title: Soybean fruit development and set at the node level under combined photoperiod and radiation conditions.
abstract: In soybean, long days during post-flowering increase seed number. This positive photoperiodic effect on seed number has been previously associated with increments in the amount of radiation accumulated during the crop cycle because long days extend the duration of the crop cycle. However, evidence of intra-nodal processes independent of the availability of assimilates suggests that photoperiodic effects at the node level might also contribute to pod set. This work aims to identify the main mechanisms responsible for the increase in pod number per node in response to long days; including the dynamics of flowering, pod development, growth and set at the node level. Long days increased pods per node on the main stems, by increasing pods on lateral racemes (usually dominated positions) at some main stem nodes. Long days lengthened the flowering period and thereby increased the number of opened flowers on lateral racemes. The flowering period was prolonged under long days because effective seed filling was delayed on primary racemes (dominant positions). Long days also delayed the development of flowers into pods with filling seeds, delaying the initiation of pod elongation without modifying pod elongation rate. The embryo development matched the external pod length irrespective of the pod's chronological age. These results suggest that long days during post-flowering enhance pod number per node through a relief of the competition between pods of different hierarchy within the node. The photoperiodic effect on the development of dominant pods, delaying their elongation and therefore postponing their active growth, extends flowering and allows pod set at positions that are usually dominated.
authors.affiliation: Cátedra de Cultivos Industriales, Facultad de Agronomía, Universidad de Buenos Aires, Av. San Martín 4453, C1417DSE Buenos Aires, Argentina mnico@agro.uba.ar.
authors.forename: Magalí
authors.initials: M
authors.lastname: Nico
authors.affiliation: Cátedra de Botánica General, Facultad de Agronomía, Universidad de Buenos Aires, Av. San Martín 4453, C1417DSE Buenos Aires, Argentina.
authors.forename: Anita I
authors.initials: AI
authors.lastname: Mantese
authors.affiliation: Cátedra de Cerealicultura, Facultad de Agronomía, Universidad de Buenos Aires, Av. San Martín 4453, C1417DSE Buenos Aires, Argentina CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas), Argentina IFEVA (Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura), Av. San Martín 4453, C1417DSE Buenos Aires, Argentina.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Miralles
authors.affiliation: Cátedra de Cultivos Industriales, Facultad de Agronomía, Universidad de Buenos Aires, Av. San Martín 4453, C1417DSE Buenos Aires, Argentina.
authors.forename: Adriana G
authors.initials: AG
authors.lastname: Kantolic
mesh_terms: D005638:Fruit / Q000254:growth & development / Q000528:radiation effects; D017440:Photoperiod; D012098:Reproduction; D012639:Seeds / Q000254:growth & development / Q000528:radiation effects; D013025:Glycine max / Q000254:growth & development* / Q000528:radiation effects; D013472:Sunlight
keywords: Development; Glycine max; elongation; embryo; flowering; fructification; lag phase; node; photoperiod; pod set; radiation; seed filling; shade; soybean.