Effects of the coordination mechanism between roots and leaves induced by root-breaking and exogenous cytokinin spraying on the grazing tolerance of ryegrass

• Published in: Journal of plant research Vol. 125; no. 3; pp. 407 - 416
• Main Authors: Wang, Xiao-Ling, Liu, Dan, Li, Zhen-Qing
• Format: Journal Article
• Language: English
• Published: Japan Springer Japan 01.05.2012; Springer Nature B.V
• Subjects: Abscisic acid; Abscisic Acid - metabolism; Acetic acid; Adaptation, Physiological; Biomass; Biomedical and Life Sciences; Carbohydrate Metabolism; Carbohydrates; Cytokinins; Cytokinins - metabolism; Defoliation; Gibberellic acid; Gibberellins - metabolism; Grasses; Grazing; Herbivory; Indoleacetic Acids - metabolism; Isopentenyladenosine - analogs & derivatives; Isopentenyladenosine - metabolism; Leaves; Life Sciences; Lolium - growth & development; Lolium - metabolism; Plant Biochemistry; Plant Ecology; Plant growth; Plant Growth Regulators - metabolism; Plant Leaves - growth & development; Plant Leaves - metabolism; Plant Physiology; Plant resistance; Plant Roots - growth & development; Plant Roots - metabolism; Plant Sciences; Plant Shoots - growth & development; Plant Shoots - metabolism; Regrowth; Regular Paper; Roots; SAP protein; Signal Transduction; Spraying; Xylem; Xylem - metabolism; zeatin riboside; Regrowth; Ryegrass; Grazing tolerance; Cytokinin; Root-breaking
• ISSN: 0918-9440; 1618-0860
• DOI: 10.1007/s10265-011-0442-x

The grazing tolerance mechanism of ryegrass was investigated by examining the effects of roots on leaves under frequent defoliation. The study consisted of four treatments: (1) with root breaking and cytokinin spraying, (2) root breaking without cytokinin spraying, (3) cytokinin spraying with no root breaking, and (4) no root breaking and no cytokinin spraying. Results showed that root breaking or frequent defoliation inhibited the ryegrass regrowth, which resulted in low biomass of the newly grown leaves and roots, as well as low soluble carbohydrate content and xylem sap quantity in the roots. Spraying with exogenous cytokinin promoted the increase in newly grown leaf biomass, but decreased root biomass, root soluble carbohydrate content, and root xylem sap quantity. Determination of gibberellic acid, indole-3-acetic acid, abscisic acid, and zeatin riboside (ZR) in roots, newly grown leaves, and stubbles showed that cytokinin is a key factor in ryegrass regrowth under frequent defoliation. Root breaking and frequent defoliation both decreased the ZR content in roots and in newly grown leaves, whereas spraying with exogenous cytokinin increased the ZR content in roots and in newly grown leaves. Therefore, cytokinin enhances the above ground productivity at the cost of root growth under frequent defoliation.