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Global radiation on cloudless days within apple trees varied considerably. At most times on any day absorption of global radiation was dependant on solar zenith angle and was greatest between 1 and 2m from the tree tops. Measurements of penetrating global radiation were similar whether made on E-W or N-W tracks and differed little in trees on M.26...
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... color. There were about twice as many apples on trees on M.7 as on M.26 but they were poorer color (Table 4). An average of 36 percent of the fruit on M.7 did not have the minimum requirement of 30 percent red color as compared to only 4 percent of fruit on M.26. ...Context 2
... average of 36 percent of the fruit on M.7 did not have the minimum requirement of 30 percent red color as compared to only 4 percent of fruit on M.26. Apple color in all locations on trees on M.26 was satisfactory (Table 4). On M.7 many of the apples low on the tree did not develop the required 30 percent red color. ...Citations
... It is known that the intensity and the composition of the light are different in the exterior and interior regions of the tree canopy. Fruit in the top of the tree may receive a higher light intensity with relatively more UV and red light, and relatively less far-red light than in other positions (Looney, 1968;Proctor et al., 1975). Such conditions would stimulate the synthesis of anthocyanin and other avonoids in fruit at the top and outer position (Kubo et al., 1988;Lister et al., 1994). ...
... It is interesting to note that differences in ripeness (as determined by starch stage, ®rmness, sugar and acid levels) between various positions in the tree and wood types were only slight (data not reported). This may be an indication that the formation of cyanidin 3-galactoside and quercetin 3-glycosides in apple fruit is mainly dependent on a speci®c spectral distribution, as also suggested for colour development by Proctor et al. (1975). ...
Variations in ¯avonoid and chlorogenic acid levels within fruit, within tree, between orchards, between cultivars and among mutants were characterised and quanti®ed iElstar' anJonagold' apples by reversed-phase high performance liquid chromatography (RP-HPLC). The sun-exposed skin of individual fruit had much higher cyanidin 3-galactoside (anthocyanin) and quercetin 3-glycoside levels than the shaded skin, while phloridzin, catechins and chlorogenic acid were similar in the skin of both sides. Individual ¯avonoid and chlorogenic acid levels were not equally distributed within the fruit. Quercetin 3-glycosides and anthocyanin were almost exclusively found in the skin. Catechins were mostly found in the skin but some were present in the ¯esh. Phloridzin was most abundant in the seeds, with intermediate levels in both the core area and the skin, and the lowest level in the ¯esh. Chlorogenic acid was mainly present in the core area and the seeds with an intermediate level in the ¯esh and a low level in the skin. The levels of anthocyanin, quercetin 3-glycosides and total ¯avonoids were highest in fruit borne in the top of the tree followed by fruit from the outer tree parts, whereas the lowest levels were found in fruit from the inner tree. Terminal fruit contained the highest levels of these compounds, including catechins, compared to lateral and spur fruit. Phloridzin and chlorogenic acid were not affected by the position of the fruit in the tree nor by the bearing wood type. There were large differences in ¯avonoid and chlorogenic acid levels iElstar' fruit between two normally productive orchards differing mainly in growth vigourJonagold' and its mutants had considerably higher levels of ¯avonoid and chlorogenic acid thaElstar' and its mutants. The most blushed mutants of both cultivars had higher levels of anthocyanin but not of ¯avonoids or chlorogenic acid compared to the standard cultivar and to the less blushed mutants. The most blushed mutants had a higher number of red cells per cell layer and Scientia Horticulturae 83 (2000) 249±263
... Greater variation due to haze and highaltitude cirrus clouds would usually be present for cloudless conditions in Blacksburg, but this uniformly clear day was presented to provide a smooth baseline to illustrate sunflecks. At a peripheral canopy position, PPD totals on the clear day varied significantly due to shading within the canopy, as previously demonstrated (Christopher, 1934;Kromenko, 1972;Proctor et al., 1975); PPD totals for overcast conditions at the peripheral canopy position were lower than ambient, but the variation was similar to ambient because of the influence of diffuse light. At the intermediate canopy position there was much variation associated with the PPD totals on the clear day, while the PPD totals on the overcast day were low but relatively stable. ...
Percent instantaneous incident photosynthetic photon flux density (%INPPFD) was measured within an apple (Malus domestica Borkh.) canopy for various sky conditions and used to predict the percent cumulative incident photosynthetic photon density (PPD) for the last 10 weeks of the growing season (%CPPD LS ) and the total growing season (%CPPD TS ). Instantaneous measurements from overcast conditions were superior to measurements from clear or hazy conditions for the prediction of %CPPD LS in 1989 and 1990. A one-to-one relationship between %INPPFD and %CPPD LS was found for overcast conditions in both years, even though there was an 11% difference in total cumulative PPD between the years. The models had good predictive accuracy, with prediction coefficients of determination (R²Pred ) >0.83 in both years (n = 30). %lNPPFD from overcast conditions also yielded accurate predictive models for %CPPD TS(R > 0.84, n = 30), which differed from the models for %CPPD LS . Predictive models (for both %CPPD LS and %CPPD TS ) from %lNPPFD made before the canopy was fully developed differed from the models developed after canopy development was complete. The models still had good predictive accuracy, with R²Pred >0.76 (n = 30). Predictive models developed for cloudless conditions had inferior predictive accuracy (R²Pred = 0.49 to 0.80, n = 30) compared to models for overcast conditions. R²Pred were higher for hazy than for clear conditions. Time of day (1000 to 1400 hr ) had no consistent effect on the development of predictive models for any weather condition. The most reliable models resulted from the average of several measurements within a day, particularly for cloudless conditions.
... The absorption and utilization of photosynthetically active radiation (PAR) is one of the most important factors that limits plant productivity (11,12). Shading reduces flower bud initia tion, fruit size, fruit quality and color, number of new shoots, and plant fresh weight (5,9,12,18,19). Tree size, spacing, and training system have a dramatic effect on light conditions within the canopy (5,8,12). ...
One-year-old peach [ Prunus persica (L.) Batsch cv. Redhaven] trees were grown outdoors under 4 different shade levels (100%, 36%, 21%, and 9% of full sun). Shoot length, internode length, and node number were unaffected by shade, but heavy shade (9% full sun) reduced stem diameter 24%. Compared to those in full sun, average leaf areas were increased 18%, 30%, and 20% by 36%, 21%, and 9% shade, respectively. Shading caused a more horizontal leaf orientation and lower specific leaf weight. Both average and maximum photosynthetic rate per unit area or per mg chlorophyll decreased with shading, but increased with shading when expressed per unit dry weight. Chlorophyll content per unit leaf area increased with shading, but stomatal resistance was unaffected. Leaves from shade treatments became light-saturated between 400 and 600 µEs ⁻¹ m ⁻² ; full-sun leaves became light-saturated at 700-900 µEs ⁻¹ m ⁻² .
... The changes in the spectral distribution within the open-center canopy agreed with reports of others (4,18). In addition, Lakso (14) has determined that changes in the 660/730 nm ratios in an apple tree closely correlated to fisheye percentage of sky changes. ...
... In addition, Lakso (14) has determined that changes in the 660/730 nm ratios in an apple tree closely correlated to fisheye percentage of sky changes. Federer and Tanner (4) suggested that varying light quality may have affected growth and photoperiod response, while Proctor et al. (18) suggested that color development in apple was de pendent on a required spectral distribution. Lavee and Erez (15) concluded that light in the 600-690 nm range was needed for leaf bud burst in peach and that small amounts in the 500-600 nm range enhanced flower-bud opening. ...
Light levels were estimated by hemispherical photography at 4 different times during the growing season, in 4 different peach [ Prunus persica (L.) Batsch] hedgerow canopies: oblique fan, canted oblique fan, modified central leader, and open center. Greatest percentage of sky levels occurred in the area from above to 25 cm below the top of the canopy. There was little difference between canopy training systems except 1 m above the ground. Hedging improved the light microclimate in the canopies, but only within the top 25 cm. Spectral distribution determined in an open-center tree did not follow the general trend of total radiation. As shading increased, not all wavelengths were absorbed equally, resulting in a decrease of the visible to infrared ratio.
... Classically, studies of light penetration into deciduous fruit tree canopies have been conducted on clear, cloud-free days to provide a smooth diurnal pattern of external light (3,4,6,7,10,12,14,15,16,18,20). Since many of the studies took place in climates with high percentages of clear days, the light regimes were well chosen; however, in climates such as the Northeastern U.S., cloudiness is a common occurrence during the growing season. ...
Interior diffuse light readings were taken in trees of semi-dwarf ‘Wayne’ and ‘Golden Delicious’ apple ( Malus domestica Borkh.) on days of varying cloudiness. Interior light to shaded spurs was found to be greatest when the total light outside the tree was 60 to 90% of maximum, due to higher diffuse light with haze or light cloudiness. Diffuse light available to a shaded site within the canopy is a function of exterior diffuse light levels and canopy density as affected by cultivar. Calculations of whole canopy photosynthetic potential from light data and photosynthetic light response, indicate that haze or cloudiness is needed to obtain maximum whole canopy rates.
... Since radiation interception by leaves on shoots is dependent on both canopy architecture and the radiation regime complete and detailed analysis would be extremely complex. Much of the information required for such analysis is lacking for apple trees but some progress has recently been made (5,6,12,17). ...
Photosynthesis and dark respiration of the above ground components of young orchard-grown apple trees (Malus domestica Borkh.) were measured by infrared gas analysis. Soil and root respiration were determined by CO2 absorption. Maximum net photosynthesis (Pn) of shoots was 2.0 g CO ² m –2 hr –1 and light saturation level was 500 Wm –2 (global solar radiation). Photosynthetic efficiencies of shoots were at a maximum (6%) at 100 Wm –2 was 2 to 3% at light saturation. Pn rates of stems and fruits were very low and even at high irradiance did not exceed the compensation point. Dark respiration (Rd) increased exponentially with temperature. Rd per unit weight was comparable for leaves and stems, less for roots and very little for fruits; per unit area the rates for leaves and fruit were small, while those for stems were large. Estimates of dry matter accumulation by growth analysis and by net CO 2 uptake were remarkably similar, despite a gross simplifying assumption with regard to light interception by the leaves.
‘Redhaven’ peach fruits were exposed to various durations of radiation at the end of stage II of fruit development. Exposure of only 3 days (totals about 6280 J·em ⁻² ) markedly stimulated anthocyanin development. Color development as a function of solar radiation followed a power curve with nearly maximal level obtained after 8 days of exposure (18,003 J·em ⁻² ). A similar response was obtained with shade screen (40% and 10% of full sun); the greater the shade the less red color developed. Shading fruit with aluminum foil resulted in softer fruit with a lower level of soluble solids as compared to control fruit. Fruit exposure to solar radiation therefore may have a direct effect on fruit sink activity.
Developments in intensification of pome‐fruit orchards have led to changes in orchard design. Dwarfing rootstocks increase the proportion of harvestable yield. Precocious and high yields are also obtained with high light utilization, which can be achieved by manipulating planting density and planting system. To demonstrate this, hedgerows, multi‐row systems, and various trellis systems are compared with full‐field systems and homogeneous canopies. Light distribution is more uniform at low rectangular designs, which favors productivity, but a higher rectangularity (e.g., single rows) may be preferred if light penetration into the center of the rows becomes too low. The importance of row orientation for various planting systems and the effect of tree design on growth and productivity are discussed. Physiological implications are indicated briefly. Conclusions are drawn on optimal orchard designs in temperate climates.
Daytime stomatal conductance of McIntosh apple leaves was variable and relatively high (1.4 to 3.8 mm s−1) up until fruit removal. Leaf chlorophyll content, total leaf water potential, and specific leaf weight were less variable. Stem water content declined linearly by 10% from mid-August to late October. After fruit removal stomatal conductance, leaf chlorphyll content, and total leaf water potential decreased to low levels. Specific leaf weight did not decline until very late in leaf senescence.A simple model of stomatal response to environmental factors was tested and, following calculation of appropriate parameter values, gave acceptable agreement between measured and calculated stomatal conductances.
