柏木根系分泌物对栾树细根形态及N、P含量的影响

为研究混交过程中柏木根系分泌物对栾树细根生长的影响,以一年生栾树盆栽幼苗为研究对象,通过施加1株、2株、4株、8株4个浓度柏木根系分泌物(分别记为G1、G2、G4、G8)于栾树盆栽中,探讨柏木根系分泌物对栾树幼苗1～5级细根形态及N、P含量的影响。结果表明:(1)栾树细根直径随根序的增加而增大,施加根系分泌物显著减小了1～2级细根的直径(P0.05);细根比根长、比表面积均随根序的增加而减小,施加根系分泌物显著增大了1～2级细根的比根长及比表面积(P0.05);随根系分泌物施加浓度的提高,栾树比根长及比表面积先增大,而直径先减小,然后均趋于平缓波动的态势。(2)栾树细根N、P含量均随根序的增加而减小,而N/P在根序间的变化不显著;施加柏木根系分泌物显著增大了栾树1～2级细根的N、P含量(P0.05),但减小了1～5级细根的N/P;随根系分泌物施加浓度的提高,栾树细根P含量增大,N/P减小,而N含量先增加后呈现平缓变化的趋势。(3)栾树细根N、P含量均与其比根长、比表面积和直径等形态特征之间呈显著的相关关系(P0.05)。研究发现,柏木根系分泌物可改善土壤养分的有效性,从而缓解栾树植株的缺P症状,细根通过调整其形态以提高养分利用效率;柏木根系分泌物主要影响栾树1～2级细根的形态及N、P含量;4株柏木根系分泌物的剂量更有利于栾树根系的生长。

Effect of Root Exudates of Cupressus funebris on Fine Root Morphology and N and P Contents of Koelreuteria paniculata

The project conducted a pot culture method to study the effect of Cupressus funebris root exudates on the growth of Koelreuteria paniculata fine roots in mixed forests. Four experiment groups of G1, G2, G4 and G8 were set up and separately added the potted seedlings of K. paniculata, followed by treatment with root exudates of 1, 2, 4, and 8 cypresses respectively, which investigated the effects of that root exudates on fine root morphology, N and P contents in orders 1-5 roots. The results showed that: (1) fine root diameter increased with root order increasing. Root exudates significantly reduced fine root diameter in orders 1-2. Specific root length and specific root surface area decreased while root order increasing. Root exudates significantly increased specific root length and specific root surface area in orders 1-2. With the increasing concentration of root exudates, specific root length and specific root surface area increased firstly, while the diameter decreased firstly, followed by all of them tended to be stable. (2) Contents of N and P decreased with the increase of root order, but the change of N/P in root order was not obvious; root exudates significantly increased N and P contents in fine root orders 1-2, but decreased N/P in orders 1-5; with the growing concentration of root exudates, fine root P content increased, N/P decreased, and N content increased primarily and then remained no change. (3) Contents of N and P in fine roots were remarkably correlated with the morphological characteristics. Root exudates could improve the availability of soil nutrients, thereby alleviating the symptoms of P deficiency in plants. Fine roots could enhance nutrient use efficiency through adjusting their morphology. Meanwhile, root exudates mainly affected morphology and contents of N and P in fine root orders 1-2. The results indicated that root exudates from 4 strains of C. funebris were more beneficial to the growth of K. paniculata.