Decreased Fruit Set Research Articles

Floral longevity and reproductive assurance: seasonal patterns and an experimental test with Kalmia latifolia (Ericaceae)

Floral longevity is assumed to reflect a balance between the benefit of increased pollination success and the cost of flower maintenance. Flowers of Kalmia latifolia (Ericaceae), mountain laurel, have a long duration and can remain viable up to 21 d if unpollinated. I experimentally tested whether this long duration increases pollination success by clipping stigmas to reduce functional floral longevity to 3-4 d. Clipping stigmas decreased fruit set from 65% to only 10%. Flowers with natural life spans were not pollination-limited, demonstrating that long floral duration ensured female reproductive success. The long floral duration of K. latifolia was unique in this site (the Great Swamp, Rhode Island, USA). Coflowering shrubs in summer had a mean floral life span of 3.4 d. Spring-flowering species had significantly longer mean floral durations (7.2 d). These duration differences may reflect seasonal variation in pollinator availability. However, K. latifolia flowers in summer, when its bumble bee pollinators are abundant but it is a poor competitor for bees because its flowers produce little nectar. The long floral duration allows K. latifolia to outlast coflowering competitors and attract sufficient pollinators. I hypothesize that the long floral duration of K. latifolia functions as a mechanism for competitive avoidance and reproductive assurance.

The beneficial effect of ants on the reproductive success of Dyckia floribunda (Bromeliaceae), an extrafloral nectary plant

Dyckia floribunda is a perennial herb from the Argentinian Chaco with extrafloral nectaries. Ants visited these nectaries while patrolling inflorescences and infructescences. We anticipated that ants attracted to extrafloral nectaries might protect the reproductive organs, increasing plant reproductive output. To evaluate the possibility of mutualism between D. floribunda and ant visitors, we determined whether ant-accessible plants showed a higher seed production than ant-excluded plants. Experimental fieldwork suggested a decrease in fruit set of ant-excluded plants compared with ant-accessible plants but the seed number per fruit was not affected by ant exclusion. Thus, total seed number per plant was highly reduced in treated spikes. Analyses of covariance confirmed these trends, indicating that total seed production per plant was strongly affected by ant exclusion. This study marks the first experimental report of this mutualistic association in Bromeliaceae.Key words: ant–plant interaction, Bromeliaceae, Chaco, Dyckia floribunda, fruit set, seed set, mutualism.

Pollination, pollen tube growth and fertilization in Chaenomeles japonica (Japanese quince)

The fertilization system in Japanese quince, Chaenomeles japonica (Thunb.) Lindl. (Maloideae, Rosaceae) was studied by fluorescence microscopy. In a compatible combination, pollen grains germinated fast and pollen tubes grew rapidly, through the stylar tissue. Most of pollen tubes reached the base of the ovary within 2–6 days. In the ovary, pollen tube growth was considerably retarded, and fertilization of ovules started at the earliest 3 days after pollination. In an incompatible combination only few pollen grains germinated, and pollen tubes grew slowly and were often completely arrested in the style. The pollen tubes reached the ovary in 6–7 days. Fertilization did not take place until 7–9 days after pollination, and the percentage of fertilized ovules was very low. The same results were obtained when selfing self-incompatible genotypes. However, a small percentage of pollen tubes reached the ovary within 3–4 days in some genotypes including self-pollination (as in a compatible cross-pollination), but fertilization was not observed or considerably delayed compared to cross-pollination. C. japonica thus shows the characteristics of a gametophytic self-incompatibility system. The viable period of the embryo sac was 6–7 days in most of the investigated genotypes, and the effective period of pollination was estimated to 5–7 days. Bagging was not necessary to avoid open pollination, provided that the flowers had been emasculated previously. Emasculation or bagging did not decrease fruit set and could, therefore, be used in breeding.

Flower Production, Fruit Set, and Physiology of Bell Pepper during Elevated Temperature and Vapor Pressure Deficit

High temperature reduces fruit set in bell pepper [Capsicum annuum L. var. annuum (Grossum Group)], and reduction of pepper productivity, resulting from high temperature, may be a direct effect of temperature or an indirect effect of water stress induced by increased vapor pressure deficits (VPDs) at high temperature. We evaluated responses of plant growth, reproduction, net photosynthesis (PN), chlorophyll fluorescence, predawn respiration, leaf water potential, and stomatal conductance of `Ace' and `Bell Boy' bell pepper to elevated temperature (33 °C) with increased VPD (2.1 kPa) or elevated temperature with no increase in VPD (1.1 kPa). VPD had no effect on flower number or fruit set and did not adversely influence the physiological processes measured. Therefore, deleterious effects of high temperature on pepper fruit set does not appear to be temperature induced water stress, but is more likely a direct temperature response. Elevated temperature decreased fruit set but not flower production. Gas exchange measurements suggest failure to set fruit was not due to reduced leaf photosynthesis.

Response of Lagerstroemia x ‘Tuscarora’ to Pistill and Atrimmec

Abstract A study was conducted in 1997, 1998 and 1999 to determine the effect of Pistill (ethephon) at rates of 333, 667 or 1000 ppm and Atrimmec (dikegulac-sodium) at rates of 723, 1446 or 2176 ppm on flower abortion, fruit set and axillary shoot stimulation of Lagerstroemia x fauriei Koehne ‘Tuscarora’ when applied at full flower. Flower abortion increased from 16.7% (1998) and 2.1% (1999) for the control to 84.2% and 64.4% respectively for Pistill (1000 ppm) at 7 days after treatment (DAT). Pistill similarly caused a significant decrease in fruit set during all three experiments with fruit set as low as 2.2% at 14 DAT in 1997 compared to 69.4% for the control. Atrimmec had no effect on flower abortion at 7 DAT in any year except 1999 with 11.3% at the 2176 ppm rate vs 2.1% for the control. Atrimmec also had little effect on fruit set except during 1998 when fruit set at 14 DAT was approximately 40% for all rates of Atrimmec compared to 65% for the non-treated control. Pistill applications resulted in more new shoots than Atrimmec in 1997, and the control in all years. Applications of Pistill at full flower can be an effective tool to abort crapemyrtle flowers resulting in reduced fruit set and increased number of new shoots

517 Bloom Thinner Wilthin Decreased Fruit Set and Increased Fruit Yield and Quality of Three Apple Cultivars

The influence of bloom chemical thinner Wilthin on three apple cultivars (Royal Gala, Blushing Gold, and Ultra Gold) was investigated. Two experiments were conducted in 1995 and 1996 to determine the effect of Wilthin at 0%, 0.5%, 1.0%, and 1.5% on fruit length, fruit diameter, fruit weight, yield, juice pH, acidity, SSC, sucrose, glucose, fructose, fruit firmness, and fruit set. Wilthin reduced fruit set of `Royal Gala', `Ultra Gold', and `Blushing Golden' and increased yield of all cultivars. In general, Wilthin increased fruit weight of `Royal Gala', `Ultra Gold', and `Blushing Golden' both years. Wilthin increased fruit length and diameter of `Royal Gala' and `Ultra Gold', but it did not affect fruit length of `Blushing Golden'. Wilthin increased fruit juice pH of `Royal Gala', `Ultra Gold', and `Blushing Golden' during both years. Wilthin decreased fruit juice acidity of `Royal Gala', `Ultra Gold', and `Blushing Golden'. In 1995, Wilthin increased SSC of `Royal Gala' and `Ultra Gold'. In 1996, Wilthin did not effect SSC of `Royal Gala' and `Blushing Golden', but increased SSC of `Ultra Gold'. Wilthin increased sucrose concentration of `Royal Gala', `Ultra Gold', and `Blushing Golden'. Wilthin did not effect fruit juice glucose concentration of `Royal Gala' but increased fruit juice glucose concentration of `Ultra Gold' and `Blushing Golden'. Wilthin did not influenced fructose content of `Royal Gala' and `Blushing Golden' apples. Wilthin increased fructose contents of `Ultra Gold'. Accel increased fruit firmness of `Royal Gala', `Ultra Gold', and `Blushing Golden' and increased fruit firmness of `Royal Gala'.

Effect of the distance between female and male jojoba plants on fruit set

Fruit set of the dioecious, wind-pollinated plant jojoba ( Simmondsia chinensis) was studied in two clones of female plants as a function of their distance between female and male plants growing in separate rows. At a distance of >27 m between the two sexes, a significant decrease of fruit set was observed. This effect was stronger in the early-flowering clone (Q-106) than in the late-flowering one (64). Fruit set tended to increase in the rows south of the male row than in those located in the opposite direction.

Comparing heat stress effects on male‐fertile and male‐sterile tomatoes

To separate the effects of heat stress on male and female reproductive tissues, male‐sterile (MSs) and male‐fertile tomatoes (MFs) were placed in growth chambers at 12 h day/12 h night temperatures of 28/22, 30/24 or 32/26 °C from flower appearance to seed maturation (daily mean temperatures of 25, 27 or 29 °C). Pollen from MFs was applied individually to MS flowers. As MFs were self‐pollinated, heat stress was experienced by both male and female tissues. At growth temperatures of 29 °C fruit number, fruit weight per plant, and seed number per fruit were only 10%, 6·4% and 16·4%, respectively, compared with those at 25 °C. Heat stress also adversely affected fruitset in MSs, especially when experienced by donor pollen. No fruit at all developed on MSs receiving pollen produced at 29 °C, even when ovule development, pollen germination and subsequent embryo development all took place at 25 °C. Effects on fruitset in MSs were reduced if donor pollen had not experienced heat stress. MSs grown at 29 °C but receiving pollen developing at 25 °C produced 73% as much fruit (both on number and weight basis), had 40% as high fruitset and produced 87% of the seed per fruit as MSs grown at 25 °C. This use of male‐sterile and male‐fertile lines of tomato provides new evidence that impairment of pollen and anther development by elevated temperature will be an important contributing factor to decreased fruit set in tomato, and possibly other crops, with global warming.

The Use of Competition for Carbohydrates Among Vegetative and Reproductive Sinks to Reduce Fruit Set and Botrytis Bunch Rot in Seyval blanc Grapevines

Three pruning severities and two times of cluster thinning were applied to Seyval blanc grapevines to vary the quantity of vegetative and reproductive sinks at fruit set. Vines were balanced pruned to either 10, 30, or 60 nodes per 454 g of cane prunings. Half were flower cluster thinned and half post-fruit-set thinned to 15 clusters per 454 g of cane prunings. Increased sink competition created by a greater number of apical meristems influenced canopy morphology and reduced cane maturation, but had no effect on Botrytis bunch rot. Delaying cluster thinning until post-fruit-set decreased fruit set, yield, and Botrytis bunch rot while increasing berry weight and °Brix. Decreasing cluster thinning severity eliminated losses in yield from reduced fruit set. Post-set cluster thinning to increase reproductive sink competition and reduce fruit set appears to be a viable cultural practice to reduce Botrytis bunch rot and improve yields.

Leaf damage by herbivores affects attractiveness to pollinators in wild radish, Raphanus raphanistrum.

We carried out two experiments to determine the effect of leaf damage on plant attractiveness to pollinators using wild radish, Raphanus raphanistrum (Brassicaceae), a self-incompatible annual herb. Pairs of plants from 36 full-sib families were grown in pots in the greenhouse. One member of each pair was damaged by Pieris rapae larvae that were allowed to remove half of the leaf area of each of the first four rosette leaves. The plants were subsequently taken out for pollinator observations once a week from the beginning of flowering in late June until the end of August. We conducted two experiments to examine how foliar damage affected visitation by pollinators. In the first experiment, numbers of pollinators visiting plants were compared between damaged and control sibling plants. In the second experiment, the number of open flowers during observations was controlled to be the same for both damaged and undamaged sibs. Damage significantly decreased the number and size of flowers during the first observations in late June. Damaged plants received fewer visits by native bees during the first week of observations. Since damage did not affect native bee visits when the number of open flowers was equalized between treatments, flower number was probably the main cue attracting native bees to plants. In the experiment without flower number control, syrphid flies, the other abundant pollinator taxon, spent more time per flower on the undamaged than on the damaged plants. When flower number was controlled, flies probed significantly more flowers during each visit on the undamaged than on the damaged plants and had higher visitation rates to undamaged plants early in the season. Since syrphid flies preferred undamaged plants both with and without flower number control, they apparently used cues apart from flower number for visitation. The difference between undamaged and damaged plants in floral characteristics and pollinator visitation vanished within a few weeks after the start of flowering. This result suggests that early damage may not have a strong fitness effect through reduction in mating success. However, poor weather conditions can cause early mortality of plants in the field, and nutrient depletion and competition decrease fruit set of later flowers. Therefore, conditions exist under which visitation to early flowers may affect plant fitness.

Some factors influencing fruit set in ‘Sundrop’ apricot

Abstract Two apricot (Prunus armeniaca L.) cultivars, ‘Sundrop’ and ‘Moorpark’ were found to be cross‐compatible with pollen of 32 genetically diverse cultivars. The flowers of ‘Valleygold’, ‘CluthaGold’, and ‘Moorpark’ remained receptive to pollination for up to 8 days after emasculation at the balloon stage. Floral receptivity declined in ‘Moorpark’, ‘Sundrop’, and ‘CluthaGold’ (but not ‘Valleygold') over the 8 days. ‘Sundrop’ had the lowest receptivity and ‘Moorpark’ the highest. Percentage set of ‘Sundrop’ flowers varied between properties and years in Central Otago, New Zealand, with significantly lower sets being recorded in 1992 and 1993 than in 1991. In these three seasons, a 2 ha block of ‘Sundrop’, with no pollenisers within it, showed a decrease in fruit set as the distance from the nearest polleniser on the edge of the block increased; fruit set was unacceptably low beyond the first four or five rows. Bee density did not decline across the block in the same manner. The fruit were smaller on tr...

Pollination disruption by European honeybees in the Australian bird-pollinated shrubGrevillea barklyana (Proteaceae)

European honeybees (Apis mellifera) were less efficient pollinators ofGrevillea barklyana than nectar-feeding birds. Nectar-collecting honeybees did not contact reproductive parts of flowers. Pollen-collecting honeybees preferentially visited malestage flowers but rarely visited female-stage flowers. Fruit set on caged inflorescences that allowed access to honeybees but excluded birds was reduced by more than 50% compared to inflorescences that were visited by both types of visitors. Further, fruit set on caged inflorescences was less than on bagged inflorescences that excluded both birds and honeybees, indicating that pollen removal by bees decreased opportunities for delayed autonomous selfing in the absence of birds. Although fruit set was not pollen-limited at the study site, pollen removal by honeybees would decrease fruit set in small populations where birds are scarce. In addition, pollen removal by honeybees would reduce opportunities for outcrossing and reproductive success through male function. Although honeybees have been in Australia for insufficient time to have exerted selection on floral traits, evolutionary shifts in response to these animals are likely to occur in the future.

EFFECT OF ETHEPHON ON BLOOM DELAY IN ALMOND TREES.

Under temperate climates almond production is restricted to areas without risk of frosts on flowering. However an artificial delay of flowering would be beneficial to avoid frost damages under such conditions. With the objetive of delay flowering, foliar applications of Ethephon were made to mature almond trees in the fall 1990 and 1991, when their natural defoliation was 10%. Three rates of Ethephon and a check were evaluated for that proposal. Bloom delay was 7, 8 and 9 days for 75, 150 and 300 mg·L-1 in the first year the three rates decreased fruit set and fruit yield. In the second year of evaluation the bloom was delayed only 3 days at the highest rate but fruit set and fruit yield was not affected. In both years fruit quality was the same for all the treatment.

Use of hydrogen cyanamide for apple and plum thinning

Effects of various concentrations of Dormex (a.i. 49% hydrogen cyanamide) on fruit thinning of ‘Rome Beauty’ apple (Malus domestica Borkh.), ‘Friar’ and ‘Simka’ plums (Prunus salicina Lindley) were studied. A full bloom application of Dormex at all tested concentrations decreased ‘Rome Beauty’ apple fruit set and yield, and increased fruit weight. Dormex at 0.25% (v/v) resulted in adequate apple thinning, indicated by production of an optimum fruit weight (320 g). Prebloom and full bloom applications of Dormex at greater than 0.75% reduced plum fruit set and yield in ‘Friar’. Full bloom application of Dormex at 0.50% showed a satisfactory fruit set, yield, and fruit weight in ‘Friar’ plum. Prebloom Dormex application had no significant effect on `Simka' plum fruit set or yield, but full bloom application decreased fruit set and yield.

Effective pollination period as related to stigma receptivity in apricot

In the warm climatic conditions of the south Mediterranean area, where mean temperatures during blooming period are as high as 15–18°C and maximum temperatures frequently exceed 25°C the effective pollination period (EPP) of apricot cultivars is extremely short. The normal duration of EPP is 4 days and fruit set decreases sharply 6 days after emasculation. In some years and cultivars this sharp fall happens as early as 4 days after emasculation. Stigma receptivity proceeds in a way similar to EPP and in general it can be said that the limiting factor of EPP is the short duration of the stigma receptivity. However, when the climatic conditions or the cultivars' behaviour are such that there is still a good stigma receptivity on Day 6 after emasculation other factors become responsible for the limitation of EPP. On Day 6, even when the stigma remains receptive, there is frequently an important decrease in fruit set.

NEW LEAVES ARE THE PRIMARY SOURCE OF RESOURCES FOR FRUIT SET IN CRANBERRY

The sources of carbohydrate and other resources for fruit growth in cranberry (Vaccinium macrocarpon Ait.) can be spatially partitioned into new growth, old leaves, and woody stems or other adjoining uprights. This research was conducted to determine which spatial source of resources was most important for fruit set in cranberry. At fruit set in late June, we removed the current season growth, one year old and older leaves, or both from 50 uprights per treatment plus a control at two locations. At harvest, fruit set, fruit number and size were determined. In all cases, removing the current season's growth significantly decreased fruit set. Removing both the current season's growth and old leaves produced an additional reduction in fruit set. Removing only old leaves reduced fruit set at one location but not the other. Fruit length, diameter or mean berry weight was not reduced by any treatment. The response of cranberry to resource limitation apparently is to reduce fruit numbers rather than fruit size. This research suggests that current season growth is the primary source of carbohydrates for fruit set in cranberry and that once the fruit are set they have sufficient sink strength to attract resources from a distance.

EFFECTS OF HYDROGEN CYANAMIDE ON APPLE AND PLUM FRUIT THINNING

Influence of various concentrations of hydrogen cyanamide (HC) on fruit thinning of `Rome Beauty' apple (Malus domestica Borkh.), `Friar,' and `Simka' plums (Prunus salicina Lindley) were studied. A full bloom application of HC at all tested concentrations decreased `Rome Beauty' apple fruit set and yield, and increased fruit weight. Hydrogen cyanamide at 0.25% (V/V) resulted in adequate apple thinning, indicated by the production of an ideal fruit weight. Prebloom and full bloom applications of HC at greater than 0.75% reduced plum fruit set and yield in `Friar.' Full bloom application of HC at 0.25% to 0.50% showed a satisfactory fruit set, yield, and fruit size in `Friar' plum. Full bloom application decreased fruit set and yield in `Simka' plum. Hand thinning, as well as chemical thinning, is recommended for plums.

O pessegueiro no sistema de pomar compacto: VI. Frutificação efetiva e raleio químico em seleções IAC

Verificou-se o potencial de frutificação e o efeito da pulverização de uréia a 12%, no raleio de frutos, em cinco pessegueiros e duas nectarineiras, cultivados em pomar compacto, na Estação Experimental de Monte Alegre do Sul (22°41'S. e 46°43'W.), do Instituto Agronômico de Campinas (IAC). Dos cultivares e seleções pesquisados, 'Talismã', IAC 6782-83, IAC N 2680-91, 'Aurora-2' e IAC 282-24 apresentaram as maiores taxas de frutificação natural, a saber: 60,9; 54,2; 44,6; 41,4 e 40,0% respectivamente. A uréia a 12%, pulverizada na plena floração, mostrou-se efetiva no raleio dos frutos, reduzindo as frutificações para a faixa de 12-17%, considerada adequada para pessegueiros e nectarineiras sob altas densidades de plantio. O número médio de pêssegos e nectarinas remanescentes por ramo foi, respectivamente, de 1,1; 1,6; 1,8; 1,9; 2,0; 2,6 e 3,2 para IAC 280-28; IAC 6782-83; 'Aurora-2'; IAC 282-24; IAC N 1880-76; IAC N 2680-91 e Talismã'. A produtividade não foi prejudicada pela ação raleadora da uréia a 12%. As plantas em que permaneceram até dois frutos em média, por ramo, apresentaram produtos de melhor padrão.

Cranberry growth and yield response to fertilizer and paclobutrazol

In glasshouse studies with cranberry, paclobutrazol (PP333) ((2RS, 3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-pentan-3-ol) applied twice as a foliar spray at 75, 150, 300, 600 or 1200 mg 1 −1 decreased shoot and root growth, and the shoot: root ratio. Paclobutrazol decreased shoot elongation within 3 weeks of application and increased the number of branches on primary shoots. Buds were formed within 7 weeks of treatment and some contained flowers. In a second experiment, flower-bud formation was greater when plants were treated with paclobutrazol at 1.25, 2.50 or 5.00 mg pot −1 as a soil drench and grown for a longer period. Plants grew more with high NPK than with low NPK but growth was diminished still by paclobutrazol. High NPK decreased floral induction. Paclobutrazol was still detected in the soil 50 weeks after application. In a cranberry field study, foliar sprays of paclobutrazol at 75 or 150 mg 1 −1 at full bloom and 2 weeks later decreased fruit set, fruit size and yield, but increassed bud set and flower-bud set on uprights. Shoot growth was decreased the following year but the number of flowers per upright was increased. Fruit set was the most important contributor to yield variation, followed by fruit size and flowers per upright. The effects of paclobutrazol upon adjusted yield components accounted for a substantial amount of yield variation. No effect of cultivar on yield was apparent as the higher proportion of adjusted number of uprights flowering in cultivar ‘McFarlin’ was offset by an increased adjusted number of flowers per upright in cultivar ‘Bergman’. Bud set and flower-bud set were greater in uprights that did not flower in the current season.

Phenological Variation in the Neotropical Understory Shrub Piper Arielanum: Causes and Consequences

This study examines the flowering, fruiting, and leafing phenology of a Costa Rican understory shrub, Piper arieianum, with an emphasis on the complexity and consequences of incomplete synchrony of reproductive events. During 1981 and 1982, flowering in P. arieianum was a mixture of (1) highly synchronized peaks in which most plants flowered and most of their inflorescences flowered and (2) more extended flowering during which few plants flowered and few of their inflorescences flowered. The probability of fruit set was greater for large plants and for plants that flowered in synchrony with other plants than for small plants and plants that did not flower in synchrony with the rest of the population. The species is mostly self—incompatible, a possible explanation for the observed decrease in fruit set when fewer plants were flowering. However, synchronization per se did not necessarily lead to high fruit set, suggesting that certain times of the year are better for flowering than others. In general, flowering was more prevalent in February and from September to October, when rainfall is predictably the lowest and pollinator services are more reliable. The primary flowering peak (February) accounted for 64% of total inflorescence and 62% of total infructescence production in 1981, and 50% of total inflorescence and 76% of total infructescence production in 1982. Fruit and seed dispersal were much less synchronous than flowering; fruits of individual plants from a single flowering period were dispersed over a 2—4 mo period. The time from flowering to final infructescence maturation was 5—9 mo. Large fruit crops and fruit set more than once per year resulted in a longer time period over which infructescences were presented to dispersers than did small fruit crops and fruit set only once per year. Flowering time was delayed by experimental leaf area removal, but the type and strength of the effect depended on the time of year. Before the small September peak of flowering (1979), 10% removal of leaf area delayed peak flowering 1 mo compared with controls and 30% removal of leaf area delayed flowering for 1.5—2 mo. In contrast, when leaf area was removed before the large February flowering peak (1981), plants with 10, 30, or 50% leaf area removal flowered simultaneously with control plants, although complete defoliation delayed flowering up to 3 mo. Similarly, although plants in light gaps flowered more frequently and more successfully during nonpeak periods than did understory plants, the level of flowering and fruit set was equally high in plants of both locations during the February flowering peak. Thus, the reproductive events occurring during the primary flowering peak (February) were less sensitive to environmental variables than at other times of the year. Leaf production was continuous throughout the study period. Previous leaf production did not affect subsequent flowering and fruiting intensity of individual plants. Predispersal seed predators were abundant following the major flowering peaks but not the minor flowering peaks, suggesting that off—peak fruit production can lead to escape from seed predators.