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  • Author or Editor: R. Moreno x
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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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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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Four ratio-based efficiency expressions (yield/trunk cross-sectional area, yield/canopy area, yield/pruning weight, CO2 assimilation/leaf area) were evaluated. These expressions depend on the size of the denominator if the function describing the relationship between the denominator and the numerator has a non-zero intercept. When this occurs, it is difficult to determine if statistically different efficiency expressions reflect physiological differences or are caused by comparing expressions with different sized denominators. When denominators and numerators of efficiency expressions are plotted, the edge of the data cloud can often be statistically identified. The function describing the edge of the data cloud defines the maximum possible value (MPV) obtainable for a given value of the denominator. The percentage of MPV (%MPV) is an alternate efficiency expression that is not influenced by differing trunk cross-sectional area, canopy area, pruning weight, or leaf area. The difference between MPV and observed performance can be used to define improvement potential (IP). These alternate assessments can supplement traditional efficiency expressions. It is also possible to determine if statistical differences in traditional efficiency expressions are caused by differences in potential, differences in a plant or leaf's ability to achieve its potential, or differences in the size of the efficiency expression denominators.

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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.

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Changes in water content of `Pinot Noir' endo- and ecodormant primary buds were gravimetrically partitioned into extracellular (ECW) and intracellular water (ICW). During endodormancy, water status remained unchanged with values of 0.6 and 0.1 mg/mg dw for ICW and ECW, respectively. Ecodormant buds, prior to budbreak, increased in ICW from 0.5 to 4.4 mg/mg dry weight for Jan. and Apr., respectively. Liquid water in the buds was determined by H-NMR. The spin-spin relaxation time (T2) at -30C represented the bound fraction, which peaked in Jan. at 0.3 mg/mg dw followed by a decrease to 0.2 mg/mg dw in March. During the dormant season the free fraction was always larger than the bound fraction. No vascular connection between bud and stem was observed by mid Jan. Changes in bound water indicated that there is a transient fraction changing to the free form. These changes were not strictly related to the bud's dormancy status.

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It is not appropriate to compare ratio-based expressions for different cultivars or treatments if a plot of the denominator versus the numerator of a ratio-based expression has a nonzero y-intercept and the values for either the denominators or numerators differ with cultivars or treatments. Whenever nonzero y-intercepts are encountered, the value for a ratio-based expression will be dependent on both the denominator and numerator. The “ratio problem” is demonstrated with shoot N concentration in blueberries (Vaccinium corymbosum L.) and amino acid accumulation in almonds [Prunis dulcis (Mill.) D.A. Webb]. Data were collected from the first and second growth flush of blueberry shoots on plants that were at two in-row spacings and two rates of N fertilizer. Free amino acid:total amino acid ratios were measured in dormant almond trees fertilized at different rates with and without foliar N supplements. Functions describing the relationship between dry weight and total N content in blueberry tissues have positive y-intercepts for both N fertilizer application rates. Functions describing the relationship between total amino acids and free amino acids in almond trees have a negative y-intercept. Differences attributable to fertilization rate in blueberries probably were the result of differences in N uptake and N utilization, but the effects of spacing and growth flush are indirect and can be accounted for by differences in dry weight. Likewise, effects of fertilization rate and foliar N supplement in almonds are indirect and can be accounted for by differences in the total amino acids in dormant trees. With regression one can determine if the relationship between the denominator and numerator differs for the groups or treatments being studied. When an analysis of covariance is used to account for differences in the denominators of ratio-based expressions, results are consistent with the regression analysis. When a conclusion is based on statistical differences of a ratio-based expression, it is the researcher's responsibility to determine whether these effects are direct or indirect.

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