The "soil microbial loop" is not always needed to explain protozoan stimulation of plants
The "soil microbial loop" is not always needed to explain protozoan stimulation of plants
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DOI：
10.1016/j.soilbio.2009.08.019
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发表时间：
2009-11-01
影响因子：
9.7
通讯作者：
Mikola, Juha
中科院分区：
文献类型：
--
作者：
Ekelund, Flemming;Saj, Stephane;Mikola, Juha
原生动物刺激植物生长，但我们并不完全了解其内在机制，不同的假说试图解释这一现象。为了验证这些假设，我们在装有土壤的花盆中种植了约克郡雾草（Holcus lanatus），土壤中要么含有（1）细菌，要么含有（2）细菌和原生动物。一半的盆接受葡萄糖处理，以模拟额外的根分泌物。我们测量了植物生长和植物氮吸收，沿着各种微生物池和支持植物生长的过程。原生动物的存在显着提高土壤氮矿化，植物从有机氮源中吸收氮，植物氮含量和植物生长。相比之下，我们没有发现任何证据表明，葡萄糖添加，模拟根系分泌，增加土壤氮的有效性和植物氮的吸收。此外，虽然原生动物的存在会影响细菌群落结构，但它并不影响IAA产生细菌在群落或植物根系形态中的比例。这些结果反驳了“土壤微生物循环”假说，该假说认为原生动物刺激植物生长是植物根系、细菌和原生动物之间复杂相互作用的结果。因此，我们的实验支持这样一个简单的解释，即增加氮的可用性是原生动物对植物生长产生积极影响的关键因素。为了以高效和环保的方式开发自然资源，我们需要详细了解生态系统的功能。这项研究强调，要实现这一目标，它仍然是迫切的，除了调查复杂的食物网和信号化合物的相互作用，也集中在生物体的基本化学计量和能量方面。(C)2009爱思唯尔有限公司保留所有权利。
Protozoa stimulate plant growth, but we do not completely understand the underlying mechanisms, and different hypotheses seek to explain this phenomenon. To test these hypotheses, we grew the grass Yorkshire fog (Holcus lanatus) in pots with soil, which contained either (1) no organisms but bacteria - or (2) bacteria and protozoa. Half of the pots received a glucose treatment so as to mimic an additional root exudation. We measured plant growth and plant nitrogen uptake, along with various microbial pools and processes that support plant growth. Protozoan presence significantly enhanced soil nitrogen mineralization, plant nitrogen uptake from organic nitrogen sources, plant nitrogen content, and plant growth. By contrast, we found no evidence that glucose addition, mimicking root exudation, increased soil nitrogen availability and plant nitrogen uptake. Moreover, although protozoan presence affected bacterial community structure, it did not affect the proportion of IAA-producing bacteria in the community or plant root morphology. These results refute the "soil microbial loop" hypotheses, which suggest that protozoan stimulation of plant growth results from complex interactions between plant roots, bacteria and protozoa. Our experiment thus favours the simple explanation that increased nitrogen availability is the key factor behind the positive protozoan effect on plant growth. To exploit natural resources in an efficient and environmentally friendly way, we need to understand in detail the functioning of ecosystems. This study stresses that to achieve this, it is still urgent, besides investigating intricate food-web and signal compound interactions, also to focus on the basic stoichiometric and energetic aspects of organisms. (C) 2009 Elsevier Ltd. All rights reserved.