Soybean fruit development and set at the node level under combined photoperiod and radiation conditions.

NICO, MAGALÍ; KANTOLIC, A.G.; MIRALLES, D.J; MANTESE, A

JOURNAL OF EXPERIMENTAL BOTANY

OXFORD UNIV PRESS

Lugar: Oxford; Año: 2016 vol. 67 p. 365 - 377

0022-0957

In soybean, long days during post-flowering increase seed number. This positive photoperiodic effect on seed numberhas been previously associated with increments in the amount of radiation accumulated during the crop cyclebecause long days extend the duration of the crop cycle. However, evidence of intra-nodal processes independent ofthe 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 responseto long days; including the dynamics of flowering, pod development, growth and set at the node level. Long daysincreased 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 openedflowers on lateral racemes. The flowering period was prolonged under long days because effective seed filling wasdelayed on primary racemes (dominant positions). Long days also delayed the development of flowers into pods withfilling seeds, delaying the initiation of pod elongation without modifying pod elongation rate. The embryo developmentmatched the external pod length irrespective of the pod?s chronological age. These results suggest that long daysduring post-flowering enhance pod number per node through a relief of the competition between pods of differenthierarchy within the node. The photoperiodic effect on the development of dominant pods, delaying their elongationand therefore postponing their active growth, extends flowering and allows pod set at positions that are usuallydominated.