Separation of seed development from monocarpic senescence in soybeans

Abstract

MONOCARPY, a single flowering phase followed by senescence and death, is a widespread phenomenon in seed plants, particularly field crops, whose large monocultures put on a dramatic display during their senescence phase^1–4. In many, but apparently not all monocarpic species, defruiting or deflowering ,can prevent or at least delay monocarpic senescence and death^1–4. For some species such as soybeans, the killing influence has been traced to the developing seeds⁵. The conspicuous correlation between the accumulation of nutrients in the developing fruit and the senescence (or apparent ‘exhaustion’) of the leaves (Fig. 1) has led to the sugegstion that developing fruits cause senescence by diverting or withdrawing needed nutrients or hormones from the leaves and other vegetative parts^1–4. Here we explore the relationship between nutrient (or hormone) withdrawal or diversion and foliar senescence. Our data indicate that the development (accumulation of dry matter) of the seeds is separable from the senescence response in soybeans, and therefore the seeds may function as more than sinks.