The Effect of Defoliation on the Carbon Balance in Dactylis glomerata

Abstract

Measurements were made of the carbon dioxide exchange of roots and shoots, changes in soluble carbohydrates, rates of root extension, and rate of phosphorus uptake of young plants of Dactylis glomerata (Cocksfoot) during eight days following defoliation. The results indicated that the soluble carbohydrates formed part of a labile pool which was used in respiration and for providing substrates for new growth. Where defoliation was not severe, the changes in reserve carbohydrates could account for net respiratory losses and amounts of new growth made. Where defoliation was severe, even high concentrations of reserve carbohydrates were inadequate and other substances, presumably proteins, must have been remobilized for use in respiration and new growth. The content of soluble carbohydrate in the root was completely inadequate to meet the needs of root respiration; transfer from the tops and/or remobilization of other substances in the roots must have occurred. Following a severe defoliation, root extension stopped and rates of respiration and phosphorus uptake fell markedly. Phosphorus uptake remained at a low level for the eight days considered. After a light defoliation the roots recovered relatively rapidly. It is suggested that, following a severe defoliation, regrowth during the first week is limited in turn first by the soluble carbohydrate content in the bases of expanding leaves, then by the rate of photosynthesis, and then in the later Stages by the rate of nutrient uptake sustained by the roots.

Root and Shoot Respiration of Perennial Ryegrass Are Supplied by the Same Substrate Pools: Assessment by Dynamic 13C Labeling and Compartmental Analysis of Tracer Kinetics

“…Thus, leaf growth seems to be much more dependent on continued assimilation of carbon, which agrees well with results on carbon allocation shortly after severe defoliation: most carbon used for leaf growth was new (Avice et al, 1996;Schnyder and de Visser, 1999), while that sustaining root respiration was largely old (Avice et al, 1996). Indeed, rapid and drastic decrease of root respiration following defoliation (Davidson and Milthorpe, 1966b) may be due to the fact that substrate for root respiration is essentially derived from current CO 2 fixation and stores in the shoot. Thus, the localization of most of the respiratory substrate in the shoot indicates that the control of root activity by the shoot would occur via the control of both current photosynthate and storage mobilization.…”

Optimization of SCoT-PCR reaction system in Dactylis glomerata by orthogonal design

“…It plays an important role as forage material in North America, Europe (Casler et al, 2000), and Oceania, as well as in grassland animal husbandry and ecological construction of southern subtropical mountains of China. Because of the importance of orchardgrass as a forage and hay grass, in recent years, a number of studies have been performed to examine orchardgrass morphology (Felfoldi, 1975;Turner et al, 2012), anatomy (Ashenden, 1978), cytology (Lentz et al, 1983;Tosun et al, 1999), physiology (Davidson and Milthorpe, 1966;Yoshida and Uemura, 1984;Volaire, 1995;Volaire and Lelièvre, 2001), ecology (Eagles, 1983;Fan, 1997;Kyriazopoulos et al, 2013), and breeding (Denchev et al, 1997;Casler et al, 2000;Hopkins and Bhamidimarri, 2009). Molecular-level studies of orchardgrass have also been conducted.…”

Carbohydrate and Organic Nitrogen Concentrations within Range Grass Parts at Maturity

“…Often no definite trends in organic nitrogen level are evident, as there are with carbohydrates; however, Dilz (1966) in studying perennial ryegrass (Lolium perenne L.), concluded that proteinaceous material should be regarded as reserve constituents. Davidson and Milthorpe (1966) concluded that nonstructural carbohydrates formed only a part of the labile pool which provided substrates for respiration and new growth of orchardgrass (Dactylis glomerata L.). They suggested that proteins must have been remobilized because the amount of nonstructurd carbohydrates was inadequate to account for respiration and new growth of roots and shoots following severe herbage removal.…”