Starch as a source, starch as a sink: the bifunctional role of starch in carbon allocation

Abstract

Starch commands a central role in the carbon budget of the majority of plants on earth, and its biological role changes during development and in response to the environment. Throughout the life of a plant, starch plays a dual role in carbon allocation, acting as both a source, releasing carbon reserves in leaves for growth and development, and as a sink, either as a dedicated starch store in its own right (in seeds and tubers), or as a temporary reserve of carbon contributing to sink strength, in organs such as flowers, fruits, and developing non-starchy seeds. The presence of starch in tissues and organs thus has a profound impact on the physiology of the growing plant as its synthesis and degradation governs the availability of free sugars, which in turn control various growth and developmental processes. This review attempts to summarize the large body of information currently available on starch metabolism and its relationship to wider aspects of carbon metabolism and plant nutrition. It highlights gaps in our knowledge and points to research areas that show promise for bioengineering and manipulation of starch metabolism in order to achieve more desirable phenotypes such as increased yield or plant biomass.

Genotypic variation in source and sink traits affects the response of photosynthesis and growth to elevated atmospheric CO2

“…Rice grain filling relies not only on newly formed assimilates but also on remobilized stem NSC reserves. Storage chiefly takes place before heading (Murchie, Pinto, & Horton, 2009;Wang et al, 2016) and continues some days after heading (Wei et al, 2018), followed by remobilization (MacNeill et al, 2017), which compensates for declining photosynthesis during the late grain-filling period (Wei et al, 2018;Yang & Zhang, 2006). Stem storage activity may resume when the grains are filled.…”

Genotypic variation in morphological source and sink traits affects the response of rice photosynthesis and growth to elevated atmospheric CO2

“…466 467 Rice grain filling relies on not only newly formed assimilates, but also on remobilized stem 468 NSC reserves. Storage chiefly takes place until heading (Murchie et al, 2009;Wang et al, 469 2016), followed by remobilization (MacNeill et al, 2017) which compensates for declining 470 photosynthesis during late grain filling period (Yang and Zhang, 2006). Stem storage activity 471 may resume when the grains are filled.…”

Transferring a Biomass Enhancement Biotechnology from Glasshouse to Field: A Case Study on Wheat GWD RNAi

“…When resources or environmental conditions were more limiting, like at Ginninderra or more in the semi-arid Western Australian region of Merredin, it seems that the GWD RNAi lines were unable to overcome the effect of reduced tillering. Manipulation of the carbohydrate pathway may have impacted source/sink relationship [10,18]. Transgenic plants might have an altered response to carbon allocation when resources become scarce.…”