空气断根对侧柏实生苗生物量分配和根系生长的影响

Effect of air root pruning on biomass allocation and root growth in Platycladus orientalis seedlings

为探求林木幼苗生物量分配和根系生长对空气断根的响应,以侧柏(Platycladus Orientalis)实生苗为材料,设置空气断根(T)和不断根(CK)处理,研究了空气断根10、30 d和50 d后对侧柏生物量、根系形态特征及吸收面积的影响。结果表明:(1)T处理的侧柏幼苗地上生物量、根生物量、总生物量、根长、根表面积、根体积及根尖数在断根10、30 d和50 d后均大于CK,且显著扩大了根系总吸收面积和活跃吸收面积。(2)空气断根显著影响了侧柏实生苗的生物量分配格局,其根冠比在整个试验阶段呈先增大后减小的趋势,而CK逐渐减小。(3)两种处理的侧柏幼苗根系直径集中在0-0.5 mm。与CK相比,T处理侧柏随空气断根时间延长,单株根系直径在0-0.5 mm的根数量急剧增多,占总根尖数的79%,根平均长度、根表面积、根体积和根尖数显著增大。(4)生物量参数和根形态参数之间关系密切。根生物量与地上生物量及总生物量呈显著正相关(P<0.05)。除根系平均直径外,根生物量、地上生物量和总生物量分别与根长、根表面积、根体积、根尖数呈显著正相关,根冠比与地上生物量呈负相关。因此,空气断根有效改善了侧柏幼苗的根系形态特征,提高了吸收面积,显著促进侧柏实生苗在生长早期快速发育。

Plant roots are important organs that function in the uptake of water and nutrients from the surrounding soil, and the physiological and morphological traits of roots affect shoot growth. Therefore, the present study assessed the effect of air root pruning for 10, 30, or 50 d on the biomass allocation, root morphology, and root absorption area of juvenile-stage Platycladus orientalis seedlings, with intact plants used as controls. The results indicated that （1） root biomass, aboveground biomass, total biomass, root length, root surface area, root volume, and root tip number all increased with air root pruning time. In addition, the total and active absorption areas of the roots significantly increased. （2） Air root pruning significantly affected the biomass allocation pattern of P. orientalis seedlings, and the root：shoot ratio initially increased but then decreased, whereas it only decreased in the control. （3） The diameters of most of the P. orientalis roots were ≤ 0.5 mm. Furthermore, air root pruning improved the length, surface area, volume, and tip number of ≤ 0.5 mm roots, when compared to the control, and the roots of this diameter range accounted for 79% of the total root tip number. （4） The biomass and root characteristics of the P. orientalis seedlings were closely related. In addition to the average root diameter, the aboveground, root, and total biomasses of the pruned seedlings were positively correlated to root length, surface area, volume, and tip number. However, the root：shoot ratio and aboveground biomass were negatively correlated. Consequently, air root pruning technology could be used to dramatically promote the growth and survival of P. orientalis seedlings by improving their root morphology and enhancing the absorption area of their roots during early growing stages.