Potential Fruit Growth Research Articles

Far-red radiation stimulates dry mass partitioning to fruits by increasing fruit sink strength in tomato.

Summary Far‐red (FR) light promotes fruit growth by increasing dry mass partitioning to fruits, but the mechanism behind this is unknown. We hypothesise that it is due to an increased fruit sink strength as FR radiation enhances sugar transportation and metabolism.Tomato plants were grown with or without 50–80 μmol m−2 s−1 of FR radiation added to a common background 150–170 μmol m−2 s−1 red + blue light‐emitting diode lighting. Potential fruit growth, achieved by pruning each truss to one remaining fruit, was measured to quantify fruit sink strength. Model simulation was conducted to test whether the measured fruit sink strength quantitatively explained the FR effect on dry mass partitioning. Starch, sucrose, fructose and glucose content were measured. Expression levels of key genes involved in sugar transportation and metabolism were determined.FR radiation increased fruit sink strength by 38%, which, in model simulation, led to an increased dry mass partitioned to fruits that quantitatively agreed very well with measured partitioning. FR radiation increased fruit sugar concentration and upregulated the expression of genes associated with both sugar transportation and metabolism.This is the first study to demonstrate that FR radiation stimulates dry mass partitioning to fruits mainly by increasing fruit sink strength via simultaneous upregulation of sugar transportation and metabolism.

Quantifying the source-sink balance and carbohydrate content in three tomato cultivars.

Supplementary lighting is frequently applied in the winter season for crop production in greenhouses. The effect of supplementary lighting on plant growth depends on the balance between assimilate production in source leaves and the overall capacity of the plants to use assimilates. This study aims at quantifying the source–sink balance and carbohydrate content of three tomato cultivars differing in fruit size, and to investigate to what extent the source/sink ratio correlates with the potential fruit size. Cultivars Komeet (large size), Capricia (medium size), and Sunstream (small size, cherry tomato) were grown from 16 August to 21 November, at similar crop management as in commercial practice. Supplementary lighting (High Pressure Sodium lamps, photosynthetic active radiation at 1 m below lamps was 162 μmol photons m-2 s-1; maximum 10 h per day depending on solar irradiance level) was applied from 19 September onward. Source strength was estimated from total plant growth rate using periodic destructive plant harvests in combination with the crop growth model TOMSIM. Sink strength was estimated from potential fruit growth rate which was determined from non-destructively measuring the fruit growth rate at non-limiting assimilate supply, growing only one fruit on each truss. Carbohydrate content in leaves and stems were periodically determined. During the early growth stage, ‘Komeet’ and ‘Capricia’ showed sink limitation and ‘Sunstream’ was close to sink limitation. During this stage reproductive organs had hardly formed or were still small and natural irradiance was high (early September) compared to winter months. Subsequently, during the fully fruiting stage all three cultivars were strongly source-limited as indicated by the low source/sink ratio (average source/sink ratio from 50 days after planting onward was 0.17, 0.22, and 0.33 for ‘Komeet,’ ‘Capricia,’ and ‘Sunstream,’ respectively). This was further confirmed by the fact that pruning half of the fruits hardly influenced net leaf photosynthesis rates. Carbohydrate content in leaves and stems increased linearly with the source/sink ratio. We conclude that during the early growth stage under high irradiance, tomato plants are sink-limited and that the level of sink limitation differs between cultivars but it is not correlated with their potential fruit size. During the fully fruiting stage tomato plants are source-limited and the extent of source limitation of a cultivar is positively correlated with its potential fruit size.

Growth characteristic and sink strength of fruit at different CO 2 concentrations in a Japanese and a Dutch tomato cultivar

The aim of the present study was to elucidate how fruit growth was limited by the source and sink capacities in a Japanese (‘Momotaro York’) and a Dutch (‘Dundee’) tomato cultivar. The two cultivars were grown hydroponically with a high-wire system in greenhouses for 25 weeks, and the growth characteristics and sink strength of fruit were determined. Fruits were pruned to four (4F) or one (1F) per truss. The latter were used to determine potential fruit growth, an indicator of fruit sink strength. Growth was also determined under normal (LC) and enriched (HC, 700 μmol mol −1) CO 2 concentrations to examine the effect of source enhancement on fruit production. In both cultivars under normal CO 2, the growth rate of fruit pruned to 4F per truss was lower than that in 1F, indicating that maximum potential fruit growth was not achieved. Under HC conditions, fruit growth rate of ‘Dundee’ achieved in 4F trusses was lower than that in 1F. In ‘Momotaro York’ in HC, fruit growth in 4F trusses was close to potential. This implies that fruit growth was source-limited irrespective of CO 2 concentrations in ‘Dundee’ cultivar while fruit growth in ‘Momotaro York’ under normal and enriched CO 2 conditions was limited by source and sink strengths, respectively. Adjustments of cultural practices including increasing fruit number per truss and/or genetic approaches to enhancing fruit sink strength by breeding may improve fruit yields of Japanese cultivars under high source/sink conditions.

USING GROWING DEGREE HOURS ACCUMULATED THIRTY DAYS AFTER BLOOM TO HELP GROWERS PREDICT DIFFICULT FRUIT SIZING YEARS

ISHS VIII International Symposium on Modelling in Fruit Research and Orchard Management USING GROWING DEGREE HOURS ACCUMULATED THIRTY DAYS AFTER BLOOM TO HELP GROWERS PREDICT DIFFICULT FRUIT SIZING YEARS

FRUIT DRY WEIGHT AND QUALITY OF 'BING' SWEET CHERRIES GROWN WITHOUT SOURCE LIMITATIONS

Understanding the seasonal pattern of potential fruit growth is important for identification and timing of possible management operations, and quantification of this pattern is an important prerequisite to serve as input for crop growth models. `Bing? sweet cherry trees were heavily thinned at 63 degree-days (DD) (=8 days) after full bloom so weight and quality of the remaining fruit could be monitored under conditions of limiting and non-limiting carbohydrate supply. The effect of fruit thinning on mean shoot growth and trunk cross-sectional area also was analysed to detect possible translocation from reproductive to vegetative growth. Mean Fruit Dry Weight (MFDW) of tagged fruit was estimated weekly, based on fruit diameter, to identify the moment of the onset of competition between fruit within trees. At harvest, Fruit Number to Leaf Area Ratio (FNLAR, fruits m-2 LA) was 52% lower in heavily-thinned trees than in non-thinned trees. Yield per tree was higher (P

Spring temperatures have a major effect on early stages of peach fruit growth

SummaryPrevious research has shown that Spring temperatures within 30 d after bloom (expressed as accumulated growing degree hours, GDH) are useful for predicting the harvest date of specific peach cultivars. The goal of the present research was to explore the relationship between GDH and additional environmental parameters on peach fruit development and growth during the period from the full bloom date (FBD) to the reference date (RD). Since heat accumulation during the first 30 d after bloom is a primary driver of fruit phenology, we hypothesised that years with high early Spring temperatures would result in smaller RD fruit size (RDFS) because trees cannot supply resources rapidly enough to support the potential growth associated with high rates of phenological development. Data on FBD, RD, and RDFS were collected at different locations in California between 1988 – 2004 and were analysed in conjunction with seasonal environmental data including accumulated GDH, rainfall, soil temperature, and solar radiation, from FBD to RD. Early Spring air temperatures appeared to be a primary environmental factor influencing RDFS. GDH accumulation during the first 30 d after bloom (GDH30) caused a decrease in the number of days between FBD and RD. RDFS increased with increases in the number of days between FBD and RD, and was negatively affected during years with high Spring temperatures. High GDH30 accumulations increased the rates of fruit growth d–1 but not enough to compensate for the shorter growth period from FBD to RD that occurred when GDH30 accumulation was high. The data supported the hypothesis that, with excessively high Spring temperatures, trees could not supply resources rapidly enough to support their maximum potential fruit growth rates.

Intra-canopy variability of fruit growth rate in peach trees grafted on rootstocks with different vigour-control capacity

SummaryThe aim of the present research was to study intra-canopy variability in fruit growth under conditions of low fruit-to-fruit competition in peach trees grafted on rootstocks with differing size-controlling capacity. The experiment was conducted on adult peach trees of two cultivars, each grafted on five rootstocks. Tree canopies were divided vertically into five layers. The diameter of 12 fruit per canopy layer was measured early in the growing season and at harvest. At harvest, the fresh weight of each selected fruit was also determined. After harvest, thirty shoots per tree bearing the selected fruit were harvested, and several parameters related to local carbon source availability, competition between vegetative and reproductive organs, vigour of the fruiting shoot, and position of the fruit on the fruiting shoot were measured. The results demonstrated that fruit variability within peach trees is very large, even when fruit-to-fruit competition is low. Fruit size at harvest decreased significantly and progressively from the top layers to the bottom layers of the canopy. Fruit growth was positively correlated with specific leaf weight, leaf area, and vigour of the fruiting shoot, and was negatively correlated with the vigour of current-season shoot growth on the fruiting shoot. However, the relative importance of each parameter depended on the cultivar. Rootstock affected the relationship between fruit growth and the measured parameters, and some rootstocks appeared to limit the maximum potential fruit growth rate. The measured parameters did not explain all the intra-canopy variability in fruit growth, suggesting that other factors also played a role. Interestingly, fruit size within 1 month of full bloom increased progressively from the top to the bottom of the canopy.

ABOVE-GROUND ASSIMILATE PARTITION IN BELL PEPPER (CAPSICUM ANNUUM L.) FOR PROCESSING UNDER MEDITERRANEAN CONDITIONS

ISHS International Workshop on Models for Plant Growth and Control of Product Quality in Horticultural Production ABOVE-GROUND ASSIMILATE PARTITION IN BELL PEPPER (CAPSICUM ANNUUM L.) FOR PROCESSING UNDER MEDITERRANEAN CONDITIONS

Ecophysiological analysis of genotypic variation in peach fruit growth

Cultivated varieties generally differ greatly from wild genotypes of the same closely related species. However, the processes responsible for these differences have not been elucidated. To analyse variations in fruit mass, fruit growth was characterized in a peach cultivar, a wild related species non-cultivated, and four hybrids derived by crossing them. These genotypes offer a wide range of agronomic values. An ecophysiological model of peach fruit growth in dry mass was used. This model simulates carbon partitioning at the 'shoot-bearing fruit' level by considering three compartments: fruits, 1-year-old stems and leafy shoots. The experimental measurements showed considerable variation between genotypes for fruit mass at maturity, fruit growth and source activity. The parameters of the ecophysiological model for each genotype were estimated from experimental data,. The model made it possible to account for genotypic variations in fruit growth and for genotype x fruit load interactions. Using the model, it was shown that the main processes explaining fruit growth variations among the genotypes studied were differences in potential fruit growth.

Irrigation and crop load interactions in relation to pear yield and fruit-size distribution

SummaryThe interaction between irrigation and crop load in their effect on fruit size distribution was investigated in a ‘Spadona’ (Pyrus communis) pear orchard located in a semi-arid zone. Five crop coefficient treatments were applied during the main fruit expansion phase: 0.25 KC, 0.40 KC, 0.60 KC, 0.80 KC, 1.00 KC where the crop coefficient (KC) is the applied irrigation level divided by the USDA "Class A" pan evaporation rate. An additional irrigation treatment (0.80 KC-ED) studied the effect of early water deficit. Crop load was adjusted to 200 to 800 fruits per tree in the 900 trees per ha orchard, by hand thinning. Cumulative irrigation levels up to harvest were 271, 351, 465, 572, 502 and 688 mm, in the 0.25 KC, 0.40 KC, 0.60 KC, 0.80 Kc, 0.80 KC-ED and 1.00 KC treatments, respectively. Crop yield increased with irrigation rate and crop load, with no interactions between the two. Total yields of fruits larger than 55, 60 and 65 mm increased with increasing irrigation level up to crop coefficient of 0.80, whereas the relative yields of fruits larger than 55, 60 and 65 mm increased with increasing crop coefficient up to 0.60,1.00 and 1.00, respectively. Relative yield of large fruits decreased with increasing crop level. The fruit weight was highly correlated with the midday stem water potential, although the maximum water potential in the present study was much lower than those reported elsewhere for non-stress conditions. This suggests that there was some limitation in the water-absorption capacity of the root system, or inefficient irrigation practice in the present study. The early water deficit here was too severe and the initial fruit diameter in the 0.80 KC-ED treatment was significantly lower than that in the 0.80 KCtreatment. Nevertheless, the fruit growth rate in the 0.80 KC-ED treatment was higher than that in the 0.80 KC, treatment, indicating that potential fruit growth rate was increased by early water deficit.

Maximum Fruit Growth Potential and Seasonal Patterns of Resource Dynamics During Peach Growth

Maximum fruit growth potential, the growth attained by fruits when they are grown under optimal environmental conditions in the presence of a non-limiting supply of resources, was estimated for two peach [ Prunus persica (L.) Batsch] cultivars that differ in the timing of resource demand for reproductive growth. Maximum potential fruit growth was estimated on trees that were heavily thinned at bloom. On these trees, resource availability exceeded resource demand for fruit growth. For both cultivars, the mean dry weights of fruits grown on unthinned trees were approximately half the mean dry weights of fruits grown on trees that were heavily thinned at bloom, indicating that fruit growth was source-limited on unthinned trees. Comparison of the seasonal patterns of relative growth rate of fruits on unthinned and heavily thinned trees indicated the source-limited fruit growth occurred during distinct periods of the growing season. On the early maturing cultivar, source-limited fruit growth occurred from 300 degree-days after bloom until harvest (4·5-10 weeks after bloom). On the late maturing cultivar, source-limited fruit growth occurred from 200-900 and 1600-1900 degree-days (3·5-12 and 18-20 weeks) after bloom. Although the final dry weight of fruits on the early maturing cultivar was only half that of fruits on the late maturing cultivar, the potential net sink strength of fruits was significantly higher on the early than the late maturing cultivar throughout the entire growth period of the early maturing cultivar. Resource availability for fruit growth was similar on the early and late maturing cultivars, indicating that selection for early maturing fruits has not changed the patterns of resource availability for fruit growth.

Competition for assimilates and fruit position affect fruit set in indeterminate greenhouse tomato

Localization and characterization of fruit set in winter tomato crops was investigated to determine the main internal and external controlling factors and to establish a quantitative relationship between fruit set and competition for assimilates. Individual fruit growth and development was assessed on a beef tomato cultivar during the reproductive period (first nine inflorescences). A non-destructive photograph technique was used to measure fruit growth from very early stages of their development and then calliper measurements were made on big fruits. From these measurements we determined the precise developmental stage at which fruit growth stopped. Fruit potential growth, which is defined as the growth achieved in non-limiting conditions for assimilate supply, was also assessed by this method on plants thinned to one flower per inflorescence. The latter was used to calculate the ratio between actual and potential growth, which was found to be a good index of the competition for assimilates. Time lags of fruit set were observed mainly on distal organs. When more than three flowers were left on each inflorescence, distal organs developed at the same time as proximal organs of the following inflorescence. Consequently they were submitted to a double competition within one inflorescence and among inflorescences. It was shown that, what is commonly named 'fruit set failure', is not an irreversible death of the organ and that a small fruit could resume growth after a delay of several weeks as soon as the first fruits ripened and thus ceased to compete for assimilates. In that case proximal fruits resumed growth before distal ones. The delayed fruits contained only few seeds but a germination test confirmed that fertilization took place before fruit set failed. Competition for assimilates was calculated during plant development by the ratio between actual and potential fruit growth. Potential growth of proximal fruits was strongly dependent on the position of the inflorescence on the stem, whereas potential growth of distal fruits was lower than or equal to that of proximal fruits of the same inflorescence and it was independent on the inflorescence position. We took into account both inflorescence and fruit positions to establish a quantitative relationship between fruit set of individual inflorescences and the ratio between actual and potential fruit growth.