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Clonal selection of European winegrapes (Vitis vinifera) allows the exploitation of an important source of genetic diversity. In the 1980s, many `Pinot noir' clones, previously unavailable in the U.S., were imported from France. To provide information on their performance under Oregon soil and climate conditions, 20 `Pinot noir' clones were established in a replicated trial in Alpine, Ore., planted in 1989. In this study, yield components, pruning weight, and juice composition of the 20 clones were measured for the 1995 through 1999 seasons. Skin anthocyanin concentration was measured for the 1996 through 1999 seasons. Clones included in the trial were Colmar (COL) 538, Dijon (DJN) 10/18, DJN 113, DJN 114, DJN 115, DJN 375, DJN 60, Espiguette (ESP) 236, ESP 374, Foundation Plant Services (FPS) 2A, FPS 4, FPS 10, FPS 16, FPS 17, FPS 22, FPS 23, FPS 29, FPS 31, FPS 32, and FPS 33. For all responses except juice pH and skin anthocyanin concentration, there were significant clone by year interactions. COL 538 had the highest 5-year mean yield (2.93 kg/vine); FPS 29 had the lowest (1.21 kg/vine). DJN 10/18, FPS 4, FPS 22, and FPS 31 were among the five highest-yielding clones. Other low-yielding clones included DJN 115, ESP 374, FPS 17, and FPS 23. Pruning weights were generally correlated with yields. COL 538 had the highest 5-year mean pruning weight (0.81 kg/vine) and FPS 17 had the lowest (0.48 kg/vine). Other clones with relatively high pruning weights were FPS 2A, FPS 4, and FPS 22. Other clones with low pruning weights were FPS 23 and FPS 29. FPS 22 and FPS 17 had the highest (1.13 g/berry) and lowest (0.93 g/berry) 5-year mean berry weights, respectively. Clones with 5-year mean cluster weights >100 g included DJN 10/18, ESP 236, and FPS 31. Those with cluster weights <80 g were DJN 115, FPS 17, and FPS 29. FPS 2A had the highest 5-year mean juice soluble solids concentration (SSC) at harvest (23.8%). FPS 10, FPS 29, DJN 113, and DJN 115 also had relatively high SSC. DJN 60 had the lowest 5-year mean SSC at harvest (22.0%). FPS 22, FPS 33, COL 538, and ESP 374 also had relatively low 5-year mean SSC at harvest. DJN 115 had the highest 5-year mean juice pH (3.15). DJN 113, FPS 29, and FPS 10 also had relatively high juice pH. FPS 22 had the lowest 5-year mean juice pH at harvest (2.97), and DJN 10/18, FPS 2A, and FPS 17 also had relatively low pH. Clones with higher SSC and pH generally had lower titratable acidity. FPS 2A had both high SSC and high titratable acidity. FPS 23 and FPS 17 had the highest skin anthocyanin concentration (2.10 and 2.07 mg·g^-1 berry, respectively). The range of skin anthocyanin concentration among the other clones was relatively narrow (1.17-1.47 mg·g^-1 berry). FPS 2A, FPS 4, and FPS 10 generally had above mean SSC and yield. FPS 29, DJN 113, DJN 114, and DJN 115 consistently had above mean SSC but below mean yield.

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.

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.

Net photosynthetic rates often are dependent on leaf size when expressed on a leaf-area basis (CO₂ assimilation as μmol·m⁻²·s⁻¹). Therefore, distinguishing between leaf-size-related and other causes of differences in net photosynthetic rate cannot be determined when data are presented on a leaf-area basis. From a theoretical perspective, CO₂ assimilation expressed on a leaf-area basis (μmol·m⁻²·s⁻¹) will be independent of leaf area only when total net CO₂ assimilation (leaf CO₂ assimilation as μmol·s⁻¹) is linearly related to leaf area and the function describing this relationship has a nonzero y intercept. This situation was not encountered in the data sets we evaluated; therefore, ratio-based estimates of CO₂ assimilation were often misleading. When CO₂ assimilation data are expressed on a per-leaf-area basis (the standard procedure in the photosynthesis literature), it is difficult to determine how photosynthetic efficiency changes as leaves or plants mature and difficult to compare the efficiency of treatments or cultivars when leaf size or total plant leaf area varies.