Howes B L, Teal J M
Biology Department, Woods Hole Oceanographic Institution, 02543, Woods Hole, MA, USA.
Oecologia. 1994 May;97(4):431-438. doi: 10.1007/BF00325879.
Spartina alterniflora has been reported to lose significant amounts of oxygen to its rhizosphere with potentially important effects on salt-marsh biogeochemical cycling and plant productivity. The potential significance of this oxidative pathway was evaluated using laboratory split-chamber experiments to quantify oxygen loss from intact root systems under a wide variety of pre-treatment and incubation conditions including antibiotics to inhibit microbial respiration. The aerenchyma system of S. alterniflora was found to transport O, N, Ar, and CH from above-ground sources to its below-ground roots and rhizomes. While non-respiratory gases were observed to move from the lacunae to water bathing the root systems, net O loss did not occur; instead oxygen present outside of the roots/rhizomes was consumed. Net oxygen loss was found when resistance to gas transport was reduced in the lacunae-rhizosphere pathway by placing the root systems in a gas phase and when plant respiration was significantly reduced. Root system respiration appeared to be the major variable in the plant oxygen balance. When root and rhizome respiration was inhibited using poisons or lowered by cooling, the oxygen deficit was greatly reduced and oxygen loss was indicated. The effect of seasonal temperature changes on root system "oxygen deficit" presents a possible explanation as to why Spartina produces root systems with respiration rates that cannot be supported by gas transport. Overall, while oxygen loss from individual plant roots is likely, integrating measured root system oxygen loss with geochemical data indicates that the mass amount of oxygen lost from S. alterniflora root systems is small compared to the total oxygen balance of vegetated salt marsh sediments.
据报道，互花米草会向其根际释放大量氧气，这可能对盐沼生物地球化学循环和植物生产力产生重要影响。利用实验室分室实验评估了这种氧化途径的潜在意义，以量化在各种预处理和培养条件下完整根系的氧气损失，包括使用抗生素抑制微生物呼吸。研究发现，互花米草的通气组织系统能将氧气、氮气、氩气和甲烷从地上部分输送到地下根系和根茎。虽然观察到非呼吸性气体从空隙中转移到浸泡根系的水中，但并未发生净氧气损失；相反，根系/根茎外部的氧气被消耗。当通过将根系置于气相中降低空隙-根际途径中的气体传输阻力时，以及当植物呼吸显著降低时，发现了净氧气损失。根系呼吸似乎是植物氧气平衡中的主要变量。当使用毒物抑制根和根茎的呼吸或通过冷却降低其呼吸时，氧气亏缺大大减少，表明有氧气损失。季节性温度变化对根系“氧气亏缺”的影响，为互花米草为何产生呼吸速率无法通过气体传输维持的根系提供了一种可能的解释。总体而言，虽然单个植物根系可能会损失氧气，但将实测的根系氧气损失与地球化学数据相结合表明，与植被盐沼沉积物的总氧气平衡相比，互花米草根系损失的氧气量很少。
