Similarity of stomatal index in the C4plantSalsola kaliL. in material Collected in 1843 and in 1987: relevance to changes in atmospheric CO2content

Publisher Website
Google Scholar
Abstract
Earlier work (by F.I. Woodward) demonstrated that those plants with the C3 pathway of photosynthesis which were examined, i.e. present day plants and dated herbarium material showed a decreased stomatal index (stomata as a percentage of stomata plus epidermal cells) over the last 200 years. Growth of some of these, and of some other, C3 plants at different CO2 partial pressures shows that the fall in stomatal index over the last 200 years is probably a consequence of the increased atmospheric CO2 partial pressure resulting from the industrial revolution. The work reported here shows that Salsola kali (one of the few plants with the C4 pathway which are native to Scotland) showed the same stomatal index 144 years ago as it does today. Properties of photosynthetic gas exchange in C3 and C4 plants are reviewed. It is concluded that responses to decreased CO2 partial pressure for growth which involve increased stomatal index in C3 plants are achieved in C4 plants without an increase in stomatal index. While C3 plants growing at low CO2 appear to sacrifice water use efficiency in partially maintaining net photosynthetic rate, the C4 plants may emphasize more the maintenance of their already high water use efficiency.