Grow tubes are well established in forestry and are gaining attention in establishing some woody perennial crops. To date, microclimate descriptions have addressed the aboveground environment, but a mulched raised bed system with organic mulch-incorporated soil requires both the above- and belowground microclimate to be quantified. We measured the microclimate of commercially used, non-ventilated translucent and non-ventilated opaque grow tubes in a model crop of blueberry (Vaccinium corymbosum L.) grown on sawdust-mulch-covered raised beds formed from sawdust-incorporated tilled soil. The differences in air temperature between tubes and ambient were consistent with those reported in the literature. Air temperature in translucent tubes was up to 19.7 °C higher than ambient. Differences in vapor pressure deficit were largely a function of differences in air temperature between tubes and ambient rather than actual vapor pressure. Stem temperatures were highest outside of the tubes as a result of radiation load. The surface temperature of ambient sawdust mulch (maximum 53 °C) was up to 14 °C above that in the translucent tube and 20 °C above that in the opaque tube. The largest gradients in the bed system were between the loose dry mulch and the soil–mulch interface. The presence of a grow tube did not influence soil temperature or its daily amplitude at 15 cm below the surface—the native tilled soil. Temperatures associated with the opaque tubes were between ambient and those in the translucent tubes. The temperature data indicate that both opaque and translucent unventilated grow tubes should influence shoot and crown growth but may have little influence on root growth in this shallow-rooted plant.
Julie M. Tarara, Bernardo Chaves and Bernadine C. Strik
Anne Fennell, Carol Wake and Paul Molitor
Changes in tissue water content have been correlated, with varying success, with changes in freezing tolerance and dormancy in woody perennials. Recent studies indicate that changes in the state of water are more strongly correlated with dormancy than are changes in bulk water content. In this study, traditional destructive methods of monitoring tissue water content and dormancy were compared with measurements using nondestructive in situ proton nuclear magnetic resonance 1H NMR to determine plant water status. These studies were designed to determine whether changes in bud water status are correlated with dormancy and can be used as a reliable indicator of the onset of dormancy. Two-year-old Vitis riparia plants were subjected to short-day (SD, 8 h daylight) or long-day (LD, 15 h daylight), dormancy-inductive or noninductive treatments, respectively. Bud water was monitored at 2, 4, and 6 weeks of photoperiod treatments. SD treatments promoted a rapid onset in bud dormancy. Water content was not different in SD or LD treatments after 2 weeks. However, it did decrease over 6 weeks in both treatments, but SD treatments promoted a more rapid decrease in water content. The nondestructive 1H NMR methods give comparable measures of water content and provide a measure of bud water status. There were shorter T1 relaxation times in the 2-, 4-, and 6-week SD treatments. The SD treatment T2 relaxation times were shorter in the 4- and 6-week SD treatments only. Changes in the T1 and T2 relaxation times indicated changes in bud water status are correlated with the onset of dormancy.
Heidi L. Hoel
The Allen Centennial Gardens are located at the Univ. of Wisconsin–Madison on the grounds of the National Historical site, the house of the first four deans of the College of Agriculture and Life Sciences. The 2.5-acre garden, developed and managed primarily by the Dept. of Horticulture, replaced the old teaching and display garden space taken over in building additions. Within the past 10 years the grounds have been designed and transformed into a garden, with 26 individual collection gardens, including: turf, fruit and vegetable gardens, classic ornamental gardens (with both herbaceous and woody perennials), and a rock alpine garden. As it receives its finishing touches, an education plan is being developed to complement the education purpose of the garden; the goal of the garden is to become an active site for learning through both observation and interaction with the garden collections. The two main themes of the learning experience are: 1) the biology of the diverse and unique plant collections (including: culture, practices, and production), and 2) the aesthetics of the garden (the organization of space, form, topography, and color). Implementation of education programs will occur on the following four levels: first the university (first the horticulture department, second other departments and university functions); second, area high schools groups; third, community and professional groups; and fourth, elementary school groups. The education programs will include mapping, internships, classes, meetings, volunteerism, and tours. The Allen Centennial Gardens, with its education mission, has already and will continue to be a meeting grounds for the university community, and a meetings ground for both the professional community and Madison-area community.
Chon C. Lim, Rajeev Arora and Stephen L. Krebs
Winter survival in woody plants is controlled by environmental and genetic factors that affect the plant's ability to cold-acclimate. A juvenile period in woody perennials raises the possibility of differences in cold-acclimating ability between juvenile vs. mature (flowering) phases. This study investigated the yearly cold hardiness (CH) changes of rhododendron populations and examined the relationship between leaf freezing tolerance (LFT) and physiological aging. Naturally acclimated leaves (January) from individual plants (parents-R. catawbiense and R. fortunei, F1, F2, and backcross) and F1 population generated from R. catawbiense and R. dichroanthum cross were subjected to controlled freeze-thaw regimes. LFT was assessed by measuring freeze-thaw-induced ion leakage from leaf discs frozen over a range of treatment temperatures. Data were then plotted with a sigmoidal (Gompertz) curve by SAS, to estimate Tmax—the temperature causing maximum rate of injury. Tmax for the 30- to 40-year-old parental plants (catawbiense, fortunei, and dichroanthum) and the F1 `Ceylon' (catawbiense × fortunei) were estimated to be about -52, -32, -16, and -43 °C, respectively. These values were consistent over the 3-year evaluation period. Data indicated the F2 (50 seedlings) and backcross (20 seedlings) populations exhibited significant, yearly Tmax increment (of ≈5-6 °C) from 1996 to 1998 as they aged from 3 to 5 years old. A similar yearly increase was observed in the 12 F1 progenies (compared 2 to 3 years old) of catawbiense × dichroanthum cross. The feasibility of identifying hardy phenotypes at juvenile period and research implications of age-dependent changes in CH will be discussed.
Hongwen Huang, Desmond R. Layne and Don E. Riemenschneider
As a new National Clonal Germplasm Repository for Asimina species at Kentucky State University (KSU), of major concern to us is the genetic variation within our germplasm collection. The present study investigated the extent of genetic diversity for the pawpaw germplasm in our collection and the geographical pattern of genetic diversity among populations using isozyme markers. Allozyme diversity was high in Asimina triloba (L.) Dunal (Annonaceae) collected from all nine different states, as is typical for temperate woody perennial, widespread and outcrossing plant species. Averaged across populations, mean number of alleles per locus (A), percent polymorphic loci (P), effective number of alleles per locus (Ae), and expected heterozygosity (He) were 1.54, 43.5, 1.209, and 0.172, respectively. Significant deviations from Hardy-Weinberg equilibrium were found in nine populations at an average of 4.8 loci. Observed heterozygosity was higher than expected. Partitioning of genetic diversity showed that 88.2% resided within populations. The proportion of genetic diversity among populations (Gst = 0.118; FST = 0.085) was either lower than or within the range of those species with similar ecological and life-history traits. The mean genetic identity among populations was high (I = 0.988). An analysis using UPGMA clustered most populations as one major group, with the southernmost (Georgia) and the westernmost (Illinois) populations readily separated from the main group. The relationships discovered by principal component analysis (PCA) were similar to those revealed by UPGMA. In addition, PCA separated the northernmost population (New York) from the major group. Sampling strategies for future germplasm collection of A. triloba are also discussed.
Lisa J. Rowland, Elizabeth L. Ogden, Mark K. Ehlenfeldt and Bryan Vinyard
Deacclimation response is an important part of reproductive success in woody perennials because late winter or early spring thaws followed by hard freezes can cause severe injury to dehardened flower buds. There is a need to develop more spring-frost tolerant cultivars for the blueberry (Vaccinium L.) industry. The identification of later or slower deacclimating genotypes could be useful in breeding for more spring-frost tolerant cultivars. This study was undertaken to investigate cold hardiness and deacclimation kinetics under field conditions for 12 Vaccinium (section Cyanococcus A. Gray) genotypes (the cultivars Bluecrop, Duke, Legacy, Little Giant, Magnolia, Northcountry, Northsky, Ozarkblue, Pearl River, Tifblue, and Weymouth; and a population of V. constablaei Gray) with different germplasm compositions and expected mid-winter bud hardiness levels. Examination of bud cold hardiness (BCH) vs. weeks of deacclimation over a 7-week period in 2 consecutive years (2002 and 2003) revealed clear genotypic differences in cold hardiness and timing and rate of deacclimation. Among cultivars, `Legacy' was the least cold hardy at initial evaluation, even less so than `Tifblue'. Regarding deacclimation kinetics, the weekly intervals with the largest losses (i.e., high rates of deacclimation) also varied among genotypes. For `Duke', the largest losses in BCH were detected at weeks 2 and 3, making it the earliest deacclimator. For `Bluecrop', `Ozarkblue', `Weymouth', `Tifblue', and `Legacy', the greatest losses in BCH were observed at weeks 3 and 4. For `Little Giant', `Magnolia', `Northcountry', `Northsky', and `Pearl River', losses in BCH were greatest at weeks 4 and 5, while for V. constablaei, losses were greatest at weeks 6 and 7, making it the latest deacclimator. Deacclimation kinetics were not correlated with mid-winter hardiness or chilling requirements in any fixed pattern. On the other hand, a strong positive correlation was found between BCH and stage of bud opening (r = 0.84). A comparison of timing of deacclimation with germplasm composition indicated that V. constablaei was particularly late to deacclimate. `Little Giant', a 50:50 hybrid of V. constablaei and V. ashei Reade, was nearly as late to deacclimate as the 100% V. constablaei selections. Thus, V. constablaei may be useful in breeding programs to contribute genes for late deacclimation, which should translate into greater spring frost tolerance, in addition to genes for mid-winter hardiness.
Cheng Bai, Charles C. Reilly and Bruce W. Wood
survival of long-lived woody perennial crops. The influences of Ni deficiency on N metabolism described above indicate that Ni deficiency can potentially influence efficiency of N conversion of plant N reserves as well as that of N management of
sources used in production over water used in the landscape for both herbaceous and woody perennials. The consumer group that did not perceive a drought, but actually experienced one, placed a higher value on ornamental plants grown with fresh water
Lailiang Cheng and Richard Raba
‘Baldwin’ apple trees (presumably on seedling rootstocks) by determining the amount of macronutrients in fruit, leaves, and new wood. Recognizing that some nutrients are remobilized from woody perennial structural parts to support new growth, Magness and
Esther Giraldo, Margarita López-Corrales and José Ignacio Hormaza
The common fig is a gynodioecious woody perennial species with two tree types: the inedible caprifig, which is functionally a male fig that produces syconia with both male and short-styled female flowers, and the female trees that produce syconia