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  • Author or Editor: R. Kammereck x
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Samples of current season shoots of Anjou, Bartlett and Bosc pears were collected throughout the year during 1990, `91 and `92. Differential thermal analysis (DTA) and vital staining with triphenyltetrazolium chloride (TTC) were used at the sampling times to determine freeze resistance. Freezing tests were conducted on greenhouse-grown trees. Temperatures to freeze the trees were predetermined by DTA. After freezing TTC staining, acid fuchsin test and growth were used to determine survival. All three varieties began to acclimate after terminal growth ceased in late June until October. Bartlett and Anjou obtained about -25°C resistance by this time and Bose about -23°C. After frost began, Anjou and Bartlett gained an additional resistance to -33°C and Bose to -28°C. Trees frozen artificially at -27°C had limited growth but did leaf out only to die a month later. Trees frozen at -33°C never leafed out Bartlett trees at -27°C looked better than Anjou and Bose trees but died also.

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Abstract

A system for monitoring CO2 flux in deciduous fruit trees was developed that allows simultaneous, independent control of climatic variables over a wide range. For such a system to work effectively, attention must be given to proper sealing of the chamber, placement of components within the system and disturbances which may arise from the functioning of control and sampling loops. Using the system described, it was found that the occurrence of a light frost after ‘Golden Delicious’ apple trees (Malus domestica Borkh.) had begun to produce vegetative growth drastically affected the carbon flux within the plant. These changes took place even though the cold stress was not severe enough to cause any discernible visual symptoms. Subsequent exposure of the trees to favorable growing conditions after a light frost resulted in the gradual recovery of the photosynthetic rate to levels approaching but not equal to that occurring in tissues of unstressed trees.

Open Access

Abstract

The effects of light intensity and leaf temperature on the net photosynthetic rate of rapidly growing ‘Golden Delicious’ apple (Malus domestica Borkh.) shoots were determined in a temperature range (-1.6 to 44°C) broader than previously reported. Under saturating light conditions the rate of CO2 uptake increased with leaf temperature to 2.7 g CO2 m2hr-1 at 25°. Optimum temperature decreased as the light intensity decreased, indicating a relationship between temperature and light saturation levels. At 25 to 30° the light saturation point was equivalent to 86 W/m2 of incident electromagnetic energy at wavelengths of 400 to 750 nm. At temperatures higher than the optimum, the rate of carbon dioxide uptake decreased rapidly. At 47 to 50° and high light intensities, the rate of carbon dioxide uptake was 0.3 to 0.5 g CO2 m-2hr-l.

Open Access

Abstract

Calyx green end disorder (GED) of ‘Golden Delicious’ apple (Malus domestica Borkh.) is a sublethal fruit disorder characterized by a flattening distortion of the calyx lobes and a persistent green coloring of the skin at the calyx end of mature fruit. The severity of the symptom varied from mild skin greening to necrosis and was subjectively evaluated on a scale of one to 5. Fluoride applied as ammonium fluoride to spur leaves, fruit, the whole canopy, and via xylem caused symptoms identical to those in an untreated commercial orchard with a serious GED problem. Increasing severity of GED up to a rating of 3 was associated with increased levels of F in cortical calyx fruit tissue (r = 0.93). In the commercial orchard, the incidence of GED was associated with elevated levels of soil- and air-borne F. Season-long calcium chloride sprays were not effective in reducing GED, but weekly overhead irrigation rinsing treatments did significantly reduce GED severity. Gibberellins A4 + 7 (GA4 + 7) plus 6-benzylamino purine (BA) applied at bloom also reduced severity of GED but, in combination with irrigation rinsing, was no more effective than rinsing alone.

Open Access

In the past, the laborious and time-consuming method of defoliation was used to determine vegetative maturity (VM) of various deciduous plants. Other methods such as water potential and electrotrical impedence have been explored without a positive response. A change of freezing events of water in plant tissue may be associated with VM. Differential thermal analysis (DTA) was tried to determine if the freezing events of water are related to VM. `Golden Delicious', `Gala', `Red Fuji' and `Antonovka' apple (Malus domestica Borkh.) trees were used to determine VM by defoliation. Different sets of 1-year-old trees grown in pots in the greenhouse were defoliated weekly from 1 Aug. until it was assured the trees had reached VM. Samples from the same trees were taken for DTA. The trees were observed for regrowth 2 weeks after they were defoliated, and the exothermic patterns from DTA were examined for the appearance of an exotherm at about –35 to –40°C. The comparison of regrowth from trees defoliated from a specific date were compared to the exothermic pattern of the same date. An exotherm appeared between –35 and –40°C ≈2 weeks before the apple trees ceased to show regrowth from the defoliation treatment. The exotherm appeared on 30 Aug. for Antonovka and `Golden Delicious' and regrowth of the trees ceased on 12 Sept. Regrowth ceased on 9 Oct. for `Gala' and `Fuji' preceded by the exotherm on 2 Oct. The conclusion was that the appearance of the exotherm at –35 to –40 °C could be used to determine VM.

Free access

Abstract

Fruits of ‘Delicious’ apple (Malus domestica Borkh.) were grown under differing radiant flux densities (rfd 400 700 nm) from 45 days post-bloom until harvest. The rfd 400 700 nm affected red fruit color, soluble solids, starch content and size, but not firmness, pH or total acidity at harvest or after 105 days of storage at −0.5°C. Levels of rfd 400 700 nm sufficient to enhance red color development in red sports of ‘Delicious’ were not necessarily sufficient to insure flesh quality.

Open Access

Abstract

The influence of 6 rootstocks on growth and productivity of spur and non-spur ‘Delicious’ and ‘Golden Delicious’ apple (Malus domestica Borkh.) trees was investigated. The spur-type ‘Delicious strain (‘Miller Spur’) consistently produced more fruit per tree than the regular-type strain (‘Red Prince’). In contrast, standard ‘Golden Delicious’ produced as much or more per tree than the spur-type strain ‘Goldspur’ even in the early years. ‘Miller Spur Delicious’ trees were largest on seedling rootstock, intermediate on Mailing (M) 104, and smallest on M 111, M 106 and M 7. ‘Goldspur Golden Delicious’ resembled ‘Miller Spur Delicious’ in size, except that trees were significantly smaller on M 7 than on M 111 and M 106. At the end of the 9th season, ‘Red Prince Delicious’ and ‘Golden Delicious’ were largest on seedling, followed by M 111, M 106, M 7 and M 26 in descending order. Biennial bearing of some trees on all rootstocks reduced yield and increased tree-to-tree yield variance.

Open Access

One-year-old `Fuji' apple trees on six rootstocks (Mark, M.9, M.26, M.7A, MM.106, and MM.111) were compared for N and water uptake and utilization. The trees were potted in sand and subjected to a 75-day N-deprivation period (supplied with modified Hoagland's solution lacking N) to deplete their N reserves. Thereafter, they were supplied with a complete modified Hoagland's solution. Uptake of water and N differed by rootstock. Water and N uptake were positively related to tree dry weight (r = +0.97, P = 0.001). Trees that had the highest N concentrations at planting were the last to set bud during the N-deprivation-phase. Tree size after one growing season depended largely on rootstock girth and whole-tree-Nconcentration at planting (r 2 = 0.80, P = 0.0001) regardless of rootstock. Water and N uptake efficiency (liter of water or mg N absorbed per g root dry weight, respectively) differed among the rootstocks, being highest for trees on MM.111 and lowest for trees on M.7A rootstock. Nitrogen and water utilization efficiency (g dry weight gained per mg N or per liter of water absorbed, respectively) were not influenced by the rootstock.

Free access