Hutton B J, Dixon K W, Sivasithamparam K, Pate J S
Kings Park and Botanic Garden, West Perth, 6005, Western Australia.
Soil Science and Plant Nutrition, University of Western Australia, Nedlands, 6009, Western Australia.
New Phytol. 1996 Dec;134(4):665-672. doi: 10.1111/j.1469-8137.1996.tb04932.x.
The nature and location of infective inocula of ericoid endophytes were examined in habitat soil sampled dry during midsummer from different depths down the rooting profile of an Epacridaceae-rich mediterranean-type ecosystem in south-western Australia. Efficacy of soil inocula was tested using aseptically germinated seedlings of Lysinema ciliatum R. Br. grown in a glasshouse. Hair roots, the principal structures colonized by endophytes, constituted c. 70% of the total length of root systems formed under glasshouse culture. Colonization of these hair roots by endophytes was greatest (17%) when seedlings had been inoculated with habitat soil from the upper 24 cm zone and declined to less than 1% following inoculation with soil obtained from a depth of 36 cm and beyond. By contrast, sampling of a naturally growing epacrid (Leucopogon conostephioides D.C.) at the same study site during the wet midwinter growing season showed uniformly high (34-43 %) infection of hair roots down to maximum rooting depth at 70 cm. The infectivity of sieved soil fractions from bulk habitat soil was considerably greater (mean of 17 % hair root infection) for glasshouse-cultured Lysinema ciliatum inoculated with the 251-305 μm particle size fraction than for that inoculated with coarser (306-5000 μm) and finer (39-250 μm) sieve fractions (0-6% infection). Dilution of bulk soil with sterilized soil indicated maximum infection at 1:16 dilution, declining to negligible infectivity at a dilution of 1:100. The data support the hypothesis that inoculum persists through summer principally in relatively coarse fractions of organic matter near the soil surface. With the onset of autumn rains, downward mycelial growth emanating from this upper zone rapidly recolonizes the soil profile and eventually promotes extensive colonization of hair roots produced that season by the epacrid root system.
在澳大利亚西南部一个富含杜鹃花科植物的地中海型生态系统中，于仲夏时节采集了不同深度根际剖面的干燥生境土壤，以此来研究石南型内生菌感染接种体的性质和位置。利用在温室中无菌萌发的纤毛裂果漆幼苗，对土壤接种体的功效进行了测试。内生菌定殖的主要结构是毛根，在温室培养条件下，毛根约占根系总长度的70%。当幼苗接种来自上部24厘米区域的生境土壤时，这些毛根的内生菌定殖率最高（17%），而接种来自36厘米及更深深度土壤后，定殖率降至1%以下。相比之下，在冬季湿润生长季节，于同一研究地点对自然生长的杜鹃花科植物（锥序白珠树）进行采样，结果显示，直至70厘米的最大生根深度，毛根的感染率均保持在较高水平（34 - 43%）。对于温室培养的纤毛裂果漆，接种251 - 305微米粒径级分的生境土壤筛分物后的感染性（毛根感染率平均为17%），远高于接种较粗（306 - 5000微米）和较细（39 - 250微米）筛分物后的感染性（0 - 6%感染）。用灭菌土壤稀释生境土壤表明，在1:16稀释时感染率最高，在1:100稀释时感染性降至可忽略不计。这些数据支持了以下假说：接种体在夏季主要存在于土壤表层附近相对较粗的有机物质级分中。随着秋雨的来临，从这个上部区域向下生长的菌丝体迅速重新定殖土壤剖面，并最终促进该季节杜鹃花科植物根系产生的毛根大量定殖。
