thermal time ( Slafer and Savin, 1991 ). Thermal time, defined as the accumulation of daily mean temperature above a base temperature, is widely used in scheduling ornamental crop production. The approach can be more useful for predicting plant development
Robyn L. Cave, Colin J. Birch, Graeme L. Hammer, John E. Erwin and Margaret E. Johnston
D. Scott NeSmith
Different planting dates were used to study the influence of thermal time on leaf appearance rate of four summer squash (Cucurbita pepo L.) cultivars. During the first year (1991), thermal time or growing degree days (GDD) were calculated using a base temperature of 8C and a ceiling temperature of 32C for several planting dates. Leaf numbers per plant were determined every 2 to 3 days. Leaves that were beginning to unfold with a width of 2 cm or greater were included in the counts. The relationship between leaf number and GDD was established from the initial data set, and data from subsequent years were used for model validation. Results indicated that single equation could be used to predict leaf appearance of all four cultivars in response to thermal time. The response of leaf appearance to GDD was curvilinear, with a lag over the first five leaves. After five leaves, the increase in leaf number per plant was linear with increased GDD. Segmented regression with two linear functions also fit the data well. With this approach, leaf 5 was the node, and a separate linear function was used to predict the leaf number below five leaves and above five leaves. The results of this model should prove to be useful in developing a model of leaf area development, and eventually a crop growth model, for summer squash.
D.A. Smith, M.L. Metz and S.L. Cuppett
Dry edible beans (Phaseolis vulgaris) represent an inexpensive way to incorporate protein into the diet as a food ingredient, but beans contain unpleasant flavors and several anti-nutritional factors that limit their use without first processing with long heat treatments. `Great Northern' bean flour was processed using either static or specially designed dynamic (continuous) processing methods. The dynamic process treated flour slurries at temperatures up to 124°for 20 sec. The slurries were quick-frozen and freeze-dried after frozen storage periods of 0, 8, 24, 120, or 504 hr. The flours were analyzed for sensory properties, emulsifying activity, foaming properties, and trypsin inhibition. The heat treatments improved sensory attributes of the flour. The foam capacity and foam stability decreased in heat-treated flours. Trypsin inhibitor activity was at a minimum level immediately following thermal processing, but increased with time in frozen storage prior to drying. Minimal thermal processes cannot be relied upon to inactivate trypsin inhibitors.
Rita Giuliani and James A. Flore
Ground-based infrared thermal imagery was applied for early detection of plant water deficit, i.e., before photosynthetic activity is depressed and before growth processes are negatively affected by water shortage. Remote and real-time sensing of radiative canopy surface temperature was performed in Michigan in Summer 1999 on peach and apple orchards, using a digital IR imaging radiometer. Still images and videos were acquired on single canopies of well-watered plants and plants subjected to water depletion. Atmospheric parameters were monitored simultaneously. On apple trees, the apparent canopy temperature showed a wider thermal dispersion [10 °C], compared to peach tree canopies [2–5 °C]. Central tendency and shape parameters describing the canopy thermal distribution could identify, even for apple canopies, the thermal signal [1–2 °C] of plant water deficit, before changes in leaf net photosynthetic rate and fruit diameter were observed. The results of this study support the application of digital infrared thermal imagery and image processing for early recognition of plant water deficit. The decrease of the cost of available thermographic cameras makes their use feasible.
Sonali R. Padhye and Arthur C. Cameron
., 2001 ; Rawson et al., 1998 ; Streck et al., 2003 ; Suzuki and Metzger, 2001 ; Yan and Hunt, 1999 ), thermal time to flower ( Rawson et al., 1998 ), number of reproductive buds at flowering ( Clough et al., 2001 ; Suzuki and Metzger, 2001 ), and
Matthew G. Blanchard and Erik S. Runkle
/b 1 ) and the amount of thermal time (units of degree-days) that were required from VI to flower (°C·d −1 = 1/b 1 ) in each Odontioda clone ( Roberts and Summerfield, 1987 ). Results During Year 1, plants of both clones displayed
Douglas G. Bielenberg and Ksenija Gasic
. We used the observed developmental rates at 12, 14, 16, 18, and 20 °C to estimate a thermal time parameter (base temperature) for the development of two different developmental events: floral budbreak in peach [ Prunus persica (L.) Batsch] and seed
Catherine M. Grieve, James A. Poss, Peter J. Shouse and Christy T. Carter
developmental timing, ion relations, growth, and quality of a commercially important cut flower. A modeling approach based on stem length development as a function of thermal time provides future growers and researchers a potentially useful tool to estimate
long production time drastically increases the cost and hence market price. In recent years, the production of potted flowering orchids has increased markedly. The wholesale value of potted orchids reached an all time high of $144 million in 2005 ( U
Andrés Javier Peña Quiñones, Melba Ruth Salazar Gutierrez and Gerrit Hoogenboom
fixedness associated with flower bud development stages by using the thermal time concept to relate the air temperature to the LT. Materials and Methods Field samples Three sweet cherry cultivars ( Prunus avium L.), Bing, Chelan, and Sweet Heart, and two