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Predicting Potential Kernel Set in Maize from Simple Flowering Characteristics

^a Dep. of Agricultural and Biosystems Engineering, Iowa State Univ., Ames, IA 50011
^b Dep. of Agronomy, Iowa State Univ., Ames, IA 50011

View larger version (24K): [in a new window]   Fig. 1. Dynamics of silk exsertion in apical and subapical ears of Asgrow 740 as influenced by plant population density. Symbols are the number of exposed silks per ear and lines are corresponding monomolecular functions fit to the data. Parameters SN, b, to and duration in Eq. [4] to predict silk emergence from subapical ears of P3925 were generated from these curves (see Table 1). Vertical lines are standard errors for five plants. Plants grown at 16 plants m-2 did not produce a second ear.

View larger version (38K): [in a new window]   Fig. 2. Seasonal dynamics of pollen shed intensity for hybrids Pioneer 3978 (P3978; a,c) and Pioneer 3925 (P3925; b,d). (a,b) Observed (symbols) and predicted (lines) rates of pollen shed at four levels of male fertility (MF). (c,d) Daily pollen shed rates normalized per fertile plant (symbols) and Gauss functions fit to the normalized data (lines). Vertical lines are standard errors for four measurements. Note that a single curve describes the seasonal pattern of pollen shed for each hybrid.

View larger version (36K): [in a new window]   Fig. 3. (a,b) Normalized percentage of plant population at three stages of pollen shed: beginning shed, maximum shed, and end shed for Pioneer 3978 (P3978; a) and Pioneer 3925 (P3925; b). (c,d) Measured pollen rates (symbols) and predicted pollen rates using the population index (lines) for hybrids P3978 (c) and P3925 (d). The population index was calculated using Eq. [3]. Vertical lines are standard errors of four measurements.

View larger version (27K): [in a new window]   Fig. 4. Seasonal progress of silk emergence for the plant population and individual apical ears. (a,c) Pioneer 3978 (P3978); (b,d) Pioneer 3925 (P3925). (a,b) Cumulative percentage of plant population at silking (solid lines) and cumulative number of silks exserted on the apical ear (broken lines). (c,d) Daily percentage of plant population that has started silking (solid lines) and daily number of silks exserted from the apical ear (broken lines).

View larger version (20K): [in a new window]   Fig. 5. Seasonal dynamics of silk exsertion on an area basis for hybrids Pioneer 3978 (P3978; top) and Pioneer 3925 (P3925; bottom). Calculated values (symbols) were generated from population and silk exsertion curves in Fig. 4a and b. Predicted curves (lines) are a double Gauss function fit to the seasonal pattern of newly exposed silks using Eq. [5].

View larger version (21K): [in a new window]   Fig. 6. Relationship used to convert daily pollen shed density into potential kernel set adopted from Bassetti and Westgate (1994). Data for pollen shed are from passive pollen traps placed at ear level, and kernel set was measured on ears exposed to pollen for 1 d at the indicated densities. The broken line indicates the predicted kernel set if pollen viability were decreased to 63% of that in the Bassetti and Westgate (1994) study.

View larger version (25K): [in a new window]   Fig. 7. Seasonal dynamics of pollen shed and potential kernel set for Pioneer 3978 (P3978; a,c) and Pioneer 3925 (P3925; b, d) at two levels of male fertility (MF). Note that all florets pollinated before maximum pollen shed develop into kernels. At low pollen density, a greater proportion of late emerging silks fail to be pollinated.

View larger version (21K): [in a new window]   Fig. 8. Kernel set expressed relative to the number of exposed silks at four levels of male fertility (MF) for Pioneer 3978 (P3978) and Pioneer 3925 (P3925). Pollen shed is presented as a fraction of the total seasonal deposition expected in a field of 100% MF plants. Symbols are measured values; lines indicate predicted values. (a) Predicted kernel set is based on silk exsertion and pollen shed dynamics for each MF treatment. (b) Predicted kernel set incorporates potential kernel loss due to asynchronous pollination within ears and asynchronous development between ears.