不同光照强度对黄波椤苗木根系形态和菌根侵染率的影响

The Effects of Different Light Intensities on Root Morphology and Mycorrhizal Colonization Rate of Phellodendron amurense Seedlings

在东北林业大学帽儿山实验林场苗圃,选取健康且长势一致的1年生黄波椤(Phellodendron amurense Rupr.)苗木(苗高15.1 cm,地径6.0 mm),统一进行切根处理(切去根系总长的2/3),移栽入塑料花盆中,移栽后缓苗1个月;利用遮光棚对盆栽苗木进行3个遮光处理(铺设1层、2层、3层遮光网),以全光(自然光)为对照,共4个处理(光照强度分别为100%(对照)、65%全光、35%全光、20%全光);遮光处理1个月后,于7、8、10月份分别对4个处理的苗木进行破坏性取样,将苗木带土完整取出剪下苗木根系,将根系分成不同根序(1级根、2级根、3级根),记录各根序细根的数量;测定主根长、根系体积、根系平均直径、比根长、组织密度、分支比、分支强度、菌根侵染率,分析不同遮光处理对黄波椤苗木根系形态和菌根侵染率的影响。结果表明:由光照强度为100%(对照)至20%全光,随遮光强度增大,苗木主根长和1级侧根数均先增大后减小;且光照强度为65%全光时的主根长,显著高于光照强度为20%全光时的主根长(P<0.05)。不同根序比根长,均随遮光强度增大而增大;2、3级根直径和分支比,均随遮光强度增大先增大后减小;10月份2级根,光照强度为65%全光时的分支强度,显著高于光照强度为100%(对照)时的分支强度(P<0.05)。苗木经遮光处理时的菌根侵染率,与光照强度为100%(对照)的菌根侵染率相比,呈降低趋势;其中,光照强度为35%全光遮光处理时的菌根侵染率,显著低于光照强度为100%(对照)时的菌根侵染率(P<0.05)。综合试验结果,适度遮光(光照强度为65%全光)有利于黄波椤苗木根系生长,重度遮光抑制根系生长;遮光对黄波椤苗木菌根侵染具有明显影响,全光有利于菌根侵染,过度遮光时菌根侵染率降低。

The 1-year old healthy and uniformly growing Phellodendron amurense seedlings(seedling height 15.1 cm,ground diameter 6.0 mm)were selected from the nursery of the Ma'ershan experimental forest farm of Northeast Forestry University,and the seedlings were carried out unified root cutting treatment(2/3 of the total root length was cut off)and transplanted into plastic pot,followed by a one-month acclimation period.The potted seedlings were subjected to three levels of shading treatments(one,two,and three layers of shading nets)in shading shed,with full light(natural light)as the control check.Four treatments were established,representing different light intensities(100%sunlight as control,65%sunlight,35%sunlight,and 20%sunlight).After one month of shading treatment,destructive sampling was carried out on 4 treated seedlings in July,August and October,and the roots of the seedlings were completely removed and cut,and the roots were divided into different root sequences(first-order roots,second-order roots and third-order roots).The number of fine roots in each root order was recorded.Measurements were taken for primary root length,root system volume,average root diameter,specific root length,tissue density,branching ratio,branching intensity,and mycorrhizal colonization rate.The effects of different shading treatments on root morphology and mycorrhizal colonization rate of Phellodendron amurense seedlings were analyzed.The results showed that when the light intensity was 100%(control)to 20%,with the increase of shading intensity,the main root length and the number of first-order lateral roots increased first and then decreased,and the main root length at 65%total light intensity was significantly higher than that at 20%total light intensity(P<0.05).The specific root length of different order of roots increases with the increase of shading intensity.The root diameter and branching ratio of order 2 and 3 increased first and then decreased with the increase of shading intensity.In October,the branching intensity of grade 2 root at 65%full light intensity was significantly higher than that at 100%light intensity(control)(P<0.05).The mycorrhizal infection rate of seedlings treated with shading showed a decreasing trend compared with that of seedlings treated with 100%light intensity(control).Among them,the mycorrhizal infection rate under 35%full light blackout treatment was significantly lower than that under 100%light intensity(control)(P<0.05).In conclusion,moderate shading(65%total light intensity)was beneficial to root growth,while severe shading inhibited root growth.Light shading had obvious effect on mycorrhizal infection,full light was beneficial to mycorrhizal infection,and the mycorrhizal infection rate decreased when excessive light shading.