Stylites, a vascular land plant without stomata absorbs CO₂ via its roots

Abstract

Photosynthetic organs of most higher plants normally have access to atmospheric CO₂ through stomatal pores which also serve as variable valves to control the loss of H₂O vapour which accompanies CO₂ uptake¹. The acquisition of stomata is commonly thought to have been a crucial development permitting ‘conquest’ of land and direct access of plants to atmospheric CO₂. Only in desert stem succulents during drought do stomata remain so tightly closed in the light that the photosynthetic tissues are dependent on internal CO₂ generated through the photosynthetic pathway known as crassulacean acid metabolism². Functional stomata are absent in submerged aquatic plants and in non-vascular land plants (for example, mosses) which are normally covered by a water film. Although it is now clearly established that some aquatic plants assimilate large amounts of CO₂ from the sediment via roots^3–5, terrestrial plants are thought to assimilate only insignificant amounts of CO₂ via this path⁶. Here we report on a terrestrial plant, Stylites andicola, which lacks stomata and is unable to exchange gas with the aerial atmosphere. Rather, it derives nearly all of its photosynthetic carbon through its roots. In addition, this species possesses characteristics of crassulacean acid metabolism.