| Glycyrrhiza inflata is a perennial herb of the genus Glycyrrhiza in the Leguminous family.Although both licorice’s roots and rhizomes are used as Chinese medicinal materials,the sales volume and price of the roots are much higher than that of the rhizomes.The vigor growth of the rhizomes will inevitably reduce the nutrient allocation to the roots,thereby reducing the yield and quality of the roots.Therefore,how to limit the growth of rhizomes but improve the yield and quality of the roots has become an urgent problem during the licorice cultivation.The rhizomes of G.inflata are distributed in shallow soil,and the development of rhizomes has a strong dependence on soil moisture.Reasonable control of soil moisture is one of the effective measures to coordinate plant growth and reproduction.Therefore,experiments of two irrigation patterns(DI and SDI)and three irrigation levels(low,medium and high soil moisture,i.e.50%,70% and 90% of the maximum water holding capacity)were carried out in this study.Our aim is to reveal the influence of different irrigation regimes on the yield of vegetative organs of G.inflata and the medicinal quality of its roots,and to explore a water management regime that could significantly promote the roots growth but inhibit the rhizomes development.The main research results are as follows:1.With the increasing of irrigation amount,the plant height,crown width,base diameter,root length and root diameter of the G.inflata showed an increasing trend and the number of root nodule of the annual G.inflata also increased with the increase of irrigation levels.Under the same irrigation levels,the the plant height,crown width,taproot length and taproot diameter of SDI treatments were all higher than those of DI treatments.In annual licorice,the plant height,crown width,basal stem,taproot length,taproot diameter and number of root nodule of SDIL treatment were increased by 95.6%,81.9%,13.5%,22.5%,20.0% and95.6% respectively compared with those of the DIL treatment.Compared with DIM treatment,the above indicators of SDIM treatment had increased by 31.8%,48.6%,31.0%,11.2%,64.0% and 66.1%respectively.Compared with DIH treatment,the above indicators of SDIH treatment had increased by 8.6%,7.1%,6.2%,6.1%,1.6% and 41.2% respectively.In biennial licorice,the plant height,crown width,taproot length and taproot diameter of SDIL treatment were increased by 31.4%,23.4%,22.4% and 1.7%respectively compared with those of the DIL treatment.Compared with DIM treatment,the above indicators of SDIM treatment had increased by 23.2%,22.3%,12.1% and 16.5% respectively.Compared with DIH treatment,the above indicators of SDIH treatment had increased by 7.9%,19.3%,21.3% and 17%respectively.It shows that SDI treatments increase the timeliness of water in the soil by reducing the amount of evaporation on the soil surface.Sufficient water enables G.inflata to invest more energy in the growth of stem and root length,thereby enhancing the ability to capture light energy and draw moisture from deep soil.Moreover,compared with DI treatments,SDI treatments could significantly promote the root nodule development of G.inflata and enhance the nitrogen fixation ability of plants.2.With the increasing of irrigation levels,the aboveground biomass,root biomass and the content of the 5 medicinal components(glycyrrhizic acid,glycyrrhetinic acid,glycyrrhizin,liquiritigenin and isoliquiritigenin)in G.inflata roots showed an increasing trend.Under the same irrigation level,the aboveground biomass,root biomass and the contents of 5 medicinal components of SDI treatments were higher than those of DI treatments.In annual licorice,the aboveground biomass,root biomass and the content of glycyrrhizic acid,glycyrrhetinic acid,glycyrrhizin,liquiritigenin and isoliquiritigenin of SDIL treatment were increased by 41.3%,72.4%,49.0%,329.4%,146.3%,135.3% and 11.3% respectively compared with those of the DIL treatment.Compared with DIM treatment,the above indicators of SDIM treatment had increased by 41.2%,48.3%,22.1%,135.6%,12.0%,47.3% and12.4% respectively.Compared with DIH treatment,the above indicators of SDIH treatment had increased by 9%,53.6%,36.4%,49.0%,22.9%,0.25% and 54.5% respectively.In biennial licorice,the above indicators of SDIL treatment had increased by 21%,59%,2.8%,6.3%,27.4%,84.0% and 74.6% respectively compared with DIL treatment.Compared with DIM treatment,the above indicators of SDIM treatment had increased by4.5%,14.3%,28.7%,29.6%,23.0%,84.1% and 57.5% respectively.Compared with DIH treatment,the above indicators of SDIH treatment had increased by 17.3%,13.1%,29.3%,33.7%,36.5%,75.6% and106.6% respectively.Therefore,the use of SDI system with higher water supply can significantly improve the yield of cultivated licorice and quality of its root.3.With the increasing of irrigation levels,the number of rhizomes,total length,total volume,biomass of rhizome and the proportion of rhizome biomass of annual licorice under DI treatments showed a trend of first increasing and then decreasing.However,the number of rhizomes,total length,total volume and biomass of SDI treatment had no significant changes with the increasing of irrigation level,but the proportion of rhizome biomass showed a downward trend.The development of biennial licorice rhizomes increased with the increasing of irrigation level under the two irrigation patterns.But SDI treatments could significantly inhibit the development of rhizomes compared with DI treatments.In annual licorice,the number of rhizomes,total length,total volume,biomass of rhizome and the proportion of rhizome biomass of SDIL treatment were reduced by 33.1%,10.9%,34.1%,73.2% and 84.1% respectively compared with those of the DIL treatment.Compared with DIM treatment,the above indicators of SDIM treatment had reduced by 55.1%,42.4%,58.3%,88.1% and 92.2% respectively.Compared with DIH treatment,the above indicators of SDIH treatment had reduced by 35.4%,28.5%,52.9%,78.3% and 91.7% respectively.In biennial licorice,the above indicators of SDIL treatment had reduced by 28.8%,34.0%,37.5%,33.2%and 15.7%,respectively compared with DIL treatment.Compared with DIM treatment,the above indicators of SDIM treatment had reduced by 12.7%,38.1%,48.1%,47.6% and 33.8% respectively.Compared with DIH treatment,the above indicators of SDIH treatment had reduced by 30.4%,54.0%,33.3%,28.2% and 27.4% respectively.This indicates that under DI conditions,the clonal growth pattern tended to be "guerrilla",which was characterized by a large number of rhizomes,long length and large biomass.The clonal growth pattern under SDI conditions tended to be "aggregated",which was characterized by a small number of rhizomes,short length and low biomass.4.Comprehensive evaluation of all indexes of G.inflata,the scores of each treatment in the annual licorice from high to low were SDIH>SDIM>DIH>SDIL>DIM>DIL,The scores of each treatment in the biennal licorice from high to low were SDIH>DIH>SDIL>SDIM>DIM>DIL.SDIH was the most beneficial irrigation regime for the production of licorice materials.In summary,although DI treatments with high level of irrigation may improve the growth of roots of G.inflata,it would spur the rhizome’s development.However,SDI treatments can not only increase the growth of root and its medicinal components content but also can significantly inhibit the development of rhizome. |
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