Phenology of flowering and starch accumulation in grape (Vitis vinifera L.) cuttings and vines

BACKGROUND AND AIMS: A reliable protocol for flowering and fruiting in cuttings was developed with the aim of (a) studying inflorescence and flower development in grapevine cuttings and field plants, and (b) assisting haploid plant production. METHODS: Inflorescence and flower development was studied in 'Gewurztraminer' (GW) and 'Pinot Noir' (PN) grape vines and cuttings grown in a glasshouse, along with variations in starch in the flowers. As there is a strong relationship between flower development and starch, the starch content of reproductive structures was estimated. KEY RESULTS: Inflorescence and flower development were similar in the vines and cuttings with consistent differences between the two cultivars. Indeed, the ontogenesis of male and female organs is not synchronous in GW and PN, with both female and male meiosis occurring earlier in PN than in GW. Moreover, changes of starch reserves were similar in the two plant types. CONCLUSIONS: Cuttings have a similar reproductive physiology to vines, and can be used to study grape physiology and to develop haploid plants.     

Spermidine and related-metabolic inhibitors modulate sugar and amino acid levels in Vitis vinifera L.: possible relationships with initial fruitlet abscission

The relationships between free polyamines (PAs), sugar and amino acid status were investigated in cuttings from two cultivars of Vitis vinifera L., Pinot noir (PN), a low abscising cultivar and Merlot (MRT), a high abscising one. In both cultivars free PAs decreased in inflorescences, but more drastically in MRT plants. Upon anthesis, this was associated with a decreased sugar content, especially sucrose, and an increase in total free amino acids. Thereafter, sucrose and amino acids showed opposite trends. In addition, darkening the PN plants at full flowering resulted in a dramatic decrease of PAs and sugars in inflorescences, but an increase in amino acid content, followed by high abscission. The concept that initial fruitlet abscission might be regulated by free PAs through changes in primary metabolites was hypothesized. Hence, the application of exogenous spermidine (Spd), but not putrescine (Put), prior to flowering markedly inhibits abscission. The Spd treatment also increased soluble sugar content but reduced amino acids in both leaves and inflorescences, while Put had no significant effect. By contrast, cyclohexylamine and beta-hydroxyethylhydrazine, as potent inhibitors of Spd synthase and PA-oxidases, respectively, exerted inverse effects on sugar, amino acid and abscission levels. Sucrose and free proline seemed to be highly sensitive to these treatments. This study suggests that Spd could regulate fruitlet abscission in grapevine by modulating, in a reverse way, the levels of sugars and amino acids in inflorescences.     

Influence of phloem transport on flower abscission in Hibiscus rosa-sinensis

Summary Flowering cultivars of Hibiscus rosa-sinensis L. were either cross-pollinated or self-pollinated. Fruit set was observed on 52% of the cross-fertilized flowers, while only 4.6% of the self-fertilized flowers were not abscised. Once during fruit and seed growth, the subtending leaf was exposed to ¹⁴CO₂, and translocation of labelled photoassimilate was recorded by macro- and microautoradiography. Phloem transport into the raphe occurred in both fruits with fertilized and fruits with non-fertilized ovules. Since empty ovules showed some sink strength, it is assumed that growth of vegetative seed-tissue signalizes the retardation of completion of the abscission process. During fruit growth a considerable amount of starch is deposited in the distal layer of the abscission zone. Part of this starch is consumed during growth of cross-fertilized fruits.     

Systemic infection of black currant flowers by Botrytis cinerea and its possible involvement in premature abscission of fruits

Emasculated flowers of several black currant cultivars were pollinated and then inoculated with dry conidia of Botrytis cinerea in the field and glasshouse. The infection of pistils was examined by U.V. fluorescence microscopy and the incidence of premature flower abscission recorded. Conidia germinated in the stigmatic fluid in all cultivars and hyphae spread symptomlessly throughout the style to infect the pericarp and ovules. Of six cultivars inoculated in the field, cv. Ojebyn was the most, and cv. Ben More the least resistant to flower shedding. Natural infection of stigmas by B. cinerea was common in the field and a high proportion of apparently healthy non-inoculated flowers which abscissed were found to contain infected ovules. Fewer flowers abscissed if inoculations were made 6 days after pollination. Symptomless or latent infection of black currant flowers by B. cinerea may be a contributory cause of premature abscission of developing fruits, or ‘running-off’, recorded in these experiments.     

Flower Abscission in Excised Inflorescences of Three Plectranthus Cultivars

Flower abscission induced by ethylene in three Plectranthus cultivars was investigated in order to characterise response to a range of inhibitory and antagonistic compounds. Excised inflorescences were exposed to 100 ml l⁻¹ ethylene gas or placed in various concentrations of ethephon (277, 27.7, 2.77, 0.277 and 0.0277 μM). Flower abscission in Plectranthus was readily induced by applying ethylene gas and by the 277 μM dose of ethephon. Removal of the inflorescences from the ethylene treatment prevented subsequent flower abscission. This implies that ethylene treatment did not induce an autocatalytic production of ethylene. Compounds that are known to compete for the ethylene receptor (100 and 500 ppb 1-methylcyclopropene or 100 and 500 ppm 2,5-norbornadiene) did not reduce abscission in this system. Also, application of the ethylene biosynthesis inhibitor, aminooxyacetic acid at 1 mM, was ineffective at preventing ethylene-induced flower abscission. In contrast, one compound known to block protein production (100 μM cycloheximide) and a non-competitive inhibitor of ethylene action (2 mM silver thiosulfate) did prevent ethylene-induced abscission. We conclude that flower abscission in cut inflorescences of Plectranthus is very likely mediated by endogenous ethylene production, but that control of ethylene-induced flower abscission in this genus can not be readily obtained by most ethylene antagonists that are known to be effective in other systems.     

Changes of Carbohydrates in Pepper (Capsicum annuum L.) Flowers in Relation to Their Abscission Under Different Shading Regimes

Abscission of pepper flowers is enhanced under conditions oflow light and high temperature. Our study shows that pepperflowers accumulate assimilates, particularly in the ovary, duringthe day time, and accumulate starch, which is then metabolizedin the subsequent dark period. With the exception of the petals,the ovary contains the highest total amounts of sugars and starch,compared with other flower parts and contains the highest totalactivity, as well as activity calculated on fresh mass basis,of sucrose synthase, in accordance with the role of this enzymein starch biosynthesis. Low light intensity or leaf removaldecreased sugar accumulation in the flower and subsequentlycaused flower abscission. The threshold of light intensity fordaily sugar accumulation in the sink leaves was much lower thanin flowers, resulting in higher daytime accumulation of sugarsin the sink leaves than in the adjacent flower buds under anylight intensity, suggesting a competition for assimilates betweenthese organs. Flowers of bell pepper cv. ‘Maor’and ‘899’ (sensitive to abscission) accumulatedless soluble sugars and starch under shade than the flowersof bell pepper cv. ‘Mazurka’ and of paprika cv.‘Lehava’ (less sensitive). The results suggest thatthe flower capacity to accumulate sugars and starch during theday is an important factor in determining flower retention andfruit set. Pepper; Capsicum annuum L.; abscission; shading; pepper flowers; ovary; leaves; sugars; starch; acid invertase; sucrose synthase     

Re-evaluating the role of selective abscission in moth/yucca mutualisms

Conflicts of interest are common to mutualisms, particularly those derived from exploitative interactions. Conflicts of interest are particularly pronounced in pollination/seed predation mutualisms, such as moth/yucca interactions, where consumption of seeds by larvae of a plant's pollinator will raise the fitness of the pollinator but lower the fitness of the plant. A central question in these mutualisms is, therefore, “what limits seed predation?” If plants with excess flowers selectively abscise flowers containing many eggs, they may reduce seed predation and overall increase their fecundity. If eggs in abscised flowers die, selective abscission may additionally contribute to the limitation or regulation of pollinator populations, thereby decreasing the probability of future overexploitation. We examined the effect of selective abscission in the mutualism between Yucca kanabensis and one of its pollinating moths, Tegeticula altiplanella. Per capita mortality of moth eggs due to abscission was high (95.5%), but did not increase on inflorescences with more ovipositions per flower. Overall mortality was partitioned into two components based upon the proportion of visited flowers abscised (i.e. resource‐limitation) and additional mortality (=selective abscission). Resource‐limitation per se inflicted 93.9% egg mortality, or most of the mortality due to abscission. But, the average number of eggs in fruit was lower than the average number of eggs in flowers, indicating that there was some selectivity of abscission. However, neither source of mortality increased on inflorescences with more ovipositions per visited flower. Egg mortality resulting from selective abscission was not as high as possible, because the yuccas appeared to use oviposition‐damaged ovules as a cue for selective abscission, and there was considerable variation in the relationship between oviposition number and damaged ovules. However, even if yuccas had retained the flowers containing the fewest eggs, selective abscission still would not have been higher on inflorescences with more ovipositions per flower. Considering also that, 1) number of ovipositions is a poor predictor of the number of larvae that hatch and feed on the developing seeds in a fruit and that, 2) there are several moth/yucca interactions in which selective abscission does not occur, we conclude that abscission, and particular selective abscission, may have density‐limiting effects on moth populations, but will fail as general explanations for regulating the dynamics of moth populations.     

Water stress effects on maize: Carbohydrate metabolism of resistant and susceptible cultivars ofZea mays L.

Carbohydrate changea in drought resistant and susceptible cultivars ofZea mays L. were studied at two different stages under imposed water stress in water culture experiments. The gradual decline in total carbohydrates with increasing stress levels was observed. At the 1st leaf stage starch content of the resistant cv. Agati-76 was lower than that of susceptible cv. Vijay but the reducing and non-reducing sugar content was much higher. At the 3rd leaf stage starch content was similar in two cultivars but sugar content was higher in the resistant cv. Agati-76. Differential changes in root and shoot carbohydrates as affected by increasing levels of stress were noticed. Carbohydrate changes have been discussed in relation to drought resistance.     

Drought-induced male sterility in rice: Changes in carbohydrate levels and enzyme activities associated with the inhibition of starch accumulation in pollen

Male reproductive development of rice (Oryza sativa L.) is very sensitive to drought. A brief, transitory episode of water stress during meiosis in pollen mother cells of rice grown under controlled environmental conditions induced pollen sterility. Anthers containing sterile pollen were smaller, thinner, and often deformed compared to normal anthers of well-watered plants. Only about 20% of the fully developed florets in stressed plants produced grains, compared to 90% in well-watered controls. Water stress treatments after meiosis were progressively less damaging. Levels of starch and sugars and activities of key enzymes involved in sucrose cleavage and starch synthesis were analyzed in anthers collected at various developmental stages from plants briefly stressed during meiosis and then re-watered. Normal starch accumulation during pollen development was strongly inhibited in stress-affected anthers. During the period of stress, both reducing and non-reducing sugars accumulated in anthers. After the relief of stress, reducing sugar levels fell somewhat below those in controls, but levels of non-reducing sugars remained higher than in controls. Activities of acid invertase and soluble starch synthase in stressed anthers were lower than in controls at comparable stages throughout development, during as well as after stress. Stress had no immediate effect on ADP-glucose pyrophosphorylase activity, but had an inhibitory aftereffect throughout post-stress development. Sucrose synthase activity, which was, relatively speaking, much lower than acid invertase activity, was only slightly suppressed by stress. The results show that it is unlikely that pollen sterility, or the attendant inhibition of starch accumulation, in water-stressed rice plants are caused by carbohydrate starvation per se. Instead, an impairment of enzymes of sugar metabolism and starch synthesis may be among the potential causes of this failure.     

Involvement of polyamines in the control of fruitlet physiological abscission in grapevine (Vitis vinifera)

The potential contribution of polyamines (PAs) in the regulation of physiologically induced fruitlet abscission was investigated in cuttings from two cultivars of Vitis vinifera L., Pinot noir (PN) and Merlot (MRT). Abscission was higher in MRT than in PN and was preceded by a decrease in free PA levels. This decline was more pronounced in inflorescences than in leaves of the sensitive cultivar. Soluble conjugated PA showed an opposite trend in both cultivars. This suggests a cause-effect relationship between free and/or conjugated PA levels in floral organs and susceptibility to abscission. Spermidine (Spd), but not putrescine (Put) or diaminopropane, supplied at 0.5–1 m M to the nutritive medium prior to the anthesis, increased free and conjugated PA levels in the inflorescences and markedly inhibited abscission. α -Difluoromethylarginine, an inhibitor of arginine decarboxylase, but not α -difluoromethylornithine, an inhibitor of ornithine decarboxylase, lowered PA levels and increased abscission. Treatment with cyclohexylamine or β -hydroxyethylhydrazine as potent inhibitors of Spd synthase and PA oxidases, respectively, reduced the Spd and/or spermine levels and enhanced free Put in the inflorescences, inducing an increased abscission of floral organs shortly after anthesis. These data suggest that PAs, particularly Spd, could be involved in the regulation of grapevine fruitlet physiological abscission.     

Changes in carbohydrates and mineral elements in Citrus leaves during flowering and fruit set

Mineral elements and metabolizable carbohydrates in Citrus leaves [ Citrus sinensis (L.) Osbeck cv. Washington navel] have been determined from bud sprouting until the end of the June drop and related to fruitlet growth and abscission. Mineral elements in old leaves decreased during the spring flush of growth and reached minimum values at flower opening, coinciding with a peak in abscission. This was followed by a rapid recovery in potassium and nitrogen to the initial values, with little change afterwards. Old leaves accumulate carbohydrates until flowering, and lose them during post-anthesis at a constant rate for more than 4 months; this rate of export is unaltered by the presence of a nearby growing fruit. Inflorescence leaves accumulate carbohydrates and mineral elements during post-anthesis; during the June drop there is an interruption in the accumulation of nitrogen and a net loss of phosphorus, potassium and carbohydrates from these leaves, coinciding with the attainment of the maximum growth rate of the fruit.
The two main periods of abscission coincide with minima in the amount of reserves in leaves, suggesting that a limitation in metabolite supply may be the primary cause of drop. There is a closer relationship of the fruit with inflorescence leaves than with old mature ones; however, the regulation of carbohydrate levels in the inflorescence leaves cannot be simply explained in terms of source-sink relationships with the nearby growing fruit, and the smaller size of inflorescence leaves vs. vegetative ones is not due to the presence of the flower during leaf development.     

Delay of early fruitlet abscission by branch girdling in citrus coincides with previous increases in carbohydrate and gibberellin concentrations

Current evidence in citrus indicates that gibberellins (GAs) are main determinants of early fruit set while subsequent growth of developing fruits is mostly dependent upon carbohydrate availability. In this work, branch girdling performed at anthesis in Satsuma mandarin (Citrus unshiu (Mak.) Marc.) cv. Okitsu transitorily reduced early abscission rates (12–32 days after anthesis, DAA) delaying initially the process of natural fruitlet drop. The effects of girdling on growth, gibberellin (GA) and carbohydrate concentrations in developing ovaries and fruitlets were assessed during this initial growth stage (0–69 DAA). In girdled branches, abscission rate reduction was preceded by elevated concentrations of carbohydrate and GA in developing ovaries and fruitlets. Girdling at anthesis stimulated higher hexose (21 DAA) and starch (6–20 DAA) concentrations and also higher GA₁ (6 DAA), GA₁₉ (13–20 DAA) and GA₂₀ (6–20 DAA). The results established a relationship between the reduction of early abscission rates and higher concentrations of carbohydrates and GAs induced by girdling in developing fruitlets. These findings revealed that girdling certainly increased GA concentration and strongly suggested that its effect on early fruitlet abscission delay is likely mediated by both GA and carbohydrates.     

Pistil Starch Reserves at Anthesis Correlate with Final Flower Fate in Avocado (Persea americana)

A common observation in different plant species is a massive abscission of flowers and fruitlets even after adequate pollination, but little is known as to the reason for this drop. Previous research has shown the importance of nutritive reserves accumulated in the flower on fertilization success and initial fruit development but direct evidence has been elusive. Avocado (Persea americana) is an extreme case of a species with a very low fruit to flower ratio. In this work, the implications of starch content in the avocado flower on the subsequent fruit set are explored. Firstly, starch content in individual ovaries was analysed from two populations of flowers with a different fruit set capacity showing that the flowers from the population that resulted in a higher percentage of fruit set contained significantly more starch. Secondly, in a different set of flowers, the style of each flower was excised one day after pollination, once the pollen tubes had reached the base of the style, and individually fixed for starch content analysis under the microscope once the fate of its corresponding ovary (that remained in the tree) was known. A high variability in starch content in the style was found among flowers, with some flowers having starch content up to 1,000 times higher than others, and the flowers that successfully developed into fruits presented significantly higher starch content in the style at anthesis than those that abscised. The relationship between starch content in the ovary and the capacity of set of the flower together with the correlation found between the starch content in the style and the fate of the ovary support the hypothesis that the carbohydrate reserves accumulated in the flower at anthesis are related to subsequent abscission or retention of the developing fruit.     

A comparison of in vitro flowers to in vivo flowers of haploid and diploidNicotiana tabacum L.

Thin cell layers (TCLs) were cultured from inflorescences of diploid (2n=4x=48) and haploid (2n=2x=24)Nicotiana tabacum L. "Samsun" and the subsequent flowers formed in vitro were then compared to in vivo flowers. Plants derived from TCLs possessed flowers that were typical of their seed or androgenetically-derived counterparts, whereas de novo flowers from TCLs were abnormal when compared to their counterparts. The TCLs of haploid plants produced more flower buds than diploid TCLs, and did so in a shorter period of time. In vitro flowers and anthers at both ploidy levels were considerably smaller than the in vivo flowers; in vitro flowers also had variable numbers of anthers and pistils. The embryogenic capacity of anthers taken from in vivo diploid flowers was 5 times greater than that of in vitro diploid or haploid anthers. In vivo haploid anthers produced no embryoids, whereas in vitro haploid anthers did produce embryoids. Observations of mitotic cells in root tips of plants derived from anther cultures of in vitro haploid flowers revealed a mixoploid nature. Diploid meiosis was regular and haploid meiosis was irregular regardless of the origin (in vitro or in vivo) of the flowers.Supported by state Hatch funds.     

Sugars and flowering in the grapevine (Vitis vinifera L.)

Sugars play an important role in grapevine flowering. This complex process from inflorescence initiation to fruit maturity takes two growing seasons. Currently, most of the available data concern the involvement of sugars as energy sources during the formation of reproductive structures from initiation of inflorescences during the summer of the first year, until flower opening during the following spring. Sugars devoted to the development of reproductive structures are supplied either by wood reserves or by photosynthesis in leaves or inflorescences, depending on the stage of development. Female meiosis appears to be a key point in the success of flower formation because (i) flowers are vulnerable at this stage and (ii) it corresponds in the whole plant to the transition between reserve mobilization from perennial organs (roots, trunk, and canes) towards efficient leaf photosynthesis. The perturbation of reserve replenishment during the previous year provokes perturbation in the development of inflorescences, whereas altering the photosynthetic sources affects the formation of flowers during the same year. In particular, a lack of sugar availability in flowers at female meiosis caused by various environmental or physiological fluctuations may lead to drastic flower abortion. Apart from energy, sugars also play roles as regulators of gene expression and as signal molecules that may be involved in stress responses. In the future, these two topics should be further investigated in the grapevine considering the sensitivity of flowers to environmental stresses at meiosis.     

Development and senescence of <Emphasis Type="Italic">Grevillea</Emphasis> ‘Sylvia’ inflorescences,flowers and flower parts

To characterise the physiology of development and senescence for Grevillea Sylvia floral organs, respiration, ethylene production and ACC concentrations in harvested flowers and flower parts were measured. The respiration rate of harvested inflorescences decreased over time during senescence. In contrast, both ethylene production and ACC concentration increased. Individual flowers, either detached from cut inflorescences held in vases at 20 °C or detached from in planta inflorescences at various stages of development, had similar patterns of change in ACC concentration and rates of respiration and ethylene production as whole inflorescences. The correlation between ACC concentration and ethylene production by individual flowers detached from cut inflorescences held in vases was poor (r² = 0.03). The isolated complete gynoecium (inclusive of the pedicel) produced increasing amounts of ethylene during development. Further sub-division of flower parts and measurement of their ethylene production at various stages of development revealed that the distal part of the gynoecium (inclusive of the stigma) had the highest rate of ethylene production. In turn, anthers had higher rates of ethylene production and also higher ACC concentrations than the proximal part of the gynoecium (inclusive of the ovary). Rates of ethylene production and ACC concentrations for tepal abscission zone tissue and adjacent central tepal zone tissue were similar. ACC concentration in pollen was similar to that in senescing perianth tissue. Overall, respiration, ethylene and ACC content measurements suggest that senescence of G. Sylvia is non-climacteric in character. Nonetheless, the phytohormone ethylene is produced and evidently mediates normal flower development and non-climacteric senescence processes.     

Reduction of geitonogamy: Flower abscission for departure of pollinators

Overproduction of flowers increases the attractiveness of a plant to pollinators, but results in increased geitonogamy. In general, flower abscission has been considered to be an event subsequent to the overproduction of flowers. We observed pollinator behavior in Tilia, a self-incompatible, insect-pollinated tree. We found that pollinators sequentially visited inflorescences within a tree; however, when they met with flower abortion by abscission, they were apt to move long distances and leave the tree. We propose that plants may utilize flower abscission as a method for regulating the movements of pollinators by disturbing them in order to prevent geitonogamy.     

Three different polygalacturonases are expressed in tomato leaf and flower abscission, each with a different temporal expression pattern.

Abscission, or organ separation, is accompanied by a marked increase in hydrolases, which are responsible for the degradation of the middle lamella and the loosening of the primary cell wall surrounding cells in the separation layer. We recently reported on the cloning of a tomato (Lycopersicon esculentum) polygalacturonase (PG) cDNA, TAPG1, expressed during leaf and flower abscission. In addition to TAPG1, we have cloned two more PG cDNAs (TAPG2 and TAPG4) that are also expressed during leaf and flower abscission. The peptide sequences for the three abscission PGs are relatively similar (76-93% identity) yet different from the those of tomato fruit PG (38-41% identity). None of the three abscission PG mRNAs are expressed in fruit, stems, petioles, or anthers of fully open flowers. An RNase protection assay revealed that all three PGs are expressed in leaf and flower abscission zones and in pistils of fully open flowers. TAPG4 mRNA is detected much earlier than TAPG1 and TAPG2 mRNA during both leaf and flower abscission.     

Carbohydrate Availability in Relation to Fruitlet Abscission in Citrus

Abscission of flowers and fruitlets in the Washington navelorange (Citrus sinensis [L.] Osbeck) has been characterizedin relation to carbohydrate availability. A main wave of flowerabscission occurs shortly after anthesis while the carbohydratereserves in the tree are high. Fruitlet abscission starts approx.30 d after the commencement of flowering, while carbohydrates(mainly starch) are being accumulated in the leaves. Flowerand early fruitlet abscission are not caused by carbohydrateshortage. During late fruitlet abscission sucrose concentrationin the leaves falls to a low value demonstrating a limitationin supply and competition among the developing fruitlets forcarbohydrates. Concentrations of sucrose and reducing sugarsin the peel of the fruitlets also fall to low values, and arelationship could be demonstrated between these free sugarlevels and abscission. Ringing increases carbohydrate supplyto fruit and reduces late fruitlet abscission, but only hasa marginal effect on the growth of the fruitlets, which seemsless sensitive than abscission to carbohydrate shortage. Thelimitation of carbohydrate supply to the fruitlets occurs whilestarch levels in the leaves remain high. Slow mobilization ofstarch reserves may be one factor limiting set in Citrus. Copyright2001 Annals of Botany Company Carbohydrate supply, citrus, fruit growth and abscission, ringing, navel orange, starch, sugar metabolism     

Synergistic roles of leaf boron and calcium during the growing season in affecting sugar and starch accumulation in ripening apple fruit

Fruit sugar content is one of the most important flavor quality traits in the fresh market. Minerals, such as boron (B) and calcium (Ca), are associated with fruit sugar and starch accumulation in many plant species. To better understand the roles of B and Ca in affecting sugar and starch accumulation in apples, 2 g L^?1 Na₂B₄O₇·10H₂O or 10 g L^?1 CaCl₂ was supplied by foliar spray to 20-year-old ‘Fuji’ (Malus domestica Borkh. cv. Fuji) trees at four developmental stages (fruit set, onset of rapid fruit growth, rapid fruit growth and the end of rapid fruit growth), in 2010–2011. The most effective treatment significantly increasing soluble sugar and starch levels in ripening fruit was the foliar application of 2 g L^?1 Na₂B₄O₇·10H₂O during rapid fruit growth, and the robustness of the effects was confirmed for two cultivars, ‘Fuji’ and ‘Orin’, at three orchards in 2011. Foliar applications of B during the onset of rapid fruit growth and rapid fruit growth, as well as the foliar application of Ca at fruit set, significantly increased the soluble sugar content in ripening fruit. In addition, the B application was effective in increasing the fruit starch content, but Ca was not. Both B and Ca treatments significantly increased the leaf concentrations of the other element at least transiently. However, B and Ca effects on fruit sugar/starch did not seem to depend on higher leaf B or Ca levels. In conclusion, B and Ca interact in enhancing fruit sugar and starch contents at the fruit ripening stage.