施氮对白羊草细根形态和生长的影响

细根作为植物吸收水分和养分的重要器官,其形态和生长也受到土壤资源有效性的影响。以多年生草本植物白羊草(Bothriochloa ischaemun)为研究对象,通过盆栽试验和连续扫描根系的方法,研究了6个施氮处理(0,0.02,0.04,0.08,0.16和0.32 g/kg)对白羊草1—4级根序根系形态特征的影响。结果表明:(1)随着根序增加,各级根序上根系的平均直径和平均根长呈显著增加趋势(p<0.05),但总根长和比根长显著下降(p<0.05);(2)除对1级根的平均直径没有显著影响外,施氮增加了白羊草其它各级根序的平均根长和平均直径,减小了比根长、总根长和生物量;(3)施氮提高了1—4级根序的根系伸长速率和直径增粗速率,且根系伸长速率和增粗速率随时间推移呈动态变化,尤其是对1,2级根序的影响较大。因此,全球氮沉降增加可能通过影响细根的平均根长、平均直径、比根长、生物量等形态特征而对草本植物地下特征产生影响,进而影响陆地生态系统的C,N循环。

Effect of N Addition on Root Morphological Characteristics and Growth of Bothriochloa Ischaemun

Both the morphology and architecture of fine roots vary according to the stage of development,which directly influences their ability to absorb water and nutrients from the soil,and consequently,influences plant growth.To understand the effect of N fertilization on the fine root architecture and growth dynamics of Bothriochloa ischaemun,six N treatments(0,0.02,0.04,0.08,0.16,0.32 g/kg) were carried out under greenhouse conditions.Using a scanning method we monitored root extension and radial growth dynamics.The scanned pictures were analyzed to obtain root length,diameter,and surface area.Dynamic cluster analysis was then used to sort the root orders according to the morphological factors.After scanning,we flushed the roots,and then dissected the individual roots according to the branching orders.The fine root samples were scanned to determine root length and diameter,and specific root length.The root was oven-dried at 65 ℃ for 48 h before being weighed.The results showed:(1) the mean fine root diameter and mean root length tended to increase(p<0.05) with ascending root order,while both specific root length(SRL) and total root length decreased(P<0.05);(2) the mean root diameter and mean root length increased with increasing N fertilization,however,the SRL,total root length and root biomass decreased with increasing N,except the diameter of the 1st order root;(3) N fertilization increased the root extension rate(RER) and increased radial growth rate(RGR).The RER and RGR for all four root orders first increased to peak levels,which then decreased,and finally held constant.