Seasonal dynamics of carbohydrate and nitrogenous components in the roots of perennial weeds

Abstract

Chicory (Cichorium itttyhus L.) and dandelion (Taraxacutn officinale L.) are persistent weeds, the aerial portions of which do not survive in winter. However, subterranean tissues remain viable and facilitate the rapid resumption of growth in early spring. The source of nutrients for gr-owth prior to the establishment of foliage is the r-oots. Carbohydrate and N reserves are accrued during late summer and attturnn, r-espectively. Hydrolysis of Iructans during late autumn occurs coincidentally with incr-ements in sucrose, the latter providing a readily accessible C pool. Nitr-ate, fr-ee amino acids and soluble protein all play substantial roles in nitrogen storage. Asparagine is the predominant amino acid in the free pool dur-ing winter, followed by glutamine, omithine, serine, aspartic acid and glutamic acid. Storage reserves remain at peak levels throughout winter and decline prior to the resumption of growth. The patterns observed here provide evidence that N is an important curr-ency of storage metabolism and, thus, a fr-amcwork has been provided for the examination of regulation of N storage in perennial weeds.

Allocation of Biomass and Carbohydrates in Waterhyacinth (Eichhornia crassipes): Pond-Scale Verification.

“…Starch is stored in the leaves during the day to counteract the otherwise high water potential that would result from a comparable amount of sugars in the leaves. Increased starch has been cited as useful in cold-hardening of temperate plants (Cyr, Brewley, and Dumbroff 1990), although this would be a secondary An analysis of percent accumulation of starch in the plant shows that roots typically held 10 percent or less of starch reserves during the growing season (except in August), with stembases accounting for between 5 and 30 percent of starch (Figure 11 a). Leaves accounted for 60 to 80 percent of starch reserves, with the majority (up to 52 percent) being in the petioles.…”

“…Low levels of starch content in roots were also observed in the small-scale WES study. The tap root of some species can store considerable quantities of starch to promote early-season growth (e.g., chicory (20 percent starch) and dandelion (30 percent starch); Cyr, Brewley, and Dumbroff 1990). Even the unmodified roots of M. spicatum can store up to 20 percent starch (Titus and Adams 1979).…”

The biology of Canadian weeds. 117. Taraxacum officinale G. H. Weber ex Wiggers

“…Taraxacum officinale overwinters as seed or it retains a reduced basal rosette under snow cover (Cyr et al 1990). …”

Protein mobilisation and proteolytic activities in root tubers of Asphodelus aestivus

“…The storage proteins usually compose a small part of the total nitrogen pool within the root; their accumulation is related to overwintering. Cyr and Bewley (1989, 1990a, 1990b suggested that, in herbaceous perennial species, some proteins can be used as a temporary nitrogen source to support plant growth when needed.…”