is an excellent predictor of mean fruit production. Furthermore, 54% of the total variance in fruit production of individual plants can be explained by inflorescence size. (2) In contrast, although fruit production within most populations is positively correlated with an index of the number of pollinator visits to an inflorescence, the relative abundance of pollinators for a population is a poor predictor of mean fruit production, and only 9% of the total variance in fruit production can be explained by the visitation index. Furthermore, at four sites studied for two years, there was little change in average inflorescence size or fruit production from 1978 to 1979, despite large differences in relative abundance of pollinators at each of the sites. (3) Based on geographic proximity, and physiographic and vegetational similarities, study sites were grouped into regional clusters. Both inflorescence size and fruit production varied considerably between regions. Of the total variation in fruit production, 27% can be attributed to differences between regions. Most of this variation is the result of regional differences in inflorescence size, which in turn influence fruit production.Why does Yucca whipplei produce such large inflorescences if so few fruits can be supported? Two relevant hypotheses are discussed: (1) the floral display is the result of selection for pollen dissemination at the expense of fruit set; and (2) the floral display is the result of selection for a bet-hedging strategy either to increase the probability of adequate pollination when pollinators are unusually rare, or to allow individuals to support more fruits when resources are unusually abundant.