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William W. Inman and William L. Bauerle

Recent work has shown that stomatal conductance (gs) and net photosynthesis (Anet) are responsive to the hydraulic conductance of the soil to leaf pathway (Xp). Two tree species with differing xylem structures were used to study the effect of systematic manipulations in Xp that elevated xylem hydraulic resistance. Simultaneous measures of gs, Anet, bulk leaf abscisic acid concentration (ABAL), leaf water potential (L), and whole plant transpiration (Ew) were taken under controlled environment conditions. Quercus shumardii Buckl. (shumard oak), a ring porous species and Acer rubrum L. `Summer Red' (red maple), a diffuse porous species, were studied to investigate the short-term hydraulic and chemical messenger response to drought. Both species decreased Anet, gs, L, and Ew in response to an immediate substrate moisture alteration. Relative to initial well-watered values, red maple Anet, gs, and Ew declined more than shumard oak. However, gs and Anet vs. whole-plant leaf specific hydraulic resistance was greater in shumard oak. In addition, the larger hydraulic resistance in shumard oak was attributed to higher shoot, as opposed to root, system resistance. The results indicate hydraulic resistance differences that may be attributed to the disparate xylem anatomy between the two species. This study also provides evidence to support the short-term hydraulic signal negative feedback link hypothesis between gs and the cavitation threshold, as opposed to chemical signaling via rapid accumulation from root-synthesized ABA.

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C. Richer-Leclerc and J.-A. Rioux

The “Réseau d'essais des plantes ligneuses ornementales du Québec” (REPLOQ) is a research project initiated in 1982 with the mandate to elaborate, develop, and coordinate a cooperative research project to evaluate the winter hardiness of ornamental plants. Systematic evaluation trials provided information on growth potential and hardiness of woody trees and shrubs evaluated over a 5-year period in the principal growing regions of Québec. Zonal range covered was 2 to 5b in the Canadian system. Adequate field testing is critical for new introductions and, since 1984, more than 400 species and cultivars have been introduced and eight evaluated in each climatic zone. Propagation methods, as well as their potential for ornamental purpose, were described. In the 1984 plantation, 30 ornamental species and cultivars were evaluated. Winter damage data observed on each plant during this period were analyzed by Clusters analysis and five groups of plants were determined. Trees, flowering shrubs, and foliage shrubs were discussed separately and winter damages of each group were submitted to “Correspondence analyses” to identify plant response to climatic conditions. Growth and production potentials were defined by SAS analysis. Hardiness zone of each species was detailed, established, or modified.

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A. Medlicott, J. Brice, T. Salgadol, and D. Ramirez

No systematic curing and storage techniques are currently used with onions in Honduras; postharvest losses occur rapidly. The objective of this study was to evaluate the use of storage bins (maximum capacity 7t) that use forced ambient air ventilation to manipulate the atmospheric conditions around the onions. The desired storage conditions were 26 to 30C and 60% to 75% relative humidity. Ventilation regimes were manipulated in an attempt to obtain these conditions. The rate of deterioration in four varieties of onions over a 3-month period was determined and compared with onions stored under normal ambient conditions. Marketable onions in the forced-air storage bin compared to the controls stored under ambient conditions after 13 weeks were 82% vs. 37% for `Granex 33'; 71% vs. 40% for `Granex 429'; 63% vs. 31% for `Granex 438'; and 90% vs. 44% for `Texas Grano 502'. This represents a significant increase in the number of marketable onions after storage. All losses were increased by rain and tornado damage after 1 month of storage. The methods used to maintain uniform temperature and humidity conditions in the storage bin are discussed together with the problems encountered. The construction and operating costs are given together with the market prices and the required returns to cover the bin costs.

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Elsa Sanchez and Richard Craig

The Plant Systematics course at Penn State University was reformatted in 1995 based on a three-dimensional model. It now includes several collaborative learning activities: a learning fair hosted by the enrolled students for elementary school students; applied laboratory exercises; and applied laboratory examinations. Each activity has a specific objective and was constructed to strengthen teaching effectiveness and to aid students in developing useful skills for future employment. A survey was administered to students enrolled in the course from 2003 through 2005 in part to assess the collaborative learning activities. Most students “strongly agreed” or “agreed” that they liked working in collaborative groups and learned from other group members. Students preferred working in groups for laboratory examinations more than for the Asteraceae Fair and learned more from their peers while completing the laboratory exercises than in laboratory examinations. Student participation in the lecture portion of the course increased as collaborative learning activities were completed. Camaraderie with peers through group work may have created an atmosphere conducive to participation and/or involvement during lectures. Organization and planning were vital to the success of these activities, as were using small groups and providing adequate incentives for completing activities. These activities engaged students to become active participants in the teaching and learning process.

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Samia Lotfy, Francois Luro, Françoise Carreel, Yann Froelicher, Delphine Rist, and Patrick Ollitrault

Somatic hybridization allows the creation of new patterns of nuclear, mitochondrial and chloroplastic association. It is therefore necessary to master cytoplasmic molecular markers to determine the genetic origin of both organelles of plantlets obtained from protoplasts fusion. In the case of Citrus and related genera, only southern blot hybridization and restriction fragment-length polymorphism (RFLP) techniques were used for this task until now. Here, we describe the use in the Aurantioideae subfamily, of a simple and non labeling cleaved amplified polymorphic sequence (CAPS) technique, to determine the cytoplasmic genome origin of intergeneric somatic hybrids. Mitochondrial and chloroplastic universal primers previously selected for population genetic studies in Quercus by Demesure et al. (1995) are used with some modifications. The variability of cytoplasmic genome among somatic fusion partners is detected by coupling amplification and restriction reactions. Digested DNA fragments are analyzed by agarose gel electrophoresis (PCR-RFLP). This technique has been applied for the analysis of the cytoplasmic constitution of somatic hybrids arising from intergeneric, intersubtribal and intertribal combinations. Systematic transmission of the mitochondria from protoplasts isolated from embryogenic callus parents was confirmed.

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E.H. Simonne, J.T. Eason, J.A. Pitts, and J.T. Owen

Bell pepper (Capsicum annuum L.) fruit are typically green in color at the immature stage, 1/3 and 2/3 colored during ripening, and red at maturity. However, this sequence does not apply to new varieties with immature colors of white or purple, intermediate colors of brown or black, and mature colors of yellow or orange. The study of physiological changes during ripening in such cultivars requires the description of color changes. Therefore, color changes of new bell pepper varieties were evaluated by subjective description and objective measurement of L, a, and b. Color changes were described with a five-color stage scale. L, a, and b were affected significantly by variety (P < 0.01), and a and b were affected significantly by color stage (P = 0.95, 0.01, and 0.01 for L, a, and b, respectively). Location and cultivar*location had no significant effect. For each cultivar, differences in a and b values defined color stages that were clearly identifiable. When plotted, color measurements (a and b) were in good agreement with the verbal descriptions. Therefore, measurements of L, a, and b are not systematically necessary when referring to bell pepper colors.

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S.S. Miller, R.W. McNew, B.H. Barritt, L. Berkett, S.K. Brown, J.A. Cline, J.M. Clements, W.P. Cowgill, R.M. Crassweller, M.E. Garcia, D.W. Greene, G.M. Greene, C.R. Hampson, I. Merwin, D.D. Miller, R.E. Moran, C.R. Rom, T.R. Roper, J.R. Schupp, and E. Stover

Cultivar and planting site are two factors that often receive minimal attention, but can have a significant impact on the quality of apple (Malus ×domestica) produced. A regional project, NE-183 The Multidisciplinary Evaluation of New Apple Cultivars, was initiated in 1995 to systematically evaluate 20 newer apple cultivars on Malling.9 (M.9) rootstock across 19 sites in North America. This paper describes the effect of cultivar and site on fruit quality and sensory attributes at a number of the planting sites for the 1998 through 2000 growing seasons. Fruit quality attributes measured included fruit weight, length: diameter ratio, soluble solids concentration (SSC), titratable acidity (TA), flesh firmness, red overcolor, and russet. Fruit sensory characteristics rated included crispness, sweetness, and juiciness, based on a unipolar intensity scale (where 1 = least and 5 = most), and acidity, flavor, attractiveness, and desirability based on a bipolar hedonic scale (where 1 = dislike and 5 = like extremely). All fruit quality and sensory variables measured were affected by cultivar. The two-way interaction of cultivar and planting site was significant for all response variables except SSC, TA, russet, crispness, and sweetness ratings. The SSC: TA ratio was strongly correlated with sweetness and acidity sensory rating, but was weakly correlated with flavor rating. The results demonstrate that no one cultivar is ideally suited for all planting sites and no planting site is ideal for maximizing the quality of all apple cultivars.

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Philip L. Forsline, Warren F. Lamboy, James R. McFerson, and Cecil Stushnoff

The USDA–ARS germplasm collection of cold-hardy Vitis held at the Plant Genetic Resources Unit, Geneva, N.Y., has over 1300 clonal accessions maintained as field-grown vines. Security back-up using field-grown or potted vines at remote sites or via in vitro methods is costly. Cryopreservation offers a safe, cost-effective alternative. While we routinely employ cryogenic storage of dormant buds of Malus, dormant buds of Vitis generally do not appear to tolerate the desiccation levels required by our current cryopreservation protocol. Since tolerance to desiccation and cold appear to be correlated in Vitis, we tested desiccation tolerance of 60 germplasm accessions selected from the core subset to represent a range of cold hardiness. Budwood was collected in December 1995 in Geneva, stored at –4°C in sealed bags, and systematically desiccated to 30% and 20% moisture. In some treatments, additional desiccation was imposed by slow freezing to –25°C. Microscopic examination of rehydrated buds indicated 60% of accessions tolerated desiccation as low as 20% moisture. Freeze-desiccation at –25°C after desiccation at –4°C neither increased nor decreased viability in these accessions. Only slight modification so current protocols should be necessary for cryopreservation of this class. Of the remaining accessions, 25% tolerated desiccation to 30% moisture, but 15% were intolerant to any desiccation level tested. Techniques must be developed to successfully cryopreserve both these classes of accessions.

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Kelly T. Morgan, T.A. Obreza, and J.M.S. Scholberg

Understanding the growth pattern of fibrous, orange tree [Citrus sinensis (L.) Osbeck] roots enables proper fertilizer placement to improve nutrient uptake efficiency and to reduce nutrient leaching below the root zone. The objective of this study was to develop relationships defining citrus fibrous root length density (FRLD) as a function of soil depth, distance from the tree trunk, and tree size. Root systems of 18 trees with tree canopy volumes (TCV) ranging from 2.4 to 34.3 m3 on two different rootstocks and growing in well-drained sandy soils were sampled in a systematic pattern extending 2 m away from the trunk and 0.9 m deep. Trees grown on Swingle citrumelo [Citrus paradisi Macf. × Poncirus trjfoliata (L.) Raf.] rootstock had significantly greater FRLD in the top 0.15 m than trees on Carrizo citrange (C. sinensis × P. trifoliata). Conversely, Carrizo citrange had greater FRLD from 0.15 to 0.75 m below the soil surface. FRLD was significantly greater for ‘Hamlin’ orange trees grown on Swingle citrumelo rootstock at distances less than 0.75 m from the tree trunk compared with those on Carrizo citrange. Fibrous roots of young citrus trees developed a dense root mat above soil depths of 0.3 m that expanded both radially and with depth with time as trees grow and TCV increased. Functional relationships developed in this study accounted for changes in FRLD with increase in tree size.

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Alan T. Bakalinsky, Hong Xu, Diane J. Wilson, and S. Arulsekar

A total of eight random amplified polymorphic DNA (RAPD) markers were generated in a screen of 77 primers of 10-base length and were detected reproducibly among nine different grape (Vitis) rootstocks. Occasional failed amplifications could not be explained rationally nor easily corrected by systematic replacement of individual reaction components. In an effort to improve their reliability, the RAPD markers were cloned, their termini sequenced, and new sequence-specific primer pairs were synthesized based on addition of 10 to 14 bases to the 3' termini of the original 10-mers. Six pairs of the new primers were evaluated at their optimal and higher-than optimal annealing temperatures. One primer pair amplified a product the same size as the original RAPD marker in all rootstocks, resulting in loss of polymorphism. Post-amplification digestion with 7 different restriction endonucleases failed to reveal restriction site differences. Three primer pairs amplified an unexpected length variant in some accessions. Two other pairs of primers amplified a number of unexpected bands. Better approaches for exploiting the sequence differences that account for the RAPD phenomenon will be discussed.