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  • Author or Editor: M.A. Moreno x
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`Lovell' peach seeds were stratified for 0 to 13 weeks at 4C under moist conditions. Heat of metabolism and CO2 evolution, measured by Differential Scanning Calorimetry, increased with stratification time. The calorespirometric ratio increased between 0 and 6 weeks and then remained constant until 13 weeks. Germination percentages paralleled this ratio and reached 80% only after 6 weeks of stratification.

After radicle emergence, seedlings from different stratification treatments were grown for 3 weeks. Increasing stratification time resulted in taller seedling growth. Calorimetrically measured CO2, evolution and the calorespirometric ratio of the apex (one cm) of the seedling increased with longer stratification time. Contrary to the observations of the seeds, metabolic heat rates decreased as stratification time increased. Yet, seedling sustained higher growth rates. These data suggest that the stratification treatment resulted in an improvement in metabolic efficiency.

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Field performance of several peach × almond hybrid [Prunus amygdalo-persica (West) Redh.] rootstocks grafted with different peach cultivars [Prunus persica (L.) Batsch] were tested for 11 to 12 years in three experiments. `Loadel' scions were grafted on Adafuel, Adarcias, Albatarrech, Calanda, and GF 677 hybrids. `Catherina' and `Flavortop' scions were grafted on Adafuel, Adarcias, and GF 677 hybrids. Adafuel was the most invigorating rootstock for `Loadel', after the 12 years of scion growth, but Adarcias also promoted higher scion productivity than other peach × almond hybrid rootstocks. Although there were no differences in `Catherina' productivity when grafted on different rootstocks, this cultivar and `Flavortop' grafted on Adarcias showed the least vigor. `Flavortop' on Adafuel had more vigor than on the other rootstocks. According to our results, Adafuel (a vigorous rootstock) seems to be suitable for peach production in low nutrient and calcareous soils unfavorable for peach seedling rootstocks. Adarcias seems promising as a peach rootstock for avoiding excessive scion growth, and it may be useful where tree size needs to be controlled.

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Olive shoots were collected at monthly intervals during an off and an on year from nonirrigated, mature `Picual' olive trees fertilized or nonfertilized with nitrogen. Young and mature leaves and stems and flowers and fruit developed during the on year were removed separately from the shoots to determine N concentration and N content per organ. N concentration decreased in young leaves and stems in spring and summer, and increased during the autumn in both off and on years. N concentration in old leaves and stems remained almost constant during the off year, and drops from April to October during the on year. The new tissues accumulated N during the off year and mobilized it during the on year to support growth. Leaves stored larger amounts of N than stems, and fruit developed during the on year became the main sink for N of the bearing shoot. Although the adjacent, mature leaves may have supported part of the N demand from the fruit, nitrogen must also have been mobilized from other storage organs to support fruit growth. No differences between fertilizer treatments were observed in the allocation pattern of N, although N reserves increased in shoots of fertilized trees.

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Previously, we reported recovery of plants from “Near-Lethal” (NL) (Sub-Lethal) stresses was dependent on stage of development and post-stress environment Dormant plants exposed to NL-heat, freezing, and hydrogen cyanamide either died or were severely injured when stored at 0°C or recovered at 23°C and natural condition. This study reports on the changes in the evolution of metabolic heat in dormant red-osier dogwood (Cornus sericea L.) stem tissues after beat stress. Heat stress (51°C for half an hour) was followed by one of two post-stress environment (PSE) (0° or 23°C dark condition). Isothermal measurements of the heat of metabolism of the tissues were taken after 0, 1, 2, 5, 7 and 11 days of PSE. A significant reduction of metabolic heat generation occured in heat stressed plants at 0°C PSE from one to 11 days of incubation as compared to the non-stressed tissues. At 23°C PSE, no significant differences of heat generation between stressed and non stressed tissues were found within 7 days of incubation. The rate of metabolic. heat measured by decreasing temperature scanning microcalorimetry (21° to 1°C) were lower in beat stressed tissues. Arrhenius plots of metabolic heat rate gave a linear slope for non-stressed tissues and a complex slop for NL-stressed tissues at lower temperatures. Energy of activation (Ea) between 1°-8°C were 15.45 and 83.882 KJ mol-1 for NL-heat and non-stressed tissues, respectively.

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In a previous study with melon (Cucumis melo L.). Spanish cv. Amarillo Oro, we reported medium, cultural, and environmental conditions that made it possible to regenerate plants from cotyledon segment-derived calli (1). Here, we present results, under the same cultural conditions, of the morphogenetic response of calli derived from the same kind of explants from several melon cultivars obtained from different countries.

Open Access

The pattern of respiratory changes during dormancy and development of `Pinot noir' primary grape (Vitis vinifera L.) buds through the broken-bud stage was determined using differential scanning calorimetry. Metabolic heat rates [μJ·s-1·mg-1 dry weight (dw)] decreased during endodormancy and increased during ecodormancy and bud development. Respiration of ecodormant buds was at its minimum (≈1 μJ·s-1·mg-1 dw) in January. Respiration steadily increased, beginning in February and continuing as buds passed through the four developmental stages: ecodormant, initial swelling, fully swollen, and broken bud. Heat of metabolism increased from 5 to 18, 28, and 29 μJ·s-1·mg-1 dw as the buds developed from ecodormant to broken-bud stage. Carbon dioxide evolution from respiring buds increased from 15.9 to 22.2, 57.9, and 68.3 × 10-6 μmol·s-1·mg-1 dw as bud development advanced. Metabolic inefficiency, as quantified by heat (kJ) released per CO2 (mol) produced, was lowest in ecodormant buds, then increased at initial bud swelling and declined again in fully swollen and broken buds. The temperature coefficient of metabolism (μ) [apparent activation energy (Ea)/gas constant (R)] was lower at low temperatures (5 to 15C) in ecodormant buds than at the three more advanced stages. At higher temperatures (20 to 35C), buds at the ecodormant and initial swelling stages had a higher μ than the fully swollen and broken buds. These results suggest there may be a major change in metabolic pathways between the ecodormant bud stage and bud swelling.

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