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Emad Bsoul, Rolston St. Hilaire, and Dawn M. VanLeeuwen

Ecological traits such as an extensive range of natural distribution and tolerance to varying soil conditions, suggest that bigtooth maples (Acer grandidentatum Nutt.) could be popular landscape trees. But information on the tolerance of bigtooth maples to environmental stresses, such as drought, is virtually nonexistent. We studied physiological, growth and developmental traits of bigtooth maple plants from 15 trees native to Arizona, New Mexico, Texas, and Utah. Plants were grown in pots in a greenhouse and maintained as well-irrigated controls or exposed to drought and irrigated in cycles based on evapotranspiration. The ratio of variable to maximal fluorescence (Fv/Fm) was not different between drought-stressed and control plants, but the low Fv/Fm in plants designated as LM2 from the Lost Maples State Natural Area in Vanderpool, Tex., suggests these plants were relatively inefficient in capturing energy at PSII. Plants from another tree (LM5) originating from Lost Maples State Natural Area maintained similar predawn water potentials between drought-stressed and control plants after five cycles of drought. Plants from Dripping Springs State Park in Las Cruces, N.M., and those from LM2 had a strong, significant linear relationship between transpiration and stomatal conductance. Drought-stressed plants from Dripping Springs State Park, two plant sources from the Guadalupe Mountains in Salt Flat, Tex., designated as GM3 and GM4, and plants from trees designated as LM1 and LM2, had high relative growth rates and net assimilation rates. Drought-stressed plants from three of the four Guadalupe Mountain sources (GM1, GM3, GM4) had among the longest and thickest stems. Drought reduced shoot and root dry weight (DW). Although bigtooth maples showed several provenance differences in drought adaptation mechanisms, the lack of an irrigation effect on biomass allocation parameters such as root to shoot DW ratio and leaf area ratio implies that altered biomass allocation patterns may not be a common drought adaptation mechanism in bigtooth maples. Plants from selected provenances from the Guadalupe Mountains and Lost Maples State Natural Area in Texas, and to a lesser extent, provenances from Dripping Springs State Park in New Mexico might hold promise for selecting bigtooth maples for arid environments.

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Heidi A. Kratsch* and William R. Graves

Alnus maritima (Marsh.) Muhl. ex Nutt. is unique among alders in its degree of preference for low-oxygen soils of wetlands. An actinorhizal species with promise for use in sustainable horticulture, A. maritima develops a root-nodule symbiosis with nitrogen-fixing Frankia. Nodules of other actinorhizal species that are obligate wetland natives are adapted to low oxygen, and expression of hemoglobin is common to these taxa. Our objectives were to determine the range of oxygen tension under which Alnus maritima subsp. maritima fixes nitrogen and to investigate a potential role for hemoglobin in adaptation of nodules to low oxygen. Roots of plants, cultured aeroponically, were subjected to eight oxygen tensions from 0 to 32 kPa. After four weeks, plant dry weight, nodule fresh weight, nitrogenase activity, and photosynthetic rate were measured. In addition, nodules were assayed spectrophotometrically for the presence of hemoglobin. A quadratic function best described the influence of oxygen on plant dry weight, nodule fresh weight, nitrogenase activity, and photosynthetic rate with maximal values above 20 kPa. Alnus serrulata (Ait.) Willd. is sympatric with A. maritima subsp. maritima but is not an obligate inhabitant of wetlands. In a separate experiment, we found higher nitrogenase activity in A. maritima subsp. maritima than in A. serrulata (0.74 vs. 0.26 μmol/h per plant) at hypoxic oxygen tensions. Further, optical absorption spectra of nodule extracts confirmed hemoglobin within nodules of A. maritima subsp. maritima. Our data suggest that hemoglobin contributes to oxygen regulation in nodules of A. maritima subsp. maritima.

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Michael S. Stanghellini, Jonathan R. Schultheis, and Gerald J. Holmes

In 1998 and 1999, a total of 27 large-fruited and 15 miniature-fruited pumpkin (Cucurbita pepo) cultivars were evaluated for adaptation to eastern North Carolina grow- ing conditions. Test categories were yield (fruit number and weight); fruit characteristics (shape, rind and stem attributes); and susceptibility to edema (wart-like growths on fruit exterior), foliar diseases, preharvest and postharvest fruit decay, and viruses. Yields of large pumpkins ranged from over 3,200 fruit/acre (7,907 fruit/ha) for `SVT 4613367', `Autumn Gold', and `Gold Standard' to less than 1,000 fruit/acre (2,471 fruit/ha) for `Gold Rush' and `Progold 200'. For miniature pumpkins, over 33,000 fruit/acre (81,542 fruit/ha) were produced by `Touch of Autumn', `Lil' Pump- ke-mon', and `HMX 5682', whereas `Mystic' and `Progold 100' produced less than 7,000 fruit/acre (17,297 fruit/ha). `Gold Rush', `Howden', and `Progold 510' (large), and `EXT 4612297', `Lil' Goblin', and `Lil' Ironsides' (miniature) appeared the most susceptible to foliar diseases. Preharvest fruit decay ranged from 0% for `Howden' and `EXT 4612297' to over 20% for `Lil' Goblin', `Jumping Jack', `Peek-A-Boo', and `Tom Fox'. Virus incidence on fruit and foliage was low on virus-resistant cultivars ('SVT 4613367' and `EXT 4612297'), and ranged from 4% to 74% for nontransgenic cultivars. Virus incidence and/or severity on foliage and fruit were not related. `Early Autumn' (large) and `Touch of Autumn' (miniature) were the most prone to edema. `Aspen' and `Magic Lantern' (large) and `Baby Pam', `Lil' Goblin', and `Spooktacular' (miniature) were the most susceptible to postharvest fruit decay. Fruit characteristics are discussed in relation to marketability and possible consumer appeal to pumpkins.

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Asadolah Aslani Aslamarz, Kourosh Vahdati, Majid Rahemi, and Darab Hassani

Adaptation is a concept related to how plants can survive and reproduce in a specific environment ( Hill et al., 1998 ), and it is reflected in the synchronization between the development stages and climate ( Dietrichson, 1964 ). Chilling

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Francisco Radillo-Juárez*

In the world horticultural production, the tomato (Lycopersicon esculentum Mill.) contributes with the 47% of the destined area. In Mexico, 10% of the area is cultivated under intensive systems, where is used one or more technologies for obtaining higher productivity and quality; however, the environmental conditions are determinant factors to produce red tomato in the dry tropic, influencing the adaptation and persistence in the market. The aim of this research was to evaluate the adaptation and yield performance of tomato hybrids in fresh production under mulching, fertilization and irrigation. The tomato cultivars used were: `Access', `Centurion', `Bishop', `Dean', and `Yaqui' (control). They were distributed under a Completely randomized blocks design with four replications. The experiment was carried out in Villa de Alvarez, Colima, México. `Yaqui' exhibited the highest plant height 98.8 cm, as web as the highest fruit diameter with 4.61 cm; `Bishop' produced the highest number with 154.5 fruits per plant, followed by `Yaqui', and `Centurion', with 91 fresh fruits. In the variable fruit weight, `Yaqui' showed 93.44 g. In total fresh fruit yield per plant, `Yaqui' produced the highest yield with 8.46 kg, followed by `Bishop' with 4.91 kg; and total yield of 117.5, and 68.2 t·ha-1, respectively. Yaqui' was the genotype with best adaptation and agronomic characteristics. We speculate that environment conditions in field are determinant factors in the introduction of new tomato introductions.

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Majken Pagter, Karen K. Petersen, Fulai Liu, and Christian R. Jensen

hormone, is suggested to mediate plant responses triggering cold acclimation and drought adaptation. ABA levels have been reported to increase in tissues of both herbaceous and woody plants subjected to drought or cold stresses ( Li et al., 2002 ; Skriver

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Suping Zhou, Roger J. Sauvé, and Margaret T. Mmbaga

A cold acclimatization mechanism regulated by the accumulation of mRNAs and proteins has been tentatively identified in japanese spurge (Pachysandra terminalis Sieb. & Zucc.). Two polypeptides and several cDNA fragments were observed in leaf tissue after acclimation. When these proteins were probed with type III fish antifreeze antibodies, an immune-cross reaction occurred. Nonacclimatized young leaves and stems of japanese spurge survived 20-minute exposures at -5 °C. Although newly emerged leaves and stems were damaged, plants resumed growth at higher temperatures. After acclimation by gradual cold treatments (4 to -5 °C), new proteins began to accumulate in young leaves and plants were more tolerant to extended treatments at -5 °C. Changes in accumulation of proteins and mRNA in leaf tissue of japanese spurge appear to be an adaptation mechanism to subfreezing conditions. This is the first report of the immune-cross reaction between antibodies of type III fish antifreeze proteins and plant proteins

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Sylvain L. Dubé and John F. Allen

Photosynthesis, a major determinant in growth and survival of plants, is very sensitive to the energy balance of the processes triggered by the physico-chemical environment. It is, therefore, an excellent indicator of the plants' physiological state. Fundamental events in photosynthesis can be studied non-invasively and non-destructively by examining there-emission of absorbed light energy as chlorophyll a fluorescence. In this study we present digitized consecutive images of fluorescence of intact leaves of Arabidopsis sp. The relative intensity and kinetics of fluorescence of several AOI (areas of interests) of each image have been analyzed and compared. We demonstrate the feasibility of this technique for studying the physiology of light adaptations (state-transitions) of several organisms simultaneously and its applicability in indentifying mutants. Implications of this technique to the horticulture industry will be discussed.

Open access

Justine Beaulieu, Bruk Belayneh, John D. Lea-Cox, and Cassandra L. Swett

benches so that there were 48 3.8-L pots/host/bench. Of the 96 pots/host in each block, 48 were filled with bark, 32 were filled with peat, and 16 were filled with HydraFiber. The unbalanced numbers reflect adaptations in the experiment due to limitations

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Alan W. McKeown*, Mary Ruth McDonald, Cathy J. Bakker, and Kevin Vander Kooi

Chives, (Allium schoenoprasum) consumption and production are increasing in Ontario. Rust (Puccinia allii F. Rudolphi) has been a problem with some chive cultivars for some growers, and in Ontario, basic information on production is nonexistent. The objectives were to identify cultivars with high yields, disease resistance and winter survivability. Plantings of six cultivars of chives were established in 2002 and 2003 in two contrasting environments, on organic (Kettleby) and mineral (Simcoe) soils; and one cultivar of garlic chives (A. tuberosum) at Kettleby. Leaves were harvested to a length of 30 cm, weighed and assessed for visible signs of rust. In Spring 2003, the number of dead plants was recorded to determine the overwinter survivability of each cultivar. Performance varied among cultivars and between locations. In Simcoe, Staro produced the highest yield in 2002 while generic (unnamed) chives produced the highest yield in the second year. In Kettleby, yield was similar among cultivars in 2002 but in 2003 generic chives produced the highest yield. Overwinter survival also varied between locations and second season yields were much higher in Kettleby. Less snow cover and subsequent winter injury is a possible explanation for the lower yields and poorer winter survival in Simcoe. No symptoms of rust were found in either location. Chives are a viable crop in Ontario, and appear to have different adaptability to regional soils and climates.