Correlation Between Root Growth Potential And Seedling Quality Of Ligustrum Vicaryi During Wintering

Ligustrum vicaryi is a semi-evergreen shrub of the genus Ligustrum of Oleaceae,which is a hybridization progeny of Ligustrum ovalifolium'Aureum'and Ligustrum vulgare Linn.The golden leaves play an important role in urban greening and park landscape.Ligustrum vicaryi has better cold tolerance,but its seedlings have poor cold tolerance.The survival rate of planting in spring is a problem for Ligustrum vicaryi seedlings to promte in northern China.The root growth potential?RGP?is the key factor to improve seedling survival rate and seedling quality.In this study,the one year old cutting seedlings of Ligustrum vicaryi were used as materials.In December,January,March and April,the seedlings were cultivated in phytotron?16 h?day?/8 h?night?,20°C?day?/15°C?night??for 3 weeks.The root parameters?length of new root,surface area of new root,volume of new root and number of new root tips?were measured,as well as physiological parameters;From September 2017to April 2018,the physiological parameters were measured in stems and roots;the correlation was explored between root parameters and physiological parameters.We want to find the best physiological parameter to reflect the RGP,and provide theoretical basis and technical guidance for Ligustrum vicaryi in transplanting.The main results are as follows:1.During wintering,in March the new root length,new root surface area and new root tip number of Ligustrum vicaryi were observed,which were 467.84 cm,244.63 cm² and1396.9.In January the new root volume of Ligustrum vicaryi was observed?9.23 cm³?.In March the root growth potential is optimal according to comprehensive evaluation.2.During wintering,the strongest cold resistance in roots and stems of Ligustrum vicaryi were-22.1°C and-34.4°C in January.3.IAA content in stem of Ligustrum vicaryi decreased in early wintering?from September 2017 to December 2017?and increased in later wintering?from January 2017 to April 2018?,the lowest IAA content was observed in December.IAA content in root has the opposite trendency in early wintering and same trendency in later wintering;During wintering,GA content in stem of Ligustrum vicaryi decreased first and then stabilized,the lowest GA conternt was observed in October,GA content in root stablilized first and then increased,the lowest GA conternt was observed in December;In December the highest ZR content(13.21 ng·g^-1·FW)in stem and lowest ZR content(7.01 ng·g^-1·FW)in root were observed.During wintering the highest ABA content(143.15 ng·g^-1·FW)in stem and lowest ABA content(108.13 ng·g^-1·FW)in root were observed in April and October,the ABA content in stems was 2-4 times in roots during wintering.During wintering,IAA content and GA content in root of Ligustrum vicaryi were significantly negatively correlated with new root length,the correlation coefficients were r=-0.58 and r=-0.63.ABA content in stem was significantly negatively correlated with new root length,and the correlation coefficient was r=-0.82;There was a significant positive correlation between ABA content in root and new root surface area,and the correlation coefficient was r=0.63,which showed that ABA content in stem was closely related to root growth.4.During wintering,the contents of N,P,K and Mg in root and stem of Ligustrum vicaryi have similar trendency,which were decreased in early wintering and increased in later wintering,and the minimum content was observed in December.There was a significant negative correlation between Cu content in root and new root length,correlation coefficient was r=-0.73.There was a significant negative correlation between Fe content in root and new root length,correlation coefficient was r=-0.60;B content in stem and new root surface area were extremely significant positive correlation,correlation coefficient was r=0.81,N,P,Mg,Ca and Cu content in stem was significantly positively correlated with new root surface area,correlation coefficient were from 0.61 to 0.69;B content in stem and new root volume were significant positive correlation,correlation coefficient was r=0.61;P content in stem and new root tip number showed a significant positive correlation,correlation coefficient was r=0.63;There were no correlation between remaining mineral elements content in stem or root and root growth parameters.The results showed that Cu content in root content and B content in stem were closely related to root growth.5.During wintering,the dry matter content in root and stem of Ligustrum vicaryi increased first and then decreased,the highest content was 63.64%in stem in February,and33.78%in root in December.There was a significant positive correlation between dry matter content in stem and new root volume,correlation coefficient was r=0.60.There was a significant negative correlation between dry matter content in root and new surface area,correlation coefficient was r=-0.65.Dry matter in root content is closely related to root growth.