Sugar and starch changes in pea cotyledons during germination

Abstract

J. L. 1986. Sugar and starch changes in pea cotyledons during germination. -Physiol. Plant. 67: 49-54.Changes in starch and sugar contents in the cotyledons during germination have been compared in a smooth (cv. Alaska) and a wrinkled (cv. Progress) cultivar of the garden pea (Pisum sativum L.). In both cultivars there was an initial accumulation of sucrose due to the hydrolysis of sucrosyl oligosaccharides, but galactose did not accumulate in the cotyledons. Starch mobilization in the Progress pea was linear with time and started before the rise in a-amylase (EC 3.2.1.1) activity in the cotyledons; sucrose was synthesized in the cotyledons, and their excision from the axis resulted in an additional accumulation of this sugar. In the Alaska pea, the onset of starch hydrolysis coincided with the rise in a-amylase activity; no accumulation of sucrose was found in excised cotyledons, whilst the sucrose content decreased continuously in attached cotyledons. The same sugars were found in the cotyledons of both cultivars, suggesting a common pathway for starch breakdown. Maltose, maltotriose and linear malto-dextrins were not present and only trace amounts of glucose were detected, suggesting a degradation of starch by phosphorylase after an initial attack by a-amylase. Q-Amylase activity in the cotyledons was higher in the presence of the axis, but was influenced by the water content of the cotyledons. Transient changes in a-amylase activity correlated well with changes in the rate of starch hydrolysis, but after 2-3 days starch mobilization was reduced in excised cotyledons probably due to the resynthesis of starch.Additional key words -Alaska pea, a-amylase, Pisum sativum. Progress pea, sucrose, sucrosyl oligosaccharides.

Alterations in seed reserves of Dalbergia nigra ((Vell.) Fr All. ex Benth.) during hydration

“…The initial increase in sugars in the cotyledons may be an accumulation of sucrose, and since these are not readily mobilized, they therefore accumulate, as observed in Pisum sativum seeds (Monerri et al, 1986). Increases in sucrose concentrations were observed in the cotyledons of Vicia faba seeds until the second day after the start of imbibition, but decreasing significantly after this until day seven (Goyoaga et al, 2011).…”

“…Germination usually starts with imbibition, when the metabolic and physiological processes associated with germination begin and the embryo grows (Nonogaki et al, 2007). In this case, water is the main agent in the germination process, affecting the percentage, the uniformity and speed of germination.…”

Characterization of α-Amylase from Shoots and Cotyledons of Pea (Pisum sativum L.) Seedlings

“…At 21°C, starch is hydrolyzed at a rate of 5.3 mg/day/seed in Progress No. 9 cultivar pea seedlings (17). With soluble starch as substrate, there is nearly 600-fold more a-amylase activity (12.8 ztmol/min/cotyledon pair, calculated from Table I assuming a Qio of two) than is necessary for in vivo rates of starch hydrolysis.…”

“…Pea cotyledons are starch-storing organs which continually increase their starch-degrading activity during the early stages of germination (17,24). It is not surprising, therefore, that they would contain higher levels of a-amylase activity than photosynthetic organs involved in the degradation of relatively low levels of transitory starch.…”

“…In pea cotyledons, amylase activity increases for at least the first 10 d of germination (17,24). The majority of the cotyledon amylolytic activity appears to be due to a-amylase (24).…”