Seasonal changes in carbohydrates of perennial root nodules of beach pea

Defoliation Influences Starch Granule Distribution and Structure in Medicago sativa L. Taproots as Revealed by SEM and TEM

“…There is evidence of disintegrated amyloplasts in other species when starch is being degraded. For example, amyloplast membranes are not seen in beach pea root nodules in winter months when starch degradation occurs, but are observed in summer months during net starch synthesis [3]. Similarly to this study, [14] observed amyloplasts in roots of 28 PD plants but they did not report this observation for Day 14 when they showed the lowest starch granule levels.…”

“…Pits are likely areas where hydrolytic enzymes are degrading the insoluble semicrystalline starch granule. Seasonal changes affect the starch granule structure in the nodules of beach pea (Lathyrus maritimus) in which cells accrue large starch granules in summer months that are changed into small shrunken amorphous structures in winter months [3] indicating that the process of starch degradation is occurring. Light induces starch granules to become smaller and rougher with funnel-shaped structures in turions of duckweed (Spirodela polyrhiza) plants as revealed by TEM [5].…”

“…Others have noted that amyloplast membranes disintegrate during the starch degradation process and thus expose the starch to cytosolic enzymes [5,[6][7][8][9]. Researchers reported the disintegration of amyloplast membranes along with total loss amyloplast structure of starch accumulation [3]. amyloplast structure within the symbiotic root nodules of beach pea (Lathyrus maritimus) plants during the winter months, when starch degradation takes place, as opposed to summer months, a period of starch accumulation.…”

“…There is a discrepancy about the granule size class that is first degraded, but evidence shows that the preferential degradation of a particular starch granule class size is likely tissue and species-specific. Researchers have reported that seasonal changes from summer growth months to winter hibernating months trigger large starch granules to shrink and appear amorphous in cells of the symbiotic root nodules of Lathyrus maritimus as revealed by TEM [3]. SEM and TEM were used to document the structure of starch granules in endosperm tissue of rice seeds germinated at 32°C in the dark showing that early stages of starch breakdown are visible two days post imbibition by the appearance of small crevices on the surface of starch granules [12].…”

“…This phosphorylation event converts the surface of starch granules from a closed to an open conformation [3]. Phosphoglucan phosphatases SEX4 and LSF2 remove phosphate groups bestowed by GWD and PWD [4].…”