Is soybean leaf senescence modulated by direct and indirect effects of post-flowering photoperiod?

KELLY, S.J.; CANO, M. G.; TAMBUSSI, E. A.; GUIAMET, J. J.

Rosario, Santa Fé

Congreso; XXXIV Reunión Argentina de Fisiología Vegetal; 2023

Sociedad Argentina de Fisiología Vegetal

In soybean (Glycine max L. Merr) massive senescence of leaves coincides with pod and seed development, and this has been interpreted as evidence for a correlative control exerted by the pods and triggering senescence of leaves. Soybeans are short-day plants for flowering and long photoperiods after anthesis delay pod development, and senescence. Although pods modulate leaf senescence there are also reports showing some changes of leaf senescence that cannot be associated exclusively with pod development; implying that other factors (e.g., photoperiod per se) could modulate senescence regardless of the effect of pods. The objective of this work was to analyze if post-anthesis photoperiod might regulate the progress of leaf senescence both through its effects delaying the development of pods (an indirect effect) and independently of the development of the pods (a direct effect). After anthesis, soybean plants were exposed to photoperiod treatments (short days, SD, vs long days, LD) combined with a pod removal treatment (plants with pods vs without pods). The progress of leaf senescence was determined from SPAD 502 measurements of leaf chlorophyll content. In plants with pods, post-anthesis LD delayed reproductive development together with a delay in leaf senescence compared to plants exposed to SD. On the other hand, in de-podded plants, post-anthesis LD also delayed leaf senescence in relation to plants exposed to SD.There also were differences in leaf senescence under LD in plant without pods vs. plants with pods. These results indicate that photoperiod is a factor that modulates leaf senescence both indirectly (i.e., mediated by the delay of pod development) and directly (i.e., independently of pod development).Therefore, in addition to source-sink effects, leaf senescence in soybean is directly regulated (at least partially) by photoperiod.