Effects Of Interaction Between Roots And Leaves On The Continous Regrowth Of Ryegrass

Grazing tolerance is important in continuation grassland production andimproving hay yield. In the current study, ryegrass was used as the subject materials,with the research method of shading, root breaking, proving the coordinationmechanism between roots and leaves though the study of non-structure carbohydratesloss ways and changes of root absorbing ability. Based on the coordination mechanismbetween roots and leaves, we used method of root breaking and exogenousphytohormone spraying, with exzaming the content of phytohormones in newly grownleave, stubble, root and root xylem sap, proving the way of root-derived zeatin andzeatin riboside in adjusting grazing tolerance of ryegrass, thus indicating that root-derived cytokinin in improving the grazing tolerance of ryegrass is a essential attribute.The main results are as follows.1. Soluble carbohydrate and organic matter stored in stems and roots areimportant sources for ryegrass to regenerate, and there were some consuming for rootbiomass to a certain degree. Compared with low stubble, the high stubble couldmaintain a relative high root function by relieving root biomass consuming inregeneration, and as a result increased regeneration effectively. There were asignificant positive correlation between ZR content and biomass in newly grownleaves under frequent defoliation.2. After leaf clipping, the root biomass of ryegrass was greatly consumed andthen root capacity declined, thereby resulting in a low ZR content in roots, which ledto the lower ZR content of newly grown leaves and as a result taking inhibitory effecton leaf growth. After leaf clipping, if the consumption of root biomass did not increase,the root capacity of ryegrass could get enhanced, resulting in a higher ZR content inroots, which could lead to a higher ZR content in newly grown leaves, thus promotingthe growth of the leaves. Although leaf clipping of ryegrass also could stimulate ABAincrease in roots, there did not existed evident direct relation between the ABA contents of roots and newly grown leaves and that the ABA content of roots did notdirectly or indirectly affected the growth of newly grown leaves.3. Under frequent defoliation, the biomass and soluble carbohydrate content inryegrass roots decreased, causing a decline of the ZR content in both xylem sap androots. Moreover, under frequent defoliation root breaking easily decrease the ZRcontent in the xylem sap and roots; however, exogenous cytokinin easily increased theZR content in the newly grown leaves and roots. High ZR content in the leavesimproved the regrowth of ryegrass, which was not determined by the absorptioncapacity of the roots.4. Under frequent defoliation, the Z+ZR and Z+ZR+IPA+IPS contents in leaveshad a significantly position correlation with the biomass of the newly grown leaves; asignificant positive correlation was observed between leaves and xylem sap, betweenleaves and roots in Z+ZR contents, between leaves and xylem sap in Z+ZR+IPA+IPScontents, between leaves and roots in Z+ZR+IPA+IPS contents. However the regrowthof ryegrass had no direct relationship with root absorbing ability or organic mattercontents stored in roots. Compared with no root breaking, severe root breaking easilycaused the exhaustion of root functions and decreasing of the Z+ZR andZ+ZR+IPA+IPS contents in roots, root xylem sap, as well as leaves, thereby restrainedregrowth of ryegrass.