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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.
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.
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.
Abstract
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.
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.
The increasing respiration of breaking `Pinot Noir' buds was measured by Differential Scanning Calorimetry. Bud development was classified into ecodormant, initial swelling, fully swollen, and breaking buds. Metabolic and CO2 evolution heat rates increased as the buds developed. Activation energy decreased steadily as development proceeded, which implied that less energy was required for metabolism to continue at later bud stages. A decrease in metabolic efficiency noted by a low calorespirometric ratio was observed during the transition from ecodormant to the initial swelling stage. From the second stage on, metabolic efficiency increased. The responsive nature of grape buds to warm temperatures was explained by increasing Q10 (10-20C) values from 2.8 to 3.8, 3.2, and 3.6 for the four developmental stages described above.