Sammanfattning

Background and Aims The efficiency of N assimilation in response to defoliation is a critical component of plant regrowth and forage production. The aim of this research was to test the effect of the internal C/N balance on NO3- assimilation and to estimate the associated cytokinin signals following defoliation of perennial ryegrass (Lolium perenne L. 'Grasslands Nui') plants.Methods Plants, manipulated to have contrasting internal N content and contrasting availability of water soluble carbohydrates (WSCs), were obtained by exposure to either continuous light or short days (8: 16 h light-dark), and watered with modified N-free Hoagland medium containing either high (5 mM) or low (50 mu M) NO3- as sole N source. Half of the plants were defoliated and the root, sheath and leaf tissue were harvested at 8, 24 and 168 h after cutting. The spatiotemporal changes in WSCs, synthesis of amino acids and associated cytokinin content were recorded after cutting.Key Results Leaf regrowth following defoliation involved changes in the low-and high-molecular weight WSCs. The extent of the changes and the partitioning of the WSC following defoliation were dependant on the initial WSC levels and the C and N availability. Cytokinin levels varied in the sheath and root as early as 8 h following defoliation and preceded an overall increase in amino acids at 24 h. Subsequently, negative feedback brought the amino acid response back towards pre-defoliation levels within 168 h after cutting, a response that was under control of the C/N ratio.Conclusions WSC remobilization in the leaf is coordinated with N availability to the root, potentially via a systemic cytokinin signal, leading to efficient N assimilation in the leaf and the sheath tissues and to early leaf regrowth following defoliation.

Nyckelord

Nitrogen; nitrate; water-soluble carbohydrates; assimilation; cytokinin; Lolium perenne; defoliation; regrowth

Publicerad i

Annals of Botany
2017, Volym: 119, nummer: 8, sidor: 1353-1364
Utgivare: OXFORD UNIV PRESS

SLU författare

• Späth, Jana

  • Institutionen för skoglig genetik och växtfysiologi, Sveriges lantbruksuniversitet
    

UKÄ forskningsämne

Botanik


Publikationens identifierare

DOI: https://doi.org/10.1093/aob/mcx014

Permanent länk till denna sida (URI)

https://res.slu.se/id/publ/91972