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H.L. Ko, R.J. Henry, P.R. Beal, J.A. Moisander, and K.A. Fisher

An assessment was made to determine the suitability of RAPD analysis for identification of the Australian wildflower Ozothamnus diosmifolius (Vent.) DC [syn. Helichrysum diosmifolium (Vent.) Sweet] cultivars and lines. Of 19 arbitrary primer sequences tested, 16 revealed a high degree of polymorphism between the six most important genotypes with commercial significance, producing a total of 166 markers, of which 70% were polymorphic. Several primers (such as OPD-03 and OPM-07) were able to distinguish all tested genotypes from one another, showing an intracultivar consistency. These results indicate that RAPD analysis is a useful tool for establishing genetic diversity in this species as well as assisting in commercial protection of plant breeders' rights.

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Justine E. Vanden Heuvel, John T.A. Proctor, K. Helen Fisher, and J. Alan Sullivan

In order to gain an understanding of the capacity of severely shaded leaves to be productive in dense canopies, the effects of increased shading on morphology, dry-matter partitioning, and whole-plant net carbon exchange rate (NCER) were investigated on greenhouse-grown Vitis vinifera L. `Chardonnay' grapevines. Vines were subjected to whole-plant shading levels of 0%, 54%, 90%, and 99% of direct sun 3 weeks after potting. Data were collected 8 to 10 weeks after potting. Nonlinear regression was used to investigate the relationship of leaf morphological traits and organ dry weights to increased shading. Leaf size was maintained with increased shading to approximately the 90% shading level, while leaf fresh weight, volume, density, and thickness were immediately reduced with increased shading. Root dry weight was most affected by increased shading, and root to shoot ratio was reduced. When nonlinear regressions were produced for light response curves, light compensation point was reduced by approximately 49% by moderate shading, and 61% by severe shading. Shaded leaves approached the asymptote of the light response curve more quickly, and had reduced dark respiration rates, indicating that the morphological compensation responses by the vine allow shaded leaves to use available light more efficiently. However, the long-term ramifications of reduced root growth in the current year on vines with shaded leaves may be significant.

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Justine E. Vanden Heuvel, Evangelos D. Leonardos, John T.A. Proctor, K. Helen Fisher, and J. Alan Sullivan

Potted `Chardonnay' grapevines (Vitis vinifera L.) with either two or three shoots were grown in a greenhouse for one month and then transferred to a phytotron room, where either one or two shoots were shaded. Twenty-four days after transfer, leaves at the fifth node of either the light-adapted or shade-adapted shoot were exposed to a 2-hour pulse of 14CO2. Both light environment and number of shade shoots on the vine had a significant effect on photosynthate partitioning within the plant following a 22-hour chase. Leaves fed with 14CO2 on a light-adapted shoot translocated 26.1% and 12.7% more radioactivity to the roots and trunk, respectively, than leaves from shade-adapted shoots. Photosynthates were exported from light-adapted leaves to shade-adapted shoots (1.3% of total 14C in plant). The number of shaded shoots and the light environment of the fed leaf had a large effect on partitioning of photosynthates among ethanol-insoluble, water-soluble, and chloroform-soluble fractions within the leaf. Recovered 14C in the water-soluble fraction of the fed leaf appeared to be affected more by number of shoots than by light environment of the fed leaf. The data suggest that there is a sink effect on initial carbon partitioning patterns in grapevine leaves. Sink strength may have a greater role than light environment. A large proportion of interior leaves versus exterior leaves may be costly with respect to the carbohydrate budget of a vine.