Flower-bud formation and shoot growth in apple as affected by temperature

Under controlled conditions, 3-year old ‘Golden Delicious’ and ‘Cox's Orange Pippin’ trees were exposed to 2 temperatures (high: 24° and low: 17° or 19° C) in various treatments in a 4-month period starting at full bloom. In general, shoot growth was reduced at the low temperature. For ‘Golden Delicious’ flowering did not respond to the various treatments; in ‘Cox's Orange Pippin’ it was stimulated at the low temperature.A rise in temperature from 17° to 24° C seven weeks before harvest, given to ‘Cox's Orange Pippin’ trees kept at 17° C from full bloom, reduced flower-bud formation and stimulated growth. A similar temperature increase applied to trees maintained at 24° C for 4–5 weeks after full bloom favoured flower-bud formation, but did not affect growth.The inhibitory effect of the high temperature on flowering is discussed in terms of an increase of the plastochron under the influence of gibberellins produced by the growing shoot tips.     

Effect of part-tree flower thinning on fruiting,vegetative growth and leaf photosynthesis in ‘Cox’s Orange Pippin’ apple

Flower clusters were removed at full bloom from ten year old ‘Cox’s Orange Pippin’ trees on M.9 rootstocks, over the whole tree, on alternate branches or on whole sides. Mean fruit weight per tree at harvest was linearly dependent on leaf area per fruit and on light interception per fruit, both relationships accounting for over 90% of the variance. These relationships did not differ between treatments, implying either a mobile pool of carbohydrate or photosynthetic adjustment within the tree to crop load. Measurements of leaf photosynthesis in July and September showed no statistically significant differences in photosynthetic rate of spur or extension shoot leaves on bearing or non-bearing branches. Although the treatments caused no overall effects on shoot growth or leaf area per tree, sides of trees without fruit had greater leaf area and shoot growth than did sides bearing fruit. Fruit mineral composition and percentage dry weight were not affected by treatment except where the treatments significantly altered fruit size. In the following spring, although the treatments did not affect the total number of flower buds produced, branches that were deflowered in the previous spring carried significantly more flower buds than did branches which had cropped.     

Varietal Reactions to Viruses Causing Star Crack and Russet Rings on Apple Fruits

English sources of viruses causing star crack and russet ring were grafted to nine apple varieties. Only Golden Delicious reacted to all virus sources. This variety differentiated most clearly between different sources of star crack inoculum. Cox’s Orange Pippin and Spartan reacted to all star crack sources; Belle de Boskoop, Weisser Winterglocken, Lord Lambourne, Laxton’s Fortune and Worcester Pearmain reacted when inoculated with some sources but not others, while Granny Smith reacted to none. Golden Delicious developed leaf and fruit symptoms when inoculated with russet ring viruses, but Cox’s Orange Pippin, Spartan, Belle de Boskoop, Weisser Winterglocken and Granny Smith did not. Mailing II rootstocks developed characteristic leaf symptoms when infected with russet ring viruses. One inoculation source caused leaf mottling and necrosis and russeted warts on the fruits of Golden Delicious and Cox’s Orange Pippin. A rough-skin condition of Belle de Boskoop was perpetuated by buds and grafts but not transmitted. Some of the English viruses caused symptoms, in certain varieties, indistinguishable from diseases reported from Germany, Switzerland, the Netherlands, and North America.     

Sind Pollenspritzungen oder Pollendispenser Alternativen zur herkömmlichen Bestäubung der Apfelbäume durch Bienen?

The efficacy of different methods of applying cv. ‘Golden Delicious‘ pollen to ‘Cox Orange‘ apple trees inside insect-proof cages was investigated: (1) spraying pollen suspended in water directly into the trees while they were in bloom (treatment A); (2) pollen transfer by honeybees (treatment B) or by bumblebees (treatment C), both of which had to pass through a dispenser loaded with cv. ‘Golden Delicious‘ pollen; (3) transfer by honeybees of pollen from cv ‘Golden Delicious‘ trees bearing compatible pollen and maintained in pots within the same cages (treatment D). Naturally pollinated cv. ‘Cox Orange‘ apple trees outside the cages in the orchard served as controls. For methods A–C normal commercially available ‘Golden Delicious‘ pollen was used for hand pollination, and its efficacy was assessed with reference to the amount of fruit that set. The fruit-set at the time of harvesting differed significantly (Nemenyi test) with the different methods of pollination: 1.0% (±2.0) of the blossoms ripened to yield marketable apples after treatment A, 6.1% (±5.2) after treatment B, 4.9% (±4.6) after treatment C, and 20.4% (±11.5) after treatment D, while the corresponding figure for the control trees was 7.3% (±2.8) and that for hand pollination, 41,9%. The low fruit-set after an aqueous suspension of cv. ‘Golden Delicious‘ pollen was sprayed on the test trees shows that this procedure did not result in adequate pollination. The density of pollen grains was determined on filter papers during spraying and was an average of 3 (±2.6, range 0.0–8.6) pollen grains/cm². When the pollen dispensers were used, the fruit-set was lower than on the hand-pollinated control trees. Despite the success of manual pollination with exogenous cv. ‘Golden Delicious‘ pollen, pollen spraying to enhance pollination, as specified in current instructions, cannot be recommended for commercial apple growing in Germany.     

Use of 6-benzylamino purine and Promalin for improved canopy development in selected apple cultivars

Foliar sprays of Promalin (gibberellins A_{4 + 7} + 6-benzylamino purine) applied to 1-year-old apple (Malus domestica Borkh.) trees at the 3–5-cm growth stage significantly increased lateral branching in 5 of 9 cultivars tested. Branching response ranged from 0% (‘Winter Banana’) to 131% (‘Starkrimson Delicious’) of the untreated controls. Total shoot growth was not consistently increased by 6-benzylamino purine or Promalin in tests over 3 years on spur and non-spur 1- and 2-year-old apple trees. Sprays of 50–300 mg l⁻¹ Promalin were ineffective for increased branch development. Sprays of 300–500 mg l⁻¹ increased total shoot numbers and reduced average shoot length. Sprays applied prior to new terminal growth in spring were ineffective. Treatment during periods of active shoot growth were generally effective, but periods of stress may have reduced response. Sprays were more effective for inducing lateral shoot formation than dormant heading or delayed dormant heading (pruning) (10 days after full bloom) in ‘Criterion Golden Delicious’. No difference in branching response was observed between BA and Promalin. Addition of a spray adjuvant (Buffer-X) did not affect branching response. Repeat annual single sprays of Promalin applied to dormant pruned trees were generally less effective for stimulating lateral branching than a single application in a given year. Phytotoxicity was associated with Promalin sprays at 300–500 mg l⁻¹ on ‘Delicious’.     

The effect of soil temperature on lateral shoot formation and flower-bud formation in apple in the first year after budding

Under controlled environment conditions the influence of four soil temperatures (7°, 14°, 21°, and 28°C) on vegetative development and flower-bud formation of apple trees (cvs ‘Rode Boskoop’ and ‘Elstar’) were evaluated in the first year after budding. Relative air humidity was high, air temperature was 20°C. Broadly speaking, for both cultivars shoot growth clearly increased with increasing soil temperature. The effects on growth were mainly reflected in the number (not length) of the lateral shoots; the growth of the main shoot was little influenced by soil temperature. At 7°C the lateral shoots usually occurred higher along the main stem than at the higher temperatures. Flowering on the parent stem and on the lateral shoots was little affected by the soil temperatures tested. In general, flower-cluster quality was rather poor. If only clusters having more than four well-developed flowers are considered, flowering was favoured by higher soil temperatures; at 28°C, especially, cluster quality was much better than at the other soil temperatures. It is concluded that soil temperature is important in controlling the degree of lateral shoot-formation as well as the formation of well-developed flower clusters.     

Storage quality of ‘Cox's Orange Pippin’ apples grown on a range of rootstocks

This study involved storing samples of ‘Cox's Orange Pippin’ from the 1974 and 1975 crops from each of 2 rootstock trials. After 12 weeks cool storage, the samples were examined for bitter pit and internal breakdown.In the high-pit year 1974, ‘Cox's Orange’ on ‘M.16’ and ‘MM.115’ had significantly more pit and breakdown than when grown on ‘MM.106’, ‘MM.112’ and ‘MM.114’, with fruit from ‘MM.104’ in between the 2 groups. However, in the low-pit year 1975 there were no differences. In the second trial in 1974, ‘Cox's Orange’ on ‘M.16’ had significantly more pit and breakdown than when on ‘Northern Spy’, ‘MM.109’ and ‘M.7’. In the following year there were no differences in the incidence of pit, but fruit from ‘M.7’ and ‘M.2’ had more breakdown than from other rootstocks in this trial.     

Flower initiation and node development of axillary buds,growth partitioning,and bleeding sap production of young apple trees as affected by fertigation

SUMMARY

Node and flower development in axillary buds of one year old 'Elshof trees, growth and dry-matter partitioning, and bleeding sap production were examined in unfertigated field-grown trees as well as in fertigated field- and pot-grown trees. Flower initiation in axillary buds was delayed by approximately 40 d as compared with spur buds, and the critical node number within the bud was only 14 or 15 against 19 nodes in spur buds. Fertigated trees exhibited increased node development, axillary flower-bud densities, extension shoot growth and trunk increments, and decreased root/top ratios. The seasonal shoot development was markedly hastened in fertigated trees, and the amount of bleeding sap was increased. Especially, trees fertigated in pots, using a nitrogen application range of 14 to 420 ppm N, had high bleeding sap concentrations of nitrogen, phosphorus and calcium. Flower-bud initiation of apple is discussed in terms of bud development, shoot growth and root activity.     

Relations between the concentration of diffusable and extractable gibberellin-like substances and the alternate-bearing behaviour in apple as affected by chemical fruit thinning

The levels of diffusable and extractable gibberellin-like substances (GA_s) of apple fruits were investigated in the alternate-bearing ‘King of the Pippins’ and the regularly fruiting ‘Golden Delicious’, using the barley endosperm bioassay. During 1977 and 1978 there were marked differences between the two cultivars in both the chronological appearance and the absolute amounts of diffusable GA_s. The application of fruit-thinning chemicals (carbaryl, ethephon, NAAm) to ‘King of the Pippins’ suppressed the early increase of GA_s in diffusates, which normally occurs during the second week after full bloom. The following year, the thinned trees exhibited heavy flower- and fruit-set, while the untreated control trees showed a very poor bloom. The later appearance of the GA peak in diffusates from fruits of ‘Golden Delicious’ (5 weeks after full bloom), was not accompanied by a similar inhibitory effect on subsequent flowering.In contrast to their effect on the levels of diffusable GA_s, the thinning-treatments caused no real change in the amount of extractable GA_s, which was very similar in fruits from both cultivars.     

Inhibition of flowering of Mexican- and Guatemalan-type avocados under tropical conditions

Avocado trees of a range of cultivars growing in Darwin, northern Australia (average yearly maximum 33°C, minimum 23°C), were observed for flower and shoot development. Terminal buds of the cultivars ‘Fuerte’, ‘Rincon’ and ‘Edranol’ sampled in July were not floral. Buds which did not burst were sampled in September and they contained developing flowers with perianth primordia. Vegetative extension growth resulted from laterals proximal to the inhibited terminal buds.Avocado trees of the cultivars ‘Fuerte’ and ‘Hass’ which had initiated floral buds were transferred to controlled environment chambers with 33°C day, 23°C night ($\text{33}\text{23}$) or 25°C day, 15°C night ($\text{25}\text{15}$) with a 12-h photoperiod and photon flux density of 400 μmol m^?2 s^?1 (400–700 nm). At $\text{33}\text{23}$ the trees had fewer flowers and a shorter flowering period than at $\text{25}\text{15}$. Inhibited floral buds and lateral vegetative extension resulted at $\text{33}\text{23}$, as observed in northern Australia. The unburst buds had developing flowers with perianth and stamen primordia.The controlled environment experiments showed that the abnormal flushing behaviour of Mexican- and Guatemalan-type avocados growing in northern Australia was due to high temperature. Floral development was inhibited at the stage of stamen differentiation.     

The effect of boron upon leaf development and growth of the apple cultivar ‘Cox’s Orange Pippin’

One-year-old ‘Cox’s Orange Pippin’ trees planted in pots in sand culture in the spring of 1970 were (during the growing seasons of 1970–72) watered with nutrient solutions containing 0, 0.12, 0.23, 1.2, 3.5 or 7.0 mg boron per litre.

With increasing boron supply, the boron concentration of the leaves increased, the growth of current year’s shoots and to some extent of other plant parts increased, and summer leaf-fall and the occurrence of necrotic leaf spots (‘Cox spots’) decreased. The percentage of healthy leaves was greatest when boron in leaf dry matter was about 30 ppm.

In 1972 the trees with highest boron supply suffered from incipient boron toxicity and increased incidence of ‘Cox disease’ flowering was delayed, and the percentage of dead buds was increased. In the latter part of the summer the leaves curled upwards, turned purple and became brittle.     

‘长富2号’苹果短枝幼果摘除对芽叶可溶性糖积累和成花相关基因表达的影响

以‘长富2号’苹果为材料,在盛花期后31d进行短枝摘果处理,研究处理后短枝顶芽生长状态、成花率以及短枝芽叶可溶性糖(蔗糖、果糖、葡萄糖及山梨醇)的动态变化,并利用实时荧光定量PCR检测顶芽糖代谢相关基因(MdSPS6、MdSUSY1、MdHXK1、MdSUT1)、MdTPS基因和成花相关基因(MdFT、MdFD、MdCO、MdSOC1、MdLFY、MdAP1)的表达模式。结果表明:摘果处理后,短枝顶芽长度、宽度及鲜样质量有一定的增加,次年成花率显著高于对照;短枝顶芽中蔗糖、果糖、山梨醇变化较为明显,在生理分化后期都显著高于对照,而葡萄糖含量变化较小;短枝叶片中,4种可溶性糖含量第1个高峰由盛花期后60 d提前至40 d;顶芽糖代谢相关基因及3个MdTPS基因(MdTPS1-1~MdTPS1-3)都响应摘果处理;MdFT、MdFD、MdCO、MdSOC1和MdLFY等的表达在盛花期后40 d均有显著的上调,其中MdLFY的变化最为明显,而MdAP1在整个生理分化期与对照无显著差异。     

Controlling growth of ‘Delicious’ apple trees with low- dosage applications of Uniconazole or BAS111

Foliar applications of 30, 60 or 120 mg I-1 uniconazole were made to ‘Delicious’ apple trees at full bloom or one, two or three weeks after full bloom. Application at full bloom reduced fruit weight and length/diameter ratio more than when applied two or more weeks after full bloom. In another experiment, a single application of uniconazole was applied to ‘Delicious’ trees three weeks after full bloom at 15, 30, 60, 120, 240 or 480 mg I-1. Posages of 240 or 480 mg I-1 controlled vegetative growth to about 50% of the control values at ten weeks after treatment. Thereafter, the rate of shoot elongation was similar to that of the controls. The lowest dosage to reduce vegetative growth was 15 mgl-1. In a third experiment, uniconazole was compared with BAS111 for controlling vegetative growth of ‘Delicious’ trees. Uniconazole or BAS111 applied six times at 350 mgl'1 reduced growth to 46% and 81% of that of the controls, respectively. Increasing the rate of surfactant from 0.1% to 1.0% reduced growth by an additional 8%. Growth reduction in the year of treatment was similar following uniconazole treatments of 350 mg l_l applied three times or 35 mg I-' applied six times.     

Hormonal regulation of physiological leaf spot and premature leaf abscission in ‘Golden Delicious’ apple trees

Exogenous growth substances (GA₄₊₇, IAA, PBA, and ABA) alone and in combination were applied as leaf dips to young ‘Golden Delicious’ apple trees in a growth room at 21 °C. All treatments containing GA₄₊₇ accelerated the incidence of physiological leaf spot over treatments without GA₄₊₇, ABA alone delayed the appearance of leaf spot. PBA, PBA + GA₄₊₇, and PBA + GA₄₊₇ + IAA retarded the abscission of spotted leaves.GA₄₊₇ and GA₄₊₇ + PBA also accelerated leaf spot development in bearing ‘Golden Delicious’ trees in the orchard.Fumigation of apple trees with ethylene at 2, 10, and 20 ppm had no influence on the occurrence of leaf spot or premature abscission.     

Long-day control of flowering in everbearing strawberries

Summary

Photoperiod and temperature control of flowering in a number of perpetual-flowering or everbearing strawberry cultivars of widely varying pedigree has been studied in controlled environments. Flower bud initiation in the cultivars ‘Flamenco’, ‘Ridder’, ‘Rita’ and ‘Rondo’ was significantly advanced by long-day (LD) conditions at temperatures of 15°C and 21ºC; while, at 27ºC, flowering took place under LD conditions only. Some plants of the seed-propagated F₁-hybrid ‘Elan’, raised at 21°C, also flowered under short-day (SD) conditions at 27°C, but reverted to the vegetative state after a few weeks when maintained under these conditions. When vegetative plants growing in SD at 27°C were transferred to LD conditions at the same temperature, they consistently initiated flower buds and started flowering after about 4 weeks. At such a high temperature, flowering could thus be turned on and off by switching between SD and LD conditions. This applied to all the cultivars studied. Also the cultivar ‘Everest’, which was tested only at 21°C, produced similar results. Night interruption for 2 h was effective in bringing about the LD response. At 9°C, flowering was substantially delayed, especially in ‘Flamenco’ and, at this temperature, flowering was unaffected by photoperiod. Runner formation was generally promoted by high temperature and SD conditions, but the photoperiodic effect varied between experiments. We conclude that everbearing strawberry cultivars, in general, whether of the older European-type or the modern Californian-type originating from crosses with selections of Fragaria virginiana ssp. glauca, are qualitative (obligatory) LD plants at high temperature (27°C), and quantitative LD plants at intermediate temperatures. Only at temperatures below 10°C are these cultivars day-neutral.     

Chemical Defoliation of Nursery Stock. I. Initial Experiments with Fruit Tree Material

Both 50 000 ppm FeEDTA and 1000 ppm N252 (2, 3-dihydro-5,6-dimethyl-l,4-dithiin-1,1,4,4-tetroxide) effectively defoliated Cox’s Orange Pippin and Golden Delicious maiden apple trees on M.9 rootstock when applied in mid-September. Defoliation of MM. 104 apple rootstocks by 30 000 ppm FeEDTA was enhanced by pretreatment with 3000 ppm MH, and defoliation of Quince A rootstocks by 30 000 ppm FeEDTA, 250 ppm N252 or 750 ppm ethephon with 13 500 ppm urea was enhanced by prior treatment with 3 000 ppm butralin.     

Effect of temperature on flowering in Primula vulgaris

When grown in a glasshouse, flowering in Primula vulgaris ‘Aalsmeer Giant’ (yellow) and ‘Ducat’ (blue) was delayed with increasing temperature from approximately 12°C to 18°C. In addition, size of the first open flower and the number of flowering axillary shoots decreased, whereas the number of leaves and leaf area increased with the temperature increase. All temperature responses were greater in ‘Aalsmeer’ than in ‘Ducat’.When grown in growth rooms at 9°C, flowering in P. vulgaris ‘Aalsmeer Giant’ (yellow) was inhibited compared with 15°C. However, when 9 weeks of 15°C was applied to plants grown for 9 weeks at 9°C, the inhibition was overcome; longer periods of 15°C being no more effective. This indicates than an early stage of flower formation, probably the initiation, in Primula vulgaris is inhibited by 9°C, and not the further development of the buds towards open flowers.     

Apple rootstock studies: growth of trees on three clonal rootstocks planted with or without roots

Trees of Cox's Orange Pippin on M.IXa, M.26 and MM. 106 were planted either normally with roots or without roots to simplify the planting operation. Pruning treatments were superimposed, the trees being cut back at planting, left unpruned the first year and cut back the second year, or left entirely unpruned. All trees survived. After two growing seasons the trees were lifted and weighed. Removal of all roots before planting reduced shoot growth, trunk girth increment, final tree weight and incremental weight. However, on all rootstocks, trees planted without roots and left unpruned were similar in size when lifted to those planted with roots and cut back at planting in the orthodox manner.

In a complementary trial lasting one season Cox's Orange Pippin trees on M.26 were planted with or without roots. All trees were cut back at planting, and four times of planting were compared. The mid-April planting included trees that had been stored at 2.8 °C and trees that had been bedded-in outdoors. There were no tree losses attributable to removal of the roots before planting. Removing the roots at planting again reduced growth and weight of tree at lifting. Month of planting had no effect upon shoot growth or trunk girth increment.

The results are discussed, together with their practical implications in relation to mechanical tree planting for high density orchards.     

Effects of NAA and Carbaryl on Fruit Set and Return Bloom for Some Apple (Malus domestica Borkh.) Cultivars

Abstract

This research was conducted in 1997 and 1998 to investigate the effects of naphthalene acetic acid (NAA) (5, 10, and 15 ppm), Carbaryl (1-naphthyl N-methylcarbamate) (750, 1000, and 1250 ppm), and NAA + Carbaryl (5 + 750, 7.5 + 750, and 10 + 750 ppm) applications on the return bloom of some standard apple (Malus domestica Borkh.) cultivars grafted on MM106 rootstock. Of these applications, 750 ppm Carbaryl for ‘Starkspur Golden Delicious’, 1250 ppm Carbaryl for ‘Granny Smith’ and ‘Starkrimson Delicious’, and 5 ppm NAA for ‘Jonagold’ increased the mean number of flower buds significantly, compared with the control treatments. The other treatments of Carbaryl, NAA, and NAA + Carbaryl also increased the mean number of flower buds in a nonsignificant sense with a few exception. A negative correlation between the final fruit set and the mean number of next year's flower buds was found for three cultivars. The correlation coefficients were r = ?0.5150 (P< 0.05), r = ? 0.6999 (P< 0.05), r = ?0.0335 for ‘Starkspur Golden Delicious’, ‘Granny Smith’, and ‘Jonagold’ cultivars, respectively. However, this relationship was positive and nonsignificant for ‘Starkrimson Delicious’ (r = 0.1980).