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| Effects of rhizospheric factors on plant neighbor effects along a salinity gradient |
| SONG Qianqian, CHEN Wenwen, TANG Jianjun*, YU Zhenxing, DING Lilian, LIU Shijun, REN Minglei, CHEN Xin* |
| (College of Life Sciences, Zhejiang University, Hangzhou 310058, China) |
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Abstract The paper examined the effects of soil salinity and rhizospheric factors (i.e. the root, arbuscular mycorrhizal fungal (AMF) hyphae, and soil solution) on the interspecific interaction of plant seedlings. The experiments were conducted by using Tamarix chinensis Lour. as neighbor plant and Medicago sativa L. as target plant. Five rhizospheric factor treatments were without rhizospheric interaction, with total rhizospheric interaction, with AMF hyphae interaction and soil solution interaction and with only soil solution. Three salinity levels were 0.05%, 0.2% and 0.5% as stress gradient for plants. A relative interaction index (RII) was used to indicate whether the effects of neighbor seedling on target seedling were positive or negative (facilitative or competitive), or neutral (without interaction). The results showed that: 1) The AMF colonization rate in the target plant seedling of M. sativa was enhanced by neighbor T. chinensis seedlings under the high soil salinity level (0.5%). Biomass of T. chinensis (neighbor species) seedling did not decrease, but biomass of M. sativa (target species) seedling decrease significantly as soil salinity increased. 2) The RII of total rhizosphere interaction between seedlings of T. chinensis and M. sativa were 0.240 0 (positive), 0.040 0 (neutral) and －0.110 0 (neutral) under 0.05%, 0.2% and 0.5% salinity levels respectively, where the total rhizosphere effect shifted from positive to neutral as the soil salinity level increased. 3) The root effects on the RII were 0.330 3 (positive), 0.294 4 (positive), 0.057 2 (neutral) under 0.05%, 0.2%, and 0.5% of salt levels, indicating the positive effect decreased with the increase of salt levels. 4) The AMF hyphae effects on RII were －0.040 0 (neutral), －0.150 0 (negative), and －0.020 0 (neutral) under 0.05 %, 0.2% and 0.5% salt levels. 5) The soil solution effects on RII were 0.006 0, 0.006 0, －0.034 0 (neutral all) under the three salinity levels. In conclusion, the rhizosphere factors (the root, AMF hyphae, and soil solution) differ in their effects on plant-plant interactions, and these effects are affected by soil salinity. The root facilitates plant-plant interactions under the low soil salinity level, but this facilitation declines as the soil salinity level increases. AMF hyphae enhance the competition under the low soil salinity level;
however, this negative effect weakens as the soil salinity level increases. Neighbor soil solutions do not affect the nature and intensity of plant-plant interactions.
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Published: 30 October 2018
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土壤盐梯度下根际因子对植物邻体效应的影响
通过受控试验研究土壤盐分和植物根际因子（根、菌丝、根际土壤溶液）对植物种间幼苗相互作用的影响。试验以柽柳（Tamarix chinensis Lour.）为邻体植物，以紫花苜蓿（Medicago sativa L.）为目标植物开展研究。试验设置5 个相互作用处理，分别为无邻体相互作用、植物间完全相互作用、根际有菌丝和土壤溶液相互作用、根际仅有土壤溶液相互作用、无根际相互作用；设置3 个土壤盐水平处理，含盐量分别为0.05%、0.2%和0.5%，采用相对邻体效应指数（relative interaction index, RII）来反映种间相互作用强度和性质。试验结果表明：1）在高盐水平下，柽柳幼苗能提高紫花苜蓿幼苗的丛枝菌根真菌（arbuscular mycorrhizal fungi, AMF）侵染率。随土壤盐水平升高，柽柳幼苗的生物量没有降低，但紫花苜蓿幼苗的生物量显著降低（P＜0.05）。2）在低盐、中盐及高盐水平下，柽柳和紫花苜蓿幼苗间的总根际效应指数（RII）依次为0.240 0（正效应）、0.040 0（中性效应）、－0.110 0（中性效应）。3）根对植物间相互作用的效应指数（RII）在低盐、中盐、高盐水平下分别为0.330 3、0.294 4、0.057 2，表现为由正效应转为中性效应。4）菌丝对植物间相互作用的效应指数（RII）在低盐、中盐、高盐下水平分别为－0.040 0、－0.150 0、－0.020 0，分别表现为中性、负和中性效应。5）土壤溶液对植物间相互作用的效应指数（RII）在低盐、中盐、高盐水平下分别为0.006 0、0.006 0、－0.034 0，均为中性效应。综上所述，根、菌丝、土壤溶液等不同根际因子对植物邻体效应的调节不同，且调节作用受盐水平影响。随盐水平升高，根正效应减弱，菌丝负效应先加强后减弱，而土壤溶液效应均不显著。
关键词：
植物种间相互作用,
根际因子,
盐胁迫,
紫花苜蓿,
柽柳,
幼苗
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