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J Plant Res

Title:		Effects of the coordination mechanism between roots and leaves induced by root-breaking and exogenous cytokinin spraying on the grazing tolerance of ryegrass
Author(s):		Wang XL; Liu D; Li ZQ;
Address:		"State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China"
Journal Title:		J Plant Res
Year:		2012
Volume:		20110712
Issue:		3
Page Number:		407 - 416
DOI:		10.1007/s10265-011-0442-x
ISSN/ISBN:		1618-0860 (Electronic) 0918-9440 (Linking)
Abstract:		"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"
Keywords:		"Abscisic Acid/metabolism Adaptation, Physiological Biomass Carbohydrate Metabolism Cytokinins/*metabolism Gibberellins/metabolism Herbivory Indoleacetic Acids/metabolism Isopentenyladenosine/analogs & derivatives/metabolism Lolium/*growth & development/*m;"
Notes:		"MedlineWang, Xiao-Ling Liu, Dan Li, Zhen-Qing eng Research Support, Non-U.S. Gov't Japan 2011/07/13 J Plant Res. 2012 May; 125(3):407-16. doi: 10.1007/s10265-011-0442-x. Epub 2011 Jul 12"