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Seed Size Variation in Grain Crops: Allometric Relationships between Rate and Duration of Seed Growth

^a South Australian Research and Development Institute and Univ. of Adelaide, Waite Campus, Adelaide, Australia
^b Dep. of Plant and Soil Sciences, Univ. of Kentucky, Lexington, KY 40546-0312

View larger version (9K): [in this window] [in a new window]   Figure 1. Comparison of scaling exponents calculated with least squares (LS) and reduced major axis regression (RMA).

View larger version (22K): [in this window] [in a new window]   Figure 2. Examples of intraspecific scaling relationships between rate and duration of seed growth. Multiple symbols for a cultivar indicate different experiments or seasons, except for sorghum where closed and open symbols indicate apical and basal grains, respectively. The solid line is the least squares regression, and dashed lines are isolines of seed size with = –1. Standard errors (SE) of the scaling exponents are also shown. Data sources: maize, Echarte et al. (2006); sunflower, López Pereira et al. (1999); rice, Fujita et al. (1984); soybean (control treatment), Egli (1999); sorghum, Gambin and Borrás (2007). For rice and soybean, rate is in mg seed–1 d–1 and duration in d, and for maize, sunflower, and sorghum rate is in mg seed–1 per degree day (°Cd) and duration in °Cd. Variate units do not affect the magnitude of the scaling exponent.

View larger version (14K): [in this window] [in a new window]   Figure 3. Relationship between seed size range and LS, the scaling exponent relating duration and rate of seed growth derived from the data sets summarized in Table 1. Emphasis is on (a) crop species and (b) sources of variation. The points inscribed in a circle or a square indicate data from the experiment of Swank et al. (1987) where cultivars were intentionally selected for comparable rates and large variation in duration of seed growth. Sources of variation where attributed to genotype (G) when experiments included several cultivars in a single treatment, site or season; environment (E) when a single genotype was grown under a range of conditions (e.g., sites, seasons, water regime), or GxE when both cultivars and environments were combined.

View larger version (19K): [in this window] [in a new window]   Figure 4. Relationships between (a) seed size range and range of rate of seed filling, and (b) the residuals of the relationship in (a) and the scaling exponent LS.

View larger version (9K): [in this window] [in a new window]   Figure 5. Relationship between seed size plasticity and the scaling exponent LS for maize, wheat, and soybean. Both variables are dimensionless. Seed size plasticity is the variability in seed size relative to the variability in seed number derived from Sadras (2007) (his Fig. 4b), and LS is the average for each species from Fig. 3.