Reproductive Allometry in Soybean, Maize and Sunflower |
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Authors: | Vega C R C; Sadras V O; Andrade F H; Uhart S A |
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Institution: | INTA BalcarceUniversidad de Mar del Plata, CC 276, 7620, Balcarce, Argentina |
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Abstract: | We compared the relationship between grain yield per plant (YP)and shoot biomass per plant (SP) in three annual crops withcontrasting reproductive strategies: sunflower, a determinatespecies with a single inflorescence; maize, a determinate specieswith a limited capacity to adjust the number of ears in responseto resource availability; and indeterminate soybean, a specieswith a large capacity to adjust the number of inflorescences.Our working hypotheses were: H1the relationship betweenYPandSP is linear; H2the intercept of the model is zero,i.e. there is not a threshold plant mass for reproduction. Awide range of YPand SPwas generated by manipulation of plantdensity;SPvaried between 0.3 and 196 g per plant in soybean,between 6 and 873 g per plant in sunflower and between 23 and697 g per plant in maize. Within these broad ranges of plantsize, both hypotheses were rejected in five out of six experiments,i.e. the relationship between YPand SPdeparted from linearityand there was a threshold for SPbelow which no grain set occurred.TheSP threshold for grain set varied widely among species; itwas close to 2 g per plant for soybean, 27 g per plant for sunflowerand 4371 g per plant for maize. Because of this sizethreshold and non-linearity, harvest index (HI = YPSP-1) wasstable for mid-size plants, diminished slightly for large plants,and diminished sharply for smaller plants in all three crops.Harvest index stability was highest in soybean, intermediatein sunflower and lowest in maize. Differential stability ofreproductive partitioning partially derived from contrastingpatterns of meristem allocation. Copyright 2000 Annals of BotanyCompany Helianthus annuus L., Zea mays L., Glycine max(L.) Merrill, grain yield, harvest index, plant density, reproductive allocation, meristem allocation, plasticity |
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