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- Author or Editor: John T.A. Proctor x
`McIntosh', `Delicious', and `Idared' apple (Malus domestica Borkh.) fruitlet ovaries were artificially damaged with a needle four times after full bloom to assess effects of such damage on fruit growth and development. The damage induced fruit drop, reduced fruit weight, and increased the incidence of fruit deformity, but had no effect on fruit length: diameter ratio. Fruit fresh weight and deformity were correlated with seed per fruit at harvest.
American ginseng is propagated by seed. In commercial practice ginseng seed is harvested in August or September, placed in a stratification box for about 12 months, and then direct seeded into raised beds. Germination takes place the following spring, some 18 to 22 months after seed harvest. Little is known about the dormancy-controlling mechanisms of ginseng seed. The objective of this study was to investigate seed development and temperature in the stratification box until it was removed 12 months later and seeded in the field. During stratification 3 embryo growth stages were identified. In Stage I of 250 days (September to mid-May) embryo length increased from about 0.5 to 1.0 mm, in Stage II of 100 days (mid-May to late August) length increased to 2.0 mm and in Stage III (late August to late November) length increased to 5.3 mm. Exocarp split width could also be placed in 3 stages. Changes in embryo length correlated with values for embryo: endosperm length ratio. The stratification box temperatures at all depths never exceeded -2°C even when the air temperatures dropped to -13°C and, therefore, were not damaging to the seeds.
The Lake Erie counties of southern Ontario, Canada are the major producers of ginseng (Panax quinquefolius) in North America. In this area there is about 1740 ha (4299.5 acres) of ginseng and an annual production of 1455 t (1603.8 tons). Spring freeze damage to the crop is rare as the mean date of last freeze in spring is 12 May. On 21 May 2002, following three to six nights when air temperatures dropped below freezing, extensive damage to the crop was evident. A survey by the Ontario Ginseng Growers Association showed that 78% of growers had gardens showing freeze damage. The extent of the damage was variable across the growing area, and on individual farms. Most damage to plants occurred in low-lying areas where heavy cold air collected. Recently germinated seedlings that were exposed above the straw mulch were severely damaged, and many did not survive because they did not have leaves and no perennating bud was formed. Damage to 2-year-old plants was expressed as leaves wilting and turning black. In some cases stems froze and the plants toppled. In 3-year-old and older plants, damage was variable with some leaf collapse and stems broken, or damaged with corking-over taking place. Damage to inflorescences ranged from death and abscission, to distorted flowers and shriveled and split peduncles. Plant health was a concern following the freeze episode, and throughout the subsequent growing season. The fungicide fenhexamid received emergency registration to combat recurring problems in Botrytis control. The seed crop for 2002 was light. Damaged seedling gardens were replanted. Older gardens will undergo a period of adjustment. Root yield in 2002 was reduced by 30%, a 500 t (551.1 tons) loss. The full extent of the damage and associated financial implications are unknown and could impact the industry until 2005.
Paclobutrazol applied as a soil drench at 0, 1, 10, 100, or 1000 μg a.i./g soil reduced vegetative growth of `Seyval blanc' grapevines (Vitis spp.). At all rates, there was a reduction in internode length, while at rates higher than 10 μg a.i/g soil, there was also a reduction in node count. Leaf area produced following treatment declined in response to increasing rates, but specific leaf weight increased. Treatment with paclobutrazol delayed senescence and increased the retention of basal leaves that were nearly fully expanded at the time of treatment. Paclobutrazol application had no effect on fruit set or berry size, but the reduction in vegetative growth following treatment decreased the ability of the vine to supply sufficient photoassimilates for fruit maturation. Chemical name used: ß[(4-chlorophenyl)-methyl]-a-(1,1-dimethylethyl)1H-1,2,4-triazole-1-ethanol (paclobutrazol).
A system was developed to evaluate the response of grapes (Vitis spp. `Seyval') to soil-applied paclobutrazol. The youngest fully expanded leaf, and its axillary bud, on single shoots 6 to 9 nodes long developing on rooted softwood cuttings, were retained for use in a bioassay. The shoot that developed from the axillary bud exhibited a dosage-dependent growth inhibition following soil applications of paclobutrazol at 4 dosages between 1 and 1000 μg·g-1 soil. Other aerial components showed no response to paclobutrazol. This test plant system has potential for use in physiological studies with soil-applied plant growth regulators. Chemical name used: β -[(4-chlorophenyl)methyl]- α -(1,1-dimethylethyl)1H-1,2,4-triazole-1-ethanol (paclobutrazol).
Paclobutrazol applied as a soil drench at 0, 1, 10, 100, or 1000 μg a.i./g soil reduced photosynthetic CO2 uptake rate of leaves formed before paclobutrazol treatment within 3 to 5 days of treatment and the reductions were maintained for 15 days after treatment. The percentage of recently assimilated 14C exported from the source leaf was reduced only at the highest paclobutrazol dose, and there was little effect of treatment on the partitioning of exported 14C between the various sinks. In response to increasing doses of paclobutrazol, particularly at the higher doses, an increasing proportion of recent photoassimilates was maintained in a soluble form in all plant components. Reduced demand for photoassimilates as a result of the inhibition of vegetative growth may have contributed to a reduction in photosynthetic CO2 uptake rate, but this reduction in photosynthesis rate could not be attributed to a feedback inhibition caused by a buildup of starch in the leaves. Paclobutrazol had only a minor effect, if any, on photosynthetic electron transport. Chemical name used: β-[(4-chlorophenyl) methyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).
Freshly harvested, immature (green) seeds of north american ginseng (Panax quinquefolius L.) were stratified for 12 months either traditionally in buried wooden boxes outdoors, or in plastic pails in a controlled environment room [3 ± 0.2 °C (37.4 ± 0.11 °F)], 85% ± 5% relative humidity) for about 9 months followed by about 3 months at 20 ± 2 °C (69.8 ± 1.1 °F). Embryo growth in Stage II (mid-May to late August when direct seeded) was more rapid [0.016 versus 0.009 mm·d-1 (0.00062 versus 0.00035 inches/day)] under controlled-temperature conditions. Seedling emergence rate did not vary between treatments. Root dry weight (economic yield) was similar for seedling, 2, 3, and 4-year-old plants whether grown from traditionally or controlled-temperature stratified seed. Controlled-temperature stratification of north american ginseng seed is an acceptable alternative to traditional outdoor, in-ground stratification.
Mature fruiting and defruited ‘McIntosh’/M.26 apple (Malus domestica Borkh.) trees were exposed to natural rainfall or to no rainfall with the use of under-canopy tent-like covers. With covers present, fruit diameter tended to be less and, on one occasion, soluble solids concentration and fruit firmness increased. Trunk growth was reduced more by fruit than by covers. Trunk growth of fruiting trees did not respond to covers, whereas trunk growth of defruited trees was reduced by covers. Fruit load and reduced soil water content did not affect terminal shoot length. In one experiment, specific leaf weight (SLW) was less for fruiting trees than for defruited trees. Fruiting increased foliar N, P, Ca, and Mg and decreased K concentration. On a leaf-area basis, K was again lower in cropping trees while other nutrients remained mostly unchanged. With tent covers, trees generally had less foliar N, P, and K based on either concentration or amount per unit of leaf area. Leaf water potential was lower for trees with fruit and tended to be lower for trees with tent covers. Leaf stomatal conductance was higher for fruiting trees than for defruited trees and higher for trees without tent covers than for trees with tent covers.
The formation of green islands in response to BA and zeatin application suggested that cytokinins were involved in the natural green island phenomenon of senescing apple leaves. The accelerated loss of chlorophyll and abscission of apple leaves following treatment with BA at 300 mg·liter–1 in both 1984 and 1985 resembled the symptoms of spotted tentiform leafminer (STLM) (Phyllonorycter blancardella F.) damage. The zeatin content of STLM-damaged leaves determined by HPLC was greater than that of undamaged leaves during the development of the third generation pre-adult STLM. The first generation STLM induced no change in zeatin levels of infested leaves. Chemical names used: N-(phenylmethyI)-1H-purine-6-amine (BA); (±-2-methyl-4-(1H-purine-6-ylamino)-2-buten-1-ol (zeatin).
Leaflet length and width were used to calculate leaflet area, lateral leaflet area, and trifoliolate area for strawberry, Fragaria × ananassa Duch. ‘Redcoat’ and genotypes 62E55 and 71M59. Using regression analysis, the product of length and width (LW) was chosen as the independent variable. On the basis of predictive ability (R 2) and/or the SE of estimation, the following equations were chosen to determine leaflet area, lateral leaflet area, and trifoliolate area, respectively: A = 0.66LW + 0.89; A = 0.68LW; A = 0.69 ΣLW. A common regression equation could be used for the cultivar and genotypes studied. If the leaf is unequally imparipinnate, then the area of the lateral leaflets and the trifoliolate must be summed to obtain total leaf area.