The Relationgship Between Hydraulic Traits And Growth In Poplar Seedling At Different Growth Rate

Poplar seedlings were used as the object in this study,hydraulic traits,xylem anatomy,growth,and growth rate of the biennial seedlings were continuously monitored.The seedlings were divided into rapid growth group,medium growth group and slow growth group according to their basic diameters and height.The correlation between the plant hydraulic traits and their growth rate and growth was analyzed,and how this relationship was affected by plant size and age was explored.The aim is to find out the hydraulic properties closely related to fast-growing and high-yielding poplars as evaluation indicators for poplar afforestation tree species selection,and to provide a new way for the rapid and accurate selection of new afforestation varieties.The main results are as follows:(1)Vessel diameter,vessel connectivity,number of vessels per unit area,leaf specific conductance and Huber value were significantly different between the first-year rapid growth group and the slow growth group(p<0.05),and the difference was reduced in the second year;there was no significant difference in the hydraulic conductance and specific conductance between the first year of three groups(p>0.05),but there was significant difference between the fast growth group and the slow growth group in the second year(p<0.05).In the second year,vessel diameter,fraction of lumen area,hydraulic conductance and specific conductance were increased in different proportions,and the vessel connectivity,number of vessels per unit area,and Huber value were decreased in different proportions.There was no special correlation between the hydraulic traits and the anatomic structure of the vessel of the stem segments in different growth rate groups(p>0.05).(2)The relationship between the hydraulic traits and growth of plants at different growth rates changed with time.In the first year,the Huber value was significantly negatively correlated with the dry weight above ground of the rapid growth group and the slow growth group(p<0.05),but no correlation in the medium growth group was found(p>0.05);in second year,specific conductance was significantly positively correlated with the dry weight above ground of the medium growth group(p<0.05),but no correlation with the rapid growth group and the slow growth group was found(p>0.05).(3)No correlation was found between stem hydraulic traits and anatomical characteristics of vessels at different time or in different growth rate groups,but the trend of the hydraulic conductance and specific conductance in the time sequence was consistent with the diameter of the vessel,and the connectivity of vessel and number of vessels per unit area were in the opposite direction.(4)The growth rate of poplar seedlings was not stable in the first two years,but the plants with higher growth rate in the second year were mostly plants with rapid growth in the first year,and some plants with lower growth rate had lower vessel diameters,connectivity of vessel,fraction of lumen area,and hydraulic conductance,higher leaf specific hydraulic conductance and Huber value.When measuring the hydraulic traits and the xylem anatomy of poplar seedlings,factors such as the season,time period and plant growth should be taken into consideration;in the selection of rapidly growing breeds,rapid growth with higher hydraulic conductance and specific hydraulic conductance and lower leaf specific hydraulic conductance and Huber value should be selected in the early stage.