Department of Plant Pathology, Department of Meterology, and Agricultural Research Service, U.S. Department of Agriculture, and University of Wisconsin, Madison, Wisconsin 53706.
Appl Environ Microbiol. 1982 Nov;44(5):1059-63. doi: 10.1128/aem.44.5.1059-1063.1982.
Vertical wind shear and concentration gradients of viable, airborne bacteria were used to calculate the upward flux of viable cells above bare soil and canopies of several crops. Concentrations at soil or canopy height varied from 46 colony-forming units per m over young corn and wet soil to 663 colony-forming units per m over dry soil and 6,500 colony-forming units per m over a closed wheat canopy. In simultaneous samples, concentrations of viable bacteria in the air 10 m inside an alfalfa field were fourfold higher than those over a field with dry, bare soil immediately upwind. The upward flux of viable bacteria over alfalfa was three- to fourfold greater than over dry soil. Concentrations of ice nucleation-active bacteria were higher over plants than over soil. Thus, plant canopies may constitute a major source of bacteria, including ice nucleation-active bacteria, in the air.
垂直风切变和空气中存活细菌的浓度梯度被用来计算裸露土壤和几种作物冠层上方存活细胞的向上通量。土壤或冠层高度处的浓度从年轻玉米和湿土上的每立方米 46 个菌落形成单位变化到干燥土壤上的每立方米 663 个菌落形成单位和封闭小麦冠层上的每立方米 6500 个菌落形成单位。在同时采集的样本中，在苜蓿地 10 米范围内空气中的活菌浓度是紧邻上风处干燥裸露土壤的四倍。苜蓿地上方存活细菌的向上通量比干燥土壤高出三到四倍。冰核活性细菌的浓度在植物上方高于土壤上方。因此，植物冠层可能是空气中细菌（包括冰核活性细菌）的主要来源。
