Search Results

You are looking at 11 - 20 of 27 items for :

  • "Richards function" x
  • All content x
Clear All
Free access

Jomo MacDermott and D.L. Coffey

Some chicory (Cichorium intybus L.) cultivars, especially early and extra-early cultivars, often bolt and flower the first year of growth, contrary to the expected behavior of biennials. The extra early hybrid cultivar `Daliva' was grown in the field under bare soil and straw mulched conditions to examine possible correlations between growth rates, leaf and root sizes and bolting. Plants, sown on 19 June, were harvested weekly from 4 July to 1 Oct.; a total of 14 harvests. Root variables of length and diameter were best described by linear equations but root dry weight was decidedly quadratic in response. Leaf number, area and dry weight and crown diameter data were fitted to the Richards function to describe their sigmoidal phases of growth. In most cases, when using the Richards function, the two treatments (mulch vs. no-mulch) required different parameters to fit a line to the observed points with r 2 values >0.95. A statistical comparison between treatment parameters (as obtained from SAS PROC NLIN and SigmaPlot) will be discussed.

Free access

Leena Lindén, Pauliina Palonen, and Mikael Lindén

Seasonal cold hardiness of red raspberry (Rubus idaeus L.) canes was measured by freeze-induced electrolyte leakage test and visual rating of injury. Leakage data were transformed to percentage-adjusted injury values and related to lethal temperature by graphical interpolation and by the midpoint (T50) and inflection point (Tmax) estimates derived from three sigmoid (the logistic, Richards, and Gompertz) functions. Tmax estimates produced by Richards and Gompertz functions were corrected further using two different procedures. The 10 leakage-based hardiness indices, thus derived, were compared to lethal-temperature estimates based on visual rating. Graphical interpolation and Tmax of the logistic or T50 of the Gompertz function yielded lethal-temperature estimates closest to those obtained visually. Also, Tmax values of the Gompertz function were well correlated with visual hardiness indices. The Richards function yielded hardiness estimates deviating largely from visual rating. In addition, the Richards function displayed a considerable lack of fit in several data sets. The Gompertz function was preferred to the logistic one as it allows for asymmetry in leakage response. Percentage-adjusted injury data transformation facilitated curve-fitting and enabled calculation of T50 estimates.

Free access

Meriam G. Karlsson and Royal D. Heins

The relative progression of lateral shoot elongation from pinch to flower of chrysanthemum [Dendranthema grandiflora (Ramat.) Kitamura `Bright Golden Anne'] plants grown under 2 to 22 mol·day-1·m-2 photosynthetic photon flux and 10 to 20C was modeled using Richards function. Parameters for the function were determined by first transforming data of shoot length and time from pinch (start of short photoperiods) to flower to a relative scale of 0.0 to 1.0 by dividing all intermediate shoot lengths and measurement dates by final shoot length and number of days to flower, respectively. Data used for parameter estimation originated with plants grown at a daily average of ≤20C, since those grown at a daily average above 20C exhibited delayed morphological flower induction and reached 50% of the final shoot length earlier in development. Relative shoot elongation was described by Richards function in the following form: Relative shoot length = SF × {1 + [(SF/SO)N-1] e-SF Kt}-1/N where t (relative time) = 0.0 to 1.0, SF (maximum relative shoot length) = 1.018, SO (relative shoot length at t = o) = 0.0131, N (model parameter related to the shape of the curve) =0.3923, and K (model parameter related to mean relative growth rate) = 5.8138.

Free access

John Frampton and D.M. Benson

Seventeen-month-old seedlings from three fraser fir (Abies fraseri [Pursh] Poir.) seed sources (Mount Mitchell, Richland Balsam and Roan Mountain) were inoculated in an outdoor lath house with five genotypes of Phytophthora cinnamomi Rands. After 122 days, overall mortality was 90.5% with significant (p ≤ 0.07) differences among seed sources. The Mount Mitchell source had lower mortality (83.2%) than the Roan Mountain source (95.8%), while the Richland Balsam source (92.5%) was intermediate. Mortality curves were developed using nonlinear regression (Richards' function). Due to a significant seed source × inoculum genotype interaction (p ≤ 0.0001), equations were developed for each combination of seed source and inoculum genotype. Results suggest that while the overall frequency of resistance in fraser fir is low, seed sources differ in their frequency of resistance and that more than one resistance gene may be present. Survivors from this or similar inoculations could be cloned via grafting or rooted cuttings for further resistance testing and/or grafted into a Phytophthora-resistant fraser fir seed orchard.

Free access

F.D. Moore III, S.R. Nath, and Y-C Wang

Duration of growth is dependent on morphological events or changes in growth rate. It is the latter that is associated with phasic development. The most productive phase of plant growth is the linear or constant rate phase, primarily because it endures longer than the exponential phase. The purpose of our research was to objectively determine the true tree-height growth pattern, the linear and stationary phases of height growth, and to mathematically derive the maximum slope (maximum growth rate) of the growth curve, its location (inflection point), and the maximum slope of the logarithmic form (maximum relative growth rate) of the growth curve. The data were composed of 333 tree-height records covering 240 years from 200 beechwoods in the U.K. Height-age data were fitted using a splined function (S) and the Chapman-Richards function (CR). The growth curve and critical points on the curve were derived from the CR model. The linear phase began when trees were 9 and lasted 43 years. However, the stationary phase did not begin until age 162. Anecdotal evidence suggests that very little fruiting occurs before age 50. Based on derived critical points and anticipated source-sink dynamics, the reproductive stage should have taken place during the progressive “deceleration phase” when trees were between 31 (location of the maximum slope, also inflection point) and 162 (from quadratic root). The linear phase ended at 52 years, (coinciding with minimum acceleration) and may prove a more accurate estimate than 31. Maximum slope was 1.2 m per year occurring at age 31. Maximum slope of the log curve was 0.14 m·m–1 per year. The advantage of the CR function and the importance of the derived quantities and growth phases will be discussed.

Free access

Sylvie Jenni, Katrine A. Stewart, Gaétan Bourgeois, and Daniel C. Cloutier

A simple method to predict time from anthesis of perfect flowers to fruit maturity (full slip) and yield is presented here for muskmelon (Cucumis melo L.) grown in a northern climate. Developmental time for individual muskmelons from anthesis to full slip could be predicted from several heat unit formulas, depending on the temperature data set used. When temperature at 7.5 cm above soil level was used, the heat unit formula resulting in the lowest coefficient of variation (cv=6.9%) accumulated daily average temperatures with a base temperature of 11 °C and an upper threshold of 25 °C. With temperatures recorded at a meteorological station located 2 km from the experimental field, the method showing the lowest cv (8.9%) accumulated daily maximum temperatures with a base temperature of 15 °C. This latter method was improved by including a 60-degree-day lag for second cycle fruit. The proportion of fruit volume at full slip of 22 fruit from the first cycle could be described by a common Richards function (R 2=0.99). Although 65% of the plants produced two fruit cycles, fruit from the first cycle represented 72% of total yield in terms of number and mass. The blooming period of productive flowers lasted 34 days, each cycle overlapping and covering an equal period of 19 days. Counting the number of developing fruit >4 cm after 225 degree days from the start of anthesis (when 90% of the plants have at least one blooming perfect flower) could rapidly estimate the number of fruit that will reach maturity.

Open access

Youn Young Hur, Su Jin Kim, Jeong Ho Roh, Kyo Sun Park, Hae Keun Yun, Jong Chul Nam, Sung Min Jung, Sang Uk Koh, Dong Jun Im, Dong Hoon Lee, Seo June Park, and Kyong Ho Chung

. Hort. Sci. Biotechnol. 88 727 734 Lim, C.C. Aurora, R. Townsend, E.C. 1998 Comparing Gompertz and Richards functions to estimate freezing injury in Rhododendron using electrolyte leakage J. Amer. Soc. Hort. Sci. 123 246 252 Reisch, B.I. Pool, R

Full access

Sueyde F. de Oliveira, Paul R. Fisher, Jinsheng Huang, and Simone da C. Mello

on three replicate columns per fertilizer and temperature, and error bars represent 95% confidence intervals of least-square means, equaling ±11.0 mg N. Curves represent the Richards function fitted separately by fertilizer, including the temperature

Free access

Clint Wall, William Dozier, Robert C. Ebel, Bryan Wilkins, Floyd Woods, and Wheeler Foshee III

. 1994 Flower and fruit development: An overview Kiwifruit growing and handling Univ. CA. Div. Agr. Nat. Res., Publication 3344 CA Lim, C.C. Arora, R. Townsend, E.C. 1998 Comparing Gompertz and Richards

Full access

Yang Yang, Runfang Zhang, Pingsheng Leng, Zenghui Hu, and Man Shen

alleviates the adverse effects of salt stress in Torreya grandis cv. merrillii seedlings by activating photosynthesis and enhancing antioxidant systems PLoS One 9 E109492 Lim, C.C. Arora, R. 1998 Comparing Gompertz and Richards functions to estimate