Taylor G E, Tingey D T
Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830.
Plant Physiol. 1983 May;72(1):237-44. doi: 10.1104/pp.72.1.237.
The concurrent exchange of SO(2) and H(2)O vapor between the atmosphere and foliage of Geranium carolinianum was investigated using a whole-plant gas exchange chamber. Total leaf flux of SO(2) was partitioned into leaf surface and internal fractions. The emission rate of SO(2)-induced H(2)S was measured to develop a net leaf budget for atmospherically derived sulfur. Stomatal resistance to SO(2) flux was estimated by two techniques: (a) R(s) (SO(2)') from SO(2) data using analog modeling techniques and (b) R(s) (SO(2) ) from analogy to H(2)O (i.e. 1.89 R(s) (H(2)o)).The emission of H(2)S was positively correlated with the rate of SO(2) flux into the leaf interior. An accounting of the simultaneous, bidirectional flux of gaseous sulfur compounds during pollutant exposure showed that sulfur accumulation in the leaf interior of G. carolinianum was 7 to 15% lower than that estimated solely from mass-balance calculations of SO(2) flux data (i.e. ignoring H(2)S emissions).The esimate of stomatal resistance to pollutant flux from the SO(2) data (R(s) (SO(2)')) was consistently less than the simultaneous estimate derived from analogy to H(2)O vapor (R(s) (SO(2) )). The resultant of R(s) (SO(2)') - R(s) (SO(2) ), which was always negative, is indicative of a residual resistance to SO(2) flux into the leaf interior. On a comparative basis, SO(2) molecules experienced less pathway resistance to diffusion than effluxing H(2)O molecules. It is proposed that the SO(2):H(2)O path length ratio is less than unity, as a consequence of the pollutant's high water solubility and unique chemical reactivity in solution. Thus, the diffusive paths for H(2)O and SO(2) in G. carolinianum are not completely synonymous.
利用全株气体交换室研究了大气与卡罗莱纳天竺葵叶片之间二氧化硫（SO₂）和水汽（H₂O）的同时交换。SO₂的总叶片通量被划分为叶片表面通量和内部通量。测量了SO₂诱导的硫化氢（H₂S）排放速率，以建立大气来源硫的叶片净收支。通过两种技术估算了气孔对SO₂通量的阻力：（a）使用模拟建模技术从SO₂数据得出的R(s)(SO₂')，以及（b）类比水汽得出的R(s)(SO₂)（即1.89R(s)(H₂O)）。H₂S的排放与SO₂进入叶片内部的通量速率呈正相关。对污染物暴露期间气态硫化合物同时双向通量的核算表明，卡罗莱纳天竺葵叶片内部的硫积累量比仅根据SO₂通量数据的质量平衡计算（即忽略H₂S排放）所估计的低7%至15%。从SO₂数据得出的气孔对污染物通量的阻力估计值（R(s)(SO₂')）始终小于类比水汽得出的同时估计值（R(s)(SO₂)）。R(s)(SO₂') - R(s)(SO₂)的结果始终为负，这表明存在对SO₂进入叶片内部通量的残余阻力。在比较的基础上，SO₂分子扩散所经历的路径阻力比流出的H₂O分子小。由于该污染物在溶液中的高水溶性和独特化学反应性，提出SO₂:H₂O路径长度比小于1。因此，卡罗莱纳天竺葵中H₂O和SO₂的扩散路径并不完全相同。
