Poster: Photosynthesis (light)

Abs # 224: Photosynthesis in seeds: localisation, feature and function

Presenter:	Borisjuk, Ljudmilla , borysyuk@ipk-gatersleben.de
Authors	Borisjuk, Ljudmilla  (A)   Tschiersch, Henning  (A)   Wobus, Ulrich  (A)   Rolletschek, Hardy  (A)
Affiliations:	(A): Institut fuer Pflanzengenetik und Kulturpflanzenforschung

Many contradicting evidence about the ability of seeds to photosynthesise in vivo have been accumulated and published. In order to analyse photosynthetic ability of crop plant seeds and to define the parameters and input of photosynthesis on seed development we applied a broad spectrum of topographical and analytical techniques, such as analysis of distribution of chlorophyll by CLS-microscopy, photosynthetic electron transport analysed by PAM-fluorescence and inhibitors, photosynthetic oxygen evolution by microsensors and ATP distribution using quantitative bioluminescence imaging. The influence of photosynthesis on metabolic fluxes was monitored by metabolite profiling (LC-MS/MS) and 14C-tracers. The low light saturated photosynthetic electron transport, detected in legume seeds, was sufficient for significant increase in internal oxygen levels via photosynthetic oxygen release. The gradients in chlorophyll content, photosynthetic electron transport and oxygen release correlated with the distribution of ATP. The highest biosynthetic fluxes were observed when the embryos turned green and contained high ATP levels. We suggest that seed photosynthesis has an impact on storage by providing ATP/reducing equivalents and oxygen, which is instantly used for respiration. In cereal grains, photosynthetic activity is found only in pericarp, but photosynthetic tissues envelop entirely the developing embryo and the storage endosperm. By supplying the oxygen to hypoxic endosperm, photosynthesis is of fundamental importance for storage processes in cereal grains, despite of its low CO2-fixation potential. We propose the model for the role of seed photosynthesis to improve the energy state of seed.