Amijee By F, Stribley D P, Lane P W
Soil Science Department AFRC Institute of Arable Crops Research, Rothamsted Experimental Station, Harpenden, Herts AL5 2JQ.
Statistics Department,AFRC Institute of Arable Crops Research, Rothamsted Experimental Station, Harpenden, Herts AL5 2JQ.
New Phytol. 1993 Nov;125(3):581-586. doi: 10.1111/j.1469-8137.1993.tb03906.x.
An apparatus in which plant roots may be challenged uniformly with inoculum of arbuscular mycorrhizal fungi is described. Seedlings of leek (Allium porrum L.) or clover (Trifolium repens L.) were first grown non-symbiotically in the apparatus for 21 d at three rates of phosphorus (P) addition to soil (150 (P1), 450 (P3) and 750 (P5) mg P kg soil). The positions of individual root tips were recorded, and the root systems then challenged with inoculum of Glomus mosseae (Nicol & Gerd.) Gerdemann & Trappe. Roots were excised 14 d later, and the probability of occurrence of internal infection in successive 3 mm (clover) or 5 mm (leek) sections of root was estimated in first-order laterals (clover) or main axes (leek) from the proportion of sections at each location of replicate roots that bore internal fungal structures. Only in the region of a root proximal to the position of the root tips at inoculation could data be used to investigate change of probability of infection with cell age. Here, there were sharp declines in probability of infection with proximal distance, in both hosts and in all P treatments. The decline of probability was greater in clover: when expressed in terms of cell age at the time of challenge, there was no infection at PI in cells ≤ 10 d old in leek and none in cells ≤ 7 d old in clover. Models of the form log , [p /(1 -p )] =α+β× distance, where p is the estimated probability of infection and a and α are constants, were fitted to these data. The odds on infection are [p /(1 -p )]. For leek, β was unaltered by P addition (P3 and P5 curves were parallel to P1) but from a it could be calculated that on average the odds on successful infection at any particular distance were reduced by 37% and 70% by P3 and P5 rates of P addition respectively. In clover the curves for the three P treatments were not parallel. Addition of P appeared to reduce the odds on infection of clover much more than those of leek. We conclude that the simplest explanation for the patterns of infection in leek is that P addition increased the time taken for soil inoculum of G. mosseae to infect roots: the mechanism in clover might be more complex.
本文描述了一种可使植物根系均匀受到丛枝菌根真菌接种物挑战的装置。韭菜（葱属）或三叶草（白车轴草）幼苗首先在该装置中以三种磷添加速率（150（P1）、450（P3）和750（P5）mg P/kg土壤）非共生培养21天。记录各个根尖的位置，然后用摩西球囊霉（Nicol & Gerd.）Gerdemann & Trappe的接种物对根系进行挑战。14天后切除根系，根据重复根系每个位置带有内部真菌结构的切片比例，估计三叶草连续3mm或韭菜连续5mm根段中一级侧根（三叶草）或主轴（韭菜）内部感染发生的概率。只有在接种时根尖位置近端的根区域，数据才可用于研究感染概率随细胞年龄的变化。在此，在两种宿主植物以及所有磷处理中，感染概率均随近端距离急剧下降。三叶草中感染概率的下降幅度更大：以挑战时的细胞年龄表示，韭菜中≤10天龄的细胞在P1处理下无感染，三叶草中≤7天龄的细胞无感染。将对数形式的模型log,[p/(1 - p)] =α +β×距离（其中p为估计的感染概率，α和β为常数）拟合到这些数据。感染几率为[p/(1 - p)]。对于韭菜，添加磷不会改变β值（P3和P5曲线与P1平行），但从α值可以计算出，在任何特定距离下，P3和P5添加速率分别使成功感染的几率平均降低37%和70%。在三叶草中，三种磷处理的曲线不平行。添加磷似乎比韭菜更能降低三叶草的感染几率。我们得出结论，韭菜感染模式的最简单解释是添加磷增加了摩西球囊霉土壤接种物感染根系所需的时间：三叶草中的机制可能更复杂。
