[Effect of Soil Contamination on the Reflective Properties of Reflective Groundcovers]. / Einfluss der Verschmutzung von Reflexionsfolien auf ihr Reflexionsverhalten.

The objective of the present work was to study the effects of contamination on the reflective properties of groundcovers used for enhancing fruit colouration in the orchard. Contamination also affects longevity and possible sustainable re-use of materials. A white, woven textile (polypropylene Lumilys™) and silver aluminium foil were experimentally contaminated with soil, similar to the situation after an autumn storm in a fruit orchard. Clean material served as control.Using a spectrophotometer (StellarNet; Tampa, FL, USA), vertically directed (0°) and diffuse (45°) light reflection in the range of 500-850 nm was compared from clean and contaminated groundcover in the laboratory. Reflection from vertically directed aluminium foil exceeded that of Lumilys™; however, the highest reflection in all spectral measurements was at 45° (diffuse) from the clean woven textile, i.e., in all directions, and exceeded that of aluminium foil. In contrast, the contaminated vertically directed (0°) aluminium foil reflected less light than the clear foil but, surprisingly, reflected much more light at 45° than the clean foil. Both materials showed reflection peaks at 625-640 nm; light spectra and peaks remained unchanged irrespective of soil contamination.Light reflection in the visible range (PAR, 400-700 nm) was concomitantly measured in the field at CKA Klein-Altendorf near Bonn (50°N), Germany, at 0.5 m and 1 m height using a portable TRP­3 light sensor (PP-Systems, Amesbury, MA, USA) on sunny and cloudy days at a solar angle of 49°. Surprisingly, in these field measurements, Lumilys and aluminium foil reflected most light in both directions (0° and 45°) when slightly to moderately contaminated. Only with heavy contamination did the reflection decrease. Both groundcovers reflected more light than the grass in alleyways of fruit orchards or open soil under the trees.UV­B reflection (280-315 nm) was examined in parallel in the field using an X1 optometer (Gigahertz Optik, Türkenfels, Deutschland), as it enhances anthocyanin biosynthesis and red fruit colouration in combination with PAR and low temperature. Straight (0°) UV­B reflection from aluminium foil exceeded that from white woven textile (Lumilys™) on both clear and overcast autumn days. As expected, straight (0°) UV­B reflection from aluminium foil decreased with soil contamination to a certain extent, but it unexpectedly increased from the woven textile with soil contamination.Surface roughness in dependence of contamination was measured non-destructively by a profilometer type VR5200 (Keyence, Osaka, Japan). The roughness index, Sa, increased from 22 to 28 µm with soil contamination of the woven textile and from to 2 to 11 µm with aluminium foil, possibly explaining differences in the observed reflectivity.Overall, the expected severe decline in light reflection (PAR and UV-B) was not seen. In contrast, light (2-3 g soil/m2) and moderate (4-12 g soil/m2) contamination improved light reflection of PAR (400-700 nm) and UV­B (280-315 nm) by woven textile (Lumilys™) and aluminum foil. Thus, with slight contamination the materials can be reused, whereas severe contamination (24-51 g soil/m2) reduces light reflection.

Preanthesis changes in freeze resistance, relative water content, and ovary growth preempt bud phenology and signify dormancy release of sour cherry floral buds.

MAIN CONCLUSION: Growing degree hours (GDH) predicted floral bud development of 'Montmorency' sour cherry and explained changes in lethal temperatures (LT50) that preempted any visible changes in bud phenology. The gradual warming during late winter and early spring promotes floral bud development and, concomitantly, the de-acclimation of Prunus sp. flowers. In fact, once ecodormancy releases, an approximate 20 °C loss of hardiness occurs prior to any distinguishable changes in external bud phenology. The aim of the following work was to characterize the physiological changes of 'Montmorency' sour cherry floral buds as they transition from endo- and ecodormancy and resume growth, and to determine whether physiological and anatomical characteristics within the buds preempt or signify dormancy release to enable a better prediction of freeze susceptibility. Here, we present a developmental timeline of the preanthesis changes of 'Montmorency' floral buds, ovaries and anthers over 2 years following their completion of chilling and relate these changes to growing degree hours (GDH) and the lethal temperature (LT50) of flowers. Changes in bud dry weight (DW), fresh weight (FW), volume, and external phenology stage including the percentage of green color development of bud scales were predicted by heat accumulation but were not early predictors of the increasing freeze susceptibility of pistils. Between endodormancy and green tip stage, ovary volume increased nearly threefold and relative water content (RWC) increased from ~ 45 to 70% in both years. A linear mixed regression model indicated that RWC and the interaction between RWC and ovary growth were significant predictors of LT50. Importantly, the loss of ~ 20 °C of freeze resistance occurred between 45 and 57% RWC and preceded any detectable changes in bud phenology. Microsporogenesis was observed after dormancy release when measurable changes in the ovary and bud RWC had already occurred. A GDH model estimated freeze sensitivity of pistils and explained 93% of the variation in LT50 during preanthesis development. A simple GDH model to predict critical freeze temperature of pistils should aid producers to manage frost protection.

Carbon reduction strategies for regionally produced and consumed wine: From farm to fork.

I) BACKGROUND: Carbon footprint studies of locally produced and consumed wine are missing. II) PURPOSE(S): The objective of the present study was to identify management strategies and carbon reduction potentials for a sustainable wine production based on the carbon footprint and the water footprint of locally grown grapes and wine locally produced and consumed. III) METHODS: Two wineries (A and B) were investigated, both of which grow the same white (Riesling) and the same red grape (Pinot Noir/Spätburgunder) on the same rootstock in the Rhine river valley of Germany. The study was based on PAS 2050-1 (BSI) and comprised 99% primary data derived from historical farm records. System boundaries ranged from planting of the grapevines to eventual disposal of a typical 0.75 L glass bottle, which served as the functional unit (FU). IV) RESULTS: The product carbon footprint (PCF) was 1.91 ±â€¯0.3 kg CO2eq/bottle (A) or 1.69 ±â€¯0.3 (B) kg CO2eq/bottle of white wine and 1.86 ±â€¯0.3 kg CO2eq/bottle of red wine for both wineries. These results were attributed to the consumer behaviour (22-30%), followed by the use and production of glass bottles (20-27%). Grapevine cultivation amounted to 0.3-0.4 kg CO2eq/bottle; grape processing caused ca. 0.05-0.06 kg CO2eq/bottle, packaging 0.5-0.6 kg CO2eq/bottle, distribution 0.2-0.4 kg CO2eq/bottle, while use and disposal of the glass bottles emitted 0.5-0.6 kg CO2eq/bottle. The plant protection chemicals caused only ca. 1.4% and organic fertilizer ca. 2.8% of the product carbon footprint (PCF). Red and white wine appeared commensurate in their PCF within 3-8% in both vineyards. The water footprint was ca. 5.7 ±â€¯0.6 (A) and 2.1 ±â€¯0.4 (B) L blue water/bottle for both red and white wine. V) DISCUSSION: The results are discussed with higher carbon footprint values for wine from overseas. We have identified the following reduction potentials such as the following management strategies: VI) RECOMMENDATIONS: a) reduction of fossil fuels for gas heating of the premises and for farm vehicles, b) the use of lightweight glass bottles and c) alternative means of transport for the consumer purchase at the winery when using a private vehicle.

Publisher Correction: The Effects of Extreme Weather on Apple Quality.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The Effects of Extreme Weather on Apple Quality.

A large literature has documented the effects of weather on agricultural yields. However, weather not only impacts the quantity produced, but also the quality of the product. Due to data limitations, the quality effects have primarily been studied using lab experiments for specific attributes, and the financial implications for farmers of a quality effect are less clear. Using a unique longitudinal micro-level data set of Swiss apple orchards that include information on both the quantity produced as well as the quality, we show that the latter can have an even larger effect on farm revenue. Ignoring the quality of the harvested product substantially biases the impact of weather extremes on agricultural income and the potential effects of climate change. Our quality measure is the orchard-year specific price shock. If an orchard gets a lower price for its specific apple variety compared to previous years and compared to other orchards in the same year, we observe the market's valuation of its inferior quality accounting for overall price movements (other orchards growing same variety that year) as well as orchard specific factors (orchard fixed effects). We find that spring frost events induce farm gate price drops and thus revenue reductions of up to 2.05% per hour of exposure.

Non-Destructive, Opto-Electronic Determination of the Freshness and Shrivel of Bell Pepper Fruits.

(1) The objective of the present study was to identify suitable parameters to determine the (degree of) freshness of Bell pepper fruit of three colors (yellow, red, and green) over a two-week period including the occurrence of shrivel using non-destructive real-time measurements (2) Materials and methods: Surface glossiness was measured non-destructively with a luster sensor type CZ-H72 (Keyence Co., Osaka, Japan), a colorimeter, a spectrometer and a profilometer type VR-5200 (Keyence) to obtain RGB images. (3) Results: During storage and shelf life, bell pepper fruit of initially 230-245 g lost 2.9-4.8 g FW per day at 17 °C and 55% rh. Shriveling started at 6-8% weight loss after 4-5 days and became more pronounced. Glossiness decreased from 450-500 a.u. with fresh fruit without shrivel, 280-310 a.u. with moderately shriveled fruit to 80-90 a.u. with severely shriveled fruit irrespective of color against a background of <40 a.u. within the same color, e.g., light red and dark red. Non-invasive color measurements showed no decline in Lab values (chlorophyll content), irrespective of fruit color and degree of shrivel. RGB images, converted into false color images, showed a concomitant increase in surface roughness (Sa) from Sa = ca. 2 µm for fresh and glossy, Sa = ca. 7 µm for moderately shriveled to Sa = ca. 24 µm for severely shriveled rough surfaces of stored pepper fruit, equivalent to a 12-fold increase in surface roughness. The light reflectance peak at 630-633 nm was universal, irrespective of fruit color and freshness. Hence, a freshness index based on (a) luster values ≥ 450 a.u., (b) Sa ≤ 2 µm and (c) the difference in relative reflectance in % between 630 nm and 500 nm is suggested. The latter values declined from ca. 40% for fresh red Bell pepper, ca. 32% after 6 days when shriveling had started, to ca. 21% after 12 days, but varied with fruit color. (4) Conclusion: overall, it can be concluded that color measurements were unsuitable to determine the freshness of Bell pepper fruit, whereas profilometer, luster sensor, and light reflectance spectra were suitable candidates as a novel opto-electronic approach for defining and parametrizing fruit freshness.

Anthocyanin synthesis and light utilisation can be enhanced by reflective mulch - Visualisation of light penetration into a tree canopy.

With the increasing use of hailnets and decrease in light availability in the ripening period of apple fruit, insufficient light exposure often causes poor colouration viz anthocyanin synthesis on certain parts of the fruit and on certain fruit within the tree. The aim of this study was to investigate the potential of improving anthocyanin synthesis, in terms of fruit colouration, the major incentive for a consumer. Therefore, the reflective ground cover Lumilys® was spread between 'Braeburn Mariri Red' apple rows under a crystalline hailnet seven weeks prior to harvest and colour measured on 240 attached apple fruit. The reflective ground cover increased the reflected light by 1.6 to 3.9 times 1.0 m above ground. The improved light utilization led to an improved peel colouration, especially on the shaded side of the apple fruit and fruit in the lower inner part of the canopy, A coloured visualization from orange (high light intensity), yellow (medium) to green (low light intensity) as a result of the individual PAR measurements every 20 cm inside the canopy showed how the reflective mulch influences the light penetration into the different parts of the tree canopy.

Changes in carbohydrate levels and relative water content (RWC) to distinguish dormancy phases in sweet cherry.

Perennial trees require chilling, i.e. a period of cold temperature in the winter, for flowering next spring; sweet cherry is particularly prone to lack of chilling. The objective of this study is to identify possible transition points to clearly distinguish dormancy phases by relating carbohydrate and relative water content (RWC) in reproductive buds to concomitant chilling fulfilment. This contribution proposes the use of four transition points between the dormancy phases and their characterization in terms of carbohydrates, water contents in combination with chilling values and may allow upscaling to other dormancy studies in trees; two groups of cherry varieties were defined based on their different initial sorbitol and starch level in the autumn. The first separation between para- and (deep) d-endo-dormancy is characterized as a transition from a decrease (variety group 1) or a constant level (variety group 2) to a sharp increase in hexoses and sorbitol and a drop of starch content. The second transition point (d-endo- to f-endo-dormancy) is characterized as the changes in both hexoses (increase) and starch (decrease) terminate and ca. 650 Chilling Hours (CH), i.e. insufficient chilling in the concomitant forcing experiment with cut branches. This third transition point (f-endo- to eco-dormancy) was characterized by ca. 1000 CH, the minimum chilling requirement and restrained flowering (cut branches). The fourth transition point (forcing initiation) marked an increase in water content at ca. 1550 CH, optimum chilling for cherry and coincided with natural flowering. A ratio of hexoses (glucose plus fructose) to starch content (<2:1) appeared to be a potential indicator of the beginning of chilling (para-dormancy) and a ratio of 14-20:1 typical for endo-dormancy, whereas the release from dormancy was associated with a decline to less than 10:1 at the end of winter (eco-dormancy). To our knowledge, this is the first time that transition points are identified based on constituents (carbohydrates and relative water content) in floral buds related to current chilling status and dormancy phases and are also presented in a schematic diagram. The understanding of these changes in relative water content and carbohydrate levels may contribute to manage insufficient chilling in the orchard and support climate change studies with trees.

Non-Destructive Sensor-Based Prediction of Maturity and Optimum Harvest Date of Sweet Cherry Fruit.

(1) Background: The aim of the study was to use innovative sensor technology for non-destructive determination and prediction of optimum harvest date (OHD), using sweet cherry as a model fruit, based on different ripening parameters. (2) Methods: Two cherry varieties in two growing systems viz. field and polytunnel in two years were employed. The fruit quality parameters such as fruit weight and size proved unsuitable to detect OHD alone due to their dependence on crop load, climatic conditions, cultural practices, and season. Coloration during cherry ripening was characterized by a complete decline of green chlorophyll and saturation of the red anthocyanins, and was measured with a portable sensor viz. spectrometer 3-4 weeks before expected harvest until 2 weeks after harvest. (3) Results: Expressed as green NDVI (normalized differential vegetation index) and red NAI (normalized anthocyanin index) values, NAI increased from -0.5 (unripe) to +0.7 to +0.8 in mature fruit and remained at this saturation level with overripe fruits, irrespective of variety, treatment, and year. A model was developed to predict the OHD, which coincided with when NDVI reached and exceeded zero and the first derivative of NAI asymptotically approached zero. (4) Conclusion: The use of this sensor technology appears suitable for several cherry varieties and growing systems to predict the optimum harvest date.

Targeted forcing improves quality, nutritional and health value of sweet cherry fruit.

BACKGROUND: Trade and consumers alike require premium-quality cherries with high nutritional and health values preferably of local origin. While early fruit imports cannot supply such fruit, a new technology of forcing cherry emerged for an early local supply by covering the crop in spring. In the apparent scarcity of data on the resulting fruit quality, fruit characteristics of forced cherries were compared with those without cover. RESULTS: Size and weight of forced cherry fruit were successfully increased by 6-14%. The less negative osmotic potential of the forced fruit (-3 to -2 MPa Ψπ ) indicates less water stress under spring cover compared with field-grown fruit (-4 MPa Ψπ ), as confirmed by the larger fruit size and weight. Greater antioxidative potentials in the lipophilic and hydrophilic extracts (control min. 185 mE vs max. 365 mE under cover) of forced fruit of two cultivars showed their healthier attribute in terms of bioactive compounds, supported also by an average 14% increase in phenolics, as a response to the modified environmental conditions, which has not been investigated before. CONCLUSION: The new technology of covering cherry trees in spring to force flowering and enhance ripening can improve the synthesis of bioactive compounds and provide the consumer with early high-quality fruit. © 2017 Society of Chemical Industry.

A collection of European sweet cherry phenology data for assessing climate change.

Professional and scientific networks built around the production of sweet cherry (Prunus avium L.) led to the collection of phenology data for a wide range of cultivars grown in experimental sites characterized by highly contrasted climatic conditions. We present a dataset of flowering and maturity dates, recorded each year for one tree when available, or the average of several trees for each cultivar, over a period of 37 years (1978-2015). Such a dataset is extremely valuable for characterizing the phenological response to climate change, and the plasticity of the different cultivars' behaviour under different environmental conditions. In addition, this dataset will support the development of predictive models for sweet cherry phenology exploitable at the continental scale, and will help anticipate breeding strategies in order to maintain and improve sweet cherry production in Europe.

Non-Invasive Examination of Plant Surfaces by Opto-Electronic Means--Using Russet as a Prime Example.

(1) BACKGROUND: Many disorders and diseases of agricultural produce change the physical features of surfaces of plant organs; in terms of russet, e.g., of apple or pear, affected fruit peel becomes rough and brown in color, which is associated with changes in light reflection; (2) OBJECTIVE AND METHODS: The objective of the present project was an interdisciplinary approach between horticultural science and engineering to examine two new innovative technologies as to their suitability for the non-destructive determination of surfaces of plant organs, using russet as an example, and (a) an industrial luster sensor (type CZ-H72, Keyence, Japan) and (b) a new type of a three-dimensional (3D) color microscope (VHX 5000); (3) RESULTS: In the case of russet, i.e., suberinization of the fruit peel, peel roughness increased by ca. 2.5-fold from ca. 20 µm to ca. 50 µm on affected fruit sections when viewed at 200× magnification. Russeted peel showed significantly reduced luster, with smaller variation than russet-devoid peel with larger variation; (4) CONCLUSION: These results indicate that both sensors are suitable for biological material and their use for non-contact, non-invasive detection of surface disorders on agricultural produce such as russet may be a very powerful tool for many applications in agriculture and beyond in the future.

Reducing ethylene levels along the food supply chain: a key to reducing food waste?

Excessive waste along the food supply chain of 71 (UK, Netherlands) to 82 (Germany) kg per head per year sparked widespread criticism of the agricultural food business and provides a great challenge and task for all its players and stakeholders. Origins of this food waste include private households, restaurants and canteens, as well as supermarkets, and indicate that 59-65% of this food waste can be avoided. Since ∼50% of the food waste is fruit and vegetables, monitoring and control of their natural ripening gas - ethylene - is suggested here as one possible key to reducing food waste. Ethylene accelerates ripening of climacteric fruits, and accumulation of ethylene in the supply chain can lead to fruit decay and waste. While ethylene was determined using a stationary gas chromatograph with gas cylinders, the new generation of portable sensor-based instruments now enables continuous in situ determination of ethylene along the food chain, a prerequisite to managing and maintaining the quality and ripeness of fruits and identifying hot spots of ethylene accumulation along the supply chain. Ethylene levels were measured in a first trial, along the supply chain of apple fruit from harvest to the consumer, and ranged from 10 ppb in the CA fruit store with an ethylene scrubber, 70 ppb in the fruit bin, to 500 ppb on the sorting belt in the grading facility, to ppm levels in perforated plastic bags of apples. This paper also takes into account exogenous ethylene originating from sources other than the fruit itself. Countermeasures are discussed, such as the potential of breeding for low-ethylene fruit, applications of ethylene inhibitors (e.g. 1-MCP) and absorber strips (e.g. 'It's Fresh', Ryan'), packages (e.g. 'Peakfresh'), both at the wholesale and retail level, vents and cooling for the supply chain, sale of class II produce ('Wunderlinge'), collection (rather than waste) of produce on the 'sell by' date ('Die Tafel') and whole crop purchase (WCP) to aid reducing food waste.

Quantifying key parameters as elicitors for alternate fruit bearing in cv. 'Elstar' apple trees.

The commonly known alternate bearing, i.e. year-to-year change of large and small yields of fruit tree crops worldwide, is often induced by abiotic stress such as late frost, which will eliminate flowers or fruitlets. This study presents an alternative form, biotic biennial bearing, i.e. change of large and small yields of the same trees within the same tree row in the same year. Three methods were developed or modified for the analysis of the number of flower clusters and yield of 2086 apple (Malus domestica Borkh.) cv. 'Elstar' trees. The first method, i.e., based on intersect between yield in year x and year x+1 and flower clusters in year x, yielded 91-106 flower clusters, whereas the second method, i.e., mean yield in year x and year x+1, resulted in a range of 72-133 flower clusters, or 9.6kg/tree necessary for sustainable cultivation of apple cv. 'Elstar'. The third 'biennial bearing index' (BBI), was calculated in three ways as the ratio of differences in tree yields to cumulative tree yield, for individual trees (rather than orchard average) to demonstrate the tree-to-tree alternation. A scheme for the possible underlying regulatory mechanisms was developed, which includes potential elicitors such as light deprivation and subsequent lack of flower initiation, are discussed as a possible result of polar basipetal GA7 transport, cytokinin level in the xylem and phloem and down-regulation of the gene expression of the flowering gene. Suggested countermeasures included early chemical or mechanical thinning.

Reflective mulch enhances ripening and health compounds in apple fruit.

BACKGROUND: The objective of the study was to improve fruit quality, including health compounds, by improving light utilization for fruit crops under hail net. Four reflective mulches including plastics such as Extenday® and a bio-degradable paper were spread in the alleyways of a cv. 'Gala Mondial' apple orchard on 10 August 2010 5 weeks before anticipated harvest. RESULTS: Reflective mulch affected neither fruit firmness nor sugar, but accelerated starch breakdown, indicative of riper fruits (smaller Streif index), compared with the uncovered grass alleyway (control). Reflective mulches also improved fruit quality such as red coloration of cv. 'Gala Mondial' apples. This was due to significantly enhanced flavonoids and anthocyanins. Flavonoids increased up to 52.4% in the Extenday® treatment (29.2 nmol cm(-2) in the grass control versus 44.5 nmol cm(-2) fruit peel with reflective mulch). Similarly, reflective mulch improved anthocyanin content in cv. 'Gala Mondial' peel up to 66% compared to grass control (14.5 nmol cm(-2) in control fruit versus 24.1 nmol cm(-2) with reflective mulch). The reflective mulch did not affect chlorophyll and carotenoid content in the 'Gala' fruit peel. CONCLUSION: Overall, the application of reflective mulches improved fruit quality in terms of better coloration and health compounds and accelerated ripening, leading to higher market value.

Identification of chilling and heat requirements of cherry trees--a statistical approach.

Most trees from temperate climates require the accumulation of winter chill and subsequent heat during their dormant phase to resume growth and initiate flowering in the following spring. Global warming could reduce chill and hence hamper the cultivation of high-chill species such as cherries. Yet determining chilling and heat requirements requires large-scale controlled-forcing experiments, and estimates are thus often unavailable. Where long-term phenology datasets exist, partial least squares (PLS) regression can be used as an alternative, to determine climatic requirements statistically. Bloom dates of cherry cv. 'Schneiders späte Knorpelkirsche' trees in Klein-Altendorf, Germany, from 24 growing seasons were correlated with 11-day running means of daily mean temperature. Based on the output of the PLS regression, five candidate chilling periods ranging in length from 17 to 102 days, and one forcing phase of 66 days were delineated. Among three common chill models used to quantify chill, the Dynamic Model showed the lowest variation in chill, indicating that it may be more accurate than the Utah and Chilling Hours Models. Based on the longest candidate chilling phase with the earliest starting date, cv. 'Schneiders späte Knorpelkirsche' cherries at Bonn exhibited a chilling requirement of 68.6 ± 5.7 chill portions (or 1,375 ± 178 chilling hours or 1,410 ± 238 Utah chill units) and a heat requirement of 3,473 ± 1,236 growing degree hours. Closer investigation of the distinct chilling phases detected by PLS regression could contribute to our understanding of dormancy processes and thus help fruit and nut growers identify suitable tree cultivars for a future in which static climatic conditions can no longer be assumed. All procedures used in this study were bundled in an R package ('chillR') and are provided as Supplementary materials. The procedure was also applied to leaf emergence dates of walnut (cv. 'Payne') at Davis, California.

A comprehensive overview of the spatial and temporal variability of apple bud dormancy release and blooming phenology in Western Europe.

In the current context of global warming, an analysis is required of spatially-extensive and long-term blooming data in fruit trees to make up for insufficient information on regional-scale blooming changes and determinisms that are key to the phenological adaptation of these species. We therefore analysed blooming dates over long periods at climate-contrasted sites in Western Europe, focusing mainly on the Golden Delicious apple that is grown worldwide. On average, blooming advances were more pronounced in northern continental (10 days) than in western oceanic (6-7 days) regions, while the shortest advance was found on the Mediterranean coastline. Temporal trends toward blooming phase shortenings were also observed in continental regions. These regional differences in temporal variability across Western Europe resulted in a decrease in spatial variability, i.e. shorter time intervals between blooming dates in contrasted regions (8-10-day decrease for full bloom between Mediterranean and continental regions). Fitted sequential models were used to reproduce phenological changes. Marked trends toward shorter simulated durations of forcing period (bud growth from dormancy release to blooming) and high positive correlations between these durations and observed blooming dates support the notion that blooming advances and shortenings are mainly due to faster satisfaction of the heating requirement. However, trends toward later dormancy releases were also noted in oceanic and Mediterranean regions. This could tend toward blooming delays and explain the shorter advances in these regions despite similar or greater warming. The regional differences in simulated chilling and forcing periods were consistent with the regional differences in temperature increases.

Does the microclimate under hail nets influence micromorphological characteristics of apple leaves and cuticles?

A higher frequency of hail storms, possibly due to climate change, has led to increased installation of hail nets worldwide. The objective of the present work was to investigate potential effects of the microclimate under these hail nets on micromorphological characteristics of the leaves and adaxial leaf cuticles. Leaves of apple cultivars 'Pinova' and 'Fuji' grown on trees under white (highly translucent) or red-black (low transmittance) hail nets or on uncovered (control) trees were evaluated in June, August, September and October. The microclimate under the colored hail nets had no impact on leaf micromorphology, amount of cuticular wax, or leaf thickness. Similarly, no differences in thickness and permeability for calcium could be established between cuticles of leaves grown on trees under the two types of hail nets or uncovered trees. For all evaluated parameters, significant differences were detected between the two cultivars examined. In both cultivars, leaf wax synthesis followed a characteristic curve, increasing from the first to the second evaluation, and then decreasing continuously without affecting cuticular penetration of calcium. Overall, our results show that a reduction of the hail nets by 6-10% in both light and humidity was insufficient to influence the surface properties of apple leaves and permeability of cuticles. This may suggest that pest management strategies, i.e. formulation of agrochemicals, their application and dose, do not need to be adapted when used under hail nets. Overall, the present results indicate that the microclimatic changes brought about by colored hail nets are sufficient to enhance the vegetative growth and induce the 'shade avoidance syndrome', but do not appear to affect the leaf cuticular properties.

Mechanical flower thinning improves the fruit quality of apples.

BACKGROUND: Apple 'Golden Delicious Reinders' and 'Gala Mondial' trees were mechanically blossom-thinned with 30-77 x g (300-480 rpm rotation) and 5 or 7.5 km h(-1) vehicle speed to improve fruit quality, minimise leaf damage, reduce hand and chemical thinning and to prevent or overcome alternate bearing; adjacent untreated or manually thinned apple trees served as controls. RESULTS: Mechanical thinning (43 x g, 360 rpm, 5-7.5 km h(-1)) had a positive effect on fruit size (15% larger), firmness (8.4 in Gala vs. 7.6 kg cm(-2) in the unthinned control), sweetness (124 vs. 117 g kg(-1) sugar in the control), contained the largest malic acid content (4 g kg(-1) vs. 3.4 g kg(-1) in the control) and 17% more anthocyanin (normalised anthocyanin index = 0.8 in Gala vs. 0.7 in the control); fruit of Golden and Gala showed additionally advanced starch breakdown and ripened earlier. CONCLUSIONS: Since increases in rotor speed, viz. centrifugal force, versus increases in the vehicle speed resulted in opposing effects, an integrated coefficient of thinning (ICT) was devised with optimum values of 10-40 (at 43 x g, 5-7.5 km h(-1)), where an ICT > 50 led to tree damage and ICT < 8 led to sub-optimum thinning efficacy.

Temperature, evapotranspiration and primary photochemical responses of apple leaves to hail.

The objective of this work was to examine immediate physiological plant responses to hail and subsequent recovery in terms of evapotranspiration, leaf temperature and primary photochemical processes using apple as a model crop. Thermal emission pictures were taken in darkness to avoid interference from stomatal movements; temperature gradients were identified in concentric rings around sites of hail injury, with a distinct drop in temperature of up to 2.3 degrees C in the center immediately after the induced hail injury. This was due to enhanced evapotranspiration from the injured tissue. Six to twelve minutes after hail injury, the initial decrease in leaf temperature partially reversed. Chlorophyll fluorescence kinetics of light-adapted leaves showed a dramatic decrease in effective photosynthetic electron transport rate (ETR), from 20.5 to 9.0 micromol electron m(-2)s(-1) within 5 min from hail injury, and a rapid recovery to 14.1 micromol electron m(-2)s(-1) within the next 5 min. After 7h, ETR partially recovered to 17.4 micromol electron m(-2)s(-1). An initial drop in non-photochemical efficiency (NPQ) from 1.07 to 0.90 units within 5 min after hail injury was followed by a sharp increase to 1.67 units after another 5 min. During the next hour, NPQ gradually decreased to the initial level. This indicates increased thermal dissipation in photosystem II (PS II) as a protective mechanism against incident excessive energy in the leaves with closed stomata for 1h after hail injury. In contrast to the fluorescence kinetics of light-adapted leaves, maximum quantum yield Fv/Fm of PSII in the dark-adapted state remained unchanged at 0.79-0.81 relative units for the first 5 min after hail injury. Thereafter, Fv/Fm slowly declined to 0.75 within 1h, and to a trough of 0.73 at 3h. Seven hours after hail injury, Fv/Fm values were at 0.76, indicating partial recovery of PS II efficiency. The discrepancy in the dynamics of ETR and Fv/Fm responses may be explained by the formation of alternative electron sinks such as reactive oxygen species, particularly superoxides, which withdraw electrons from the photosynthetic transport, resulting in apparently higher values of calculated ETR.