Mobilisation of storage reserves during germination and early seedling growth of sugar beet

Abstract

The principal storage reserve of sugar beet seeds is starch, which is localised in the perisperm. Additional storage reserves include the seed proteins, albumins, globulins and glutclins, which are exclusively located in the embryo. Soluble sugars are also detectable in all the organs of the mature seed. The time‐course of reserve mobilisation in the different organs of the sugar beet (Beta vulgaris L. cv. Regina) seed during germination and early seedling growth is documented, with particular reference to changes in (a) activities of hydrolases: a‐amylase, β‐amylase, and α‐glucosidases; (b) levels of carbohydrates and (c) proteins. Amylase activities increase substantially in both cotyledons, as well as the perisperm, whereas the increase in α‐glucosidase activities is largely confined to the perisperm.

Carbohydrate starvation is a major determinant of the loss of greening capacity in cotyledons of dark-grown sugar beet seedlings

“…The developmental processes of gemnination and early growth were found to take place at about the same rate as in previous studies where 50% of the seeds had completed their germination after 45 and 55 h, respectively (Lawrence et al, 1990, Elanirani et al, 1992, The timing of the events, in these two previous studies and in the present one, was essentially the same.…”

“…The starch in dry sugar beet seeds is exclusively confined to the perisperm whereas lipids are stored primarily iti the cotyledons, and reserve proteins are found in the different organs of the seedling (Lawrence et al, 1990, Elamrani et al, 1992, In the cotyledons, substantial amounts of storage proteins are mobilized by day 4, this occurring with no obvious decrease in the total amount of protein per cotyledon up to day 6 (Lawrence et al, 1990), Here, in agreement with their results, we found only a small decrease in the total amount of soluble protein up to day 6 (Fig, 3A) and no change in total reduced nitrogen between days 4 and 6 (Fig, 3B); however, after day 6, both parameters decreased rapidly. At this time, growth almost stopped, and a transfer of nitrogen to other organs is unlikely.…”

“…In contrast with previous studies, which generally covered short periods (less then one week), of etiolation (Lawrence et al, 1990), we carried out a study from imbibition until 12 days of dark growth. Our results suggest that in the case of dark-grown sugar beet seedlings a situation of sugar starvation occurred immediately after the optimum stage for greening was reached (6 days after sowing).…”

Differential induction of glyoxylate cycle enzymes by stress as a marker for seedling vigor in sugar beet (Beta vulgaris)

“…In contrast, Elamrani et al (1992) indicated that there is virtually no lipid in the perisperm but $15% lipid content in the embryo, and showed that lipids are likely to be the initial substrate for respiration during germination of sugar beet, with carbohydrates assuming greater importance after radicle protrusion from the seed ball. Similarly, Lawrence et al (1990) showed differences in organ-specific starch, protein, and sugar contents in excised seeds and seedlings, and suggested a specialization of the inner cotyledon (in closest proximity to the perisperm) for carbohydrate uptake. Differences between varieties in lipid and carbohydrate content may account for differences in emergence potential.…”

How does Dryobalanops aromatica supply carbohydrate resources for reproduction in a masting year?

“…The fractional transmittance was read using UV/VIS spectrophotometers (Shimadzu UV-1400, Kyoto, Japan) at 490 nm. Starch was determined using a modified version of the method of Lawrence et al (1990) and Newell et al (2002). Following total sugar extraction, the residue was oven-dried at 60 • C for 2 days.…”