Partitioning of reserve and newly assimilated carbon in roots and leaf tissues of Lolium perenne during regrowth after defoliation: assessment by ¹³C steady‐state labelling and carbohydrate analysis

Abstract

The relative significance of the use of stored or currently absorbed C for the growth of leaves or roots of Lolium perenne L. after defoliation was assessed by steady‐state labelling of atmospheric CO2. Leaf growth for the first two days after defoliation was to a large extent dependent on the use of C reserves. The basal part of the elongating leaves was mainly new tissue and 91% of the C in this part of the leaf was derived from reserves assimilated prior to defoliation. However, half of the sucrose in the growth zone was produced from photosynthesis by the emerged leaves. Fructans that were initially present in elongating leaf bases were hydrolysed (loss of 93 to 100%) and the resulting fructose was found in the new leaf bases, suggesting that this pool may be used to support cell division and elongation. Despite a negative C balance at the whole‐plant level, fructans were synthesized from sucrose that was translocated to the new leaf bases. After a regrowth period of 28 d, 45% of the C fixed before defoliation was still present in the root and leaf tissue and only 1% was incorporated in entirely new tissue.

Defoliation, Shoot Plasticity, Sward Structure and Herbage Utilization in Pasture: Review of the Underlying Ecophysiological Processes

“…Although no definitive arguments have been made with respect to whether post defoliation leaf growth is predominantly limited by carbon or by nitrogen, recent studies suggest that C and N co-regulate leaf growth in general [85], and thus either C or N may play the predominant role depending on prevailing conditions in nitrogen supply and PAR prior to defoliation. Recent studies clearly show that the dependence of leaf growth on non-structural carbon accumulated prior to defoliation is shorter (about 2 days) than previously thought [85,86].…”

Partitioning of water soluble carbohydrates in vegetative tissues of Lolium multiflorum Lam. ssp. italicum cv. Lema

“…No significant differences in total fructose were found in the elongating leaf blades in comparison with the expanded leaf blades (figure 2). In L. perenne, Guerrand et al (1996) and Morvan-Bertrand et al (1999) reported higher fructan contents in the elongating leaves than in expanded leaves. These results suggest that fructose polymers could have functions such as energy supply, unloading of sucrose from phloem and regulation of osmotic potential (Volenec, 1986;Cairns et al, 1991).…”

Defoliation frequency effects on winter forage production and nutritive value of different entries ofDactylis glomerataL.

“…in this phase, leaf regrowth assumes the highest priority in allocation of current photosynthates, followed by commencement of root regrowth and daughter tiller initiation in L. perenne (Donaghy & Fulkerson 1998;Morvan-bertrand et al 1999) and D. glomerata (Rawnsley et al 2002). This means that following defoliation plants initially replace the removed leaf area and then invest energy into shoot and root growth.…”